GRB follow-up team

GRB 050408

On April 8, 2005, an optical afterglow of the GRB 050408 was discovered with the SAO's telescopes (the 1-meter telescope Zeiss and 6-meter telescope BTA) within the framework of a joint BTA request (SAO RAS + IAA CSIC, Granada, Spain) on optical identification of gamma-ray bursts. We first detected a variable object only by our own data in the localization error-box reported by the space observatory HETE and then it was confirmed by our observations in SAO. (On the territory of the Commonwealth of Independent States nobody managed to do that yet...)

Then multiband observations of this variable object were continued by a collaboration of 10 telescopes: SAO RAS, Spain, Denmark, England, India, Taiwan, Japan. As a result, on the 6-th day an unusual increase of the object brightness was detected. Its nature can be related to a dense envelope around a massive star-progenitor of SN/GRB. Allowing for a redshift z=1.2357, the observed nonmonotony (nonuniformity) of the light curve is analogous to that observed in optical afterglow of GRB 050708 on the second day after the GRB itself (the brightness increased 1.5 st.magn.)

Figure 1. Only SAO's data (the 1-meter and 6-meter telescope).

Figure 2. The total light curve of the optical object detected by data of the1-meter and 6-meter SAO telescopes. Open circles are for SAO's first RBV observations (published in GCN #3192 and GCN #3197). Filled circles are for BVRI observations by other members of an international collaboration of 10 telescopes with the use of SAO's data.

The observational results were obtained under a joint porgram of Instituto de Astrofisica de Andalucia (Alberto J. Castro-Tirado, IAA-CSIC, Spain) and SAO RAS