Chad Bender

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• Beard, C., Robertson, P., Lubin, J., Ford, E. B., Mahadevan, S., Stefansson, G., Wright, J. T., Wolf, E., Kofman, V., Venkatesan, V., Kopparapu, R., Arendtsz, R., Holcomb, R., Martinez, R. A., Sallum, S., Luhn, J. K., Bender, C. F., Blake, C. H., Cochran, W. D., , Delamer, M., et al. (2025). Discovery of a Nearby Habitable Zone Super-Earth Candidate Amenable to Direct Imaging. Astronomical Journal, 170(Issue 5). doi:10.3847/1538-3881/ae0e20
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  We present the discovery of GJ 251 c, a candidate super-Earth orbiting in the habitable zone (HZ) of its M dwarf host star. Using high-precision Habitable-zone Planet Finder and NEID RVs, in conjunction with archival RVs from the Keck I High Resolution Echelle Spectrometer, the Calar Alto High-resolution Search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrograph, and the Spectropolarimétre Infrarouge, we improve the measured parameters of the known planet, (Formula presented), and we significantly constrain the minimum mass of GJ 251 c, placing it in a plausibly terrestrial regime (Formula presented). Using activity mitigation techniques that leverage chromatic information content, we perform a color-dependent analysis of the system and a detailed comparison of more than 50 models that describe the nature of the planets and stellar activity in the system. Due to GJ 251’s proximity to Earth (5.5 pc), next generation, 30 meter class telescopes will likely be able to image terrestrial planets in GJ 251’s HZ. In fact, GJ 251 c is currently the best candidate for terrestrial, HZ planet imaging in the northern sky.
• Doyle, L., Cañas, C. I., Libby-Roberts, J. E., Cegla, H. M., Stefánsson, G. K., Anderson, D., Armstrong, D. J., Bender, C., Bayliss, D., Carmichael, T. W., Casewell, S., Kanodia, S., Lafarga, M., Lin, A. S., Mahadevan, S., Monson, A., Robertson, P., & Veras, D. (2025). The First Spin-Orbit Obliquity of an M dwarf/brown dwarf system: an eccentric and aligned TOI-2119 b. Monthly Notices of the Royal Astronomical Society, 536(Issue 4). doi:10.1093/mnras/stae2819
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  We report the first instance of an M dwarf/brown dwarf obliquity measurement for the TOI-2119 system using the Rossiter–McLaughlin effect. TOI-2119 b is a transiting brown dwarf orbiting a young, active early M dwarf (Teff = 3553 K). It has a mass of 64.4 MJ and radius of 1.08 RJ, with an eccentric orbit (e = 0.3) at a period of 7.2 d. For this analysis, we utilize NEID spectroscopic transit observations and ground-based simultaneous transit photometry from the Astrophysical Research Consortium and the Las Campanas Remote Observatory. We fit all available data of TOI-2119 b to refine the brown dwarf parameters and update the ephemeris. The classical Rossiter–McLaughlin technique yields a projected star–planet obliquity of λ = −0.8 ± 1.1◦ and a three-dimensional obliquity of ψ = 15.7 ± 5.5◦. Additionally, we spatially resolve the stellar surface of TOI-2119 utilizing the Reloaded Rossiter–McLaughlin technique to determine the projected star–planet obliquity as λ = 1.26 ± 1.3◦. Both of these results agree within 2σ and confirm the system is aligned, where TOI-2119 b joins an emerging group of aligned brown dwarf obliquities. We also probe stellar surface activity on the surface of TOI-2119 in the form of centre-to-limb variations as well as the potential for differential rotation. Overall, we find tentative evidence for centre-to-limb variations on the star but do not detect evidence of differential rotation.
• Fernandes, R. B., Kanodia, S., Delamer, M., Hotnisky, A., Han, T., Cañas, C. I., Libby-Roberts, J., Reji, V., Gupta, A. F., Alvarado-Montes, J. A., Bender, C. F., Blake, C. H., Cochran, W. D., de Beurs, Z. L., Diddams, S. A., Dong, J., Everett, M. E., Ford, E. B., Halverson, S., , Higuera, J., et al. (2025). Searching for GEMS: Confirmation of TOI-5573 b, a Cool, Saturn-like Planet Orbiting an M Dwarf. Astronomical Journal, 170(Issue 1). doi:10.3847/1538-3881/addc51
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  We present the confirmation of TOI-5573 b, a Saturn-sized exoplanet on an 8.79 days orbit around an early M dwarf (3790 K, 0.59 R⊙, 0.61 M⊙, 12.30 Jmag). TOI-5573 b has a mass of 11 2 − 19 + 18 M⊕(0.35 ± 0.06 MJup) and a radius of 9.75 ± 0.47 R⊕(0.87 ± 0.04 RJup), resulting in a density of 0.6 6 − 0.13 + 0.16 g cm−3, akin to that of Saturn. The planet was initially discovered by the Transiting Exoplanet Survey Satellite (TESS) and confirmed using a combination of 11 transits from four TESS Sectors (20, 21, 47, and 74), ground-based photometry from the Red Buttes Observatory, and high-precision radial velocity data from the Habitable-zone Planet Finder and NN-EXPLORE Exoplanet Investigations with Doppler spectrographs, achieving a 5σ precision on the planet’s mass. TOI-5573 b is one of the coolest Saturn-like exoplanets discovered around an M-dwarf, with an equilibrium temperature of only 528 ± 10 K, making it a valuable target for atmospheric characterization. Saturn-like exoplanets around M dwarfs likely form through core accretion, with increased disk opacity slowing gas accretion and limiting their mass. The host star’s supersolar metallicity supports core accretion, but uncertainties in M-dwarf metallicity estimates complicate definitive conclusions. Compared to other GEMS (Giant Exoplanets around M-dwarf Stars) orbiting metal-rich stars, TOI-5573 b aligns with the observed pattern that giant planets preferentially form around M-dwarfs with supersolar metallicity. Further high-resolution spectroscopic observations are needed to explore the role of stellar metallicity in shaping the formation and properties of giant exoplanets like TOI-5573 b.
• Gupta, A. F., Fitzmaurice, E., Mahadevan, S., Robertson, P., Luhn, J. K., Wright, J. T., Logsdon, S. E., Krolikowski, D. M., Paredes, L. A., Bender, C. F., Giovinazzi, M. R., Lin, A. S., Blake, C. H., Cañas, C. I., Ford, E. B., Halverson, S., Kanodia, S., McElwain, M. W., Monson, A., , Ninan, J. P., et al. (2025). The NEID Earth Twin Survey. III. Survey Performance after Three Years on Sky. Astronomical Journal, 170(Issue 5). doi:10.3847/1538-3881/ae0339
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  The NEID Earth Twin Survey (NETS) has been delivering a rich set of precise radial velocity (RV) measurements for 41 bright, nearby main-sequence stars. Here, we describe the status of the survey after 3 yr on sky, and we present the full set of RV measurements and accompanying stellar activity indicators. We discuss intermediate survey diagnostics, including calibration of the known RV zero-point offset introduced following the Contreras fire in 2022 and the identification of an undiagnosed and previously unknown zero-point offset in 2021. An analysis of our data set using RVSearch demonstrates that for these target stars, NEID is independently sensitive to nearly all known planets with periods shorter than the NETS observing baseline. We also highlight a number of newly detected RV signals, which present exciting opportunities for future investigations.
• Gupta, A. F., Luhn, J. K., Wright, J. T., Mahadevan, S., Robertson, P., Krolikowski, D. M., Ford, E. B., Cañas, C. I., Halverson, S., Lin, A. S., Kanodia, S., Fitzmaurice, E., Gilbertson, C., Bender, C. F., Blake, C. H., Dong, J., Giovinazzi, M. R., Logsdon, S. E., Monson, A., , Ninan, J. P., et al. (2025). The NEID Earth Twin Survey. I. Confirmation of a 31 Day Planet Orbiting HD 86728. Astronomical Journal, 169(Issue 1). doi:10.3847/1538-3881/ad89bf
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  With close to 3 yr of observations in hand, the NEID Earth Twin Survey (NETS) is starting to unearth new astrophysical signals for a curated sample of bright, radial velocity (RV)-quiet stars. We present the discovery of the first NETS exoplanet, HD 86728b, a m p sin i = 9.16 − 0.56 + 0.55 M ⊕ planet on a circular, P = 31.1503 − 0.0066 + 0.0062 day orbit, thereby confirming a candidate signal identified by L. A. Hirsch et al. We confirm the planetary origin of the detected signal, which has a semi-amplitude of just K = 1.91 − 0.12 + 0.11 m s−1, via careful analysis of the NEID RVs and spectral activity indicators, and we constrain the mass and orbit via fits to NEID and archival RV measurements. The host star is intrinsically quiet at the ∼1 m s−1 level, with the majority of this variability likely stemming from short-timescale granulation. HD 86728b is among the small fraction of exoplanets with similar masses and periods that have no known planetary siblings.
• Kanodia, S., Cañas, C. I., Mahadevan, S., Lin, A. S., Kobulnicky, H. A., Karfs, I., Birkholz, A., Monson, A., Gupta, A. F., Everett, M., Rodruck, M., Glusman, R. I., Han, T., Cochran, W. D., Bender, C. F., Diddams, S. A., Krolikowski, D., Halverson, S., Libby-Roberts, J., , Ninan, J. P., et al. (2025). Searching for GEMS: TOI-7149 b, an Inflated Giant Planet Causing a 12% Transit of a Fully Convective M-dwarf. Astronomical Journal, 170(Issue 4). doi:10.3847/1538-3881/adf6db
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  We describe the discovery and characterization of TOI-7149 b, a 0.705 ± 0.075 MJ, 1.18 ± 0.045 RJ gas giant on a ∼2.65 days period orbit transiting an M4V star with a mass of 0.344 ± 0.030 M⊙ and an effective temperature of 3363 ± 59 K. The planet was first discovered using NASA’s TESS mission, which we confirmed using a combination of ground-based photometry, radial velocities, and speckle imaging. The planet has one of the deepest transits of all known main-sequence planet hosts at ∼12% (Rp/R⋆ ∼ 0.33). Pushing the bounds of previous discoveries of giant exoplanets around M-dwarf stars (GEMS), TOI-7149 is one of the lowest mass M-dwarfs to host a transiting giant planet. We compare the sample of transiting GEMS to stars within 200 pc with a Gaia color-magnitude diagram and find that the GEMS hosts are likely to be high metallicity stars. We also analyze the sample of transiting giant planets using the nonparametric MRExo framework to compare the bulk density of warm Jupiters across stellar masses. We confirm our previous result that transiting Jupiters around early M-dwarfs have similar masses and densities to warm Jupiters around FGK stars, and extend this to mid M-dwarfs, thereby suggesting a potential commonality in their formation mechanisms.
• Kreider, M. K., Fredrick, C., Diddams, S. A., Terrien, R. C., Mahadevan, S., Ninan, J. P., Halverson, S., Bender, C. F., Hearty, F., Mitchell, D., Rajagopal, J., Roy, A., Schwab, C., & Wright, J. T. (2025). Quantification of broadband chromatic drifts in Fabry–Pérot resonators for exoplanet science. Nature Astronomy, 9(Issue 4). doi:10.1038/s41550-025-02486-x
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  Finding an Earth–Sun analogue is one of the longest-standing goals in astronomy. The detection of such a system using the radial velocity (RV) technique is highly challenging, and would require coordinated advances in astronomical telescopes, fibre optics, precision spectrographs, large-format detector arrays and data processing. Measurements at the necessary 10−10 level over multiyear periods would also require a highly precise calibrator. Here we explore simple and robust white-light-illuminated Fabry–Pérot (FP) etalons as spectral calibrators for precise RV measurements. We track the frequencies of up to 13,000 FP modes against laser frequency combs at two state-of-the-art spectrographs and trace unexpected chromatic variations of the modes to subpicometre changes in the dielectric layers of the broad-bandwidth FP mirrors, corresponding to a RV precision at the centimetres per second level. These results represent critical progress in precision RV measurements in two ways—they validate FP etalons as a more powerful stand-alone calibration tool and demonstrate the capability of laser frequency combs to extend RV measurement precision at the centimetres per second level over periods approaching a year. These advances highlight a path to achieving spectroscopic calibration at levels that will be critical for finding Earths like our own.
• Larsen, A., Swaby, T. N., Kobulnicky, H. A., Cañas, C. I., Kanodia, S., Libby-Roberts, J., Monson, A., Gupta, A. F., Cochran, W., Mahadevan, S., Bender, C., Diddams, S. A., Halverson, S., Lin, A. S., Moe, M., Ninan, J., Robertson, P., Roy, A., Schwab, C., & Stefansson, G. (2025). Searching for GEMS: Discovery and Characterization of Two Brown Dwarfs Around M Dwarfs. Astronomical Journal, 169(Issue 5). doi:10.3847/1538-3881/adbb54
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  Brown dwarfs bridge the gap between stars and planets, providing valuable insight into both planetary and stellar-formation mechanisms. Yet the census of transiting brown-dwarf companions, in particular around M-dwarf stars, remains incomplete. We report the discovery of two transiting brown dwarfs around low-mass hosts using a combination of space- and ground-based photometry along with near-infrared radial velocities. We characterize TOI-5389Ab ( 68 . 0 − 2.2 + 2.2 M J ) and TOI-5610b ( 40 . 4 − 1.0 + 1.0 M J ), two moderately massive brown dwarfs orbiting early M-dwarf hosts (Teff = 3569 ± 59 K and 3618 ± 59 K, respectively). For TOI-5389Ab, the best fitting parameters are period P = 10.40046 ± 0.00002 days, radius R BD = 0.82 4 − 0.031 + 0.033 RJ, and low eccentricity e = 0.096 2 − 0.0046 + 0.0027 . In particular, this constitutes one of the most extreme substellar-stellar companion-to-host mass ratios of q = 0.150. For TOI-5610b, the best-fitting parameters are period P = 7.95346 ± 0.00002 days, radius R BD = 0.88 7 − 0.031 + 0.031 RJ, and moderate eccentricity e = 0.35 4 − 0.012 + 0.011 . Both targets are expected to have shallow, but potentially observable, occultations: ≲500 ppm in the Johnson K band. A statistical analysis of M-dwarf/BD systems reveals for the first time that those at short orbital periods (P < 13 days) exhibit a dearth of 13 MJ < MBD < 40 MJ companions (q < 0.1) compared to those at slightly wider separations.
• Luhn, J. K., Robertson, P., Halverson, S., Gupta, A. F., Siegel, J. C., Wright, J. T., Ford, E. B., Mahadevan, S., Bedding, T. R., Alvarado-Montes, J. A., Bender, C. F., Dong, J., Hearty, F., Logsdon, S. E., Monson, A., McElwain, M. W., Ninan, J. P., Rajagopal, J., Roy, A., , Schwab, C., et al. (2025). Time-resolved p-mode Oscillations for Subgiant HD 142091 with NEID at WIYN. Astrophysical Journal, 987(Issue 2). doi:10.3847/1538-4357/adda44
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  Detections of Earth-analog planets in radial velocity (RV) observations are limited by stellar astrophysical variability occurring on a variety of timescales. Current state-of-the-art methods to disentangle potential planet signals from intrinsic stellar signals assume that stellar signals introduce asymmetries to the line profiles that can therefore be separated from the pure translational Doppler shifts of planets. Here, we examine this assumption using a time series of resolved stellar p-mode oscillations in HD 142091 (κ CrB), as observed on a single night with the NEID spectrograph at 2 minutes cadence and with 25 cm s−1 precision. As an evolved subgiant star, this target has p-mode oscillations that are larger in amplitude (4-8 m s−1) and occur on longer timescales (80 minutes) than those of typical Sun-like stars of RV surveys, magnifying their corresponding effects on the stellar spectral profile. We show that for HD 142091, p-mode oscillations manifest primarily as pure Doppler shifts in the average line profile—measured by the cross-correlation function (CCF)—with “shape-driven” CCF variations as a higher-order effect. Specifically, we find that the amplitude of the shift varies across the CCF bisector, with 10% larger oscillation amplitudes closer to the core of the CCF and 25% smaller oscillation amplitudes for bisector velocities derived near the wings; we attribute this trend to larger oscillation velocities higher in the stellar atmosphere. Using a line-by-line analysis, we verify that a similar trend is seen as a function of average line depth, with deeper lines showing larger oscillation amplitudes. Finally, we find no evidence that p-mode oscillations have a chromatic dependence across the NEID bandpass beyond that due to intrinsic line depth differences across the spectrum.
• Reji, V., Kanodia, S., Ninan, J. P., Cañas, C. I., Libby-Roberts, J., Lin, A. S., Gupta, A. F., Swaby, T. N., Larsen, A., Kobulnicky, H. A., Choi, P. I., Evans, N., Santomenna, S., Winnick, I., Yu, L., Alvarado-Montes, J. A., Bender, C. F., Bernabó, L. M., Blake, C. H., , Cochran, W. D., et al. (2025). Searching for GEMS: TOI-5688 A b, a Low-density Giant Orbiting a High-metallicity Early M-dwarf. Astronomical Journal, 169(Issue 3). doi:10.3847/1538-3881/ada7ea
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  We present the discovery of a low-density planet orbiting the high-metallicity early M-dwarf TOI-5688 A b. This planet was characterized as part of the search for transiting giant planets (R ≳ 8 R⊕) through the Searching for Giant Exoplanets around M-dwarf Stars (GEMS) survey. The planet was discovered with the Transiting Exoplanet Survey Satellite, and characterized with ground-based transits from Red Buttes Observatory, the Table Mountain Observatory of Pomona College, and radial velocity (RV) measurements with the Habitable-Zone Planet Finder on the 10 m Hobby Eberly Telescope and NEID on the WIYN 3.5 m telescope. From the joint fit of transit and RV data, we measure a planetary mass and radius of 124 ± 24 M⊕ (0.39 ± 0.07 MJ) and 10.4 ± 0.7 R⊕ (0.92 ± 0.06 RJ), respectively. The spectroscopic and photometric analysis of the host star TOI-5688 A shows that it is a metal-rich ([Fe/H] = 0.47 ± 0.16 dex) M2V star, favoring the core-accretion formation pathway as the likely formation scenario for this planet. Additionally, Gaia astrometry suggests the presence of a wide-separation binary companion, TOI-5688 B, which has a projected separation of ~5″ (1110 au) and is an M4V, making TOI-5688 A b part of the growing number of GEMS in wide-separation binary systems.
