Photometry and Spectroscopy of GRB 060526 : A detailed study of the afterglow and host of a high-redshift gamma-ray burst

With this paper we want to investigate the highly variable afterglow light curve and environment of Gamma-Ray Burst (GRB) 060526 at z=3.221. We present one of the largest photometric datasets ever obtained for a GRB afterglow, consisting of multi-color photometric data from the optical to the NIR. The data set contains 218 data points in total to which we add additional data from the literature. Furthermore, we present low-resolution high signal-to-noise spectra of the afterglow. The afterglow light curve is modeled with both an analytical model using broken power-law fits and with a broadband numerical energy injection model. The absorption lines detected in the spectra are used to derive column densities using a multi-ion single-component curve-of-growth analysis from which we derive the metallicity of the host of GRB 060526. The overall light curve follows a broken power-law with a break at t = 2.401 +- 0.061 days. It shows deviations from the smooth power-law that can be explained by additional energy injections from the central engine. The broadband SED of the afterglow shows little extinction along the line of sight. The metallicity derived from S II and Fe II is relatively high for a galaxy at that redshift but comparable to the metallicity of other GRB hosts at similar redshifts. There is a candidate host galaxy at a relatively large offset of 7.7 kpc from the afterglow position with R =26.4 mag which would imply a rather luminous host.