G. Grant Williams

Interests

Research

Supernovae, Instrumentation, Spectropolarimetry

Courses

No activities entered.

Scholarly Contributions

Journals/Publications

• Hiramatsu, D., Howell, D. A., Van, D., Goldberg, J. A., Maeda, K., Moriya, T. J., Tominaga, N., Nomoto, K., Hosseinzadeh, G., Arcavi, I., McCully, C., Burke, J., Bostroem, K. A., Valenti, S., Dong, Y., Brown, P. J., Andrews, J. E., Bilinski, C., Williams, G. G., , Smith, P. S., et al. (2021). "The electron-capture origin of supernova 2018zd". Nature Astronomy, 5, 903-910.
• Leonard, D. C., Dessart, L., Hillier, D. J., Pignata, G., Williams, G. G., Hoffman, J. L., Milne, P., Smith, N., Smith, P. S., & Khandrika, H. G. (2021). "A High-velocity Scatterer Revealed in the Thinning Ejecta of a Type II Supernova". apjl, 921(2), L35.
• Bilinski, C., Smith, N., Williams, G. G., Smith, P., Andrews, J., Clubb, K. I., Zheng, W., Filippenko, A. V., Fox, O. D., Hosseinzadeh, G., Howell, D. A., Kelly, P. L., Milne, P., Sand, D., Hoffman, J. L., Leonard, D. C., Cargill, S., Casper, C., Halevy, G., , Kim, H., et al. (2020). SN 2014ab: an aspherical Type IIn supernova with low polarization. \mnras, 498(3), 3835-3851.
• , K. A., , S. V., , D. J., , J. E., , S. D., , L. G., , D. P., , R. C., , N. S., , S. Y., , G. C., , I. A., , E. B., , P. J., , J. B., , R. C., , D. H., , Y. D., , E. E., , , S. E., et al. (2019). Discovery and Rapid Follow-up Observations of the Unusual Type II SN 2018ivc in NGC 1068.
  More info

  We present the discovery and high-cadence follow-up observations of SN2018ivc, an unusual Type II supernova that exploded in NGC 1068 (D = 10.1 Mpc).The light curve of SN 2018ivc declines piecewise-linearly, changing slopefrequently, with four clear slope changes in the first 40 days of evolution.This rapidly changing light curve indicates that interaction between thecircumstellar material and ejecta plays a significant role in the evolution.Circumstellar interaction is further supported by a strong X-ray detection. Thespectra are rapidly evolving and dominated by hydrogen, helium, and calciumemission lines. We identify a rare high-velocity emission-line featureblueshifted at ~7800 km/s (in Ha, Hb, Pb, Pg, HeI, CaII), which is visible fromday 18 until at least day 78 and could be evidence of an asymmetric progenitoror explosion. From the overall similarity between SN 2018ivc and SN 1996al, theHa equivalent width of its parent HII region, and constraints frompre-explosion archival Hubble Space Telescope images, we find that SN 2018ivcmay have had a high-mass progenitor (with initial mass > 25 Msun). SN 2018ivcdemonstrates the importance of the early discovery and rapid follow-upobservations of nearby supernovae to study the physics and progenitors of thesecosmic explosions.[Journal_ref: ]
• Chornock, R., Cowperthwaite, P. S., Margutti, R., Milisavljevic, D., {Alexand, e., Andreoni, I., Arcavi, I., Baldeschi, A., Barnes, J., Bellm, E., Beniamini, P., Berger, E., Berry, C. P., Bianco, F., Blanchard, P., Bloom, J. S., Burke-Spolaor, S., Burns, E., Carbone, D., , Cenko, S. B., et al. (2019). Multi-Messenger Astronomy with Extremely Large Telescopes. baas, 51(3), 237.
• Graham, M., Milisavljevic, D., Rest, A., Wheeler, J. C., Chornock, R., Margutti, R., Rho, J., Lee, C., Yoon, S., Kilpatrick, C. D., Narayan, G., Smith, N., Williams, G. G., Sravan, N., Cowperthwaite, P., Coppejans, D., Terreran, G., Baldeschi, A., Golkhou, V. Z., & Starrfield, S. (2019). Discovery Frontiers of Explosive Transients: An ELT and LSST Perspective. baas, 51(3), 339.
• Lundquist, M., Paterson, K., Fong, W., Sand, D., Andrews, J., Shivaei, I., Daly, P., Valenti, S., Yang, S., Christensen, E., Gibbs, A., Shelly, F., Wyatt, S., Eskandari, O., Kuhn, O., Amaro, R., Arcavi, I., Behroozi, P., Butler, N., , Chomiuk, L., et al. (2019). Searches after Gravitational Waves Using ARizona Observatories (SAGUARO): System Overview and First Results from Advanced LIGO/Virgotextquoterights Third Observing Run. apjl, 881(2), L26.
• Rho, J., Milisavljevic, D., Sarangi, A., Margutti, R., Chornock, R., Rest, A., Graham, M., Wheeler, J. C., DePoy, D., Williams, G., Street, R., Skidmore, W., Haojing, Y., Bloom, J., Starrfield, S., Lee, C., Cowperthwaite, P. S., Stringfellow, G. S., Coppejans, D., , Terreran, G., et al. (2019). Are Supernovae the Dust Producer in the Early Universe?. baas, 51(3), 351.
• Bilinski, C., Smith, N., Williams, G., Smith, P., Zheng, W., Graham, M., Mauerhan, J., Andrews, J., Filippenko, A., Akerlof, C., Chatzopoulos, E., Hoffman, J., Huk, L., Leonard, D., Marion, G., Milne, P., Quimby, R., Silverman, J., Vink{'o}, J., , Wheeler, J., et al. (2018). "SN2012ab: a peculiar Type IIn supernova with aspherical circumstellar material". mnras, 475, 1104-1120.
• Bullivant, C., Smith, N., Grant Williams, G., Mauerhan, J., Andrews, J., Fong, W., Bilinski, C., Kilpatrick, C., Milne, P., Fox, O., Bradley Cenko, S., Filippenko, A., Zheng, W., Kelly, P., & Clubb, K. (2018). "SN 2013fs and SN 2013fr: Exploring the circumstellar-material diversity in Type II supernovae". mnras.
• Milne, P. A., Williams, G. G., Porter, A., Smith, P. S., Smith, N., Leising, M. D., Jannuzi, B. T., & Green, E. M. (2017). Multiepoch Spectropolarimetry of SN 2011fe. ASTROPHYSICAL JOURNAL, 835(1).
• Porter, A. L., Leising, M. D., Williams, G. G., Milne, P., Smith, P., Smith, N., Bilinski, C., Hoffman, J. L., Huk, L., & Leonard, D. C. (2016). ASYMMETRIES IN SN 2014J NEAR MAXIMUM LIGHT REVEALED THROUGH SPECTROPOLARIMETRY. ASTROPHYSICAL JOURNAL, 828(1).
• Williams, G. G., Ortiz, R., Goble, W., & Gibson, J. D. (2016). The 6.5-m MMT Telescope: Status and Plans for the Future. GROUND-BASED AND AIRBORNE TELESCOPES VI, 9906.
• Bilinski, C., Smith, N., Li, W., Williams, G. G., Zheng, W., & Filippenko, A. V. (2015). Constraints on Type IIn supernova progenitor outbursts from the Lick Observatory Supernova Search. Monthly Notices of the Royal Astronomical Society, 450, 246-265. doi:10.1093/mnras/stv566
• Del Castillo, E. A., Corbally, C., Falco, E. E., Green, R. F., Hall, J. C., & Williams, G. G. (2015). Dark Sky Collaborators: Arizona (AZ) Observatories, Communities, and Businesses. Highlights of Astronomy, 16, 747-747. doi:10.1017/S1743921314013295
• Mauerhan, J. C., Williams, G. G., Leonard, D. C., Smith, P. S., Filippenko, A. V., Smith, N., Hoffman, J. L., Huk, L., Clubb, K. I., Silverman, J. M., Cenko, S. B., Milne, P., Gal-Yam, A., & Ben-Ami, S. (2015). Spectropolarimetry of SN 2011dh in M51: geometric insights on a Type IIb supernova progenitor and explosion. Monthly Notices of the Royal Astronomical Society, 453, 4467-4484. doi:10.1093/mnras/stv1944
• Smith, N., Mauerhan, J. C., Cenko, S. B., Kasliwal, M. M., Silverman, J. M., Filippenko, A. V., Gal-Yam, A., Clubb, K. I., Graham, M. L., Leonard, D. C., Horst, J. C., Williams, G. G., Andrews, J. E., Kulkarni, S. R., Nugent, P., Sullivan, M., Maguire, K., Xu, D., & Ben-Ami, S. (2015). PTF11iqb: cool supergiant mass-loss that bridges the gap between Type IIn and normal supernovae. Monthly Notices of the Royal Astronomical Society, 449, 1876-1896. doi:10.1093/mnras/stv354
• Williams, G. G. (2014). Multi-epoch spectropolarimetry of SN 2009ip: direct evidence for aspherical circumstellar material. Monthly Notices of the Royal Astronomical Society, 442(Issue 2), 1166-1180.
• Henze, M., Pietsch, W., Haberl, F., Della Valle, M., Riffeser, A., Sala, G., Hatzidimitriou, D., Hofmann, F., Hartmann, D. H., Koppenhoefer, J., Seitz, S., Williams, G. G., Hornoch, K., Itagaki, K., Kabashima, F., Nishiyama, K., Xing, G., Lee, C. H., Magnier, E., & Chambers, K. (2013). Supersoft X-rays reveal a classical nova in the M 31 globular cluster Bol 126. Astronomy & Astrophysics, 549, A120. doi:10.1051/0004-6361/201220196
• Virgili, F. J., Mundell, C. G., Pal'Shin, V., Guidorzi, C., Margutti, R., Melandri, A., Harrison, R., Kobayashi, S., Chornock, R., Henden, A., Updike, A. C., Cenko, S. B., Tanvir, N. R., Steele, I. A., Cucchiara, A., Gomboc, A., Levan, A., Cano, Z., Mottram, C. J., , Clay, N. R., et al. (2013). GRB 091024A and the nature of ultra-long gamma-ray bursts. Astrophysical Journal, 778(1).
  More info

