The Search for an Optical Counterpart

We report results of follow-up multicolor photometry of the optical variable source that is a probable remnant of the gamma-ray burst GRB970508 discovered by the Bep-poSAX satellite (IAUC 6649). Observations were carried out in Johnson-Kron-Cousins BVR c I c system with the 1-m and 6-m telescopes of SAO RAS. Between the 2nd and the 5th day after the burst a fading of the remnant is well fitted with an exponential law in all four bands. During this period the 'broadband spectrum' of the object was unchanged and can be approximated by a power-law, F ν ∝ ν −1.1. After the 5th day the decline of brightness is slowed down. In the R c band until the 32nd day, the light curve can be described by a power-law relation, F t ∝ t −1.2 .