• Stefánsson, G., Mahadevan, S., Winn, J. N., Marcussen, M. L., Kanodia, S., Albrecht, S., Fitzmaurice, E., Mikulskytė, O., Cañas, C. I., Espinoza-Retamal, J. I., Zwart, Y., Krolikowski, D. M., Hotnisky, A., Robertson, P., Alvarado-Montes, J. A., Bender, C. F., Blake, C. H., Callingham, J. R., Cochran, W. D., , Delamer, M., et al. (2025). Gaia-4b and 5b: Radial Velocity Confirmation of Gaia Astrometric Orbital Solutions Reveal a Massive Planet and a Brown Dwarf Orbiting Low-mass Stars. Astronomical Journal, 169(Issue 2). doi:10.3847/1538-3881/ada9e1
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  Gaia astrometry of nearby stars is precise enough to detect the tiny displacements induced by substellar companions, but radial velocity (RV) data are needed for definitive confirmation. Here we present RV follow-up observations of 28 M and K stars with candidate astrometric substellar companions, which led to the confirmation of two systems, Gaia-4b and Gaia-5b, identification of five systems that are single lined but require additional data to confirm as substellar companions, and the refutation of 21 systems as stellar binaries. Gaia-4b is a massive planet (M = 11.8 ± 0.7 MJ) in a P = 571.3 ± 1.4 day orbit with a projected semimajor axis a0 = 0.312 ± 0.040 mas orbiting a 0.644 ± 0.02M⊙ star. Gaia-5b is a brown dwarf (M = 20.9 ± 0.5MJ) in a P = 358.62 ± 0.20 days eccentric e = 0.6423 ± 0.0026 orbit with a projected angular semimajor axis of a0 = 0.947 ± 0.038 mas around a 0.34 ± 0.03M⊙ star. Gaia-4b is one of the first exoplanets discovered via the astrometric technique, and is one of the most massive planets known to orbit a low-mass star.
• Tran, Q. H., Bowler, B. P., Cochran, W. D., Bender, C. F., Halverson, S., Mahadevan, S., Ninan, J. P., Robertson, P., Roy, A., Stefánsson, G., & Terrien, R. C. (2025). The Epoch of Giant Planet Migration Planet Search Program. III. The Occurrence Rate of Young Giant Planets inside the Water Ice Line. Astronomical Journal, 170(Issue 2). doi:10.3847/1538-3881/ade230
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  We present statistical results from the Epoch of Giant Planet Migration RV planet search program. This survey was designed to measure the occurrence rate of giant planets interior to the water ice line of young Sun-like stars, compare this to the prevalence of giant planets at older ages, and provide constraints on the timescale and dominant inward migration mechanism of giant planets. Our final sample amounts to 85 single young (20-200 Myr) G and K dwarfs that we target across a 4 yr time baseline with the near-infrared Habitable-zone Planet Finder spectrograph at McDonald Observatory’s Hobby-Eberly Telescope. As part of this survey, we discovered the young hot Jupiter HS Psc b. We characterize survey detection completeness with realistic injection-recovery tests and measure an occurrence rate of 1 . 9 − 1.4 + 2.6 % for intermediate-age giant planets ( 0.3 M J < m sin i < 13 M J ) within 2.5 au. This is lower than the field age occurrence rate for the same planet masses and separations and favors an increase in the prevalence of giant planets over time from ∼100 Myr to several Gyr, although our results cannot rule out a constant rate. A decaying planet occurrence rate is, however, strongly excluded. This suggests that giant planets located inside the water ice line originate from a combination of in situ formation or early migration coupled with longer-term inward scattering. The completeness-corrected prevalence of young hot Jupiters in our sample is 1 . 5 − 1.1 + 2.2 % —similar to the rate for field stars—and the 95% upper limit for young brown dwarfs within 5000 days is
• Beard, C., Robertson, P., Giovinazzi, M., Murphy, J., Ford, E., Halverson, S., Han, T., Holcomb, R., Lubin, J., Luque, R., Premnath, P., Bender, C., Blake, C., Gong, Q., Isaacson, H., Kanodia, S., Li, D., Lin, A., Logsdon, S., , Lubar, E., et al. (2024). Utilizing Photometry from Multiple Sources to Mitigate Stellar Variability in Precise Radial Velocities: A Case Study of Kepler-21. Astronomical Journal, 168(4). doi:10.3847/1538-3881/ad6b22
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  We present a new analysis of Kepler-21, the brightest (V = 8.5) Kepler system with a known transiting exoplanet, Kepler-21 b. Kepler-21 b is a radius valley planet (R = 1.6 ± 0.2R ⊕) with an Earth-like composition (8.38 ± 1.62 g cm-3), though its mass and radius fall in the regime of possible “water worlds.” We utilize new Keck/High-Resolution Echelle Spectrometer and WIYN/NEID radial velocity (RV) data in conjunction with Kepler and Transiting Exoplanet Survey Satellite (TESS) photometry to perform a detailed study of activity mitigation between photometry and RVs. We additionally refine the system parameters, and we utilize Gaia astrometry to place constraints on a long-term RV trend. Our activity analysis affirms the quality of Kepler photometry for removing correlated noise from RVs, despite its temporal distance, though we reveal some cases where TESS may be superior. Using refined orbital parameters and updated composition curves, we rule out a water world scenario for Kepler-21 b, and we identify a long-period super-Jupiter planetary candidate, Kepler-21 (c).
• Berkson, J., Angel, R., Bender, C., Monson, A., Gray, P., Schwab, C., Foster, W., & Kim, D. (2024). Large Fiber Array Spectroscopic Telescope: Optical Design for a Scalable Unit Telescope. Nanomanufacturing and Metrology, 7(1). doi:10.1007/s41871-024-00235-8
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  The Large Fiber Array Spectroscopic Telescope (LFAST) concept involves the utilization of 2640 individual, 0.76 m “unit telescopes” to collect light from a target object. Through optical fibers, the lights from all telescope foci are directed to a high-resolution spectrograph, with fibers subtending a 1.47 arcsec diameter on the sky. The total light-collecting area of all telescopes combined is 1200 m2. Given the telescope’s application for spectroscopy of seeing-limited images, the need for coherence is eliminated. The primary goal of the LFAST prototype is to demonstrate a telescope design that can be rapidly and cost-effectively replicated to achieve a 1200 m2 collecting area and match the capabilities of extremely large telescopes (ELTs) presently under construction. Engineering, manufacturing, and design challenges unique to LFAST differ significantly from those encountered in traditional ELTs. Considering that the unit telescope is to be replicated thousands of times, reducing the manufacturing cost per telescope is essential. The aim of the described design is to achieve this goal, with strong considerations for manufacturability, alignment, few moving parts, and high yield. Experience from the first prototype unit telescope built in 2022 will be leveraged to build the first 20-unit tracking module in 2024, with a collecting area of a 3.4-m-diameter mirror. The design is minimalistic and features commercial tolerances, thereby ensuring cost-effectiveness in manufacturing, assembly, and alignment processes. Moreover, the telescope is designed to operate at angles as low as 70° from the zenith by laterally translating a single lens to correct for atmospheric dispersion. We present a combined average of over 80% encircled energy across 2640 Monte Carlo trials. Simulations were conducted using commercially specified tolerances and capabilities to model the overall performance of the array.
• Burrows, A., Halverson, S., Siegel, J., Gilbertson, C., Luhn, J., Burt, J., Bender, C., Roy, A., Terrien, R., Vangstein, S., Mahadevan, S., Wright, J., Robertson, P., Ford, E., Ninan, J., Blake, C., McElwain, M., Schwab, C., Zhao, J., & Stefánsson, G. (2024). The Death of Vulcan: NEID Reveals That the Planet Candidate Orbiting HD 26965 Is Stellar Activity. Astronomical Journal, 167(5). doi:10.3847/1538-3881/ad34d5
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  We revisit the long-studied radial velocity (RV) target HD 26965 using recent observations from the NASA-NSF “NEID” precision Doppler facility. Leveraging a suite of classical activity indicators, combined with line-by-line RV analyses, we demonstrate that the claimed 45-day signal previously identified as a planet candidate is most likely an activity-induced signal. Correlating the bulk (spectrally averaged) RV with canonical line activity indicators confirms a multiday “lag” between the observed activity indicator time series and the measured RV. When accounting for this lag, we show that much of the observed RV signal can be removed by a linear detrending of the data. Investigating activity at the line-by-line level, we find a depth-dependent correlation between individual line RVs and the bulk RVs, further indicative of periodic suppression of convective blueshift causing the observed RV variability, rather than an orbiting planet. We conclude that the combined evidence of the activity correlations and depth dependence is consistent with an RV signature dominated by a rotationally modulated activity signal at a period of ∼42 days. We hypothesize that this activity signature is due to a combination of spots and convective blueshift suppression. The tools applied in our analysis are broadly applicable to other stars and could help paint a more comprehensive picture of the manifestations of stellar activity in future Doppler RV surveys.
• Delamer, M., Kanodia, S., Helled, R., Lin, A., Libby-Roberts, J., Gupta, A., Mahadevan, S., Teske, J., Butler, R., Yee, S., Crane, J., Shectman, S., Osip, D., Beletsky, Y., Monson, A., Hebb, L., Powers, L., Wisniewski, J., Alvarado-Montes, J., , Bender, C., et al. (2024). TOI-4201: An Early M Dwarf Hosting a Massive Transiting Jupiter Stretching Theories of Core Accretion. Astrophysical Journal Letters, 962(2). doi:10.3847/2041-8213/ad1a19
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  We confirm TOI-4201 b as a transiting Jovian-mass planet orbiting an early M dwarf discovered by the Transiting Exoplanet Survey Satellite. Using ground-based photometry and precise radial velocities from NEID and the Planet Finder Spectrograph, we measure a planet mass of 2.59 − 0.06 + 0.07 M J, making this one of the most massive planets transiting an M dwarf. The planet is ∼0.4% of the mass of its 0.63 M ⊙ host and may have a heavy-element mass comparable to the total dust mass contained in a typical class II disk. TOI-4201 b stretches our understanding of core accretion during the protoplanetary phase and the disk mass budget, necessitating giant planet formation to take place either much earlier in the disk lifetime or perhaps through alternative mechanisms like gravitational instability.
• Gupta, A., Millholland, S., Im, H., Dong, J., Jackson, J., Carleo, I., Libby-Roberts, J., Delamer, M., Giovinazzi, M., Lin, A., Kanodia, S., Wang, X., Stassun, K., Masseron, T., Dragomir, D., Mahadevan, S., Wright, J., Alvarado-Montes, J., Bender, C., , Blake, C., et al. (2024). A hot-Jupiter progenitor on a super-eccentric retrograde orbit. Nature, 632(8023). doi:10.1038/s41586-024-07688-3
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  Giant exoplanets orbiting close to their host stars are unlikely to have formed in their present configurations1. These ‘hot Jupiter’ planets are instead thought to have migrated inward from beyond the ice line and several viable migration channels have been proposed, including eccentricity excitation through angular-momentum exchange with a third body followed by tidally driven orbital circularization2,3. The discovery of the extremely eccentric (e = 0.93) giant exoplanet HD 80606 b (ref. 4) provided observational evidence that hot Jupiters may have formed through this high-eccentricity tidal-migration pathway5. However, no similar hot-Jupiter progenitors have been found and simulations predict that one factor affecting the efficacy of this mechanism is exoplanet mass, as low-mass planets are more likely to be tidally disrupted during periastron passage6–8. Here we present spectroscopic and photometric observations of TIC 241249530 b, a high-mass, transiting warm Jupiter with an extreme orbital eccentricity of e = 0.94. The orbit of TIC 241249530 b is consistent with a history of eccentricity oscillations and a future tidal circularization trajectory. Our analysis of the mass and eccentricity distributions of the transiting-warm-Jupiter population further reveals a correlation between high mass and high eccentricity.
• Han, T., Robertson, P., Kanodia, S., Lin, A., Libby-Roberts, J., Larsen, A., Kobulnicky, H., Mahadevan, S., Bender, C., Cochran, W., Endl, M., Everett, M., Gupta, A., Halverson, S., Hearty, F., Monson, A., Ninan, J., Roy, A., Schwab, C., , Terrien, R., et al. (2024). TOI-5344 b: A Saturn-like Planet Orbiting a Super-solar Metallicity M0 Dwarf. Astronomical Journal, 167(1). doi:10.3847/1538-3881/ad09c2
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  We confirm the planetary nature of TOI-5344 b as a transiting giant exoplanet around an M0-dwarf star. TOI-5344 b was discovered with the Transiting Exoplanet Survey Satellite photometry and confirmed with ground-based photometry (the Red Buttes Observatory 0.6 m telescope), radial velocity (the Habitable-zone Planet Finder), and speckle imaging (the NN-Explore Exoplanet Stellar Speckle Imager). TOI-5344 b is a Saturn-like giant planet (ρ = 0.80 − 0.15 + 0.17 g cm−3) with a planetary radius of 9.7 ± 0.5 R ⊕ (0.87 ± 0.04 R Jup) and a planetary mass of 135 − 18 + 17 M ⊕ (0.42 − 0.06 + 0.05 M Jup ). It has an orbital period of 3.792622 − 0.000010 + 0.000010 days and an orbital eccentricity of 0.06 − 0.04 + 0.07 . We measure a high metallicity for TOI-5344 of [Fe/H] = 0.48 ± 0.12, where the high metallicity is consistent with expectations from formation through core accretion. We compare the metallicity of the M-dwarf hosts of giant exoplanets to that of M-dwarf hosts of nongiants (≲8 R ⊕). While the two populations appear to show different metallicity distributions, quantitative tests are prohibited by various sample caveats.
• Jiang, S., Roy, A., Halverson, S., Bender, C., Selgas, C., Otor, O., Mahadevan, S., Terrien, R., Schwab, C., & Stefánsson, G. (2024). Revisiting ϵ Eridani with NEID: Identifying New Activity-sensitive Lines in a Young K Dwarf Star. Astronomical Journal, 167(1). doi:10.3847/1538-3881/ad0b0b
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  Recent improvements in the sensitivity and precision of the radial velocity (RV) method for exoplanets have brought it close, but not quite to, the threshold (∼10 cm s−1) required to detect Earth-mass and other potentially habitable planets around Sun-like stars. Stellar activity-driven noise in RV measurements remains a significant hurdle to achieving this goal. While various efforts have been made to disentangle this noise from real planetary signals, a greater understanding of the relationship between spectra and stellar activity is crucial to informing stellar activity mitigation. We use a partially automated method to analyze spectral lines in a set of observations of the young, active star ϵ Eridani from the high-precision spectrograph NEID, correlate their features (depth, FWHM, and integrated flux) with known activity indicators, and filter and curate for well-defined lines whose shape changes are sensitive to certain types of stellar activity. We then present a list of nine lines correlated with the S-index in all three line features, including four newly identified activity-sensitive lines, as well as additional lines correlated with the S-index in at least one feature, and discuss the possible implications of the behavior observed in these lines. Our line lists represent a step forward in the empirical understanding of the complex relationships between stellar activity and spectra and illustrate the importance of studying the time evolution of line morphologies with stabilized spectrographs in the overall effort to mitigate activity in the search for small, potentially Earth-like exoplanets.
• Jones, S., Masuda, K., Libby-Roberts, J., Gardner, C., Holcomb, R., Beard, C., Robertson, P., Mahadevan, S., Kanodia, S., Lin, A., Kobulnicky, H., Parker, B., Bender, C., Cochran, W., Diddams, S., Fernandes, R., Gupta, A., Halverson, S., Hawley, S., , Hearty, F., et al. (2024). TOI-2015 b: A Warm Neptune with Transit Timing Variations Orbiting an Active Mid-type M Dwarf. Astronomical Journal, 168(2). doi:10.3847/1538-3881/ad55ea
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  We report the discovery of a close-in (P orb = 3.349 days) warm Neptune with clear transit timing variations (TTVs) orbiting the nearby (d = 47.3 pc) active M4 star, TOI-2015. We characterize the planet's properties using Transiting Exoplanet Survey Satellite (TESS) photometry, precise near-infrared radial velocities (RVs) with the Habitable-zone Planet Finder Spectrograph, ground-based photometry, and high-contrast imaging. A joint photometry and RV fit yields a radius R p = 3.37 − 0.20 + 0.15 R ⊕ , mass m p = 16.4 − 4.1 + 4.1 M ⊕ , and density ρ p = 2.32 − 0.37 + 0.38 g cm − 3 for TOI-2015 b, suggesting a likely volatile-rich planet. The young, active host star has a rotation period of P rot = 8.7 ± 0.9 days and associated rotation-based age estimate of 1.1 ± 0.1 Gyr. Though no other transiting planets are seen in the TESS data, the system shows clear TTVs of super-period P sup ≈ 430 days and amplitude ∼100 minutes. After considering multiple likely period-ratio models, we show an outer planet candidate near a 2:1 resonance can explain the observed TTVs while offering a dynamically stable solution. However, other possible two-planet solutions—including 3:2 and 4:3 resonances—cannot be conclusively excluded without further observations. Assuming a 2:1 resonance in the joint TTV-RV modeling suggests a mass of m b = 13.3 − 4.5 + 4.7 M ⊕ for TOI-2015 b and m c = 6.8 − 2.3 + 3.5 M ⊕ for the outer candidate. Additional transit and RV observations will be beneficial to explicitly identify the resonance and further characterize the properties of the system.
