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تسجيل مستخدم جديدOptical afterglow of the not so dark GRB 021211
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We determine Johnson $B,V$ and Cousins $R,I$ photometric CCD magnitudes for the afterglow of GRB 021211 during the first night after the GRB trigger. The afterglow was very faint and would have been probably missed if no prompt observation had been conducted. A fraction of the so-called ``dark GRBs may thus be just ``optically dim and require very deep imaging to be detected. The early-time optical light curve reported by other observers shows prompt emission with properties similar to that of GRB 990123. Following this, the afterglow emission from $sim 11$ min to $sim 33$ days after the burst is characterized by an overall power-law decay with a slope $1.1pm0.02$ in the $R$ passband. We derive the value of spectral index in the optical to near-IR region to be 0.6$pm$0.2 during 0.13 to 0.8 day after the burst. The flux decay constant and the spectral slope indicate that optical observations within a day after the burst lies between cooling frequency and synchrotron maximum frequency.
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Afterglows of Gamma-Ray Bursts (GRBs) are simple in the most basic model, but can show many complex features. The ultra-long duration GRB 111209A, one of the longest GRBs ever detected, also has the best-monitored afterglow in this rare class of GRBs
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