GRB 081008: FROM BURST TO AFTERGLOW AND THE TRANSITION PHASE IN BETWEEN

Journal Article · Tue Mar 09 23:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/711/2/870· OSTI ID:21394342

Yuan, F; Akerlof, C W ^[1]; Schady, P; Oates, S R ^[2]; Racusin, J L ^[3]; Willingale, R; O'Brien, P T ^[4]; Kruehler, T; Greiner, J; Filgas, R ^[5]; Rykoff, E S ^[6]; Aharonian, F; Horns, D ^[7]; Ashley, M C. B. ^[8]; Barthelmy, S D; Gehrels, N ^[9]; Flewelling, H A ^[10]; Goegues, E ^[11]; Guever, T ^[12]; Kiziloglu, Ue ^[13]

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1. Physics Department, University of Michigan, Ann Arbor, MI 48109 (United States)
2. UCL Mullard Space Science Laboratory, Holmbury St Mary, Surrey, RH5 6NT (United Kingdom)
3. Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)
4. Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom)
5. Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany)
6. Physics Department, University of California at Santa Barbara, 2233B Broida Hall, Santa Barbara, CA 93106 (United States)
7. Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)
8. School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia)
9. NASA Goddard, Greenbelt, MD 20771 (United States)
10. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
11. Faculty of Engineering and Natural Sciences, Sabanci University, Orhanli, Tuzla 34956, Istanbul (Turkey)
12. Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
13. Department of Physics, Middle East Technical University, 06531 Ankara (Turkey)

We present a multi-wavelength study of GRB 081008, at redshift 1.967, by Swift, ROTSE-III, and Gamma-Ray Burst Optical/NearInfrared Detector. Compared to other Swift GRBs, GRB 081008 has a typical gamma-ray isotropic equivalent energy output ({approx}10{sup 53} erg) during the prompt phase, and displayed two temporally separated clusters of pulses. The early X-ray emission seen by the Swift X-Ray Telescope was dominated by the softening tail of the prompt emission, producing multiple flares during and after the Swift Burst Alert Telescope detections. Optical observations that started shortly after the first active phase of gamma-ray emission showed two consecutive peaks. We interpret the first optical peak as the onset of the afterglow associated with the early burst activities. A second optical peak, coincident with the later gamma-ray pulses, imposes a small modification to the otherwise smooth light curve and thus suggests a minimal contribution from a probable internal component. We suggest the early optical variability may be from continuous energy injection into the forward shock front by later shells producing the second epoch of burst activities. These early observations thus provide a potential probe for the transition from the prompt phase to the afterglow phase. The later light curve of GRB 081008 displays a smooth steepening in all optical bands and X-ray. The temporal break is consistent with being achromatic at the observed wavelengths. Our broad energy coverage shortly after the break constrains a spectral break within optical. However, the evolution of the break frequency is not observed. We discuss the plausible interpretations of this behavior.

• OSTI ID: 21394342
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 711; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AFTERGLOW
COSMIC GAMMA BURSTS
COSMIC RADIATION
ELECTROMAGNETIC RADIATION
EMISSION
GAMMA RADIATION
IONIZING RADIATIONS
PHASE TRANSFORMATIONS
PRIMARY COSMIC RADIATION
PULSES
RADIATIONS
RED SHIFT
TELESCOPES