• Kanodia, S., Cochran, W., Csizmadia, S., Mahadevan, S., Gupta, A., Monson, A., Kobulnicky, H., Larsen, A., Cotter, E., Birkholz, A., Swaby, T., Zeimann, G., Bender, C., Diddams, S., Libby-Roberts, J., Lin, A., Ninan, J., Rauer, H., Reji, V., , Robertson, P., et al. (2024). Searching for GEMS: TOI-6383Ab, a Giant Planet Transiting an M3-dwarf Star in a Binary System. Astronomical Journal, 168(6). doi:10.3847/1538-3881/ad7fe8
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  We report on the discovery of a transiting giant planet around the 3500 K M3-dwarf star TOI-6383A located 172 pc from Earth. It was detected by the Transiting Exoplanet Survey Satellite and confirmed by a combination of ground-based follow-up photometry and precise radial velocity measurements. This planet has an orbital period of ∼1.791 days, a mass of 1.040 ± 0.094 M J , and a radius of 1.008 − 0.033 + 0.036 R J , resulting in a mean bulk density of 1.26 − 0.17 + 0.18 g cm−3. TOI-6383A has an M dwarf companion star, TOI-6383B, which has a stellar effective temperature of T eff ∼ 3100 K and a projected orbital separation of 3126 au. TOI-6383A is a low-mass dwarf star hosting a giant planet and is an intriguing object for planetary evolution studies due to its high planet-to-star mass ratio. This discovery is part of the Searching for Giant Exoplanets around M-dwarf Stars (GEMS) Survey, intending to provide robust and accurate estimates of the occurrence of GEMS and the statistics on their physical and orbital parameters. This paper presents an interesting addition to the small number of confirmed GEMS, particularly notable since its formation necessitates massive, dust-rich protoplanetary discs and high accretion efficiency (>10%).
• Kanodia, S., Gupta, A., Reji, V., Han, T., Brady, M., Seifahrt, A., Cochran, W., Morrell, N., Basant, R., Bean, J., Bender, C., de Beurs, Z., Bieryla, A., Birkholz, A., Brown, N., Chapman, F., Ciardi, D., Clark, C., Cotter, E., , Diddams, S., et al. (2024). Searching for GEMS: Characterizing Six Giant Planets Around Cool Dwarfs. Astronomical Journal, 168(6). doi:10.3847/1538-3881/ad7796
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  Transiting giant exoplanets around M-dwarf stars (GEMS) are rare, owing to the low-mass host stars. However, the all-sky coverage of TESS has enabled the detection of an increasingly large number of them to enable statistical surveys like the Searching for GEMS survey. As part of this endeavor, we describe the observations of six transiting giant planets, which include precise mass measurements for two GEMS (K2-419Ab, TOI-6034b) and statistical validation for four systems, which includes validation and mass upper limits for three of them (TOI-5218b, TOI-5616b, TOI-5634Ab), while the fourth one—TOI-5414b is classified as a “likely planet.” Our observations include radial velocities from the Habitable-zone Planet Finder on the Hobby-Eberly Telescope, and MAROON-X on Gemini-North, along with photometry and high-contrast imaging from multiple ground-based facilities. In addition to TESS photometry, K2-419Ab was also observed and statistically validated as part of the K2 mission in Campaigns 5 and 18, which provide precise orbital and planetary constraints despite the faint host star and long orbital period of ∼20.4 days. With an equilibrium temperature of only 380 K, K2-419Ab is one of the coolest known well-characterized transiting planets. TOI-6034 has a late F-type companion about 40″ away, making it the first GEMS host star to have an earlier main-sequence binary companion. These confirmations add to the existing small sample of confirmed transiting GEMS.
• Sekhar, P., Kreider, M., Fredrick, C., Ninan, J., Bender, C., Terrien, R., Mahadevan, S., & Diddams, S. (2024). Tunable 30 GHz laser frequency comb for astronomical spectrograph characterization and calibration. Optics Letters, 49(21). doi:10.1364/ol.537385
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  The search for Earth-like exoplanets with the Doppler radial velocity (RV) technique is an extremely challenging and multifaceted precision spectroscopy problem. Currently, one of the limiting instrumental factors in reaching the required long-term 10−10 level of radial velocity precision is the defect-driven subpixel quantum efficiency (QE) variations in the large-format detector arrays used by precision echelle spectrographs. Tunable frequency comb calibration sources that can fully map the point spread function (PSF) across a spectrograph’s entire bandwidth are necessary for quantifying and correcting these detector artifacts. In this work, we demonstrate a combination of laser frequency and mode spacing control that allows full and deterministic tunability of a 30 GHz electro-optic comb together with its filter cavity. After supercontinuum generation, this gives access to any optical frequency across 700–1300 nm. Our specific implementation is intended for the comb deployed at the Habitable-Zone Planet Finder (HPF) spectrograph and its near-infrared Hawaii-2RG array, but the techniques apply to all laser frequency combs (LFCs) used for precision astronomical spectrograph calibration and other applications that require broadband tuning.
• Siegel, J., Halverson, S., Luhn, J., Zhao, L., Al Moulla, K., Robertson, P., Bender, C., Terrien, R., Roy, A., Mahadevan, S., Hearty, F., Ninan, J., Wright, J., Ford, E., Schwab, C., Blake, C., McElwain, M., & Stefánsson, G. (2024). Quiet Please: Detrending Radial Velocity Variations from Stellar Activity with a Physically Motivated Spot Model. Astronomical Journal, 168(4). doi:10.3847/1538-3881/ad6768
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  For solar-type stars, spots and their associated magnetic regions induce radial velocity perturbations through the Doppler rotation signal and the suppression of convective blueshift, collectively known as rotation modulation. We developed the Rotation-Convection (RC) model: a method of detrending and characterizing rotation modulation using only cross-correlation functions or one-dimensional spectra without the need for continuous high-cadence measurements. The RC method uses a simple model for the anomalous radial velocity induced by an active region and has two inputs: stellar flux (or a flux proxy) and the relative radial velocity between strongly and weakly absorbed wavelengths (analogous to the bisector-inverse slope). On NEID solar data (3 month baseline), the RC model lowers the amplitude of rotationally modulated stellar activity to below the meter-per-second level. For the standard star HD 26965, the RC model detrends the activity signal to the meter-per-second level for HARPS, EXPRES, and NEID observations, even though the temporal density and time span of the observations differ by an order of magnitude between the three data sets. In addition to detrending, the RC model also characterizes the rotation-modulation signal. From comparison with the Solar Dynamics Observatory, we confirmed that the model accurately recovers and separates the rotation and convection radial velocity components. We also mapped the amplitude of the rotation and convection perturbations as a function of height within the stellar atmosphere. Probing stellar atmospheres with our revised spot model will fuel future innovations in stellar activity mitigation, enabling robust exoplanet detection.
• Almeida, A., Anderson, S., Badenes, C., Barger, K., Barrera-Ballesteros, J., Bender, C., Benitez, E., Besser, F., Bird, J., Bizyaev, D., Blanton, M., Bochanski, J., Bovy, J., Brandt, W., Brownstein, J., Buchner, J., Bulbul, E., Burchett, J., Carlberg, J., , Casey, A., et al. (2023). The Eighteenth Data Release of the Sloan Digital Sky Surveys: Targeting and First Spectra from SDSS-V. Astrophysical Journal, Supplement Series, 267(2). doi:10.3847/1538-4365/acda98
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  The eighteenth data release (DR18) of the Sloan Digital Sky Survey (SDSS) is the first one for SDSS-V, the fifth generation of the survey. SDSS-V comprises three primary scientific programs or “Mappers”: the Milky Way Mapper (MWM), the Black Hole Mapper (BHM), and the Local Volume Mapper. This data release contains extensive targeting information for the two multiobject spectroscopy programs (MWM and BHM), including input catalogs and selection functions for their numerous scientific objectives. We describe the production of the targeting databases and their calibration and scientifically focused components. DR18 also includes ∼25,000 new SDSS spectra and supplemental information for X-ray sources identified by eROSITA in its eFEDS field. We present updates to some of the SDSS software pipelines and preview changes anticipated for DR19. We also describe three value-added catalogs (VACs) based on SDSS-IV data that have been published since DR17, and one VAC based on the SDSS-V data in the eFEDS field.
• Bender, C., Mahadevan, S., Bizyaev, D., De Lee, N., Fleming, S., Hearty, F., Majewski, S., Nitschelm, C., Schneider, D., Serna, J., Stassun, K., Stringfellow, G., Wilson, J., Cañas, C., & Stefánsson, G. (2023). Characterization of Low-mass Companions to Kepler Objects of Interest Observed with APOGEE-N. Astrophysical Journal, Supplement Series, 265(2). doi:10.3847/1538-4365/acbcbe
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  We report the characterization of 28 low-mass (0.02 M ⊙ ≤ M 2 ≤ 0.25 M ⊙) companions to Kepler objects of interest (KOIs), eight of which were previously designated confirmed planets. These objects were detected as transiting companions to Sunlike stars (G and F dwarfs) by the Kepler mission and are confirmed as single-lined spectroscopic binaries in the current work using the northern multiplexed Apache Point Observatory Galactic Evolution Experiment near-infrared spectrograph (APOGEE-N) as part of the third and fourth Sloan Digital Sky Surveys. We have observed hundreds of KOIs using APOGEE-N and collected a total of 43,175 spectra with a median of 19 visits and a median baseline of ∼1.9 yr per target. We jointly model the Kepler photometry and APOGEE-N radial velocities to derive fundamental parameters for this subset of 28 transiting companions. The radii for most of these low-mass companions are overinflated (by ∼10%) when compared to theoretical models. Tidally locked M dwarfs on short-period orbits show the largest amount of inflation, but inflation is also evident for companions that are well separated from the host star. We demonstrate that APOGEE-N data provide reliable radial velocities when compared to precise high-resolution spectrographs that enable detailed characterization of individual systems and the inference of orbital elements for faint (H > 12) KOIs. The data from the entire APOGEE-KOI program are public and present an opportunity to characterize an extensive subset of the binary population observed by Kepler.
• Frazier, R. C., Stefánsson, G., Mahadevan, S., Yee, S. W., Cañas, C. I., Winn, J. N., Luhn, J., Dai, F., Doyle, L., Cegla, H., Kanodia, S., Robertson, P., Wisniewski, J., Bender, C. F., Dong, J., Gupta, A. F., Halverson, S., Hawley, S., Hebb, L., , Holcomb, R., et al. (2023). NEID Reveals That the Young Warm Neptune TOI-2076 b Has a Low Obliquity. Astrophysical Journal Letters, 944(Issue 2). doi:10.3847/2041-8213/acba18
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  TOI-2076 b is a sub-Neptune-sized planet (R = 2.39 ± 0.10 R ⊕) that transits a young (204 ± 50 MYr) bright (V = 9.2) K-dwarf hosting a system of three transiting planets. Using spectroscopic observations obtained with the NEID spectrograph on the WIYN 3.5 m Telescope, we model the Rossiter-McLaughlin effect of TOI-2076 b, and derive a sky-projected obliquity of λ = − 3 − 15 + 16 ° . Using the size of the star (R = 0.775 ± 0.015 R ⊙), and the stellar rotation period (P rot = 7.27 ± 0.23 days), we estimate an obliquity of ψ = 18 − 9 + 10 ° (ψ < 34° at 95% confidence), demonstrating that TOI-2076 b is in a well-aligned orbit. Simultaneous diffuser-assisted photometry from the 3.5 m telescope at Apache Point Observatory rules out flares during the transit. TOI-2076 b joins a small but growing sample of young planets in compact multi-planet systems with well-aligned orbits, and is the fourth planet with an age ≲300 Myr in a multi-transiting system with an obliquity measurement. The low obliquity of TOI-2076 b and the presence of transit timing variations in the system suggest the TOI-2076 system likely formed via convergent disk migration in an initially well-aligned disk.
• Kanodia, S., Libby-Roberts, J., Lin, A., Schutte, M., Powers, L., Jones, S., Monson, A., Wang, S., Cochran, W., Robertson, P., Mahadevan, S., Kowalski, A., Wisniewski, J., Parker, B., Larsen, A., Chapman, F., Kobulnicky, H., Gupta, A., Everett, M., , Penprase, B., et al. (2023). TOI-3984 A b and TOI-5293 A b: Two Temperate Gas Giants Transiting Mid-M Dwarfs in Wide Binary Systems. Astronomical Journal, 166(1). doi:10.3847/1538-3881/acdac7
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  We confirm the planetary nature of two gas giants discovered by TESS to transit M dwarfs with stellar companions at wide separations. TOI-3984 A (J = 11.93) is an M4 dwarf hosting a short-period (4.353326 ± 0.000005 days) gas giant (M p = 0.14 ± 0.03 M J and R p = 0.71 ± 0.02 R J) with a wide-separation white dwarf companion. TOI-5293 A (J = 12.47) is an M3 dwarf hosting a short-period (2.930289 ± 0.000004 days) gas giant (M p = 0.54 ± 0.07 M J and R p = 1.06 ± 0.04 R J) with a wide-separation M dwarf companion. We characterize both systems using a combination of ground- and space-based photometry, speckle imaging, and high-precision radial velocities from the Habitable-zone Planet Finder and NEID spectrographs. TOI-3984 A b (T eq = 563 ± 15 K and TSM = 138 − 27 + 29 ) and TOI-5293 A b ( T eq = 675 − 30 + 42 K and TSM = 92 ± 14) are two of the coolest gas giants among the population of hot Jupiter-sized gas planets orbiting M dwarfs and are favorable targets for atmospheric characterization of temperate gas giants and 3D obliquity measurements to probe system architecture and migration scenarios.
• Kanodia, S., Lin, A., Lubar, E., Halverson, S., Mahadevan, S., Bender, C., Logsdon, S., Ramsey, L., Ninan, J., Monson, A., Schwab, C., Roy, A., Paredes, L., Golub, E., Higuera, J., Klusmeyer, J., McBride, W., Blake, C., Diddams, S., , Gupta, A., et al. (2023). Stable Fiber-illumination for Extremely Precise Radial Velocities with NEID. Astronomical Journal, 166(3). doi:10.3847/1538-3881/acea60
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  NEID is a high-resolution red-optical precision radial velocity (RV) spectrograph recently commissioned at the WIYN 3.5 m telescope at Kitt Peak National Observatory, Arizona, USA. NEID has an extremely stable environmental control system, and spans a wavelength range of 380-930 nm with two observing modes: a High Resolution mode at R ∼ 112,000 for maximum RV precision, and a High Efficiency mode at R ∼ 72,000 for faint targets. In this paper we present a detailed description of the components of NEID’s optical fiber feed, which include the instrument, exposure meter, calibration system, and telescope fibers. Many parts of the optical fiber feed can lead to uncalibratable RV errors, which cannot be corrected for using a stable wavelength reference source. We show how these errors directly cascade down to performance requirements on the fiber feed and the scrambling system. We detail the design, assembly, and testing of each component. Designed and built from the bottom-up with a single-visit instrument precision requirement of 27 cm s−1, close attention is paid to the error contribution from each NEID subsystem. Finally, we include the lab and on-sky tests performed during instrument commissioning to test the illumination stability, and discuss the path to achieving the instrumental stability required to search for a true Earth twin around a solar-type star.
• Lambert, M., Bender, C., Kanodia, S., Monson, A., Cochran, W., Everett, M., Gupta, A., Hearty, F., Kobulnicky, H., Libby-Roberts, J., Lin, A., Mahadevan, S., Ninan, J., Parker, B., Robertson, P., Schwab, C., Terrien, R., Cañas, C., & Stefánsson, G. (2023). TOI-5375 B: A Very Low Mass Star at the Hydrogen-burning Limit Orbiting an Early M-type Star. Astronomical Journal, 165(5). doi:10.3847/1538-3881/acc651
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  The Transiting Exoplanet Survey Satellite (TESS) mission detected a companion orbiting TIC 71268730, categorized it as a planet candidate, and designated the system TOI-5375. Our follow-up analysis using radial-velocity data from the Habitable-zone Planet Finder, photometric data from Red Buttes Observatory, and speckle imaging with NN-EXPLORE Exoplanet Stellar Speckle Imager determined that the companion is a very low mass star near the hydrogen-burning mass limit with a mass of 0.080 ± 0.002M ⊙ (83.81 ± 2.10M J ), a radius of 0.1114-0.0050+0.0048R⊙ (1.0841 0.04870.0467RJ ), and brightness temperature of 2600 ± 70 K. This object orbits with a period of 1.721553 ± 0.000001 days around an early M dwarf star (0.62 ± 0.016M ⊙). TESS photometry shows regular variations in the host star's TESS light curve, which we interpreted as an activity-induced variation of ∼2%, and used this variability to measure the host star's stellar rotation period of 1.9716-0.0083+0.0080 days. The TOI-5375 system provides tight constraints on stellar models of low-mass stars at the hydrogen-burning limit and adds to the population in this important region.