  Abstract: We present a broadband study of gamma-ray burst (GRB) 091024A within the context of other ultra-long-duration GRBs. An unusually long burst detected by Konus-Wind (KW), Swift, and Fermi, GRB 091024A has prompt emission episodes covering ∼1300 s, accompanied by bright and highly structured optical emission captured by various rapid-response facilities, including the 2 m autonomous robotic Faulkes North and Liverpool Telescopes, KAIT, S-LOTIS, and the Sonoita Research Observatory. We also observed the burst with 8 and 10 m class telescopes and determine the redshift to be z = 1.0924 ± 0.0004. We find no correlation between the optical and γ-ray peaks and interpret the optical light curve as being of external origin, caused by the reverse and forward shock of a highly magnetized jet (RB ≈ 100-200). Low-level emission is detected throughout the near-background quiescent period between the first two emission episodes of the KW data, suggesting continued central-engine activity; we discuss the implications of this ongoing emission and its impact on the afterglow evolution and predictions. We summarize the varied sample of historical GRBs with exceptionally long durations in gamma-rays (≳1000 s) and discuss the likelihood of these events being from a separate population; we suggest ultra-long GRBs represent the tail of the duration distribution of the long GRB population. © 2013. The American Astronomical Society. All rights reserved..
• Gibson, J. D., Williams, G. G., & Trebisky, T. (2012). Seeing trends from Deployable Shack-Hartmann wavefront sensors, MMT Observatory, Arizona, USA. Proceedings of SPIE - The International Society for Optical Engineering, 8444.
  More info

  Abstract: Deployable Shack-Hartmann wavefront sensors (WFS) for the f/5 and f/9 secondary configurations have been used at the 6.5-meter MMT Observatory (MMTO) since 2003. Probe mirrors for these WFS's are moved into the optical path of the telescope between scientific observations multiple times each night. Results from the wavefront measurements are then used to bend the primary mirror (M1) and to reposition the secondary mirror (M2) to correct for wavefront errors. In addition to measuring the optical wavefront error, the Shack-Hartmann data are used to determine the delivered seeing using the measured spot sizes. This study attempts to analyze the more than 75,000 WFS measurements and associated seeing values obtained at the MMTO since 2003. The overall WFS data reduction and analysis procedure is discussed. This data analysis includes: 1) finding the spots in each image, 2) centroiding the spots, 3) measuring a point-spread function, 4) determining an average spot width and a derived seeing value, and 5) computing the best-fit Zernike polynomial coefficients. Wavefront slopes are calculated from spot displacements and wavefront aberrations are fit with a 19-term Zernike polynomial. As part of this study, the WFS-derived seeing values are correlated with other observing parameters, such as mirror-air temperature contrasts. Finally, seasonal climate and local weather (e.g., prevailing wind direction) effects on astronomical seeing are evaluated. © 2012 SPIE.
• Porter, D., Gibson, J. D., & Williams, G. G. (2012). An integrated scheduling and program management system. Proceedings of SPIE - The International Society for Optical Engineering, 8448.
  More info

  Abstract: An integrated scheduling and program management system is being developed for the MMT Observatory (MMTO), Arizona, USA. A systems engineering approach is used to combine existing and new relational databases, spreadsheets, file storage systems, and web-based user interfaces into a single unified system. An overview of software design, data management, user interfaces, and techniques for performance assessment is presented. Goals of this system include streamlined data management and an optimized user experience. The MMTO has over a dozen different telescope configurations, including three secondary mirrors and a wide range of observing instruments. Scheduling is complex for the varying telescope configurations, limited available observing time, and appropriate astronomic conditions (e.g., lunar phase) for each science project. Scheduled telescope configurations can be used to perform safety checks of actual configuration during telescope operations. Programmatic information is automatically input into nightly telescope operator (TO) logs by the system. The TO's provide additional information into the system on telescope usage, observing conditions (e.g., weather conditions), and observatory closure (e.g., from instrument malfunction or inclement weather). All of this information is synthesized to assess telescope and observatory performance. Web interfaces to the system can be used by observers to submit information, such as travel plans, instrumentation requirements, and observing catalogs. A service request (SR) (i.e., trouble report) system has also been developed for tracking operational issues. The specific needs of the MMTO have been met through in-house software development of this integrated scheduling and program management system. © 2012 SPIE.
• Williams, G. G., Smith, P., Schmidt, G., & Dessart, L. (2012). The identification and investigation of gamma-ray burst progenitors: A spectropolarimetric survey of Wolf-Rayet stars in the milky way and M33. AIP Conference Proceedings, 1429, 183-193.
  More info

  Abstract: There is now irrefutable observational evidence that long duration gamma-ray bursts (GRBs) are linked to Type Ic core collapse supernovae (SNe Ic). This association has resulted in a wide acceptance of the collapsar model to explain the origin of GRBs. The collapsar model requires three physical characteristics: 1.) a massive core, 2.) a hydrogen free stripped envelope, and 3.) rapid rotation. These three characteristics are present in a rapidly rotating Wolf-Rayet (WR) star. © 2012 American Institute of Physics.
• Perley, D. A., Morgan, A. N., Updike, A., Yuan, F., Akerlof, C. W., Miller, A. A., Bloom, J. S., Cenko, S. B., Li, W., Filippenko, A. V., Prochaska, J. X., Kann, D. A., Tanvir, N. R., Levan, A. J., Butler, N. R., Christian, P., Hartmann, D. H., Milne, P., Rykoff, E. S., , Rujopakarn, W., et al. (2011). Monster in the dark: The ultraluminous GRB 080607 and its dusty environment. Astronomical Journal, 141(2).
  More info

  Abstract: We present early-time optical through infrared photometry of the bright Swift gamma-ray burst (GRB) 080607, starting only 6 s following the initial trigger in the rest frame. Complemented by our previously published spectroscopy, this high-quality photometric data set allows us to solve for the extinction properties of the redshift 3.036 sightline, giving perhaps the most detailed information to date on the ultraviolet continuum absorption properties of any sightline outside our Local Group. The extinction properties are not adequately modeled by anyordinary extinction template (including the average Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud curves), partially because the 2175 Å feature (while present) is weaker by about a factor of two than when seen under similar circumstances locally. However, the spectral energy distribution is exquisitely fitted by the more general Fitzpatrick & Massa parameterization of Local-Group extinction, putting it in the same family as some peculiar Milky Way extinction curves. After correcting for this (considerable, AV = 3.3 ± 0.4 mag) extinction, GRB 080607 is revealed to have been among the most optically luminous events ever observed, comparable to the naked-eye burst GRB 080319B. Its early peak time (t rest < 6 s) indicates a high initial Lorentz factor (F > 600), while the extreme luminosity may be explained in part by a large circumburst density. Only because of its early high luminosity could the afterglow of GRB 080607 be studied in such detail in spite of the large attenuation and great distance, making this burst an excellent prototype for the understanding of other highly obscured extragalactic objects, and of the class of "dark" GRBs in particular. © 2011. The American Astronomical Society.
• Gibson, J. D., Williams, G. G., Callahan, S., Comisso, B., Ortiz, R., & Williams, J. T. (2010). Advances in thermal control and performance of the MMT M1 mirror. Proceedings of SPIE - The International Society for Optical Engineering, 7733(PART 1).
  More info

