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).
Please use publisher's recommended citation.