• Lin, A., Libby-Roberts, J., Alvarado-Montes, J., Kanodia, S., Han, T., Hebb, L., Jensen, E., Mahadevan, S., Powers, L., Swaby, T., Wisniewski, J., Beard, C., Bender, C., Blake, C., Cochran, W., Diddams, S., Frazier, R., Fredrick, C., Gully-Santiago, M., , Halverson, S., et al. (2023). The Unusual M-dwarf Warm Jupiter TOI-1899 b: Refinement of Orbital and Planetary Parameters. Astronomical Journal, 166(3). doi:10.3847/1538-3881/ace1ef
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  TOI-1899 b is a rare exoplanet, a temperate warm Jupiter orbiting an M dwarf, first discovered by Cañas et al. (2020) from a TESS single-transit event. Using new radial velocities (RVs) from the precision RV spectrographs HPF and NEID, along with additional TESS photometry and ground-based transit follow-up, we are able to derive a much more precise orbital period of P = 29.090312 − 0.000035 + 0.000036 days, along with a radius of R p = 0.99 ± 0.03 R J. We have also improved the constraints on planet mass, M p = 0.67 ± 0.04 M J, and eccentricity, which is consistent with a circular orbit at 2σ ( e = 0.044 − 0.027 + 0.029 ). TOI-1899 b occupies a unique region of parameter space as the coolest known (T eq ≈ 380 K) Jovian-sized transiting planet around an M dwarf; we show that it has great potential to provide clues regarding the formation and migration mechanisms of these rare gas giants through transmission spectroscopy with JWST, as well as studies of tidal evolution.
• Lubin, J., Wang, X., Rice, M., Dong, J., Wang, S., Radzom, B., Robertson, P., Stefansson, G., Alvarado-Montes, J., Beard, C., Bender, C., Gupta, A., Halverson, S., Kanodia, S., Li, D., Lin, A., Logsdon, S., Lubar, E., Mahadevan, S., , Ninan, J., et al. (2023). TOI-1670 c, a 40 day Orbital Period Warm Jupiter in a Compact System, Is Well Aligned. Astrophysical Journal Letters, 959(1). doi:10.3847/2041-8213/ad0fea
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  We report the measurement of the sky-projected obliquity angle λ of the warm Jovian exoplanet TOI-1670 c via the Rossiter-McLaughlin effect. We observed the transit window during UT 2023 April 20 for 7 continuous hours with NEID on the 3.5 m WIYN Telescope at Kitt Peak National Observatory. TOI-1670 hosts a sub-Neptune (P ∼ 11 days; planet b) interior to the warm Jovian (P ∼ 40 days; planet c), which presents an opportunity to investigate the dynamics of a warm Jupiter with an inner companion. Additionally, TOI-1670 c is now among the longest-period planets to date to have its sky-projected obliquity angle measured. We find planet c is well aligned to the host star, with λ = − 0.°3 ± 2.°2. TOI-1670 c joins a growing census of aligned warm Jupiters around single stars and aligned planets in multiplanet systems.
• Stefánsson, G., Mahadevan, S., Miguel, Y., Robertson, P., Delamer, M., Kanodia, S., Cañas, C. I., Winn, J. N., Ninan, J. P., Terrien, R. C., Holcomb, R., Ford, E. B., Zawadzki, B., Bowler, B. P., Bender, C. F., Cochran, W. D., Diddams, S., Endl, M., Fredrick, C., , Halverson, S., et al. (2023). A Neptune-mass exoplanet in close orbit around a very low-mass star challenges formation models. Science, 382(6674), 1031-1035. doi:10.1126/science.abo0233
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  Theories of planet formation predict that low-mass stars should rarely host exoplanets with masses exceeding that of Neptune. We used radial velocity observations to detect a Neptune-mass exoplanet orbiting LHS 3154, a star that is nine times less massive than the Sun. The exoplanet's orbital period is 3.7 days, and its minimum mass is 13.2 Earth masses. We used simulations to show that the high planet-to-star mass ratio (>3.5 × 10-4) is not an expected outcome of either the core accretion or gravitational instability theories of planet formation. In the core-accretion simulations, we show that close-in Neptune-mass planets are only formed if the dust mass of the protoplanetary disk is an order of magnitude greater than typically observed around very low-mass stars.
• Zhao, L. L., Dumusque, X., Ford, E. B., Llama, J., Mortier, A., Bedell, M., Al Moulla, K., Bender, C. F., Blake, C. H., Brewer, J. M., Collier Cameron, A., Cosentino, R., Figueira, P., Fischer, D. A., Ghedina, A., Gonzalez, M., Halverson, S., Kanodia, S., Latham, D. W., , Lin, A. S., et al. (2023). The Extreme Stellar-signals Project. III. Combining Solar Data from HARPS, HARPS-N, EXPRES, and NEID. Astronomical Journal, 166(Issue 4). doi:10.3847/1538-3881/acf83e
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  We present an analysis of Sun-as-a-star observations from four different high-resolution, stabilized spectrographs—HARPS, HARPS-N, EXPRES, and NEID. With simultaneous observations of the Sun from four different instruments, we are able to gain insight into the radial velocity precision and accuracy delivered by each of these instruments and isolate instrumental systematics that differ from true astrophysical signals. With solar observations, we can completely characterize the expected Doppler shift contributed by orbiting Solar System bodies and remove them. This results in a data set with measured velocity variations that purely trace flows on the solar surface. Direct comparisons of the radial velocities measured by each instrument show remarkable agreement with residual intraday scatter of only 15-30 cm s−1. This shows that current ultra-stabilized instruments have broken through to a new level of measurement precision that reveals stellar variability with high fidelity and detail. We end by discussing how radial velocities from different instruments can be combined to provide powerful leverage for testing techniques to mitigate stellar signals.
• , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , , ., et al. (2022). The Seventeenth Data Release of the Sloan Digital Sky Surveys: Complete Release of MaNGA, MaStar, and APOGEE-2 Data. Astrophysical Journal, Supplement Series, 259(Issue 2). doi:10.3847/1538-4365/ac4414
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  This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the subsurvey Time Domain Spectroscopic Survey data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey subsurvey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated value-added catalogs. This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper, Local Volume Mapper, and Black Hole Mapper surveys.
• Avsar, A., Beard, C., Bender, C. F., Blake, C. H., Dai, F., Dalba, P. A., Dressing, C. D., Esposito, T. M., Giacalone, S., Halverson, S., Hearty, F., Holden, B., Howard, A. W., Huber, D., Isaacson, H., Jackman, J. A., Klusmeyer, J., Laughlin, G., Llama, J., , Logsdon, S. E., et al. (2022). The Aligned Orbit of WASP-148b, the Only Known Hot Jupiter with a nearby Warm Jupiter Companion, from NEID and HIRES. The Astrophysical Journal Letters, 926(2), L8. doi:10.3847/2041-8213/ac4f44
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  Abstract We present spectroscopic measurements of the Rossiter–McLaughlin effect for WASP-148b, the only known hot Jupiter with a nearby warm-Jupiter companion, from the WIYN/NEID and Keck/HIRES instruments. This is one of the first scientific results reported from the newly commissioned NEID spectrograph, as well as the second obliquity constraint for a hot Jupiter system with a close-in companion, after WASP-47. WASP-148b is consistent with being in alignment with the sky-projected spin axis of the host star, with λ = − 8 .° 2 − 9 .° 7 + 8 .° 7 . The low obliquity observed in the WASP-148 system is consistent with the orderly-alignment configuration of most compact multi-planet systems around cool stars with obliquity constraints, including our solar system, and may point to an early history for these well-organized systems in which migration and accretion occurred in isolation, with relatively little disturbance. By contrast, previous results have indicated that high-mass and hot stars appear to more commonly host a wide range of misaligned planets: not only single hot Jupiters, but also compact systems with multiple super-Earths. We suggest that, to account for the high rate of spin–orbit misalignments in both compact multi-planet and isolated-hot-Jupiter systems orbiting high-mass and hot stars, spin–orbit misalignments may be caused by distant giant planet perturbers, which are most common around these stellar types.
• Barkaoui, K., Belinski, A. A., Bender, C. F., Benkhaldoun, Z., Bieryla, A., Blake, C. H., Ciardi, D. R., Collins, K. A., Dawson, R. I., Dong, J., Douglas, S., Dressing, C. D., Feliz, D. L., Ford, E. B., Fores-toribio, R., Giacalone, S., Gnilka, C. L., Halverson, S., Horta, F. G., , Howell, S. B., et al. (2022). NEID Rossiter–McLaughlin Measurement of TOI-1268b: A Young Warm Saturn Aligned with Its Cool Host Star. The Astrophysical Journal Letters, 926(2), L7. doi:10.3847/2041-8213/ac4da0
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  Abstract Close-in gas giants present a surprising range of stellar obliquity, the angle between a planet’s orbital axis and its host star’s spin axis. It is unclear whether the obliquities reflect the planets’ dynamical history (e.g., aligned for in situ formation or disk migration versus misaligned for high-eccentricity tidal migration) or whether other mechanisms (e.g., primordial misalignment or planet–star interactions) are more important in sculpting the obliquity distribution. Here we present the stellar obliquity measurement of TOI-1268 (TIC-142394656, V mag ∼ 10.9), a young K-type dwarf hosting an 8.2 day period, Saturn-sized planet. TOI-1268’s lithium abundance and rotation period suggest the system age between the ages of the Pleiades cluster (∼120 Myr) and the Prasepe cluster (∼670 Myr). Using the newly commissioned NEID spectrograph, we constrain the stellar obliquity of TOI-1268 via the Rossiter–McLaughlin effect from both radial velocity and Doppler tomography signals. The 3σ upper bounds of the projected stellar obliquity ∣λ∣ from both models are below 60°. The large host star separation (a/R ⋆ ∼ 17), combined with the system’s young age, makes it unlikely that the planet has realigned its host star. The stellar obliquity measurement of TOI-1268 probes the architecture of a young gas giant beyond the reach of tidal realignment (a/R ⋆ ≳ 10) and reveals an aligned or slightly misaligned system.
• Beard, C., Bender, C. F., Canas, C. I., Cochran, W. D., Fredrick, C., Gupta, A. F., Hearty, F., Jones, S., Kanodia, S., Lin, A. S., Lubin, J., Mahadevan, S., Monson, A., Ninan, J. P., Ramsey, L. W., Rivera, N. I., Robertson, P., Schwab, C., & Stefansson, G. (2022). An Eccentric Brown Dwarf Eclipsing an M dwarf. The Astronomical Journal, 163(2), 89. doi:10.3847/1538-3881/ac415f
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  Abstract We report the discovery of an M = 67 ± 2M J brown dwarf transiting the early M dwarf TOI-2119 on an eccentric orbit (e = 0.3362 ± 0.0005) at an orbital period of 7.200861 ± 0.000005 days. We confirm the brown dwarf nature of the transiting companion using a combination of ground-based and space-based photometry and high-precision velocimetry from the Habitable-zone Planet Finder. Detection of the secondary eclipse with TESS photometry enables a precise determination of the eccentricity and reveals the brown dwarf has a brightness temperature of 2100 ± 80 K, a value which is consistent with an early L dwarf. TOI-2119 is one of the most eccentric known brown dwarfs with P < 10 days, possibly due to the long circularization timescales for an object orbiting an M dwarf. We assess the prospects for determining the obliquity of the host star to probe formation scenarios and the possibility of additional companions in the system using Gaia EDR3 and our radial velocities.
• Beard, C., Bender, C. F., Cochran, W. D., Cunha, K., Diddams, S. A., Fredrick, C., Halverson, S., Hearty, F., Ickler, A., Kanodia, S., Keen, A., Libby-roberts, J. E., Lubin, J., Mahadevan, S., Metcalf, A. J., Ninan, J. P., Oda, K., Olsen, F., Ramsey, L. W., , Robertson, P., et al. (2022). Rotational Modulation of Spectroscopic Zeeman Signatures in Low-mass Stars. The Astrophysical Journal Letters, 927(1), L11. doi:10.3847/2041-8213/ac4fc8
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  Abstract Accurate tracers of the stellar magnetic field and rotation are cornerstones for the study of M dwarfs and for reliable detection and characterization of their exoplanetary companions. Such measurements are particularly challenging for old, slowly rotating, fully convective M dwarfs. To explore the use of new activity and rotation tracers, we examined multiyear near-infrared (NIR) spectroscopic monitoring of two such stars—GJ 699 (Barnard’s Star) and Teegarden’s Star—carried out with the Habitable-zone Planet Finder spectrograph. We detected periodic variations in absorption line widths across the stellar spectrum, with higher amplitudes toward longer wavelengths. We also detected similar variations in the strength and width of the 12435.67 Å neutral potassium (K i) line, a known tracer of the photospheric magnetic field. Attributing these variations to rotational modulation, we confirm the known 145 ± 15 day rotation period of GJ 699, and measure the rotation period of Teegarden’s Star to be 99.6 ± 1.4 days. Based on simulations of the K i line and the wavelength dependence of the line-width signal, we argue that the observed signals are consistent with varying photospheric magnetic fields and the associated Zeeman effect. These results highlight the value of detailed line profile measurements in the NIR for diagnosing stellar magnetic field variability. Such measurements may be pivotal for disentangling activity and exoplanet-related signals in spectroscopic monitoring of old, low-mass stars.
• Beard, C., Robertson, P., Kanodia, S., Libby-Roberts, J., Cañas, C. I., Gupta, A. F., Holcomb, R., Jones, S., Kobulnicky, H. A., Lin, A. S., Lubin, J., Maney, M., Parker, B. A., Stefánsson, G., Cochran, W. D., Endl, M., Hebb, L., Mahadevan, S., Wisniewski, J., , Bender, C. F., et al. (2022). TOI-1696 and TOI-2136: Constraining the Masses of Two Mini-Neptunes with the Habitable-Zone Planet Finder. Astronomical Journal, 163(Issue 6). doi:10.3847/1538-3881/ac69ec
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  We present the validation of two planets orbiting M dwarfs, TOI-1696b and TOI-2136b. Both planets are mini-Neptunes orbiting nearby stars, making them promising prospects for atmospheric characterization with the James Webb Space Telescope (JWST). We validated the planetary nature of both candidates using high-contrast imaging, ground-based photometry, and near-infrared radial velocities. Adaptive optics images were taken using the ShARCS camera on the 3 m Shane Telescope. Speckle images were taken using the NN-Explore Exoplanet Stellar Speckle Imager on the WIYN 3.5 m telescope. Radii and orbital ephemerides were refined using a combination of the Transiting Exoplanet Survey Satellite, the diffuser-assisted Astrophysical Research Consortium (ARC) Telescope Imaging Camera (ARCTIC) imager on the 3.5 m ARC telescope at Apache Point Observatory, and the 0.6 m telescope at Red Buttes Observatory. We obtained radial velocities using the Habitable-Zone Planet Finder on the 10 m Hobby-Eberly Telescope, which enabled us to place upper limits on the masses of both transiting planets. TOI-1696b (P = 2.5 days; R p = 3.24 R pdbl; M p < 56.6 M pdbl) falls into a sparsely populated region of parameter space considering its host star's temperature (T eff = 3168 K, M4.5), as planets of its size are quite rare around mid- to late-M dwarfs. On the other hand, TOI-2136b (P = 7.85 days; R p = 2.09 R pdbl; M p < 15.0 M pdbl) is an excellent candidate for atmospheric follow-up with the JWST.
• Beard, C., Robertson, P., Kanodia, S., Lubin, J., Cañas, C. I., Gupta, A. F., Holcomb, R., Jones, S., Libby-Roberts, J. E., Lin, A. S., Mahadevan, S., Stefánsson, G., Bender, C. F., Blake, C. H., Cochran, W. D., Endl, M., Everett, M., Ford, E. B., Fredrick, C., , Halverson, S., et al. (2022). GJ 3929: High-precision Photometric and Doppler Characterization of an Exo-Venus and Its Hot, Mini-Neptune-mass Companion. Astrophysical Journal, 936(Issue 1). doi:10.3847/1538-4357/ac8480
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  We detail the follow-up and characterization of a transiting exo-Venus identified by TESS, GJ 3929b (TOI-2013b), and its nontransiting companion planet, GJ 3929c (TOI-2013c). GJ 3929b is an Earth-sized exoplanet in its star’s Venus zone (P b = 2.616272 ± 0.000005 days; Sb = 17.3 − 0.7 + 0.8 S ⊕) orbiting a nearby M dwarf. GJ 3929c is most likely a nontransiting sub-Neptune. Using the new, ultraprecise NEID spectrometer on the WIYN 3.5 m Telescope at Kitt Peak National Observatory, we are able to modify the mass constraints of planet b reported in previous works and consequently improve the significance of the mass measurement to almost 4σ confidence (M b = 1.75 ± 0.45 M ⊕). We further adjust the orbital period of planet c from its alias at 14.30 ± 0.03 days to the likely true period of 15.04 ± 0.03 days, and we adjust its minimum mass to m sin i = 5.71 ± 0.92 M ⊕. Using the diffuser-assisted ARCTIC imager on the ARC 3.5 m telescope at Apache Point Observatory, in addition to publicly available TESS and LCOGT photometry, we are able to constrain the radius of planet b to R p = 1.09 ± 0.04 R ⊕. GJ 3929b is a top candidate for transmission spectroscopy in its size regime (TSM = 14 ± 4), and future atmospheric studies of GJ 3929b stand to shed light on the nature of small planets orbiting M dwarfs.
• Beaton, R. L., Bender, C. F., Canas, C. I., Cunha, K., Fleming, S. W., Garcia-hernandez, D. A., Ghezzi, L., Hasselquist, S., Hayes, C. R., Jonsson, H., Mahadevan, S., Majewski, S. R., Nitschelm, C., Smith, V. V., Stassun, K., Tayar, J., Teske, J., & Wilson, R. F. (2022). The Influence of 10 Unique Chemical Elements in Shaping the Distribution of Kepler Planets. The Astronomical Journal, 163(3), 128. doi:10.3847/1538-3881/ac3a06
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  Abstract The chemical abundances of planet-hosting stars offer a glimpse into the composition of planet-forming environments. To further understand this connection, we make the first ever measurement of the correlation between planet occurrence and chemical abundances for ten different elements (C, Mg, Al, Si, S, K, Ca, Mn, Fe, and Ni). Leveraging data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and Gaia to derive precise stellar parameters ( σ R ⋆ ≈ 2.3 % , σ M ⋆ ≈ 4.5 % ) for a sample of 1018 Kepler Objects of Interest, we construct a sample of well-vetted Kepler planets with precisely measured radii ( σ R p ≈ 3.4 % ). After controlling for biases in the Kepler detection pipeline and the selection function of the APOGEE survey, we characterize the relationship between planet occurrence and chemical abundance as the number density of nuclei of each element in a star’s photosphere raised to a power, β. varies by planet type, but is consistent within our uncertainties across all ten elements. For hot planets (P = 1–10 days), an enhancement in any element of 0.1 dex corresponds to an increased occurrence of ≈20% for super-Earths (R p = 1–1.9 R ⊕) and ≈60% for sub-Neptunes (R p = 1.9–4 R ⊕). Trends are weaker for warm (P = 10–100 days) planets of all sizes and for all elements, with the potential exception of sub-Saturns (R p = 4–8 R ⊕). Finally, we conclude this work with a caution to interpreting trends between planet occurrence and stellar age due to degeneracies caused by Galactic chemical evolution and make predictions for planet occurrence rates in nearby open clusters to facilitate demographics studies of young planetary systems.
