Schedule Feb 10, 2006
A common feature of long GRB early afterglow
Urata, Huang, Ip, Hu, Qiu, Kuo, Tamagawa, Tashiro, Onda, EAFON team

Utilizing East Asian GRB Follow-up Observation Network (EAFON) we have observed 55 GRB optical afterglows and detected 15 early optical afterglow behavior including two short GRBs in multi-bands. We have found a common feature in long GRB early afterglow light curves. These early light curves show re-brightening and/or plateau phase around 0.1 days (2.4hours) after bursts. Combine with other prompt optical observations and X-ray data, overall behavior of thesemulti-band light curves may be interpreted in terms of the sum of two separate components, one showing a monotonic decay from prompt while the other having a rising and a falling phase. These results imply that prompt optical emission continue until 0.1 days and afterglow components dominate than prompt emission around 0.1 days.

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