GRB000301C with peculiar afterglow emission

The CCD magnitudes in Johnson V and Cousins R and I photometric passbands are determined for GRB 000301C afterglow starting ∼ 1.5 day after the γ−ray burst. In fact we provide the earliest optical observations for this burst. Light curves of the afterglow emissions are obtained by combining the published data with the present measurements in B,V,R, I, J and K ′ passbands. Flux decay shows a very uncommon variation relative to other well observed GRBs. Early time (∆t < 4 days) flux decay varies with wavelength from optical to near-infrared. The values of α are ∼ 0.6 in optical, 0.4 at 1.2 μm and 0.3 at 2.1 μm. While late time decay seems to be similar in all passbands with α > 2.2. Steepening in the flux decay seems to have started around ∆t ∼ 4 day in all passbands. During ∆t = 5.6 to 33.5 day, the value of α becomes ∼ 3 making the flux decay one of the steepest amongst the GRBs observed so far. On the other hand such variations are not observed in the quasi-simultaneous broad-band photometric spectral energy distributions of the afterglow. The value of spectral index in the optical-near IR region is ∼ −0.9. The afterglow emission of GRB 000301C is therefore peculiar and presently can not be understood in terms of fireball synchrotron emission model. Redshift determination with z = 2.0335 indicates cosmological origin of the GRB having a luminosity distance of 16.6 Gpc. Thus it becomes the second farthest amongst the GRBs with known distances. An indirect estimate of the fluence > 20 keV indicates, if isotropic, ≥ 10 ergs of release of energy. The enormous amount of released energy will be reduced, if the radiation is beamed which seems to be the case for this event. The prompt γ−ray emission in the energy band 100 to 1000 KeV has only one strong peak.