Hi, The extract below is from a paper on ARXIV that I was reading recently. In this paper (and a number of others that I have read recently) there are a number of references to "wind" in a cosmic context. What is this wind? I have tried to do a number of searches to try to find out, but I can't find anything that describes the basics of this wind. Thanks in advance for your assistance. Regards, Noel. GRB Afterglows from Anisotropic Jets Authors: Z. G. Dai, L. J. Gou (Nanjing University) (Submitted on 13 Oct 2000 (v1), last revised 11 Dec 2000 (this version, v4)) Abstract: Some progenitor models of gamma-ray bursts (GRBs) (e.g., collapsars) may produce anisotropic jets in which the energy per unit solid angle is a power-law function of the angle (∝θ−k ). We calculate light curves and spectra for GRB afterglows when such jets expand either in the interstellar medium or in the wind medium. In particular, we take into account two kinds of wind: one (n∝r−3/2 ) possibly from a typical red supergiant star and another (n∝r−2 ) possibly from a Wolf-Rayet star. We find that in each type of medium, one break appears in the late-time afterglow light curve for small k but becomes weaker and smoother as k increases. When k≥2 , the break seems to disappear but the afterglow decays rapidly. Thus, one expects that the emission from expanding, highly anisotropic jets provides a plausible explanation for some rapidly fading afteglows whose light curves have no break. We also present good fits to the optical afterglow light curve of GRB 991208. Finally, we argue that this burst might arise from a highly anisotropic jet expanding in the wind (n∝r−3/2 ) from a red supergiant to interpret the observed radio-to-optical-band afterglow data (spectrum and light curve).