Document Type


Publication Date

Summer 6-1-2002

Publication Title

The Astrophysical Journal


The American Astronomical Society


We present multi-instrument optical observations of the High Energy Transient Explorer (HETE-2) and In-terplanetary Network error box of GRB 010921. This event was the first gamma-ray burst (GRB) partly localized by HETE-2 that has resulted in the detection of an optical afterglow. In this Letter, we report the earliest known observations of the GRB 010921 field, taken with the 0.11 m Livermore Optical Transient Imaging System (LOTIS) telescope, and the earliest known detection of the GRB 010921 optical afterglow, using the 0.5 m Sloan Digital Sky Survey Photometric Telescope (SDSS PT). Observations with the LOTIS telescope began during a routine sky patrol 52 minutes after the burst. Observations were made with the SDSS PT, the 0.6 m Super-LOTIS telescope, and the 1.34 m Tautenburg Schmidt telescope 21.3, 21.8, and 37.5 hr, respectively, after the GRB. In addition, the host galaxy was observed with the US Naval Observatory Flagstaff Station 1.0 m telescope 56 days after the burst. We find that at later times ( t >1 day after the burst), the optical afterglow exhibited a power-law decline with a slope of α - 1.75 + or - 0.28. However, our earliest observations show that this power-law decline cannot have extended to early times ( t < 0.035 days).


Additional authors: S. D. Barthelmy, J. W. Briggs, J. Brinkmann, B. Chen, T. Cline, I Csabai, N. Gehrels, M. Harvanek, G. S. Hennessy, K. Hurley, Zeljko Ivezić, S. Kent, S. J. Kleinman, J. Krzesinski, K. Lindsay, D. Long, R. Nemiroff, E. H. Neilsen, A. Nitta, H. J. Newberg, P. R. Newman, D. Perex, W. Periera, D. P. Schneider, S. A. Snedden, C. Stoughton, D. E. Vanden Berk, D. York, and K. Ziock