Observations of GRB 060526 Optical Afterglow with Russian-Turkish 1.5-m Telescope

TL;DR

This study presents detailed multicolor optical observations of GRB 060526's afterglow, revealing a power-law decay, color stability, and variability that suggest the shell's motion is no longer ultrarelativistic.

Contribution

First detailed multicolor optical afterglow observations of GRB 060526, analyzing variability and color changes over five nights with implications for jet dynamics.

Findings

Power-law decay with index -1.14±0.02 from 6 to 16 hours post-burst

Detection of variability on short time scales, violating some ultrarelativistic jet constraints

Color of the afterglow remains approximately constant at V-R≈0.5

Abstract

We present the results of the photometric multicolor observations of GRB 060526 optical afterglow obtained with Russian-Turkish 1.5-m Telescope (RTT150, Mt. Bakirlitepe, Turkey). The detailed measurements of afterglow light curve, starting from about 5 hours after the GRB and during 5 consecutive nights were done. In addition, upper limits on the fast variability of the afterglow during the first night of observations were obtained and the history of afterglow color variations was measured in detail. In the time interval from 6 to 16 hours after the burst, there is a gradual flux decay, which can be described approximately as a power law with an index of -1.14+-0.02. After that the variability on the time scale \delta t < t is observed and the afterglow started to decay faster. The color of the afterglow, V-R=~0.5, is approximately the same during all our observations. The variability is detected on time scales up to \delta t/t =~ 0.0055 at \Delta F_\nu/F_\nu =~ 0.3, which violates some constraints on the variability of the observed emission from ultrarelativistic jet obtained by Ioka et al. (2005). We suggest to explain this variability by the fact that the motion of the emitting shell is no longer ultrarelativistic at this time.