期刊
ASTROPHYSICAL JOURNAL
卷 686, 期 2, 页码 1209-1230出版社
IOP PUBLISHING LTD
DOI: 10.1086/591243
关键词
gamma rays: bursts
资金
- Royal Society and Research Councils UK
- Dill Faulkes Educational Trust
- National Aeronautics and Space Administration
- Science and Technology Facilities Council [PP/E002064/1, PP/E003303/1, PP/E001149/1] Funding Source: researchfish
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 R = 10 to 22 mag in the first 10 minutes after the burst. By comparing optical and X-ray light curves from t = 100 to similar to 10(6) 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 ( R < 22 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 similar to 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.
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