  Abstract: Strategies for thermal control of the 6.5-meter diameter borosilicate honeycomb primary (M1) mirror at the MMT Observatory have included: 1) direct control of ventilation system chiller setpoints by the telescope operator, 2) semi-automated control of chiller setpoints, using a fixed offset from the ambient temperature, and 3) most recently, an automated temperature controller for conditioned air. Details of this automated controller, including the integration of multiple chillers, heat exchangers, and temperature/dew point sensors, are presented here. Constraints and sanity checks for thermal control are also discussed, including: 1) mirror and hardware safety, 2) aluminum coating preservation, and 3) optimization of M1 thermal conditions for science acquisition by minimizing both air-to-glass temperature differences, which cause mirror seeing, and internal glass temperature gradients, which cause wavefront errors. Consideration is given to special operating conditions, such as high dew and frost points. Precise temperature control of conditioned ventilation air as delivered to the M1 mirror cell is also discussed. The performance of the new automated controller is assessed and compared to previous control strategies. Finally, suggestions are made for further refinement of the M1 mirror thermal control system and related algorithms. © 2010 SPIE.
• Hastie, M., & Williams, G. G. (2010). Instrumentation suite at the MMT Observatory. Proceedings of SPIE - The International Society for Optical Engineering, 7735(PART 1).
  More info

  Abstract: In the ten years since the converted 6.5m MMT was dedicated the observatory has built up an impressive suite of instrumentation to compliment the three interchangeable secondary mirrors. This review paper presents an up-to-date perspective on all the capabilities of our full range of instrumentation, highlighting newly commissioned instruments (the MMT and Magellan InfraRed Spectrograph (MMIRS), an infrared spectrograph) and new modes or upgrades for established instruments (such as; Red Channel, the MMT's workhorse spectrograph, Hectochelle, an optical fiber-fed, multi-object spectrograph and the AO instruments CLIO, a 5 micron camera and BLINC, a mid-infrared camera). The MMT's pioneering adaptive secondary mirror can be used with both natural guide stars (NGS) or with a Rayleigh laser guide star (LGS) system. The LGS has recently demonstrated wide-field partial compensation with ground layer adaptive optics and here we present progress to date. Finally, we report on the start of a project to investigate how the instrument suite has contributed to the science productivity the MMT over the last 10 years. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Perley, D. A., Bloom, J. S., Klein, C. R., Covino, S., Minezaki, T., Woźniak, P., Vestrand, W. T., Williams, G. G., Milne, P., Butler, N. R., Updike, A. C., Krühler, T., Afonso, P., Antonelli, A., Cowie, L., Ferrero, P., Greiner, J., Hartmann, D. H., Kakazu, Y., , Yoldaş, A. K., et al. (2010). Evidence for supernova-synthesized dust from the rising afterglow of GRB 071025 at z ∼ 5. Monthly Notices of the Royal Astronomical Society, 406(4), 2473-2487.
  More info

  Abstract: We present observations and analysis of the broad-band afterglow of Swift GRB 071025. Using optical and infrared (RIYJHK) photometry, we derive a photometric redshift of 4.4 < z < 5.2; at this redshift our simultaneous multicolour observations begin at ∼30 s after the gamma-ray burst trigger in the host frame, during the initial rising phase of the afterglow. We associate the light-curve peak at ∼580 s in the observer frame with the formation of the forward shock, giving an estimate of the initial Lorentz factor Γ0 ∼ 200. The red spectral energy distribution (even in regions not affected by the Lyman α break) provides secure evidence of a large dust column. However, the inferred extinction curve shows a prominent flat component between 2000 and 3000 Å in the rest frame, inconsistent with any locally observed template but well fitted by models of dust formed by supernovae. Time-dependent fits to the extinction profile reveal no evidence of dust destruction and limit the decrease in the extinction column to ΔA3000 < 0.54 mag after t = 50 s in the rest frame. Together with studies of high-z quasars, our observations suggest a transition in dust properties in the early Universe, possibly associated with a transition between supernova-dominated and asymptotic giant branch-dominated modes of dust production. © 2010 The Authors. Journal compilation © 2010 RAS.
• D'Arcangelo, F. D., Marscher, A. P., Jorstad, S. G., Smith, P. S., Larionov, V. M., Hagen-Thorn, V. A., Williams, G. G., Gear, W. K., Clemens, D. P., Sarcia, D., Grabau, A., Tollestrup, E. V., Buie, M. W., Taylor, B., & Dunham, E. (2009). Synchronous optical and radio polarization variability in the blazar OJ287. Astrophysical Journal Letters, 697(2), 985-995.
  More info

  Abstract: We explore the variability and cross-frequency correlation of the flux density and polarization of the blazar OJ287, using imaging at 43 GHz with the Very Long Baseline Array, as well as optical and near-infrared (near-IR) polarimetry. The polarization and flux density in both the optical waveband and the 43 GHz compact core increased by a small amount in late 2005, and increased significantly along with the near-IR polarization and flux density over the course of 10 days in early 2006. Furthermore, the values of the electric vector position angle (EVPA) at the three wavebands are similar. At 43 GHz, the EVPA of the blazar core is perpendicular to the flow of the jet, while the EVPAs of emerging superluminal knots are aligned parallel to the jet axis. The core polarization is that expected if shear aligns the magnetic field at the boundary between flows of disparate velocities within the jet. Using variations in flux density, percentage polarization, and EVPA, we model the inner jet as a spine-sheath system. The model jet contains a turbulent spine of half-width 12 and maximum Lorentz factor of 16.5, a turbulent sheath with Lorentz factor of 5, and a boundary region of sheared field between the spine and sheath. Transverse shocks propagating along the fast, turbulent spine can explain the superluminal knots. The observed flux density and polarization variations are then compatible with changes in the direction of the inner jet caused by a temporary change in the position of the core if the spine contains wiggles owing to an instability. In addition, we can explain a stable offset of optical and near-IR percentage polarization by a steepening of spectral index with frequency, as supported by the data. © 2009. The American Astronomical Society.
• Henze, M., Pietsch, W., Haberl, F., Sala, G., Quimby, R., Hernanz, M., Valle, M. D., Milne, P., Williams, G. G., Burwitz, V., Greiner, J., Stiele, H., Hartmann, D. H., Kong, A. K., & Hornoch, K. (2009). The first two transient supersoft X-ray sources in M 31 globular clusters and the connection to classical novae. Astronomy and Astrophysics, 500(2), 769-779.
  More info

  Abstract: Context. Classical novae (CNe) have been found to represent the major class of supersoft X-ray sources (SSSs) in our neighbour galaxy M 31. Aims. We determine the properties and evolution of the two first SSSs ever discovered in the M 31 globular cluster (GC) system. Methods. We have used XMM-Newton, Chandra and. Swift observations of the centre region of M 31 to discover both SSSs and to determine their X-ray light curves and spectra. We performed detailed analysis of XMM-Newton EPIC PN spectra of the source in Bol 111 (SS1) using blackbody and NLTE white dwarf (WD) atmosphere models. For the SSS in Bol 194 (SS2) we used optical monitoring data to search for an optical counterpart. Results. Both GC X-ray sources were classified, as SSS. We identify SS1 with the CN M31N 2007-06b recently discovered in the M 31 GC Bol 111. For SS2 we did not find evidence for a recent nova outburst and can only provide useful constraints on the time of the outburst of a hypothetical nova. Conclusions. The only known CN in a M 31 GC can be identified with the first SSS found in a M 31 GC. We discuss the impact of our observations on the nova rate for the M 31 GC system. © ESO 2009.
• Henze, M., Pietsch, W., Sala, G., Valle, M. D., Hernanz, M., Greiner, J., Burwitz, V., Freyberg, M. J., Haberl, F., Hartmann, D. H., Milne, P., & Williams, G. G. (2009). The very short supersoft X-ray state of the classical nova M31N 2007-11a. Astronomy and Astrophysics, 498(2), L13-L16.
  More info