• Bender, C. F., Blake, C. H., Canas, C. I., Ford, E. B., Gupta, A. F., Halverson, S., Hearty, F., Hunting, E., Kanodia, S., Laher, R. R., Lin, A. S., Logsdon, S. E., Lubar, E., Luhn, J. K., Mahadevan, S., Mcbride, W. R., Mcelwain, M. W., Monson, A., Ninan, J. P., , Nitroy, C., et al. (2022). Observing the Sun as a Star: Design and Early Results from the NEID Solar Feed. The Astronomical Journal, 163(4), 184. doi:10.3847/1538-3881/ac5622
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  Abstract Efforts with extreme-precision radial velocity (EPRV) instruments to detect small-amplitude planets are largely limited, on many timescales, by the effects of stellar variability and instrumental systematics. One avenue for investigating these effects is the use of small solar telescopes which direct disk-integrated sunlight to these EPRV instruments, observing the Sun at high cadence over months or years. We have designed and built a solar feed system to carry out “Sun-as-a-star” observations with NEID, a very high precision Doppler spectrometer recently commissioned at the WIYN 3.5 m Telescope at Kitt Peak National Observatory. The NEID solar feed has been taking observations nearly every day since 2020 December; data is publicly available at the NASA Exoplanet Science Institute NEID Solar Archive: https://neid.ipac.caltech.edu/search_solar.php. In this paper, we present the design of the NEID solar feed and explanations behind our design intent. We also present early radial velocity (RV) results which demonstrate NEID’s RV stability on the Sun over 4 months of commissioning: 0.66 m s−1 rms under good sky conditions and improving to 0.41 m s−1 rms under best conditions.
• Cañas, C. I., Kanodia, S., Bender, C. F., Mahadevan, S., Stefánsson, G. H., Cochran, W. D., Lin, A. S., Hwang, H. C., Powers, L., Monson, A., Green, E. M., Parker, B. A., Swaby, T. N., Kobulnicky, H. A., Wisniewski, J., Gupta, A. F., Everett, M. E., Jones, S., Anjakos, B., , Beard, C., et al. (2022). TOI-3714 b and TOI-3629 b: Two Gas Giants Transiting M Dwarfs Confirmed with the Habitable-zone Planet Finder and NEID. Astronomical Journal, 164(Issue 2). doi:10.3847/1538-3881/ac7804
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  We confirm the planetary nature of two gas giants discovered by the Transiting Exoplanet Survey Satellite to transit M dwarfs. TOI-3714 (V = 15.24, J = 11.74) is an M2 dwarf hosting a hot Jupiter (M p = 0.70 ± 0.03 M J and R p = 1.01 ± 0.03 R J ) on an orbital period of 2.154849 ± 0.000001 days with a resolved white dwarf companion. TOI-3629 (V = 14.63, J = 11.42) is an M1 dwarf hosting a hot Jupiter (M p = 0.26 ± 0.02 M J and R p =0.74 ± 0.02 R J ) on an orbital period of 3.936551-0.000006+0.000005 days. We characterize each transiting companion using a combination of ground-based and space-based photometry, speckle imaging, and high-precision velocimetry from the Habitable-zone Planet Finder and the NEID spectrographs. With the discovery of these two systems, there are now nine M dwarfs known to host transiting hot Jupiters. Among this population, TOI-3714 b (T eq = 750 ± 20 K and TSM = 98 ± 7) and TOI-3629 b (T eq = 690 ± 20 K and TSM = 80 ± 9) are warm gas giants amenable to additional characterization with transmission spectroscopy to probe atmospheric chemistry and, for TOI-3714, obliquity measurements to probe formation scenarios.
• Ervin, T., Halverson, S., Burrows, A., Murphy, N., Roy, A., Haywood, R. D., Rescigno, F., Bender, C. F., Lin, A. S., Burt, J., & Mahadevan, S. (2022). Leveraging Space-based Data from the Nearest Solar-Type Star to Better Understand Stellar Activity Signatures in Radial Velocity Data. Astronomical Journal, 163(Issue 6). doi:10.3847/1538-3881/ac67e6
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  Stellar variability is a key obstacle in reaching the sensitivity required to recover Earth-like exoplanetary signals using the radial velocity (RV) detection method. To explore activity signatures in Sun-like stars, we present SolAster, a publicly distributed analysis pipeline1010 https://tamarervin.github.io/SolAster/ that allows for comparison of space-based measurements with ground-based disk-integrated RVs. Using high-spatial-resolution Dopplergrams, magnetograms, and continuum filtergrams from the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory (SDO), we estimate "Sun-As-A-star"disk-integrated RVs due to rotationally modulated flux imbalances and convective blueshift suppression, as well as other observables such as unsigned magnetic flux. Comparing these measurements with ground-based RVs from the NEID instrument, which observes the Sun daily using an automated solar telescope, we find a strong relationship between magnetic activity indicators and RV variation, supporting efforts to examine unsigned magnetic flux as a proxy for stellar activity in slowly rotating stars. Detrending against measured unsigned magnetic flux allows us to improve the NEID RV measurements by a1/420% (a1/450 cm s-1 in a quadrature sum), yielding an rms scatter of a1/460 cm s-1 over five months. We also explore correlations between individual and averaged spectral line shapes in the NEID spectra and SDO-derived magnetic activity indicators, motivating future studies of these observables. Finally, applying SolAster to archival planetary transits of Venus and Mercury, we demonstrate the ability to recover small amplitude (
• Gupta, A. F., Luhn, J., Wright, J. T., Mahadevan, S., Ford, E. B., Stefánsson, G., Bender, C. F., Blake, C. H., Halverson, S., Hearty, F., Kanodia, S., Logsdon, S. E., McElwain, M. W., Ninan, J. P., Robertson, P., Roy, A., Schwab, C., & Terrien, R. C. (2022). Detection of p-mode Oscillations in HD 35833 with NEID and TESS. Astronomical Journal, 164(Issue 6). doi:10.3847/1538-3881/ac96f3
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  We report the results of observations of p-mode oscillations in the G0 subgiant star HD 35833 in both radial velocities and photometry with NEID and TESS, respectively. We achieve separate, robust detections of the oscillation signal with both instruments (radial velocity amplitude A RV = 1.11 ± 0.09 m s−1, photometric amplitude A phot = 6.42 ± 0.60 ppm, frequency of maximum power ν max = 595.71 ± 17.28 μHz, and mode spacing Δν = 36.65 ± 0.96 μHz) as well as a nondetection in a TESS sector concurrent with the NEID observations. These data shed light on our ability to mitigate the correlated noise impact of oscillations with radial velocities alone and on the robustness of commonly used asteroseismic scaling relations. The NEID data are used to validate models for the attenuation of oscillation signals for exposure times t < ν max − 1 , and we compare our results to predictions from theoretical scaling relations and find that the observed amplitudes are weaker than expected by >4σ, hinting at gaps in the underlying physical models.
• Hambleton, K., Prša, A., Fleming, S. W., Mahadevan, S., & Bender, C. F. (2022). The SDSS-HET Survey of Kepler Eclipsing Binaries. A Sample of Four Benchmark Binaries. Astrophysical Journal, 931(Issue 2). doi:10.3847/1538-4357/ac69d7
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  The purpose of this work is to extend a sample of accurately modeled, benchmark-grade eclipsing binaries (EBs) with accurately determined masses and radii. We select four "well-behaved"Kepler binaries, KIC 2306740, KIC 4076952, KIC 5193386 and KIC 5288543, each with at least eight double-lined spectra from the Apache Point Observatory Galactic Evolution Experiment instrument that is part of the Sloan Digital Sky Surveys III and IV, and from the Hobby-Eberly High Resolution Spectrograph. We obtain masses and radii with uncertainties of 2.5% or less for all four systems. Three of these systems have orbital periods longer than 9 days, and thus populate an undersampled region of the parameter space for extremely well-characterized detached EBs. We compare the derived masses and radii against mesa mist isochrones to determine the ages of the systems. All systems were found to be coeval, showing that the results are consistent across mesa mist and phoebe.
• Kanodia, S., Libby-Roberts, J., Cañas, C. I., Ninan, J. P., Mahadevan, S., Stefansson, G., Lin, A. S., Jones, S., Monson, A., Parker, B. A., Kobulnicky, H. A., Swaby, T. N., Powers, L., Beard, C., Bender, C. F., Blake, C. H., Cochran, W. D., Dong, J., Diddams, S. A., , Fredrick, C., et al. (2022). TOI-3757 b: A Low-density Gas Giant Orbiting a Solar-metallicity M Dwarf. Astronomical Journal, 164(Issue 3). doi:10.3847/1538-3881/ac7c20
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  We present the discovery of a new Jovian-sized planet, TOI-3757 b, the lowest-density transiting planet known to orbit an M dwarf (M0V). This planet was discovered around a solar-metallicity M dwarf, using Transiting Exoplanet Survey Satellite photometry and confirmed with precise radial velocities from the Habitable-zone Planet Finder (HPF) and NEID. With a planetary radius of 12.0 − 0.5 + 0.4 R ⊕ and mass of 85.3 − 8.7 + 8.8 M ⊕, not only does this object add to the small sample of gas giants (∼10) around M dwarfs, but also its low density ( ρ = 0.27 − 0.04 + 0.05 g cm−3) provides an opportunity to test theories of planet formation. We present two hypotheses to explain its low density; first, we posit that the low metallicity of its stellar host (∼0.3 dex lower than the median metallicity of M dwarfs hosting gas giants) could have played a role in the delayed formation of a solid core massive enough to initiate runaway accretion. Second, using the eccentricity estimate of 0.14 ± 0.06, we determine it is also plausible for tidal heating to at least partially be responsible for inflating the radius of TOI-3757b b. The low density and large scale height of TOI-3757 b makes it an excellent target for transmission spectroscopy studies of atmospheric escape and composition (transmission spectroscopy measurement of ∼ 190). We use HPF to perform transmission spectroscopy of TOI-3757 b using the helium 10830 Å line. Doing this, we place an upper limit of 6.9% (with 90% confidence) on the maximum depth of the absorption from the metastable transition of He at ∼10830 Å, which can help constraint the atmospheric mass-loss rate in this energy-limited regime.
• Sneden, C., Afşar, M., Bozkurt, Z., Adamów, M., Mallick, A., Reddy, B. E., Janowiecki, S., Mahadevan, S., Bowler, B. P., Hawkins, K., Lind, K., Dupree, A. K., Ninan, J. P., Nagarajan, N., Topcu, G. B., Froning, C. S., Bender, C. F., Terrien, R., Ramsey, L. W., & Mace, G. N. (2022). The Active Chromospheres of Lithium-rich Red Giant Stars* * Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.. Astrophysical Journal, 940(Issue 1). doi:10.3847/1538-4357/ac922e
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  We have gathered near-infrared zyJ-band high-resolution spectra of nearly 300 field red giant stars with known lithium abundances in order to survey their He i λ10830 absorption strengths. This transition is an indicator of chromospheric activity and/or mass loss in red giants. The majority of stars in our sample reside in the red clump or red horizontal branch based on their V − J, M V color-magnitude diagram, and Gaia T eff and log(g) values. Most of our target stars are Li-poor in the sense of having normally low Li abundances, defined here as log ϵ(Li) < 1.25. Over 90% of these Li-poor stars have weak λ10830 features. However, more than half of the 83 Li-rich stars (log ϵ(Li) > 1.25) have strong λ10830 absorptions. These large λ10830 lines signal excess chromospheric activity in Li-rich stars; there is almost no indication of significant mass loss. The Li-rich giants may also have a higher binary fraction than Li-poor stars, based on their astrometric data. It appears likely that both residence on the horizontal branch and present or past binary interaction play roles in the significant Li-He connection established in this survey.
• Stefànsson, G., Mahadevan, S., Petrovich, C., Winn, J. N., Kanodia, S., Millholland, S. C., Maney, M., Cañas, C. I., Wisniewski, J., Robertson, P., Ninan, J. P., Ford, E. B., Bender, C. F., Blake, C. H., Cegla, H., Cochran, W. D., Diddams, S. A., Dong, J., Endl, M., , Fredrick, C., et al. (2022). The Warm Neptune GJ 3470b Has a Polar Orbit. Astrophysical Journal Letters, 931(Issue 2). doi:10.3847/2041-8213/ac6e3c
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  The warm Neptune GJ 3470b transits a nearby (d = 29 pc) bright slowly rotating M1.5-dwarf star. Using spectroscopic observations during two transits with the newly commissioned NEID spectrometer on the WIYN 3.5 m Telescope at Kitt Peak Observatory, we model the classical Rossiter-McLaughlin effect, yielding a sky-projected obliquity of λ=98-12+15° and a vsini=0.85-0.33+0.27kms-1 . Leveraging information about the rotation period and size of the host star, our analysis yields a true obliquity of ψ=95-8+9°, revealing that GJ 3470b is on a polar orbit. Using radial velocities from HIRES, HARPS, and the Habitable-zone Planet Finder, we show that the data are compatible with a long-term radial velocity (RV) slope of γ=-0.0022±0.0011ms-1day-1 over a baseline of 12.9 yr. If the RV slope is due to acceleration from another companion in the system, we show that such a companion is capable of explaining the polar and mildly eccentric orbit of GJ 3470b using two different secular excitation models. The existence of an outer companion can be further constrained with additional RV observations, Gaia astrometry, and future high-contrast imaging observations. Lastly, we show that tidal heating from GJ 3470b's mild eccentricity has most likely inflated the radius of GJ 3470b by a factor of ∼1.5-1.7, which could help account for its evaporating atmosphere.
• Beaton, R. L., Oelkers, R. J., Hayes, C. R., Covey, K. R., Chojnowski, S., De, L. N., Sobeck, J. S., Majewski, S. R., Cohen, R. E., Fern{'andez-Trincado}, J., Longa-Pe{~na}, P., O'Connell, J. E., Santana, F. A., Stringfellow, G. S., Zasowski, G., Aerts, C., Anguiano, B., Bender, C., Ca{~nas}, C. I., , Cunha, K., et al. (2021). "Final Targeting Strategy for the Sloan Digital Sky Survey IV Apache Point Observatory Galactic Evolution Experiment 2 North Survey". AJ, 162(6), 302. doi:10.3847/1538-3881/ac260c
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• Finnerty, L., Buzard, C., Pelletier, S., Piskorz, D., Lockwood, A. C., Bender, C. F., Benneke, B., & Blake, G. A. (2021). "Contrast and Temperature Dependence of Multi-epoch High-resolution Cross-correlation Exoplanet Spectroscopy". AJ, 161(3), 104. doi:10.3847/1538-3881/abd6ec
• Gupta, A. F., Wright, J. T., Robertson, P., Halverson, S., Luhn, J., Roy, A., Mahadevan, S., Ford, E. B., Bender, C. F., Blake, C. H., Hearty, F., Kanodia, S., Logsdon, S. E., McElwain, M. W., Monson, A., Ninan, J. P., Schwab, C., Stef{'ansson}, G., & Terrien, R. C. (2021). "Target Prioritization and Observing Strategies for the NEID Earth Twin Survey". AJ, 161(3), 13. doi:10.3847/1538-3881/abd79e
• Kanodia, S., Halverson, S., Ninan, J. P., Mahadevan, S., Stefansson, G., Roy, A., Ramsey, L. W., Bender, C. F., Janowiecki, S., Cochran, W. D., Diddams, S. A., Drory, N., Endl, M., Ford, E. B., Hearty, F., Metcalf, A. J., Monson, A., Robertson, P., Schwab, C., , Terrien, R. C., et al. (2021). "A Harsh Test of Far-Field Scrambling with the Habitable Zone Planet Finder and the Hobby Eberly Telescope". ApJ, 912, 11. doi:10.3847/1538-4357/abec83
• Kanodia, S., Stefansson, G., Ca{~nas}, C. I., Maney, M., Lin, A. S., Ninan, J. P., Jones, S., Monson, A., Parker, B. A., Kobulnicky, H. A., Rothenberg, J., Beard, C., Lubin, J., Robertson, P., Gupta, A. F., Mahadevan, S., Cochran, W. D., Bender, C. F., Diddams, S. A., , Fredrick, C., et al. (2021). "TOI-532b: The Habitable-zone Planet Finder confirms a Large Super Neptune in the Neptune Desert orbiting a metal-rich M-dwarf host". AJ, 162(4), 135. doi:10.3847/1538-3881/ac1940
• Krishnamurthy, V., Hirano, T., Stef{'ansson}, G., Ninan, J. P., Mahadevan, S., Gaidos, E., Kopparapu, R., Sato, B., Hori, Y., Bender, C. F., Ca{~nas}, C. I., Diddams, S. A., Halverson, S., Harakawa, H., Hawley, S., Hearty, F., Hebb, L., Hodapp, K., Jacobson, S., , Kanodia, S., et al. (2021). "Nondetection of Helium in the Upper Atmospheres of TRAPPIST-1b, e, and f". AJ, 162, 82. doi:10.3847/1538-3881/ac0d57
• Lubin, J., Robertson, P., Stefansson, G., Ninan, J., Mahadevan, S., Endl, M., Ford, E., Wright, J. T., Beard, C., Bender, C., Cochran, W. D., Diddams, S. A., Fredrick, C., Halverson, S., Kanodia, S., Metcalf, A. J., Ramsey, L., Roy, A., Schwab, C., & Terrien, R. (2021). "Stellar Activity Manifesting at a One-year Alias Explains Barnard b as a False Positive". AJ, 162(2), 61. doi:10.3847/1538-3881/ac0057
• Mahadevan, S., Stef{'ansson}, G., Robertson, P., Terrien, R. C., Ninan, J. P., Holcomb, R. J., Halverson, S., Cochran, W. D., Kanodia, S., Ramsey, L. W., Wolszczan, A., Endl, M., Bender, C. F., Diddams, S. A., Fredrick, C., Hearty, F., Monson, A., Metcalf, A. J., Roy, A., & Schwab, C. (2021). "The Habitable-zone Planet Finder Detects a Terrestrial-mass Planet Candidate Closely Orbiting Gliese 1151: The Likely Source of Coherent Low-frequency Radio Emission from an Inactive Star". ApJL, 919, 9. doi:10.3847/2041-8213/abe2b2
• Sneden, C., Af{c{s}ar}, M., Bozkurt, Z., Topcu, G. B., {"Ozdemir}, S., Zeimann, G. R., Froning, C. S., Mahadevan, S., Ninan, J. P., Bender, C. F., Terrien, R., Ramsey, L. W., Lind, K., Mace, G. N., Kaplan, K. F., Kim, H., Hawkins, K., & Bowler, B. P. (2021). "Chemical Compositions of Red Giant Stars from Habitable Zone Planet Finder Spectroscopy". AJ, 161(3), 128. doi:10.3847/1538-3881/abd7ee
• Terrien, R. C., Ninan, J. P., Diddams, S. A., Mahadevan, S., Halverson, S., Bender, C., Fredrick, C., Hearty, F., Jennings, J., Metcalf, A. J., Monson, A., Roy, A., Schwab, C., & Stefansson, G. (2021). "Broadband stability of the Habitable Zone Planet Finder Fabry-P'erot etalon calibration system: evidence for chromatic variation". AJ, 161, 252. doi:10.3847/1538-3881/abef68
• Tran, Q. H., Bowler, B. P., Cochran, W. D., Endl, M., Stef{'ansson}, G., Mahadevan, S., Ninan, J. P., Bender, C. F., Halverson, S., Roy, A., & Terrien, R. C. (2021). "The Epoch of Giant Planet Migration Planet Search Program. I. Near-infrared Radial Velocity Jitter of Young Sun-like Stars". AJ, 161(4), 173. doi:10.3847/1538-3881/abe041
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• Buzard, C., Finnerty, L., Piskorz, D., Pelletier, S., Benneke, B., Bender, C. F., Lockwood, A. C., Wallack, N. L., Wilkins, O. H., & Blake, G. A. (2020). "Simulating the Multi-epoch Direct Detection Technique to Isolate the Thermal Emission of the Non-transiting Hot Jupiter HD187123b". aj, 160(1), 1.
