On some statistical properties of GRB prompt optical emissions and afterglows

Presenter: Sergey Karpov

We studied the subset of an optical light curves of gamma-ray bursts with measured redshifts and well-sampled R band data, which have clearly detected peaks. Among 44 such events, 11 are prompt optical peaks (P), coincident with gamma-ray activity, 23 are purely afterglows (A) and 10 more carry the signatures of an underlying activity (A(U)). We studied pair correlations of their gamma-ray and optical parameters like total energetics, peak optical luminosities, durations etc. Main result is the detection of a source frame correlation between optical peak luminosity and total energy for A and A(U) classes and absence of such correlation for P class events. This result seems to be an evidence of a cosmological evolution of a medium around the burst defining A and A(U) classes energetics, and the absence of cosmological evolution of internal properties of GRB engines. We also discuss some other prominent correlations as well.

G.Beskin
G.Greco
G.Oganesyan