  Abstract: Context. Short supersoft X-ray source (SSS) states (durations ≤100 days) of classical novae (CNe) indicate massive white dwarfs that are candidate progenitors of supernovae type Ia.Aims. We carry out a dedicated optical and X-ray monitoring program of CNe in the bulge of M 31.Methods. We discovered M31N 2007-11a and determined its optical and X-ray light curve. We used the robotic Super-LOTIS telescope to obtain the optical data and XMM-Newton and Chandra observations to discover an X-ray counterpart to that nova.Results. Nova M31N 2007-11a is a very fast CN, exhibiting a very short SSS state with an appearance time of 6-16 days after outburst and a turn-off time of 45-58 days after outburst.Conclusions. The optical and X-ray light curves of M31N 2007-11a suggest a binary containing a white dwarf with MWD > 1.0 M ⊙. © 2009 ESO.
• Modjaz, M., Li, W., Butler, N., Chornock, R., Perley, D., Blondin, S., Bloom, J. S., Filippenko, A. V., Kirshner, R. P., Kocevski, D., Poznanski, D., Hicken, M., Foley, R. J., Stringfellow, G. S., Berlind, P., Barrado, D., Blake, C. H., Bouy, H., Brown, W. R., , Challis, P., et al. (2009). From shock breakout to peak and beyond: Extensive panchromatic observations of the type Ib supernova 2008D associated with swift x-ray transient 080109. Astrophysical Journal Letters, 702(1), 226-248.
  More info

  Abstract: We present extensive early photometric (ultraviolet through near-infrared) and spectroscopic (optical and near-infrared) data on supernova (SN) 2008D as well as X-ray data analysis on the associated Swift X-ray transient (XRT) 080109. Our data span a time range of 5 hr before the detection of the X-ray transient to 150days after its detection, and a detailed analysis allowed us to derive constraints on the nature of the SN and its progenitor; throughout we draw comparisons with results presented in the literature and find several key aspects that differ. We show that the X-ray spectrum of XRT 080109 can be fit equally well by an absorbed power law or a superposition of about equal parts of both power law and blackbody. Our data first established that SN 2008D is a spectroscopically normal SN Ib (i.e., showing conspicuous He lines) and showed that SN 2008D had a relatively long rise time of 18days and a modest optical peak luminosity. The early-time light curves of the SN are dominated by a cooling stellar envelope (for Δt0.1-4days, most pronounced in the blue bands) followed by 56Ni decay. We construct a reliable measurement of the bolometric output for this stripped-envelope SN, and, combined with estimates of E K and M ej from the literature, estimate the stellar radius R ⊙ of its probable Wolf-Rayet progenitor. According to the model of Waxman etal. and Chevalier & Fransson, we derive R W07⊙ = 1.2 0.7R ⊙ and R CF08⊙ = 12 7 R ⊙, respectively; the latter being more in line with typical WN stars. Spectra obtained at three and four months after maximum light show double-peaked oxygen lines that we associate with departures from spherical symmetry, as has been suggested for the inner ejecta of a number of SN Ib cores. © 2009. The American Astronomical Society. All rights reserved.
• Callahan, S., Caldwell, N., Williams, G. G., Chute, C., & Pickering, T. E. (2008). The MMT f/5 optical baffles. Proceedings of SPIE - The International Society for Optical Engineering, 7018.
  More info

  Abstract: The 6.5m MMT telescope currently has three focal configurations. The f/5 optical configuration has a system of optical baffles to prevent stray light from entering the focal plane. The system consists of a cone baffle supported on the secondary (M2) structure and set of concentric rings suspended between the secondary and the primary (M1). This paper reviews the optical configurations, mechanical design, alignment, installation, and measured performance of the system.
• Marscher, A. P., Jorstad, S. G., D'Arcangelo, F. D., Smith, P. S., Williams, G. G., Larionov, V. M., Haruki, O. h., Olmstead, A. R., Aller, M. F., Aller, H. D., McHardy, I. M., Lähteenmäki, A., Tornikoski, M., Valtaoja, E., Hagen-Thorn, V. A., Kopatskaya, E. N., Gear, W. K., Tosti, G., Kurtanidze, O., , Nikolashvili, M., et al. (2008). The inner jet of an active galactic nucleus as revealed by a radio-to-γ-ray outburst. Nature, 452(7190), 966-969.
  More info

  PMID: 18432239;Abstract: Blazars are the most extreme active galactic nuclei. They possess oppositely directed plasma jets emanating at near light speeds from accreting supermassive black holes. According to theoretical models, such jets are propelled by magnetic fields twisted by differential rotation of the black hole's accretion disk or inertial-frame-dragging ergosphere. The flow velocity increases outward along the jet in an acceleration and collimation zone containing a coiled magnetic field. Detailed observations of outbursts of electromagnetic radiation, for which blazars are famous, can potentially probe the zone. It has hitherto not been possible to either specify the location of the outbursts or verify the general picture of jet formation. Here we report sequences of high-resolution radio images and optical polarization measurements of the blazar BL Lacertae. The data reveal a bright feature in the jet that causes a double flare of radiation from optical frequencies to TeV γ-ray energies, as well as a delayed outburst at radio wavelengths. We conclude that the event starts in a region with a helical magnetic field that we identify with the acceleration and collimation zone predicted by the theories. The feature brightens again when it crosses a standing shock wave corresponding to the bright 'core' seen on the images. ©2008 Nature Publishing Group.
• Updike, A. C., Haislip, J. B., Nysewander, M. C., Fruchter, A. S., Kann, D. A., Klose, S., Milne, P. A., Williams, G. G., Zheng, W., Hergenrother, C. W., Prochaska, J. X., Halpern, J. P., Mirabal, N., Thorstensen, J. R., J., A., L., R., Racusin, J. L., Burrows, D. N., Kuin, N. P., , W., P., et al. (2008). The rapidly flaring afterglow of the very bright and energetic GRB 070125. Astrophysical Journal, 685(1), 361-375.
  More info

  Abstract: We report on multiwavelength observations, ranging from X-ray to radio wave bands, of the IPN-localized gamma-ray burst GRB 070125. Spectroscopic observations reveal the presence of absorption lines due to O I, Si II, and C IV, implying a likely redshift of z = 1.547. The well-sampled light curves, in particular from 0.5 to 4 days after the burst, suggest ajet break at 3.7 days, corresponding to a jet opening angle of ∼7.0°, and implying an intrinsic GRB energy in the 1-10,000 keV band of around Eγ = (6.3-6.9) × 1051 ergs (based on the fluences measured by the gamma-ray detectors of the IPN). GRB 070125 is among the brightest afterglows observed to date. The SED implies a host extinction of AV < 0.9 mag. Two rebrightening episodes are observed, one with excellent time coverage, snowing an increase in flux of 56% in ∼8000 s. The evolution of the afterglow light curve is achromatic at all times. Late-time observations of the afterglow do not show evidence for emission from an underlying host galaxy or supernova. Any host galaxy would be subluminous, consistent with current GRB host galaxy samples. Evidence for strong Mg ii absorption features is not found, which is perhaps surprising in view of the relatively high redshift of this burst and the high likelihood for such features along GRB-selected lines of sight. © 2008. The American Astronomical Society. All rights reserved.
• Updike, A. C., Hartmann, D. H., Milne, P. A., Williams, G. G., & Haislip, J. B. (2008). Rapid flaring in GRB 070125. AIP Conference Proceedings, 1000, 232-236.
  More info

  Abstract: GRB 070125 was one of the brightest afterglows observed to date. We report on the characteristics of this burst, and focus on a well-resolved re-brightening episode observed by the Bok telescope about one day after the trigger. We conclude that the flare is indicative of an energy injection episode, increasing the flux by 56%. © 2008 American Institute of Physics.
• Williams, G. G., Milne, P. A., Park, H. S., Barthelmy, S. D., Hartmann, D. H., Updike, A., & Hurley, K. (2008). The Robotic Super-LOTIS Telescope: Results & Future Plans. AIP Conference Proceedings, 1000, 535-538.
  More info

  Abstract: We provide an overview of the robotic Super-LOTIS (Livermore Optical Transient Imaging System) telescope and present results from gamma-ray burst (GRB) afterglow observations using Super-LOTIS and other Steward Observatory telescopes. The 0.6-m Super-LOTIS telescope is a fully robotic system dedicated to the measurement of prompt and early time optical emission from GRBs. The system began routine operations from its Steward Observatory site atop Kitt Peak in April 2000 and currently operates every clear night. The telescope is instrumented with an optical CCD camera and a four position filter wheel. It is capable of observing Swift Burst Alert Telescope (BAT) error boxes as early or earlier than the Swift UV/Optical Telescope (UVOT). Super-LOTIS complements the UVOT observations by providing early R-and I-band imaging. We also use the suite of Steward Observatory telescopes including the 1.6-m Kuiper, the 2.3-m Bok, the 6.5-m MMT, and the 8.4-m Large Binocular Telescope to perform follow-up optical and near infrared observations of GRB afterglows. These follow-up observations have traditionally required human intervention but we are currently working to automate the 1.6-m Kuiper telescope to minimize its response time. © 2008 American Institute of Physics.
• D'Arcangelo, F. D., Marscher, A. P., Jorstad, S. G., Smith, P. S., Larionov, V. M., Hagen-Thorn, V. A., Kopatskaya, E. N., Williams, G. G., & Gear, W. K. (2007). Rapid multiwaveband polarization variability in the quasar PKS 0420-014: Optical emission from the compact radio jet. Astrophysical Journal, 659(2 II), L107-L110.
  More info

