RIMOTSによるGRB041006の可視光残光の早期観測

概要

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GRB041006 was first detected by HETE-2 on 2004 Oct. 6 at 12:18:08 UT. We haveobserved it's earliest optical afterglow from 12:19:18 UT to through the night. Ourobservation was performed by using the unfiltered CCD camera on the 30-cm telescope. Wecombined our converted R band data with those reported by GCN. Statistics don't allow us tosay in detail but the light curve shows two slope changes. The power-low index α of theflux decay is α =0.62 before about 0.0053 day after the burst, α =-0.45 from 0.0053 day to0.077 day after the burst, and α =-1 after 0.077 day. These index changes can be explainedby forward shock in synchrotron shock model. During the first flat period, optical emission isgenerated by cooling of all electrons, which are accelerated by forward shock. But the speedof the shell become slower, then the critical frequency becomes lower than the optical band.The light curve, therefore, got dark slowly. And finally, since the minimum frequency atwhich the slowest ones among the accelerated electrons emit is below the optical frequency,the electrons that can emit optical light decrease rapidly. So the afterglow darkened fast.
宮崎大学の論文