• Ca{~nas}, C. I., Stefansson, G., Kanodia, S., Mahadevan, S., Cochran, W. D., Endl, M., Robertson, P., Bender, C. F., Ninan, J. P., Beard, C., Lubin, J., Gupta, A. F., Everett, M. E., Monson, A., Wilson, R. F., Lewis, H. M., Brewer, M., Majewski, S. R., Hebb, L., , Dawson, R. I., et al. (2020). "A Warm Jupiter Transiting an M Dwarf: A TESS Single-transit Event Confirmed with the Habitable-zone Planet Finder". aj, 160(3), 147.
• Kanodia, S., Ca{~nas}, C. I., Stefansson, G., Ninan, J. P., Hebb, L., Lin, A. S., Baran, H., Maney, M., Terrien, R. C., Mahadevan, S., Cochran, W. D., Endl, M., Dong, J., Bender, C. F., Diddams, S. A., Ford, E. B., Fredrick, C., Halverson, S., Hearty, F., , Metcalf, A. J., et al. (2020). "TOI-1728b: The Habitable-zone Planet Finder Confirms a Warm Super-Neptune Orbiting an M-dwarf Host". apj, 899(1), 29.
• Ninan, J. P., Stefansson, G., Mahadevan, S., Bender, C., Robertson, P., Ramsey, L., Terrien, R., Wright, J., Diddams, S. A., Kanodia, S., Cochran, W., Endl, M., Ford, E. B., Fredrick, C., Halverson, S., Hearty, F., Jennings, J., Kaplan, K., Lubar, E., , Metcalf, A. J., et al. (2020). "Evidence for He I 10830 {r{A} Absorption during the Transit of a Warm Neptune around the M-dwarf GJ 3470 with the Habitable-zone Planet Finder}". apj, 894(2), 97.
• Robertson, P., Stefansson, G., Mahadevan, S., Endl, M., Cochran, W. D., Beard, C., Bender, C. F., Diddams, S. A., Duong, N., Ford, E. B., Fredrick, C., Halverson, S., Hearty, F., Holcomb, R., Juan, L., Kanodia, S., Lubin, J., Metcalf, A. J., Monson, A., , Ninan, J. P., et al. (2020). "Persistent Starspot Signals on M Dwarfs: Multiwavelength Doppler Observations with the Habitable-zone Planet Finder and Keck/HIRES". apj, 897(2), 125.
• Roy, A., Halverson, S., Mahadevan, S., Stefansson, G., Monson, A., Logsdon, S. E., Bender, C. F., Blake, C. H., Golub, E., Gupta, A., Jaehnig, K. P., Kanodia, S., Kaplan, K., McElwain, M. W., Ninan, J. P., Rajagopal, J., Robertson, P., Schwab, C., Terrien, R. C., , Wang, S. X., et al. (2020). "Solar Contamination in Extreme-precision Radial-velocity Measurements: Deleterious Effects and Prospects for Mitigation". aj, 159(4), 161.
• Stefansson, G., Ca{~nas}, C., Wisniewski, J., Robertson, P., Mahadevan, S., Maney, M., Kanodia, S., Beard, C., Bender, C. F., Brunt, P., Clemens, J. C., Cochran, W., Diddams, S. A., Endl, M., Ford, E. B., Fredrick, C., Halverson, S., Hearty, F., Hebb, L., , Huehnerhoff, J., et al. (2020). "A Sub-Neptune-sized Planet Transiting the M2.5 Dwarf G 9-40: Validation with the Habitable-zone Planet Finder". aj, 159(3), 100.
• Stefansson, G., Mahadevan, S., Maney, M., Ninan, J. P., Robertson, P., Rajagopal, J., Haase, F., Allen, L., Ford, E. B., Winn, J., Wolfgang, A., Dawson, R. I., Wisniewski, J., Bender, C. F., Ca{~nas}, C., Cochran, W., Diddams, S. A., Fredrick, C., Halverson, S., , Hearty, F., et al. (2020). "The Habitable Zone Planet Finder Reveals a High Mass and Low Obliquity for the Young Neptune K2-25b". aj, 160(4), 192.
• Stef{'ansson}, G., Kopparapu, R., Lin, A., Mahadevan, S., Ca{~nas}, C. I., Kanodia, S., Ninan, J. P., Cochran, W. D., Endl, M., Hebb, L., Wisniewski, J., Gupta, A., Everett, M., Bender, C. F., Diddams, S. A., Ford, E. B., Fredrick, C., Halverson, S., Hearty, F., , Levi, E., et al. (2020). "A Mini-Neptune and a Radius Valley Planet Orbiting the Nearby M2 Dwarf TOI-1266 in Its Venus Zone: Validation with the Habitable-zone Planet Finder". aj, 160(6), 259.
• Blake, C. H., Li, D., Tufts, J. R., Ninan, J., Mahadevan, S., Bender, C., Hearty, F. R., Monson, A., & Giovinazzi, M. (2019). Improving the thermal stability of a CCD through clocking. JOURNAL OF ASTRONOMICAL TELESCOPES INSTRUMENTS AND SYSTEMS, 5(4).
• Canas, C. I., Stefansson, G., Monson, A. J., Teske, J. K., Bender, C. F., Mahadevan, S., Aerts, C., Beaton, R. L., Butler, R. P., Covey, K. R., Crane, J. D., De, L. N., Diaz, M. R., Fleming, S. W., Garcia-Hernandez, D. A., Hearty, F. R., Kollmeier, J. A., Majewski, S. R., Nitschelm, C., , Schneider, D. P., et al. (2019). TOI-150: A Transiting Hot Jupiter in the TESS Southern CVZ. ASTROPHYSICAL JOURNAL LETTERS, 877(2).
• Kaplan, K. F., Bender, C. F., Terrien, R. C., Ninan, J., Roy, A., & Mahadevan, S. (2019). The Algorithms Behind the HPF and NEID Pipeline. ASTRONOMICAL DATA ANALYSIS SOFTWARE AND SYSTEMS XXVIII, 523, 567-570.
• Mahadevan, S., Bender, C. F., Hambleton, K., Fleming, S. W., Deshpande, R., Conroy, K., Matijevic, G., Hebb, L., Roy, A., Ak, H., Leban, B., & Prsa, A. (2019). The SDSS-HET Survey of Kepler Eclipsing Binaries. Description of the Survey and First Results. ASTROPHYSICAL JOURNAL, 884(2).
• Metcalf, A. J., Anderson, T., Bender, C. F., Blakeslee, S., Brand, W., Carlson, D. R., Cochran, W. D., Diddams, S. A., Endl, M., Fredrick, C., Halverson, S., Hickstein, D. D., Hearty, F., Jennings, J., Kanodia, S., Kaplan, K. F., Levi, E., Lubar, E., Mahadevan, S., , Monson, A., et al. (2019). Stellar spectroscopy in the near-infrared with a laser frequency comb. OPTICA, 6(2), 233-239.
• Ninan, J. P., Mahadevan, S., Stefansson, G., Bender, C., Roy, A., Kaplan, K. F., Fredrick, C., Metcalf, A. J., Monson, A., Terrien, R., Ramsey, L. W., & Diddams, S. A. (2019). Impact of crosshatch patterns in H2RGs on high-precision radial velocity measurements: exploration of measurement and mitigation paths with the Habitable-Zone Planet Finder. JOURNAL OF ASTRONOMICAL TELESCOPES INSTRUMENTS AND SYSTEMS, 5(4).
• Robertson, P., Anderson, T., Stefansson, G., Hearty, F. R., Monson, A., Mahadevan, S., Blakeslee, S., Bender, C., Ninan, J. P., Conran, D., Levi, E., Lubar, E., Cole, A., Dykhouse, A., Kanodia, S., Nitroy, C., Smolsky, J., Tuggle, D., Blank, B., , Nelson, M., et al. (2019). Ultrastable environment control for the NEID spectrometer: design and performance demonstration. JOURNAL OF ASTRONOMICAL TELESCOPES INSTRUMENTS AND SYSTEMS, 5(1).
• Wang, S. X., Wright, J. T., Bender, C., Howard, A. W., Isaacson, H., Veyette, M., & Muirhead, P. S. (2019). The Effects of Telluric Contamination in Iodine-calibrated Precise Radial Velocities*(?) Based on observations obtained at the Keck Observatory, which is operated by the University of California. The Keck Observatory was made possible by the generous financial support of the W. M. Keck Foundation.. ASTRONOMICAL JOURNAL, 158(5).
• Abolfathi, B., Aguado, D. S., Aguilar, G., Prieto, C. A., Almeida, A., Ananna, T. T., Anders, F., Anderson, S. F., Andrews, B. H., Anguiano, B., Aragon-Salamanca, A., Argudo-Fernandez, M., Armengaud, E., Ata, M., Aubourg, E., Avila-Reese, V., Badenes, C., Bailey, S., Balland, C., , Barger, K. A., et al. (2018). The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the Extended Baryon Oscillation Spectroscopic Survey and from the Second Phase of the Apache Point Observatory Galactic Evolution Experiment. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 235(2).
• Canas, C. I., Bender, C. F., Mahadevan, S., Fleming, S. W., Beatty, T. G., Covey, K. R., De, L. N., Hearty, F. R., Garcia-Hernandez, D. A., Majewski, S. R., Schneider, D. P., Stassun, K. G., & Wilson, R. F. (2018). Kepler-503b: An Object at the Hydrogen Burning Mass Limit Orbiting a Subgiant Star. ASTROPHYSICAL JOURNAL LETTERS, 861(1).
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  Canas is a Penn State graduate student being jointly supervised by C. Bender and S. Mahadevan
• Canas, C. I., Wang, S., Mahadevan, S., Bender, C. F., De, L. N., Fleming, S. W., Garcia-Hernandez, D. A., Hearty, F. R., Majewski, S. R., Roman-Lopes, A., Schneider, D. P., & Stassun, K. G. (2019). Kepler-730: A Hot Jupiter System with a Close-in, Transiting, Earth-sized Planet. ASTROPHYSICAL JOURNAL LETTERS, 870(2).
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  Canas is a Penn State graduate student being jointly supervised by C. Bender and S. Mahadevan.
• Gilhool, S. H., Blake, C. H., Terrien, R. C., Bender, C., Mahadevan, S., & Deshpande, R. (2018). The Rotation of M Dwarfs Observed by the Apache Point Galactic Evolution Experiment. ASTRONOMICAL JOURNAL, 155(1).
• Kanodia, S., Mahadevan, S., Ramsey, L. W., Stefansson, G. K., Monson, A. J., Hearty, F. R., Blakeslee, S., Lubar, E., Bender, C. F., Ninan, J. P., Sterner, D., Roy, A., Halverson, S. P., & Robertson, P. M. (2018). Overview of the spectrometer optical fiber feed for the Habitable-zone Planet Finder. GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY VII, 10702.
• Logsdon, S. E., McElwain, M. W., Gong, Q., Liang, M., Santoro, F., Schwab, C., Bender, C., Blake, C., Halverson, S., Hearty, F., Hunting, E., Jaehnig, K. P., Mahadevan, S., Monson, A. J., Percival, J. W., Rajagopal, J., Ramsey, L., Roy, A., Smith, M. P., , Terrien, R. C., et al. (2018). The NEID precision radial velocity spectrometer: port adapter overview, requirements, and test plan. GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY VII, 10702.
• Ninan, J. P., Bender, C. F., Mahadevana, S., Ford, E. B., Monson, A. J., Kaplan, K. F., Terrien, R. C., Roy, A., Robertson, P. M., Kanodia, S., & Stefansson, G. K. (2018). The Habitable-Zone Planet Finder: Improved flux image generation algorithms for H2RG up-the-ramp data. HIGH ENERGY, OPTICAL, AND INFRARED DETECTORS FOR ASTRONOMY VIII, 10709.
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  Ninan is a postdoctoral associate on the NEID instrument team being supervised by C. Bender.
• Piskorz, D., Buzard, C., Line, M. R., Knutson, H. A., Benneke, B., Crockett, N. R., Lockwood, A. C., Blake, G. A., Barman, T. S., Bender, C. F., Deming, D., & Johnson, J. A. (2018). Ground- and Space-based Detection of the Thermal Emission Spectrum of the Transiting Hot Jupiter KELT-2Ab. ASTRONOMICAL JOURNAL, 156(3).
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• Skinner, J., Covey, K. R., Bender, C. F., Rivera, N., De, L. N., Souto, D., Chojnowski, D., Troup, N., Badenes, C., Bizyaev, D., Blake, C. H., Burgasser, A., Canas, C., Carlberg, J., Maqueo, C., Deshpande, R., Fleming, S. W., Fernandez-Trincado, J. G., Garcia-Hernandez, D. A., , Hearty, F., et al. (2018). Forty-four New and Known M-dwarf Multiples in the SDSS-III/APOGEE M-dwarf Ancillary Science Sample. ASTRONOMICAL JOURNAL, 156(2).
• Strassmeier, K. G., Ilyin, I., Weber, M., Jaervinen, A., Woche, M., Jaervinen, S., Sablowski, D., Mallonn, M., Keles, E., Carroll, T., Johnson, M. C., Bender, C., Wagner, R. M., & Veillet, C. (2018). Want a PEPSI? Performance status of the recently commissioned high-resolution spectrograph and polarimeter for the 2x8.4m Large Binocular Telescope. GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY VII, 10702.
• Wilson, R. F., Teske, J., Majewski, S. R., Cunha, K., Smith, V., Souto, D., Bender, C., Mahadevan, S., Troup, N., Prieto, C. A., Stassun, K. G., Skrutskie, M. F., Almeida, A., Garcia-Hernandez, D. A., Zamora, O., & Brinkmann, J. (2018). Elemental Abundances of Kepler Objects of Interest in APOGEE. I. Two Distinct Orbital Period Regimes Inferred from Host Star Iron Abundances. ASTRONOMICAL JOURNAL, 155(2).
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• Blanton, M., Bershady, M., Abolfathi, B., Albareti, F., Allende Prieto, C., Almeida, A., Alonso-Garc{'{i}a}, J., Anders, F., Anderson, S., Andrews, B., & al., e. (2017). "Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe". Astronomical Journal, 154, 28.
• Piskorz, D., Benneke, B., Crockett, N. R., Lockwood, A. C., Blake, G. A., Barman, T. S., Bender, C. F., Carr, J. S., & Johnson, J. A. (2017). Detection of Water Vapor in the Thermal Spectrum of the Non-transiting Hot Jupiter Upsilon Andromedae b. ASTRONOMICAL JOURNAL, 154(2).