  Abstract: An 11 day monitoring campaign in late 2005 reveals clear correlation in polarization between the optical emission and the region of the intensity peak (the "pseudocore") at the upstream end of the jet in 43 GHz VLBA (Very Long Baseline Array) images in the highly variable quasar PKS 0420-014. The electric-vector position angle (EVPA) of the pseudocore rotated by about 80° in four VLBA observations over a period of 9 days, matching the trend of the optical EVPA. In addition, the 43 GHz EVPAs agree well with the optical values when we correct the former for Faraday rotation. Fluctuations in the polarization at both wave bands are consistent with the variable emission arising from a standing conical shock wave that compresses magnetically turbulent plasma in the ambient jet. The volume of the variable component is the same at both wave bands, although only ∼20% of the total 43 GHz emission arises from this site. The remainder of the 43 GHz flux density must originate in a separate region with very low polarization. If 0420-014 is a typical case, the nonthermal optical emission from blazars originates primarily in and near the pseudocore rather than closer to the central engine where the flow collimates and accelerates. © 2007. The American Astronomical Society. All rights reserved.
• Smith, P. S., Williams, G. G., Schmidt, G. D., Diamond-Stanic, A. M., & Means, D. L. (2007). Highly polarized optically selected BL Lacertae objects. Astrophysical Journal, 663(1 I), 118-124.
  More info

  Abstract: Observations of candidate BL Lacertae objects spectroscopically selected from the Sloan Digital Sky Survey (SDSS) reveal a large fraction of objects with high polarizations (P > 3%). This result confirms that synchrotron radiation makes an important contribution to the observed optical continuum for most objects in the sample. The SDSS sample can be divided into separate categories, with objects of undetermined redshift generally having the highest optical polarization. Polarization as high as 23% and the lack of spectral features suggests that the synchrotron continuum completely dominates the spectra of these sources. The mean polarization levels observed for objects that have measured redshifts is much lower, with the maximum observed polarization for this group being ∼10%. The lower polarizations of these objects are reminiscent of the less spectacular polarization levels shown by BL Lac objects discovered in X-ray surveys. We find no SDSS BL Lac candidates at z ≳ 1 with P > 3%, which calls their classification as BL Lac objects into question. In addition, the existence of radio-quiet BL Lac objects is not verified, since none of the 10 potentially radio-weak BL Lac candidates observed are highly polarized. Regardless of whether the high-redshift and radio-weak objects are included in this optical sample, the overall levels of polarization observed are intermediate between those seen for X-ray- and radio-selected BL Lac objects. © 2007. The American Astronomical Society. All rights reserved.
• Haislip, J. B., Nysewander, M. C., Reichart, D. E., Levan, A., Tanvir, N., Cenko, S. B., Fox, D. B., Price, P. A., Castro-Tirado, A., Gorosabel, J., Evans, C. R., Figueredo, E., MacLeod, C. L., Kirschbrown, J. R., Jelinek, M., Guziy, S., De, A., Cypriano, E. S., LaCluyze, A., , Graham, J., et al. (2006). A photometric redshift of z = 6.39 ± 0.12 for GRB 050904. Nature, 440(7081), 181-183.
  More info

  PMID: 16525465;Abstract: Gamma-ray bursts (GRBs) and their afterglows are the most brilliant transient events in the Universe. Both the bursts themselves and their afterglows have been predicted to be visible out to redshifts of z ≈ 20, and therefore to be powerful probes of the early Universe1,2. The burst GRB 000131, at z = 4.50, was hitherto the most distant such event identified3. Here we report the discovery of the bright near-infrared afterglow of GRB 050904 (ref. 4). From our measurements of the near-infrared afterglow, and our failure to detect the optical afterglow, we determine the photometric redshift of the burst to be z = 6.39-0.12+0.11 (refs 5-7). Subsequently, it was measured8 spectroscopically to be z = 6.29 ± 0.01, in agreement with our photometric estimate. These results demonstrate that GRBs can be used to trace the star formation, metallicity, and reionization histories of the early Universe. © 2006 Nature Publishing Group.
• Lair, J. C., Leising, M. D., Milne, P. A., & Williams, G. G. (2006). Late light curves of normal Type Ia supernovae. Astronomical Journal, 132(5), 2024-2033.
  More info

  Abstract: We present late-epoch optical photometry (BVRI) of seven normally luminous and superluminous Type la super-novae: SN 2000E, SN 2000ce, SN 2000cx, SN 2001C, SN 2001V, SN 2001bg, and SN 2001dp. The photometry of these objects was obtained using a template subtraction method to eliminate galaxy light contamination during aperture photometry. We show the optical light curves of these supernovae out to epochs of up to ∼640 days after the explosion of the supernova. We show a linear decline in these data during the epoch of 200-500 days after explosion, with the decline rate in the B, V, and R bands equal to about 1.4 mag per 100 days, but the decline rate of the I-band is much shallower at 0.94 mag per 100 days. © 2006. The American Astronomical Society. All rights reserved.
• Lair, J. C., Leising, M. D., Milne, P. A., & Williams, G. G. (2006). Late light curves of normally luminous Type Ia supernovae. New Astronomy Reviews, 50(7-8), 570-573.
  More info

  Abstract: The use of Type Ia supernovae as cosmological tools has reinforced the need to better understand these objects and their light curves. The light curves of Type Ia supernovae are powered by the nuclear decay of 56Ni → 56Co → 56Fe. The late time light curves can provide insight into the behavior of the decay products and their effect of the shape of the curves. We present the optical light curves of six "normal" Type Ia supernovae, obtained at late times with template image subtraction, and the fits of these light curves to supernova energy deposition models. © 2006 Elsevier B.V. All rights reserved.
• Nysewander, M. C., Reichart, D. E., Park, H. -., Williams, G. G., Kinugasa, K., Lamb, D. Q., Henden, A. A., Klose, S., Kato, T., Harper, A., Yamaoka, H., Laws, C., Torii, K., York, D. G., Barentine, J. C., Dembicky, J., Mcmillan, R. J., Moran, J. A., Hartmann, D. H., , Ketzeback, B., et al. (2006). Early time chromatic variations in the wind-swept medium of GRB 021211 and the faintness of its afterglow. Astrophysical Journal Letters, 651(2 I), 994-1004.
  More info

  Abstract: We present Follow-Up Network for Gamma-Ray Bursts (FUN GRB) Collaboration observations of the optical afterglow of GRB 021211 made between 143 s and 102 days after the burst. Our unique data set includes the earliest filtered detections and color information for an afterglow in the pre-Swift era. We find that the afterglow is best described by (1) a propagation through a wind-swept medium, (2) a cooling break that is blueward of the observed optical frequencies, and (3) a hard electron energy distribution. However, superimposed on this "standard model" behavior we find, one and possibly two, significant chromatic variations during the first few hours after the burst. We consider possible reasons for these variations, including the possibility that they are due to a dust echo. Finally, we constrain physical parameters that describe the afterglow and the surrounding medium for a variety of scenarios and find that GRB 021211's afterglow is faint for a combination of reasons: (1) a low fraction of energy in relativistic electrons, (2) a low density for the wind-swept medium, implying either a low mass-loss rate and/or a high wind velocity for the progenitor, (3) a wide opening/viewing angle for the jet, and possibly (4) moderate source-frame extinction. The jet appears to be significantly far from equipartition and magnetically dominated. More extreme versions of this might explain the darkness of many afterglows in the Swift era. © 2006. The American Astronomical Society. All rights reserved.
• Blanco, D., Alegria, M., Callahan, S., Clark, D., Comisso, B., Foltz, C., Gibson, J. D., Heller, C., James, R., Kindred, W., King, S., Knop, C., Lester, H., McAfee, J., Milone, A. A., Ortiz, R., Pickering, T. E., Ritz, P., Russ, B., , Schmidt, G., et al. (2004). The new MMT. Proceedings of SPIE - The International Society for Optical Engineering, 5489(PART 1), 300-311.
  More info

