GRB 010921: Discovery of the First HETE Afterglow
P.A. Price, S.R. Kulkarni, E. Berger, S.G. Djorgovski, D.A. Frail, A. Mahabal, D.W. Fox, F.A. Harrison, J.S. Bloom, S.A. Yost, D.E. Reichart, A.A. Henden, G.R. Ricker, R. van der Spek, K. Hurley, J.-L. Atteia, N. Kawai, E. Fenimore, C. Graziani
Abstract
We report the discovery of the optical and radio afterglow of GRB 010921, the first gamma-ray burst afterglow to be found from a localization by the High Energy Transient Explorer (HETE) satellite. We present optical spectroscopy of the host galaxy which we find to be a dusty and apparently normal star-forming galaxy at z = 0.451. The unusually steep optical spectral slope of the afterglow can be explained by heavy extinction, A_V > 0.5 mag, along the line of sight to the GRB. Dust with similar A_V for the the host galaxy as a whole appears to be required by the measurement of a Balmer decrement in the spectrum of the host galaxy. Thanks to the low redshift, continued observations of the afterglow will enable the strongest constraints, to date, on the existence of a possible underlying supernova.