Details

Autor(en) / Beteiligte

• Melandri, A
• Mundell, C. G
• Kobayashi, S
• Guidorzi, C
• Gomboc, A
• Steele, I. A
• Smith, R. J
• Bersier, D
• Mottram, C. J
• Carter, D
• Bode, M. F
• O’Brien, P. T
• Tanvir, N. R
• Rol, E
• Chapman, R

Titel

The Early-Time Optical Properties of Gamma-Ray Burst Afterglows

Ist Teil von

• The Astrophysical journal, 2008-10, Vol.686 (2), p.1209-1230

Ort / Verlag

Chicago, IL: IOP Publishing

Erscheinungsjahr

2008

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• We present a multiwavelength analysis of 63 gamma-ray bursts observed with the world's three largest robotic optical telescopes, the Liverpool and Faulkes Telescopes (North and South). Optical emission was detected for 24 GRBs with brightnesses ranging from [image] to 22 mag in the first 10 minutes after the burst. By comparing optical and X-ray light curves from [image] to [image] seconds, we introduce four main classes, defined by the presence or absence of temporal breaks at optical and/or X-ray wavelengths. While 14/24 GRBs can be modeled with the forward-shock model, explaining the remaining 10 is very challenging in the standard framework even with the introduction of energy injection or an ambient density gradient. Early X-ray afterglows, even segments of light curves described by a power law, may be due to additional emission from the central engine. Thirty-nine GRBs in our sample were not detected and have deep upper limits ([image] mag) at early time. Of these, only 10 were identified by other facilities, primarily at near infrared wavelengths, resulting in a dark burst fraction of [image]50%. Additional emission in the early-time X-ray afterglow due to late-time central engine activity may also explain some dark bursts by making the bursts brighter than expected in the X-ray band compared to the optical band.