  Abstract: Originally commissioned in 1979, the Multiple Mirror Telescope was a highly innovative and successful facility that pioneered many of the technologies that are used in the new generation of 8 to 10 m class telescopes. After 19 years of operations the MMT was decommissioned in March of 1998: the enclosure was modified, the optics support structure was replaced, and a single 6.5-meter primary mirror was installed and aluminized in-situ. First light for the new MMT was celebrated on May 13, 2000. Operations began with an f/9 optical configuration compatible with existing instruments. Work has continued commissioning two new optical configurations that will serve a suite of new instruments: an f/15 deformable secondary mirror and adaptive optics facility that has obtained diffraction-limited images; and an f/5.4 secondary mirror and refractive corrector that provides a one-degree diameter field of view. The wide-field instrument suite includes two fiber-fed bench spectrographs, a robotic fiber positioner, and a wide-field imaging camera.
• Fabricant, D., Fata, R., McLeod, B., Szentgyorgyi, A., Barberis, J., Bergner, H., Brown, W., Caldwell, N., Conroy, M., Eng, R., Epps, H., Furesz, G., Gauron, T., Geary, J., Goddard, R., Hartmann, L., Hertz, E., Honsa, M., Mueller, M., , Norton, T., et al. (2004). The 6.5 meter MMT's f/5 wide-field optics and instruments. Proceedings of SPIE - The International Society for Optical Engineering, 5492(PART 2), 767-778.
  More info

  Abstract: In 2003, the converted MMT's wide-field f/5 focus was commissioned. A 1. 7-m diameter secondary and a large refractive corrector offer a 1° diameter field of view for spectroscopy and a 0.5° diameter field of view for imaging. Stellar images during excellent seeing are smaller than 0.5″ FWHM across the spectroscopic field of view, and smaller than 0.4″ across the imaging field of view. Three wide-field f/5 instruments are now in routine operation: Hectospec (an R∼1000 optical spectrograph fed by 300 robotically-positioned optical fibers), Hectochelle (an R∼40,000 optical spectrograph fed by the same fibers), and Megacam (a 340 megapixel, 36 CCD optical imager covering a 25′ by 25′ format).
• Pérz-Ramírez, D., Park, H. S., & Williams, G. G. (2004). Super-LOTIS (Livermore Optical Transient Imaging System). Astronomische Nachrichten, 325(6-8), 667-668.
  More info

  Abstract: The 0.6-m Super-LOTIS telescope is a fully robotic system dedicated to the search for prompt optical emission from gamma-ray bursts (GRBs). The telescope began routine operations from its Steward Observatory site atop Kitt Peak (KPNO) in April 2000. This system is capable of responding to the Gamma-ray burst Coordinate Network (GCN) triggers within seconds. Together with LOTIS, these systems have been monitoring the GCN real-time data for automatic HETE2 GRB triggers. We will summarize the current capabilities of the system and present recent scientific results.
• Williams, G. G., Gibson, J. D., Callahan, S., Blanco, D., Williams, J. T., & Spencer, P. (2004). Performance and control of the MMT thermal system. Proceedings of SPIE - The International Society for Optical Engineering, 5489(PART 2), 938-949.
  More info

  Abstract: We present results from a study of the performance of the MMT thermal system. The 6.5-m MMT primary mirror consists of a borosilicate honeycomb structure that is thermally controlled with a forced-air ventilation system. We will give an overview of both the measurement and control systems. Our goal is to define an algorithm for control of the ventilation system such that the primary mirror temperature closely tracks ambient while minimizing thermal gradients. Future work will include a study of correlations between the thermal state of the primary mirror and both seeing and wavefront errors. The thermal system is currently controlled by the telescope operators, but the results from this work will assist in fully automating the system.
• Blake, C., Fox, D. W., Park, H. S., & Williams, G. G. (2003). A search for period changes in δ Scuti stars with the super-LOTIS sky patrol system. Astronomy and Astrophysics, 399(1), 365-372.
  More info

  Abstract: We have observed a sample of δ Scuti stars discovered by the ROTSE collaboration in 1999 with Super-LOTIS in order to characterize changes in their pulsation periods over a time baseline of roughly three years. Achieving these goals required the creation of an automated astrometric and photometric data reduction pipeline for the Super-LOTIS camera. Applying this pipeline to data from a June 2002 observing campaign, we detect pulsations in 18 objects, and find that in two cases the periods have changed significantly over the three years between the ROTSE and Super-LOTIS observations. Since theory predicts the evolutionary period changes should be quite small, sources of non-evolutionary period changes due to the interactions of pulsations modes are discussed.
• Greiner, J., Klose, S., Reinsch, K., Schmid, H. M., Sari, R., Hartmann, D. H., Kouveliotou, C., Rau, A., Palazzi, E., Straubmeier, C., Stecklum, B., Zharikov, S., Tovmassian, G., Bärnbantner, O., Ries, C., Jehin, E., Henden, A., Kaas, A. A., Grav, T., , Hjorth, J., et al. (2003). Evolution of the polarization of the optical afterglow of the γ-ray burst GRB030329. Nature, 426(6963), 157-159.
  More info

  PMID: 14614499;Abstract: The association of a supernova with GRB030329 strongly supports the 'collapsar' model of γ-ray bursts, where a relativistic jet forms after the progenitor star collapses. Such jets cannot be spatially resolved because γ-ray bursts lie at cosmological distances; their existence is instead inferred from 'breaks' in the light curves of the afterglows, and from the theoretical desire to reduce the estimated total energy of the burst by proposing that most of it comes out in narrow beams. Temporal evolution of the polarization of the afterglows may provide independent evidence for the jet structure of the relativistic outflow. Small-level polarization (∼1-3 per cent) has been reported for a few bursts, but its temporal evolution has yet to be established. Here we report polarimetric observations of the afterglow of GRB030329. We establish the polarization light curve, detect sustained polarization at the per cent level, and find significant variability. The data imply that the afterglow magnetic field has a small coherence length and is mostly random, probably generated by turbulence, in contrast with the picture arising from the high polarization detected in the prompt γ-rays from GRB021206 (ref. 18).
• Matheson, T., Garnavich, P. M., Foltz, C., West, S., Williams, G., Falco, E., Calkins, M. L., Castander, F. J., Gawiser, E., Jha, S., Bersier, D., & Stanek, K. Z. (2003). The spectroscopic variability of GRB 021004. Astrophysical Journal Letters, 582(1 II), L5-L9.
  More info

  Abstract: We present spectra of the optical transient (OT) associated with GRB 021004. The spectra show a blue continuum with superposed absorption features and one emission line. We confirm two intervening metal-line systems at z = 1.380 and z = 1.602 and one very strong absorption system at a redshift of z = 2.323. Lyα emission is also seen at this redshift. While the spectrum of the OT overall cannot be simply described with a power law, the spectral index over the range 5500-8850 Å is steep, Fv ∝ v- 0.93±0.03. Comparison of spectra from multiple epochs shows a distinct color evolution with the OT becoming redder with time over the first 3 days. This is the first clear example of color change in an OT detected spectroscopically.
• Cerón, J. C., Castro-Tirado, A., Gorosabel, J., Hjorth, J., Fynbo, J. U., Jensen, B. L., Pedersen, H., Andersen, M. I., López-Corredoira, M., Suárez, O., Grosdidier, Y., Casares, J., Pérez-Ramírez, D., Milvang-Jensen, B., Mallén-Ornelas, G., Fruchter, A., Greiner, J., Pian, E., Vreeswijk, P. M., , Barthelmy, S. D., et al. (2002). The bright optical afterglow of the long GRB 001007. Astronomy and Astrophysics, 393(2), 445-451.
  More info

  Abstract: We present optical follow up observations of the long GRB 001007 between 6.14 hours and ∼468 days after the event. An unusually bright optical afterglow (OA) was seen to decline following a steep power law decay with index α = -2.03 ± 0.11, possibly indicating a break in the light curve at t - t0 < 3.5 days, as found in other bursts. Upper limits imposed by the LOTIS alerting system 6.14 hours after the gamma ray event provide tentative (1.2σ) evidence for a break in the optical light curve. The spectral index β of the OA yields - 1.24 ± 0.57. These values may be explained both by several fireball jet models and by the cannonball model. Fireball spherical expansion models are not favoured. Late epoch deep imaging revealed the presence of a complex host galaxy system, composed of at least two objects located 1.2″ (1.7σ) and 1.9″ (2.7σ) from the afterglow position.
• Hurley, K., Berger, E., Castro-Tirado, A., Cerón, J. C., Cline, T., Feroci, M., Frail, D. A., Frontera, F., Masetti, N., Guidorzi, C., Montanari, E., Hartmann, D. H., Henden, A., Levine, S. E., Mazets, E., Golenetskii, S., Frederiks, D., Morrison, G., Oksanen, A., , Moilanen, M., et al. (2002). Afterglow upper limits for four short-duration, hard spectrum gamma-ray bursts. Astrophysical Journal Letters, 567(1 I), 447-453.
  More info