• Piskorz, D., Benneke, B., Crockett, N., Lockwood, A., Blake, G., Barman, T., Bender, C., Carr, J., & Johnson, J. (2017). "Detection of Water Vapor in the Thermal Spectrum of the Non-transiting Hot Jupiter Upsilon Andromedae b". Astronomical Journal, 154, 78.
• Stefansson, G., Mahadevan, S., Hebb, L., Wisniewski, J., Huehnerhoff, J., Morris, B., Halverson, S., Zhao, M., Wright, J., O'rourke, J., Knutson, H., Hawley, S., Kanodia, S., Li, Y., Hagen, L., Liu, L. J., Beatty, T., Bender, C., Robertson, P., , Dembicky, J., et al. (2017). Toward Space-like Photometric Precision from the Ground with Beam-shaping Diffusers. ASTROPHYSICAL JOURNAL, 848(1).
• Stefansson, G., Mahadevan, S., Hebb, L., Wisniewski, J., Huehnerhoff, J., Morris, B., Halverson, S., Zhao, M., Wright, J., O'rourke, J., Knutson, H., Hawley, S., Kanodia, S., Li, Y., Hagen, L., Liu, L., Beatty, T., Bender, C., Robertson, P., , Dembicky, J., et al. (2017). "Toward Space-like Photometric Precision from the Ground with Beam-shaping Diffusers". Astrophysical Journal, 848, 9.
• Zasowski, G., Cohen, R., Chojnowski, S., Santana, F., Oelkers, R., Andrews, B., Beaton, R., Bender, C., Bird, J., Bovy, J., Carlberg, J., Covey, K., Cunha, K., Dell'Agli, F., Fleming, S., Frinchaboy, P., Garc{'{i}a-Hern'andez}, D., Harding, P., Holtzman, J., , Johnson, J., et al. (2017). "Target Selection for the SDSS-IV APOGEE-2 Survey". Astronomical Journal, 154, 198.
• Bender, C. F., Robertson, P., Stefansson, G. K., Monson, A., Anderson, T., Halverson, S., Hearty, F., Levi, E., Mahadevan, S., Nelson, M., Ramsey, L., Roy, A., Schwab, C., Shetrone, M., & Terrien, R. (2016). The instrument control software package for the Habitable-Zone Planet Finder Spectrometer. SOFTWARE AND CYBERINFRASTRUCTURE FOR ASTRONOMY IV, 9913.
• Gaulme, P., McKeever, J., Jackiewicz, J., Rawls, M. L., Corsaro, E., Mosser, B., Southworth, J., Mahadevan, S., Bender, C., & Deshpande, R. (2016). TESTING THE ASTEROSEISMIC SCALING RELATIONS FOR RED GIANTS WITH ECLIPSING BINARIES OBSERVED BY KEPLER. ASTROPHYSICAL JOURNAL, 832(2).
• Halverson, S., Terrien, R., Mahadevan, S., Roy, A., Bender, C., Stefansson, G. K., Monson, A., Levi, E., Hearty, F., Blake, C., McElwain, M., Schwab, C., Ramsey, L., Wright, J., Wang, S., Gong, Q., & Robertson, P. (2016). A comprehensive radial velocity error budget for next generation Doppler spectrometers. GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY VI, 9908.
• Piskorz, D., Benneke, B., Crockett, N. R., Lockwood, A. C., Blake, G. A., Barman, T. S., Bender, C. F., Bryan, M. L., Carr, J. S., Fischer, D. A., Howard, A. W., Isaacson, H., & Johnson, J. A. (2016). EVIDENCE FOR THE DIRECT DETECTION OF THE THERMAL SPECTRUM OF THE NON-TRANSITING HOT GAS GIANT HD 88133 b. ASTROPHYSICAL JOURNAL, 832(2).
• Robertson, P., Bender, C., Mahadevan, S., Roy, A., & Ramsey, L. W. (2016). PROXIMA CENTAURI AS A BENCHMARK FOR STELLAR ACTIVITY INDICATORS IN THE NEAR-INFRARED. ASTROPHYSICAL JOURNAL, 832(2).
• Robertson, P., Hearty, F. R., Anderson, T. B., Stefansson, G. K., Levi, E. I., Bender, C. F., Mahadevan, S., Halverson, S. P., Monson, A. J., Ramsey, L. W., Roy, A., Schwab, C., Terrien, R. C., Nelson, M. J., & Blank, B. (2016). A system to provide sub-milliKelvin temperature control at T similar to 300K for extreme precision optical radial velocimetry. GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY VI, 9908.
• Schwab, C., Rakich, A., Gong, Q., Mahadevan, S., Halverson, S. P., Roy, A., Terrien, R. C., Robertson, P. M., Hearty, F. R., Levi, E. I., Monson, A. J., Wright, J. T., McElwain, M. W., Bender, C. F., Blake, C. H., Sturmer, J., Gurevich, Y. V., Chakraborty, A., & Ramsey, L. W. (2016). Design of NEID, an extreme precision Doppler spectrograph for WIYN. GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY VI, 9908.
• Stefansson, G. K., Hearty, F. R., Robertson, P. M., Levi, E. I., Mahadevan, S., Anderson, T. B., Monson, A. J., Bender, C. F., Halverson, S. P., Li, Y., Ramsey, L. W., Roy, A., Schwab, C., Terrien, R. C., Nelson, M. J., & Blank, B. (2016). Ultra-stable temperature and pressure control for the Habitable zone Planet Finder spectrograph. GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY VI, 9908.
• Stefansson, G., Hearty, F., Robertson, P., Mahadevan, S., Anderson, T., Levi, E., Bender, C., Nelson, M., Monson, A., Blank, B., Halverson, S., Henderson, C., Ramsey, L., Roy, A., Schwab, C., & Terrien, R. (2016). A VERSATILE TECHNIQUE TO ENABLE SUB-MILLI-KELVIN INSTRUMENT STABILITY FOR PRECISE RADIAL VELOCITY MEASUREMENTS: TESTS WITH THE HABITABLE-ZONE PLANET FINDER. ASTROPHYSICAL JOURNAL, 833(2).
• Terrien, R. C., Monson, A. J., Mahadevan, S., Bender, C., Halverson, S. P., & Ramsey, L. (2016). Measuring extended red sensitivity in a 1.7 mu m-cutoff HgCdTe detector array. HIGH ENERGY, OPTICAL, AND INFRARED DETECTORS FOR ASTRONOMY VII, 9915.
• Alam, S., Albareti, F. D., Allende, P. C., Anders, F., Anderson, S. F., Anderton, T., Andrews, B. H., Armengaud, E., Aubourg, E., Bailey, S., Basu, S., Bautista, J. E., Beaton, R. L., Beers, T. C., Bender, C. F., Berlind, A. A., Beutler, F., Bhardwaj, V., Bird, J. C., , Bizyaev, D., et al. (2015). THE ELEVENTH AND TWELFTH DATA RELEASES OF THE SLOAN DIGITAL SKY SURVEY: FINAL DATA FROM SDSS-III. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 219(1).
• Fleming, S. W., Mahadevan, S., Deshpande, R., Bender, C. F., Terrien, R. C., Marchwinski, R. C., Wang, J. i., Roy, A., Stassun, K. G., Allende, P. C., Cunha, K., Smith, V. V., Agol, E., Ak, H., Bastien, F. A., Bizyaev, D., Crepp, J. R., Ford, E. B., Frinchaboy, P. M., , Anibal, G. D., et al. (2015). THE APOGEE SPECTROSCOPIC SURVEY OF KEPLER PLANET HOSTS: FEASIBILITY, EFFICIENCY, AND FIRST RESULTS. ASTRONOMICAL JOURNAL, 149(4).
• Nidever, D. L., Holtzman, J. A., Allende, P. C., Beland, S., Bender, C., Bizyaev, D., Burton, A., Desphande, R., Fleming, S. W., Garcia, P., Hearty, F. R., Majewski, S. R., Meszaros, S., Muna, D., Nguyen, D., Schiavon, R. P., Shetrone, M., Skrutskie, M. F., Sobeck, J. S., & Wilson, J. C. (2015). THE DATA REDUCTION PIPELINE FOR THE APACHE POINT OBSERVATORY GALACTIC EVOLUTION EXPERIMENT. ASTRONOMICAL JOURNAL, 150(6).
• Terrien, R. C., Mahadevan, S., Bender, C. F., Deshpande, R., & Robertson, P. (2015). M DWARF LUMINOSITY, RADIUS, AND alpha-ENRICHMENT FROM I-BAND SPECTRAL FEATURES. ASTROPHYSICAL JOURNAL LETTERS, 802(1).
• Terrien, R. C., Mahadevan, S., Deshpande, R., & Bender, C. F. (2015). A NEAR-INFRARED SPECTROSCOPIC SURVEY OF 886 NEARBY M DWARFS. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 220(1).
• Ahn, C. P., Alexandroff, R., Allende, P. C., Anders, F., Anderson, S. F., Anderton, T., Andrews, B. H., Aubourg, E., Bailey, S., Bastien, F. A., Bautista, J. E., Beers, T. C., Beifiori, A., Bender, C. F., Berlind, A. A., Beutler, F., Bhardwaj, V., Bird, J. C., Bizyaev, D., , Blake, C. H., et al. (2014). THE TENTH DATA RELEASE OF THE SLOAN DIGITAL SKY SURVEY: FIRST SPECTROSCOPIC DATA FROM THE SDSS-III APACHE POINT OBSERVATORY GALACTIC EVOLUTION EXPERIMENT. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 211(2).
• Halverson, S., Mahadevan, S., Ramsey, L., Terrien, R., Roy, A., Schwab, C., Bender, C., Hearty, F., Levi, E., Osterman, S., Ycas, G., & Diddams, S. (2014). The Habitable-zone Planet Finder Calibration System. GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V, 9147.
• Hearty, F., Levi, E., Nelson, M., Mahadevan, S., Burton, A., Ramsey, L., Bender, C., Terrien, R., Halverson, S., Robertsonl, P., Roy, A., Blank, B., Blanchard, K., & Stefansson, G. (2014). Environmental control system for Habitable-zone Planet Finder (HPF). GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V, 9147.
• Lockwood, A. C., Johnson, J. A., Bender, C. F., Carr, J. S., Barman, T., Richert, A., & Blake, G. A. (2014). NEAR-IR DIRECT DETECTION OF WATER VAPOR IN TAU BOOTIS b. ASTROPHYSICAL JOURNAL LETTERS, 783(2).
• Mahadevan, S., Ramsey, L. W., Terrien, R., Halverson, S., Roy, A., Hearty, F., Levi, E., Stefansson, G. K., Robertson, P., Bender, C., Schwab, C., & Nelson, M. (2014). The Habitable-zone Planet Finder: A status update on the development of a stabilized fiber-fed near-infrared spectrograph for the Hobby-Eberly telescope. GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V, 9147.
• Terrien, R. C., Bender, C. F., Mahadevan, S., Halverson, S. P., Ramsey, L. W., & Hearty, F. R. (2014). Developments in simulations and software for a near-infrared precision radial velocity spectrograph. SOFTWARE AND CYBERINFRASTRUCTURE FOR ASTRONOMY III, 9152.
• Terrien, R. C., Mahadevan, S., Deshpande, R., Bender, C. F., Cargile, P. A., Hearty, F. R., Cottaar, M., Allende, P. C., Fleming, S. W., Frinchaboy, P. M., Jackson, K. M., Johnson, J. A., Majewski, S. R., Nidever, D. L., Pepper, J., Rodriguez, J. E., Schneider, D. P., Siverd, R. J., Stassun, K. G., , Weaver, B. A., et al. (2014). NEW RED JEWELS IN COMA BERENICES. ASTROPHYSICAL JOURNAL, 782(2).
• Deshpande, R., Blake, C. H., Bender, C. F., Mahadevan, S., Terrien, R. C., Carlberg, J. K., Zasowski, G., Crepp, J., Rajpurohit, A. S., Reyle, C., Nidever, D. L., Schneider, D. P., Allende, P. C., Bizyaev, D., Ebelke, G., Fleming, S. W., Frinchaboy, P. M., Ge, J., Hearty, F., , Hernandez, J., et al. (2013). THE SDSS-III APOGEE RADIAL VELOCITY SURVEY OF M DWARFS. I. DESCRIPTION OF THE SURVEY AND SCIENCE GOALS. ASTRONOMICAL JOURNAL, 146(6).
• Bender, C. F., Mahadevan, S., Deshpande, R., Wright, J. T., Roy, A., Terrien, R. C., Sigurdsson, S., Ramsey, L. W., Schneider, D. P., & Fleming, S. W. (2012). THE SDSS-HET SURVEY OF KEPLER ECLIPSING BINARIES: SPECTROSCOPIC DYNAMICAL MASSES OF THE KEPLER-16 CIRCUMBINARY PLANET HOSTS. ASTROPHYSICAL JOURNAL LETTERS, 751(2).
• Mahadevan, S., Ramsey, L., Bender, C., Terrien, R., Wright, J. T., Halverson, S., Hearty, F., Nelson, M., Burton, A., Redman, S., Osterman, S., Diddams, S., Kasting, J., Endl, M., & Deshpande, R. (2012). The Habitable-Zone Planet Finder: A Stabilized Fiber-Fed NIR Spectrograph for the Hobby-Eberly Telescope. GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY IV, 8446.
• Osterman, S., Ycas, G. G., Diddams, S. A., Quinlan, F., Mahadevan, S., Ramsey, L., Bender, C. F., Terrien, R., Botzer, B., Sigurddson, S., & Redman, S. L. (2012). A near infrared frequency comb for Y plus J band astronomical spectroscopy. MODERN TECHNOLOGIES IN SPACE-AND GROUND-BASED TELESCOPES AND INSTRUMENTATION II, 8450.
• Redman, S. L., Ycas, G. G., Terrien, R., Mahadevan, S., Ramsey, L. W., Bender, C. F., Osterman, S. N., Diddams, S. A., Quinlan, F., Lawler, J. E., & Nave, G. (2012). A HIGH-RESOLUTION ATLAS OF URANIUM-NEON IN THE H BAND. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 199(1).
• Terrien, R. C., Fleming, S. W., Mahadevan, S., Deshpande, R., Feiden, G. A., Bender, C. F., & Ramsey, L. W. (2012). THE METALLICITY OF THE CM DRACONIS SYSTEM. ASTROPHYSICAL JOURNAL LETTERS, 760(1).
• Terrien, R. C., Mahadevan, S., Bender, C. F., Deshpande, R., Ramsey, L. W., & Bochanski, J. J. (2012). AN H-BAND SPECTROSCOPIC METALLICITY CALIBRATION FOR M DWARFS. ASTROPHYSICAL JOURNAL LETTERS, 747(2).
• Ycas, G. G., Quinlan, F., Diddams, S. A., Osterman, S., Mahadevan, S., Redman, S., Terrien, R., Ramsey, L., Bender, C. F., Botzer, B., & Sigurdsson, S. (2012). Demonstration of on-sky calibration of astronomical spectra using a 25 GHz near-IR laser frequency comb. OPTICS EXPRESS, 20(6), 6631-6643.
• van, E., Ciardi, D. R., von, B. K., Kane, S. R., Plavchan, P., Bender, C. F., Brown, T. M., Crepp, J. R., Fulton, B. J., Howard, A. W., Howell, S. B., Mahadevan, S., Marcy, G. W., Shporer, A., Szkody, P., Akeson, R. L., Beichman, C. A., Boden, A. F., Gelino, D. M., , Hoard, D. W., et al. (2012). THE PTF ORION PROJECT: A POSSIBLE PLANET TRANSITING A T-TAURI STAR. ASTROPHYSICAL JOURNAL, 755(1).
• Ramsey, L., Mahdevan, S., Redman, S., Bender, C., Roy, A., Zonak, S., Sigursdson, S., & Wolszczan, A. (2010). The Pathfinder Testbed: Exploring Techniques for Achieving Precision Radial Velocities in the Near-Infrared. GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY III, 7735.
• Bender, C. F., & Simon, M. (2008). THE DETECTION OF LOW-MASS COMPANIONS IN HYADES CLUSTER SPECTROSCOPIC BINARY STARS. ASTROPHYSICAL JOURNAL, 689(1), 416-429.
• Simon, M., Bender, C., & Prato, L. (2006). The Gl569 multiple system. ASTROPHYSICAL JOURNAL, 644(2), 1183-1192.
• Bender, C., Simon, M., Prato, L., Mazeh, T., & Zucker, S. (2005). An upper bound on the 1.6 micron flux ratio of the companion to rho Coronae Borealis. ASTRONOMICAL JOURNAL, 129(1), 402-408.
• Dietrich, M., Bender, C. F., Bergmann, D. J., Bills, T. E., Bochkarev, N. G., Burenkov, A., Gaskell, C. M., Gutzmer, D. D., Grove, R., Hiller, M. E., Huchra, J. P., Klimek, E. S., Lund, C., Merkulova, N., Pebley, S., Poulsen, M. A., Pronik, V. I., Sergeev, S. G., Sergeeva, E. A., , Shapovalova, A. I., et al. (2001). A spectroscopic and photometric study of short-timescale variability in NGC 5548. ASTRONOMY & ASTROPHYSICS, 371(1), 79-92.
• McCullough, P. R., Bender, C., Gaustad, J. E., Rosing, W., & Van, B. D. (2001). The 5 degrees diameter ionized halo of the planetary nebula Abell 36. ASTRONOMICAL JOURNAL, 121(3), 1578-1582.

Proceedings Publications

• Choi, S., Angel, R., Bender, C., Berkson, J., Bugueno, E., Chavez-Lopez, G., Dibelka, J., Didato, N., Ford, J., Foster, W., Garcia, N., Gilliam, K., Gray, P., Halverson, S., Huang, Y., Ketelsen, D., Kim, D., Monson, A., Oh, C., , Patrou, J., et al. (2024). The Large Fiber Array Spectroscopic Telescope: fiber feed fabrication and characterization. In Ground-Based and Airborne Instrumentation for Astronomy X 2024, 13096.
