LOOKING INTO THE FIREBALL: ROTSE-III AND SWIFT OBSERVATIONS OF EARLY GAMMA-RAY BURST AFTERGLOWS
- Physics Department, University of California at Santa Barbara, 2233B Broida Hall, Santa Barbara, CA 93106 (United States)
- Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)
- Department of Physics, University of Michigan, Ann Arbor, MI 48109 (United States)
- School of Physics, Department of Astrophysics and Optics, University of New South Wales, Sydney, NSW 2052 (Australia)
- NASA Goddard Space Flight Center, Laboratory for High Energy Astrophysics, Greenbelt, MD 20771 (United States)
- Faculty of Engineering and Sciences, Sabanci University, Orhanli-Tuzla, 34956 Istanbul (Turkey)
- Department of Astronomy, University of Arizona, Tucson, AZ 85721 (United States)
- Middle East Technical University, 06531 Ankara (Turkey)
- Cag Ueniversitesi, Faculty of Arts and Sciences, Yenice-Tarsus/Mersin (Turkey)
- Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)
- School of Chemistry and Physics, University of Adelaide, Adelaide 5005 (Australia)
- Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States)
- Guilford College, Greensboro, NC 27410 (United States)
We report on a complete set of early optical afterglows of gamma-ray bursts (GRBs) obtained with the Robotic Optical Transient Search Experiment (ROTSE-III) telescope network from 2005 March through 2007 June. This set is comprised of 12 afterglows with early optical and Swift/X-Ray Telescope observations, with a median ROTSE-III response time of 45 s after the start of {gamma}-ray emission (8 s after the GCN notice time). These afterglows span 4 orders of magnitude in optical luminosity, and the contemporaneous X-ray detections allow multi-wavelength spectral analysis. Excluding X-ray flares, the broadband synchrotron spectra show that the optical and X-ray emission originate in a common region, consistent with predictions of the external forward shock in the fireball model. However, the fireball model is inadequate to predict the temporal decay indices of the early afterglows, even after accounting for possible long-duration continuous energy injection. We find that the optical afterglow is a clean tracer of the forward shock, and we use the peak time of the forward shock to estimate the initial bulk Lorentz factor of the GRB outflow, and find 100 {approx}< {gamma}{sub 0} {approx}< 1000, consistent with expectations.
- OSTI ID:
- 21333809
- Journal Information:
- Astrophysical Journal, Vol. 702, Issue 1; Other Information: DOI: 10.1088/0004-637X/702/1/489; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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