  Abstract: We present interplanetary network localization, spectral, and time history information for four short-duration, hard spectrum gamma-ray bursts, GRB 000607, GRB 001025B, GRB 001204, and GRB 010119. All of these events were followed up with sensitive radio and optical observations (the first and only such bursts to be followed up in the radio to date), but no detections were made, demonstrating that the short bursts do not have anomalously intense afterglows. We discuss the upper limits and show that the lack of observable counterparts is consistent with both the hypothesis that the afterglow behavior of the short bursts is like that of the long-duration bursts, many of which similarly have no detectable afterglows, as well as the hypothesis that the short bursts have no detectable afterglows at all. Small number statistics do not allow a clear choice between these alternatives, but given the present detection rates of various missions, we show that progress can be expected in the near future.
• Park, H. S., Williams, G. G., Hartmann, D. H., Lamb, D. Q., Lee, B. C., Tucker, D. L., Klose, S., Stecklum, B., Henden, A., Adelman, J., Barthelmy, S. D., Briggs, J. W., Brinkmann, J., Chen, B., Cline, T., Csabai, I., Gehrels, N., Harvanek, M., Hennessy, G. S., , Hurley, K., et al. (2002). Lotis, super-lotis, sloan digital sky survey, and tautenburg observations of GRB 010921. Astrophysical Journal Letters, 571(2 II), L131-L135.
  More info

  Abstract: We present multi-instrument optical observations of the High Energy Transient Explorer (HETE-2) and Interplanetary Network error box of GRB 010921. This event was the first gamma-ray burst (GRB) partly localized by HETE-2 that has resulted in the detection of an optical afterglow. In this Letter, we report the earliest known observations of the GRB 010921 field, taken with the 0.11 m Livermore Optical Transient Imaging System (LOTIS) telescope, and the earliest known detection of the GRB 010921 optical afterglow, using the 0.5 m Sloan Digital Sky Survey Photometric Telescope (SDSS PT). Observations with the LOTIS telescope began during a routine sky patrol 52 minutes after the burst. Observations were made with the SDSS PT, the 0.6 m Super-LOTIS telescope, and the 1.34 m Tautenburg Schmidt telescope 21.3, 21.8, and 37.5 hr, respectively, after the GRB. In addition, the host galaxy was observed with the US Naval Observatory Flagstaff Station 1.0 m telescope 56 days after the burst. We find that at later times (t > 1 day after the burst), the optical afterglow exhibited a power-law decline with a slope of α = 1.75 ± 0.28. However, our earliest observations show that this power-law decline cannot have extended to early times (t < 0.035 days).
• Catanzaro, B., Connell, S., Mimovich, M., Backovsky, S., Williams, G., Thomas, J. A., Barber, D., Johnston, R., Hylton, J., Dodson, K., & Cohen, E. (2001). Cryogenic (70K) measurement of an all-composite 2-meter diameter mirror. Proceedings of SPIE - The International Society for Optical Engineering, 4444, 238-255.
  More info

  Abstract: The Herschel Space Observatory (formerly known as FIRST) consists of a 3.5 m space telescope. As part of a JPL-funded effort to develop lightweight telescope technology suitable for this mission, COI designed and fabricated a spherical, F/1, 2 m aperture prototype primary mirror using solely carbon fiber reinforced polymer (CFRP) materials. To assess the performance of this technology, optical metrology of the mirror surface was performed from ambient to an intended operational temperature for IR-telescopes of 70K. Testing was performed horizontally in a cryogenic vacuum chamber at Arnold Engineering Development Center (AEDC), Tennessee. The test incorporated a custom thermal shroud, a characterization and monitoring of the dynamic environment, and a stress free mirror mount. An IR-wavelength phase shifting interferometer (IR PSI) was the primary instrument used to measure the mirror surface. From an initial surface figure of 2.1 microns RMS at ambient, a modest 3.9 microns of additional RMS surface error was induced at 70K, The thermally induced error was dominated by low-order deformations, of the type that could easily be corrected with secondary or tertiary optics. In addition to exceptional thermal stability, the mirror exhibited no significant change in the figure upon returning to room temperature.
• Park, H. S., Porrata, R. A., Williams, G. G., Ables, E., Band, D. L., Barthelmy, S. D., Bionta, R. M., Cline, T. L., Fishman, G. J., Gehrels, N., Hartmann, D., Hurley, K., Kouveliotou, C., & Meegan, C. A. (1999). LOTIS: GRB follow-up observations at early times. Astronomy and Astrophysics Supplement Series, 138(3), 577-578.
  More info

  Abstract: LOTIS is an automated wide field-of-view telescope system capable of responding to GRB events as early as 10 s after a trigger from the GCN which rapidly distributes coordinates from the BeppoSAX, BATSE and RXTE instruments. Measurements of optical activity at these early times will provide important clues to the GRB production mechanism. In over two year's of operation, LOTIS has responded to 40 GCN triggers including GRB 971227 within 10 s and GRB 980703 within 5 hours. We report results from these events and constraints on simultaneous optical signals during these GRBs.
• Schaefer, B. E., Snyder, J. A., Hernandez, J., Roscherr, B., Deng, M., Ellman, N., Bailyn, C., Rengstorf, A., Smith, D., Levine, A., Barthelmy, S., Butterworth, P., Hurley, K., Cline, T., Meegan, C., Kouveliotou, C., Kippen, R. M., Park, H. -., Williams, G. G., , Porrata, R., et al. (1999). Discovery of the optical transient of GRB 990308. Astrophysical Journal Letters, 524(2 PART 2), L103-L106.
  More info

  Abstract: The optical transient of the faint gamma-ray burst GRB 990308 was detected by the QUEST camera on the Venezuelan 1 m Schmidt telescope starting 3.28 hr after the burst. Our photometry gives V= 18.32 ± 0.07, R = 18.14 ± 0.06, B = 18.65 ± 0.23, and R = 18.22 ± 0.05 for times ranging from 3.28 to 3.47 hr after the burst. The colors correspond to a spectral slope of close to fv ∝ v1/3. Within the standard synchrotron fireball model, this requires that the external medium be less dense than 104 cm-3, the electrons contain more than 20% of the shock energy, and the magnetic field energy be less than 24% of the energy in the electrons for normal interstellar or circumstellar densities. We also report upper limits of V > 12.0 at 132 s (with LOTIS), V > 13.4 from 132 to 1029 s (with LOTIS), V > 15.3 at 28.2 minutes (with Super-LOTIS), and a 8.5 GHz flux of less than 114 μJy at 110 days (with the Very Large Array). Wisconsin-Indiana-Yale-NOAO 3.5 m and Keck 10 m telescopes reveal this location to be empty of any host galaxy to R > 25.7 and K > 23.3. The lack of a host galaxy likely implies that it is either substantially subluminous or more distant than a redshift of ∼1.2.
• Williams, G. G., Park, H. S., Ables, E., Band, D. L., Barthelmy, S. D., Bionta, R., Butterworth, P. S., Cline, T. L., Ferguson, D. H., Fishman, G. J., Gehrels, N., Hartmann, D. H., Hurley, K., Kouveliotou, C., Meegan, C. A., Ott, L., Parker, E., & Porrata, R. (1999). LOTIS search for early-time optical afterglows: GRB 971227. Astrophysical Journal Letters, 519(1 PART 2), L25-L29.
  More info

  Abstract: We report on the very early time search for an optical afterglow from GRB 971227 with the Livermore Optical Transient Imaging System (LOTIS). LOTIS began imaging the "original" BATSE error box of GRB 971227 ∼14 s after the onset of gamma-ray emission. Continuous monitoring of the position throughout the evening yielded a total of 499 images (10 s integration). Analysis of these images revealed no steady optical afterglow brighter than R = 12.3 ± 0.2 in any single image. Co-addition of the LOTIS images also failed to uncover transient optical emission. In particular, assuming a constant early-time flux, no optical afterglow brighter than R = 14.2 ± 0.2 was present within the first 1200 s, and no optical afterglow brighter than R= 15.0 ± 0.2 was present in the first 6.0 hr. Follow-up observations by other groups revealed a likely X-ray afterglow and a possible optical afterglow. Although subsequent deeper observations could not confirm a fading source, we show that these transients are not inconsistent with our present knowledge of the characteristics of gamma-ray burst afterglows. We also demonstrate that with the upgraded thermoelectrically cooled CCDs, LOTIS is capable of either detecting very early time optical afterglow or placing stringent constraints on the relationship between the gamma-ray emission and the longer wavelength afterglow in relativistic blast-wave models.
• Park, H. S., Ables, E., Barthelmy, S. D., Bionta, R. M., Ott, L. L., Parker, E. L., & Williams, G. G. (1998). Instrumentation of LOTIS: Liver more optical transient imaging system; A fully automated wide-field-of-view telescope system searching for simultaneous optical counterparts of gamma-ray bursts. Proceedings of SPIE - The International Society for Optical Engineering, 3355, 658-664.
  More info