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  The Large Fiber Array Spectroscopic Telescope (LFAST) project seeks to construct large arrays of small, individual fiber-fed telescopes for very high resolution spectroscopy. We are currently developing a prototype of a 20× telescope to investigate the technical requirements for LFAST. For each unit telescope, the 0.76 m primary mirror operates at f/3.5, focusing light onto our fused silica fiber with an 18 µm core, which subtends 1.4” on the sky. This receiving fiber collects and transmits light to the entrance slit of the spectrograph. We are developing a reliable fiber fabrication recipe, including fiber-end termination and polishing, to ensure consistency, efficiency, and affordability in mass manufacturing of the thousands of fibers that the future LFAST arrays require. The 18 µm core size places our optical fiber in the “few-mode” regime, which is not widely used in astronomy. Since the properties of “few-mode” fibers are not yet well characterized, extensive testing is required to gain a comprehensive understanding of their behaviors, such as focal ratio degradation, throughput and modal scrambling. We are designing optical tests to study the optical properties of the LFAST custom fibers. In this paper, we present the fiber feed design and fabrication recipe of our prototype. We also outline our optical test procedures and report results on surface flatness of our fibers.
• Foster, W., Angel, R., Bender, C., Didato, N., Gilliam, K., Gray, P., Huang, Y., Ketelsen, D., Monson, A., Patrou, J., Sisco, M., & Wortley, R. (2024). The LFAST 0.76m primary mirrors: mass production, active control and on-sky performance. In Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI 2024, 13100.
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  The Large Fiber Array Spectroscopic Telescope (LFAST) pursues large collecting aperture at low cost. Arrays of 0.76m, f/3.5 mirrors will focus light into fibers that are combined at a high-resolution spectrograph. The mirror substrates are fabricated from 25.4mm thick Schott Borofloat® discs in a one week slump and polish process that leaves less than 80nm rms wavefront error in medium and high spatial frequency modes. Low-order figure errors are corrected with a perimeter ring of thermoelectric controllers that induce expansion or contraction with top-to-bottom thermal gradients. In operation, temperature variations from nighttime cooling cause time-varying aberration modes. Using feedback from a stellar wavefront sensor, these aberrations can be compensated to focus starlight energy into a 1.4 arcsec fiber.
• Kreider, M. K., Fredrick, C., Terrien, R., Mahadevan, S., Ninan, J. P., Bender, C. F., Mitchell, D., Rajagopal, J., Roy, A., Schwab, C., Wright, J. T., & Diddams, S. A. (2024). Understanding a Fabry-Pérot Etalon that Expands and Contracts at the Same Time. In 2024 Frontiers in Optics, FiO 2024.
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  We quantify the complicated chromatic drift of ∼ 5, 000 modes across ∼ 500 nm of bandwidth of Fabry-Pérot etalons used for radial velocity measurements at the 10-10 level. We trace the behavior to the dielectric mirrors.
• Kreider, M. K., Fredrick, C., Terrien, R., Mahadevan, S., Ninan, J. P., Bender, C. F., Mitchell, D., Rajagopal, J., Roy, A., Schwab, C., Wright, J. T., & Diddams, S. A. (2024). Understanding a Fabry-Pérot Etalon that Expands and Contracts at the Same Time. In 2024 Laser Science, LS 2024.
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  We quantify the complicated chromatic drift of ∼ 5,000 modes across ∼ 500 nm of bandwidth of Fabry-Pérot etalons used for radial velocity measurements at the 10-10 level. We trace the behavior to the dielectric mirrors.
• Monson, A., Berkson, J., Bender, C., Angel, R., Gray, P., Gilliam, K., Schwab, C., & Foster, W. (2024). LFAST- Large Fiber Array Spectroscopic Telescope: Prime Focus Corrector Optics. In Ground-Based and Airborne Telescopes X 2024, 13094.
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  The Large Fiber Array Spectroscopic Telescope (LFAST) is designed to be a cost-efficient way to provide a large collecting area for spectroscopy by duplicating large numbers of small (0.76m f/3.33) spherical mirror 'unit' telescopes. Each telescope is equipped with a prime focus corrector (PFC) feeding a guider and an optical fiber; and all the fiber optics will feed into a large spectrograph. The design of the PFC is driven by the need to minimize costs while achieving acceptable performance. We are currently constructing a prototype 20-unit system for testing in the second half of 2024. For this 20-unit system we have begun coordinating with industry about scaling for mass fabrication. In this paper we will present status updates from the performance of this early version of the prime focus corrector.
• Zariski, J., Kratter, K., Logsdon, S., Bender, C., Li, D., Schweiker, H., Rajagopal, J., McBride, B., & Hunting, E. (2024). Deep learning solutions to telescope pointing and guiding. In Software and Cyberinfrastructure for Astronomy VIII 2024, 13101.
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  The WIYN 3.5m Telescope at Kitt Peak National Observatory hosts a suite of optical and near-infrared instruments, including an extreme precision, optical spectrograph, NEID, built for exoplanet radial velocity studies. In order to achieve sub ms−1 precision, NEID has strict requirements on survey efficiency, stellar image positioning, and guiding performance, which have exceeded the native capabilities of the telescope’s original pointing and tracking system. In order to improve the operational efficiency of the telescope we have developed a novel telescope pointing system, built on a recurrent neural network, that does not rely on the usual pointing models (TPoint or other quasi-physical bases). We discuss the development of this system, how the intrinsic properties of the pointing problem inform our network design, and show preliminary results from our best models. We also discuss plans for the generalization of this framework, so that it can be applied at other sites.
• Angel, R., Bender, C., Berkson, J., Didato, N., Ford, J., Gray, P., Jannuzi, B., Ketelsen, D., Kim, D., Chavez Lopez, G., Monson, A., Oh, C. J., Patrou, J., Rademacher, M., Schwab, C., Sisco, M., Wortley, R., & Young, A. (2022). LFAST, the Large Fiber Array Spectroscopic Telescope. In Ground-Based and Airborne Telescopes IX 2022, 12182.
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  The LFAST concept is to use thousands of small telescopes combined by fibers for high resolution (R=150,000) spectroscopy, in a way that will realize large cost savings and lead to an affordable aperture as large as 20,000 m2. Such large aperture is needed, for example, to make a comprehensive search for biosignatures in the atmospheres of transiting exoplanets. Each unit telescope of 0.76 m aperture (0.43 m2) will focus the image of a single star onto a small (17 μm core) fiber, subtending 1.32 arcsec. Our telescope design calls for a spherical mirror, with a 4-lens assembly at prime focus that corrects not only for spherical aberration, but also for atmospheric dispersion down to 30° elevation, from 390 nm-1700 nm, and for rapid image motion caused by seeing or wind jitter. A method for rapid production of such mirrors has been tested, in which a disc of borosilicate float glass is slumped over a high-precision polished mandrel to an accuracy that greatly reduces subsequent optical finishing time. A method for active thermal control of mirror figure using Peltier devices will be incorporated. The projected cost of each unit telescope, when mass produced by the thousand, would then be approximately $8,000. The telescopes will be mounted in the open in groups of 20 located 12 m apart. The mirrors will be arrayed on either side of a central, pedestal-mounted alt-az drive using commercial worm gear bearings. Protection against rain and dust will be provided by automated covers above and below the mirrors, and by pointing the mirrors down (-20° elevation). The first LFAST array, some 150 m in diameter, will comprise 132 mounts carrying a total of 2,640 mirrors and having 1,200 m2 in collecting area. The light from all the fibers is combined at the central spectrographs, with little increase in etendue, by a 5 x 528 array of adjacent hexagonal lenses. A telecentric lens is used to reimage the lens array at the entrance slits of two echelle spectrographs. Together, these two cover simultaneously the full 390 nm-1700 nm spectral range of the star being observed. The targeted cost for the installed LFAST telescope and fiber array is $60M.
• Bender, C. F., Angel, J. R., Berkson, J., Gray, P., Halverson, S., Kang, H., Kim, D., Monson, A., Oh, C. J., Rademacher, M., Schwab, C., Young, A., & Zaritsky, D. (2022). The Large Fiber Array Spectroscopic Telescope: Fiber Feed and Spectrometer Conceptual Design. In Ground-based and Airborne Instrumentation for Astronomy IX 2022, 12184.
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  The Large Fiber Array Spectroscopic Telescope, LFAST, will use optical fibers to combine light from thousands of small telescopes at centrally located high-resolution spectrometers. LFAST aims to use mass replication of small, self-contained telescope systems to provide ELT sized collecting area and spectroscopic capabilities at a drastically reduced price. However, fundamental constraints such as étendue, fiber modal noise, and focal-plane sampling that affect the size and complexity of spectrometers for single telescope ELTs also impact LFAST. We are carrying out a three year study to tackle these challenges. In this paper, we describe the conceptual designs for the fiber feed assemblies that carry light from the individual telescopes to a centralized location, and the high-resolution spectrometer that accepts this light.
• Berkson, J., Angel, R., Bender, C., Young, A., & Gray, P. (2022). The Large Fiber Array Spectroscopic Telescope: optical design of the unit telescope. In Ground-Based and Airborne Telescopes IX 2022, 12182.
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  The concept for the Large Fiber Array Spectroscopic Telescope (LFAST) (Angel et al, these proceedings) is to collect the light from a target object using thousands of individual, small, low-cost telescopes, and bring it via optical fibers to a high resolution (R=150,000) spectrograph. Each mirror has a prime focus corrector feeding a 17 micron fiber at f/3.5, subtending a 1.3 arcsec diameter on the sky. Each LFAST unit has 20 separate 30 inch telescopes carried by a single alt-az mount to provide collecting area equivalent to a 3.5 m traditional aperture. Each mirror has a 4-element corrector provides subarcsecond imaging over an 8 arcmin field. The field is reflected by a mirror puck (which contains the receiving fiber) through relay optics to a CMOS camera for rapid guiding and wavefront measurement. The corrector optical design incorporates elements of common crown and flint glass to obtain achromaticity over a broad wavelength range of 380 nm-1700 nm. Large, slow lateral translations of the final 4th element correlated with primary mirror tilt correct for atmospheric dispersion, and small, rapid lateral translations correct for image motion without significantly disrupting atmospheric dispersion correction. We have explored both aspherical and spherical primary mirror designs and have chosen spherical, based on impacts to unit telescope cost.
• Gupta, A. F., Bender, C. F., Ninan, J. P., Logsdon, S. E., Kanodia, S., Golub, E., Higuera, J., Klusmeyer, J., Halverson, S., Mahadevan, S., McElwain, M., Schwab, C., Stefansson, G., Robertson, P., Roy, A., Terrien, R., & Wright, J. (2022). Real-time exposure control and instrument operation with the NEID spectrograph GUI. In Software and Cyberinfrastructure for Astronomy VII 2022, 12189.
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  The NEID spectrograph on the WIYN 3.5-m telescope at Kitt Peak has completed its first full year of science operations and is reliably delivering sub-m/s precision radial velocity measurements. The NEID instrument control system uses the TIMS package (Bender et al. 2016), which is a client-server software system built around the twisted python software stack. During science observations, interaction with the NEID spectrograph is handled through a pair of graphical user interfaces (GUIs), written in PyQT, which wrap the underlying instrument control software and provide straightforward and reliable access to the instrument. Here, we detail the design of these interfaces and present an overview of their use for NEID operations. Observers can use the NEID GUIs to set the exposure time, signal-to-noise ratio (SNR) threshold, and other relevant parameters for observations, configure the calibration bench and observing mode, track or edit observation metadata, and monitor the current state of the instrument. These GUIs facilitate automatic spectrograph configuration and target ingestion from the nightly observing queue, which improves operational efficiency and consistency across epochs. By interfacing with the NEID exposure meter, the GUIs also allow observers to monitor the progress of individual exposures and trigger the shutter on user-defined SNR thresholds. In addition, inset plots of the instantaneous and cumulative exposure meter counts as each observation progresses allow for rapid diagnosis of changing observing conditions as well as guiding failure and other emergent issues.
• Logsdon, S. E., Wolf, M. J., Li, D., Rajagopal, J., Everett, M., Gong, Q., Golub, E., Higuera, J., Hunting, E., Jaehnig, K. P., Klusmeyer, J., Liang, M., Liu, W., McBride, W. R., McElwain, M. W., Percival, J. W., Ridgway, S., Schweiker, H., Smith, M. P., , Timmermann, E., et al. (2022). The NEID Port Adapter: On-Sky Performance. In Ground-based and Airborne Instrumentation for Astronomy IX 2022, 12184.
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  Here we detail the on-sky performance of the NEID Port Adapter one year into full science operation at the WIYN 3.5m Telescope at Kitt Peak National Observatory. NEID is an optical (380-930 nm), fiber-fed, precision Doppler radial velocity system developed as part of the NASA-NSF Exoplanet Observational Research (NN-EXPLORE) partnership. The NEID Port Adapter mounts directly to a bent-Cassegrain port on the WIYN Telescope and is responsible for precisely and stably placing target light on the science fibers. Precision acquisition and guiding is a critical component of such extreme precision spectrographs. In this work, we describe key on-sky performance results compared to initial design requirements and error budgets. While the current Port Adapter performance is more than sufficient for the NEID system to achieve and indeed exceed its formal instrumental radial velocity precision requirements, we continue to characterize and further optimize its performance and efficiency. This enables us to obtain better NEID datasets and in some cases, improve the performance of key terms in the error budget needed for future extreme precision spectrographs with the goal of observing ExoEarths, requiring ∼ 10 cm/s radial velocity measurements.
• Wilson, J. C., Davidson, J. W., Bender, C., Dow, P., Nelson, M., Walters, L., Irving, D., Farr, E., Tuttle, S., Nidever, D., De Lee, N., Holtzman, J., Majewski, S., Fox, J., Harkins, D., Green, L., Eriksen, J., Wagner, R., Derwent, M., , Jurgenson, C., et al. (2022). External upgrades to improve the RV precision of the APOGEE Spectrographs. In Ground-based and Airborne Instrumentation for Astronomy IX 2022, 12184.
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  Several external hardware upgrades have been developed for the APOGEE Spectrographs as part of the Sloan Digital Sky Survey-V (SDSS-V) to improve their radial velocity (RV) precision from a floor of 100-200 m/sec to approx. 30 m/sec. The upgrades include: (1) Back Pressure Regulator (BPR) systems to stabilize the internal instrument LN2 tank boil-off pressure, lessening induced movement of the APOGEE optical bench; (2) Fabry-Perot Interferometer (FPI) calibration sources to improve wavelength calibration; and (3), the use of octagonal core fiber segments in the fiber train to improve radial scrambling. We discuss the fabrication, commissioning, and early performance of these upgrades.
• Kanodia, S., Ninan, J. P., Monson, A. J., Mahadevan, S., Nitroy, C., Schwab, C., Halverson, S., Bender, C. F., Terrien, R., Hearty, F. R., Lubar, E., McElwain, M. W., Ramsey, L. W., Robertson, P. M., Roy, A., Stefansson, G., & Stevens, D. J. (2020, dec). "Ghosts of NEID's past". In Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, 11447.
• Schwab, C., Monson, A. J., Kanodia, S., Lubar, E., Lin, A. S., Nitroy, C., Halverson, S., Gong, Q., Terrien, R. C., Ninan, J. P., Bender, C., Blake, C., Hearty, F. R., Mahadevan, S., McElwain, M. W., Robertson, P. M., Roy, A., & Stefansson, G. (2020, dec). "The NEID spectrometer: fibre injection system design". In Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, 11447.

Presentations

• Bender, C. (2020, July). Why are RVs Important?. NASA Sagan Exoplanet Summer School. zoom: NASA Exoplanet Science Center.
• Bender, C. (2020, Nov). NEID: A next generation extreme precision RV spectrometer and the quest for Earth twins. JPL Colloquium. zoom: JPL.
• Bender, C. (2019, March). Automated data reduction pipelines for the HPF and NEID spectrometers. Extreme Precision in Radial Velocity IV. Grindelwald, Switzerland.
• Bender, C. (2019, September). The NEID Precision Radial Velocity Spectrometer: Laboratory AI&V and Commissioning Update. EPSC-DPS Joint Meeting 2019. Geneva, Switzerland.
• Bender, C. (2018, August). How to establish queues, formal and informal. Precision Radial Velocity Landscapes Meeting. Caltech: Keck Observatories.
• Bender, C. (2018, February). Binaries: What have we done in SDSS-III/IV with APOGEE. SDSSV Milky Way Mapper Meeting. Flatiron Institute, New York: Simons Institution.
• Bender, C. (2018, June). A decade of dynamical stellar astrophysics with RVs from APOGEE and SDSS (II, IV, and V). SDSSIV Collaboration Meeting. Seoul, South Korea.
• Bender, C. (2018, November). Exploring the Kepler Object of Interest Planet Sample with SDSS-APOGEE Spectroscopy. University of Texas Astronomy Seminar. Austin, TX: Dept of Astronomy, U Texas Austin.
• Bender, C. (2018, November). The Habitable Zone Planet Finder: Engineering & Comissioning Results and Data Analysis Workshop. HPF Users Workshop. UT Austin: Dept of Astronomy UT Austin.
• Bender, C. (2017, Dec). NEID: A next generation Doppler spectrometer for exoplanet discovery and followup at the WIYN telescope. American Geophysical Union 2017 Fall Meeting. New Orleans, LA: AGU.
• Bender, C. (2017, July). APOGEE - Kepler Object of Interest Goal Program Status. SDSSIV Collaboration Meeting. Santiago, Chile: SDSS.
• Bender, C. (2017, Sept). The Search for Earth-Twins with a New Generation of Doppler Spectrometers. Steward Observatory Colloquium. Tucson, AZ: Steward Observatory.