期刊
ASTROPHYSICAL JOURNAL
卷 758, 期 1, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/758/1/27
关键词
gamma-ray burst: general; methods: statistical; radiation mechanisms: non-thermal
资金
- National Natural Science Foundation of China [11025313, 10873002, 11078008, 11063001, 11163001]
- 973 Program of China [2009CB824800]
- Special Foundation for Distinguished Expert Program of Guangxi
- Guangxi SHI-BAI-QIAN project [2007201]
- Guangxi Natural Science Foundation [2010GXNSFA013112, 2011GXNSFB018063, 2010GXNSFC013011]
- Third Innovation Project of Guangxi University
- NSF [AST-0908362]
- [2011-135]
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [0908362] Funding Source: National Science Foundation
Well-sampled optical light curves of 146 gamma-ray bursts (GRBs) are compiled from the literature. By empirical fitting, we identify eight possible emission components and summarize the results in a synthetic light curve. Both optical flare and early shallow-decay components are likely related to long-term central engine activities. We focus on their statistical properties in this paper. Twenty-four optical flares are obtained from 19 GRBs. The isotropic R-band energy is smaller than 1% of E-gamma,E-iso. The relation between the isotropic luminosities of the flares and gamma rays follows L-R,iso(F) proportional to L-gamma,iso(1.11 +/- 0.27). Later flares tend to be wider and dimmer, i.e., w(F) similar to t(p)(F)/2 and L-R,iso(F) proportional to [t(p)(F)/(1 + z)](-1.15 +/- 0.15). The detection probability of the optical flares is much smaller than that of X-ray flares. An optical shallow-decay segment is observed in 39 GRBs. The relation between the break time and break luminosity is a power law, with an index of -0.78 +/- 0.08, similar to that derived from X-ray flares. The X-ray and optical breaks are usually chromatic, but a tentative correlation is found. We suggest that similar to the prompt optical emission that tracks gamma-rays, the optical flares are also related to the erratic behavior of the central engine. The shallow-decay component is likely related to a long-lasting spinning-down central engine or piling up of flare materials onto the blast wave. Mixing of different emission components may be the reason for the diverse chromatic afterglow behaviors.
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