  Abstract: LOTIS is a rapidly slewing wide-field-of-viewtelescope which was designed and constructed to search for simultaneous gamma-ray burst (GRB) optical counterparts. This experiment requires a rapidly slewing (< 10 sec), wide-field-of-view(> 15°), automatic and dedicated telescope. LOTIS utilizes commercial tele-photo lenses and custom 2048 × 2048 CCD cameras to view a 17.6 × 17.6° field of view. It can point to any part of the sky within 5 sec and is fully automated. It is connected via Internet socket to the GRB coordinate distribution network which analyzes telemetry from the satellite and delivers GRB coordinate information in real-time. LOTIS started routine operation in Oct. 1996. In the idle time between GRB triggers, LOTIS systematically surveys the entire available sky every night for new optical transients. This paper will describe the system design and performance.
• Park, H. S., Williams, G. G., Ables, E., Band, D. L., Barthelmy, S. D., Bionta, R., Butterworth, P. S., Cline, T. L., Ferguson, D. H., Fishman, G. J., Gehrels, N., Hartmann, D., Hurley, K., Kouveliotou, C., Meegan, C. A., Ott, L., Parker, E., & Wurtz, R. (1997). New constraints on simultaneous optical emission from gamma-ray bursts measured by the livermore optical transient imaging system experiment. Astrophysical Journal Letters, 490(1 PART II), L21-L24.
  More info

  Abstract: LOTIS is a gamma-ray burst optical counterpart search experiment located near Lawrence Livermore National Laboratory in California. Since operations began in 1996 October, LOTIS has responded to five triggers as of 1997 July 30, which occurred during good weather conditions. GRB 970223 (BATSE trigger 6100) was an exceptionally strong burst, lasting ∼30 s with a peak at ∼8 s. LOTIS began imaging the error box ∼11 s after the burst began and achieved simultaneous optical coverage of 100% of the region enclosed by the BATSE 3 σ error circle and the interplanetary network annulus. No optical transients were observed brighter than the mv ∼ 11 completeness limit of the resulting images, providing a new upper limit on the ratio of simultaneous optical to gamma-ray fluence of RL < 1.1 × 10-4 and on the ratio of simultaneous optical (at 700 nm) to gamma-ray (at 100 keV) flux density of RF < 305 for a B-type spectrum and RF < 475 for an M-type spectrum. © 1997. The American Astronomical Society. All rights reserved.

Proceedings Publications

• Allen, L., Walker, C., Hall, J., Larson, S., Williams, G., Falco, E., Hinz, J., Fortin, P., Brocious, D., Corbally, C., Gabor, P., Veillet, C., Shankland, P., Jannuzi, B., Cotera, A., & Luginbuhl, C. (2018, jan). Protecting Dark Skies as a State-Wide Resource. In American Astronomical Society Meeting Abstracts #231, 231.
• Williams, G. (2018, jul). The MMT Observatory: entering a new era of scientific discovery. In Ground-based and Airborne Telescopes VII, 10700.
• Williams, G. G., Leonard, D., Smith, N., Smith, P., Milne, P., Hoffman, J. L., & Bilinski, C. (2018, Jan). The Supernova Spectropolarimetry (SNSPOL) Project; Probing the Geometry of Supernova Explosions. In American Astronomical Society Meeting Abstracts #231, 231.
• Hoffman, J., Williams, G. G., Bilinski, C., Dessart, L., Huk, L. N., Leonard, D. C., Mauerhan, J., Smith, N., & Smith, P. S. (2014, jul). The Supernova Spectropolarimetry Project: Probing the Evolution of Asymmetries in Supernovae. In Thirty Meter Telescope Science Forum, 42.

Presentations

• Williams, G. G. (2016, 2016-03-04). Whipping Supernovae Into Shape; The Supernova Spectropolarimetry Project. Steward Observatory Internal Symposium. Tucson, AZ: Steward Observatory.
• Williams, G. G. (2016, 2016-04-14). The 3D Nature of Supernovae; The Supernova Spectropolarimetry Project. Clemson University Physics and Astronomy Colloquium. Clemson, SC: Clemson University.
• Williams, G. G. (2016, 2016-09-26). The 3D Nature of Supernovae; The Supernova Spectropolarimetry Project. Northern Arizona University Physics and Astronomy Colloquium. Flagstaff, AZ: Northern Arizona University.
• Del Castillo, E. A., Corbally, C., Falco, E. E., Green, R. F., Hall, J. C., & Williams, G. G. (2015, mar). Dark Sky Collaborators: Arizona (AZ) Observatories, Communities, and Businesses. Highlights of Astronomy.
• Green, R. F., Diaz Castro, J., Allen, L., Del Castillo, E. A., Corbally, C. J., Davis, D., Falco, E., Gabor, P., Hall, J. C., Monrad, C. K., & Williams, G. G. (2015, August). A Tale of Two Regions: Site Protection Experience and Updated Regulations in Arizona and the Canary Islands. IAU General Assembly.
• Green, R. F., Allen, L., Alvarez Del Castillo, E. M., Brocious, D. K., Corbally, C. J., Davis, D. R., Falco, E. E., Gabor, P., Hall, J. C., Jannuzi, B., Larson, S. M., Mighell, K. J., Nance, C., Shankland, P. D., Walker, C. E., Williams, G., & Zaritsky, D. F. (2014, jan). Progress in Dark Sky Protection in Southern Arizona. American Astronomical Society Meeting Abstracts #223.

Poster Presentations

• Porter, A. L., Leising, M. D., Milne, P., Williams, G., & Smith, P. S. (2016, January). Spectropolarimetry of ASASSN-14lp. American Astronomical Society Meeting Abstracts.
• Williams, G. G., Smith, P. S., Smith, N., Milne, P. A., Bilinski, C., Dessart, L., Hoffman, J., Leonard, D., Huk, L., Mauerhan, J., & Porter, A. (2016, 2016-05-16). The Supernova Spectropolarimetry Project. The Transient Sky. Cambridge, MA: Harvard-Smithsonian Center for Astrophysics.
• Porter, A. L., Leising, M. D., Milne, P., Williams, G., Smith, P. S., & Smith, N. (2015, jan). Polarized Light of SN 2014J. American Astronomical Society Meeting Abstracts.
• Bilinski, C., Williams, G. G., Smith, P. S., Smith, N., Milne, P., Hoffman, J. L., Huk, L. N., Leonard, D. C., & Dessart, L. (2014, jan). The Supernova Spectropolarimetry Project: Results from Multi-Epoch Observations of the Type IIb SN 2011dh. American Astronomical Society Meeting Abstracts #223.
• Hoffman, J. L., Smith, N., Bilinski, C., Dessart, L., Huk, L. N., Leonard, D. C., Milne, P., Smith, P. S., & Williams, G. (2014, jan). The Supernova Spectropolarimetry Project: Evolution of Asymmetries in the Very Luminous Type Ib SN 2012au. American Astronomical Society Meeting Abstracts #223.
• Khandrika, H. G., Leonard, D. C., Horst, C., Rachubo, A., Duong, N., Williams, G. G., Smith, P. S., Smith, N., Milne, P., Hoffman, J. L., Huk, L. N., & Dessart, L. (2014, jun). The Supernova Spectropolarimetry Project: Photometric Followup in the Optical and Near-Infrared by the Mount Laguna Supernova Survey. American Astronomical Society Meeting Abstracts #224.
• Milne, P., Williams, G., Smith, P. S., & Smith, N. (2014, jan). Spectropolarimetry of SN 2011fe. American Astronomical Society Meeting Abstracts #223.
• Williams, G. G., Dessart, L., Hoffman, J. L., Huk, L. N., Leonard, D. C., Milne, P., Smith, N., & Smith, P. S. (2014, jan). The Supernova Spectropolarimetry Project: Results from Multi-Epoch Observations of the Type IIn SN 2010jl. American Astronomical Society Meeting Abstracts #223.