2002/05/08 by Jens Hjorth, Bjarne Thomsen, Svend R. Nielsen +17 · 2 citations
Engineering · Physics and Astronomy · #Astronomy and Astrophysical Research #CCD and CMOS Imaging Sensors #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1086/341624
published as Astrophys.J. 576 (2002) 113-119 · 22 pages, 5 figures, ApJ, in press
arxiv created 2002/05/08 · openalex publication_date 2002/09/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We report the identification of the optical afterglow of GRB 980613 in R- and I-band images obtained between 16 and 48 hours after the gamma-ray burst. Early near-infrared (NIR) H and K' observations are also reported. The afterglow was optically faint (R ~ 23) at discovery but did not exhibit an unusually rapid decay (power-law decay slope alpha < 1.8 at 2 sigma). The optical/NIR spectral index (betaRH < 1.1) was consistent with the optical-to-X-ray spectral index (betaRX ~ 0.6), indicating a maximal reddening of the afterglow of ~0.45 mag in R. Hence the dimness of the optical afterglow was mainly due to the fairly flat spectral shape rather than internal reddening in the host galaxy. We also present late-time HST/STIS images of the field in which GRB 980613 occurred, obtained 799 days after the burst. These images show that GRB 980613 was located close to a very compact, blue V = 26.1 object inside a complex region consisting of star-forming knots and/or interacting galaxy fragments. Therefore, GRB 980613 constitutes a strong case for the association of cosmological gamma-ray bursts with star-forming regions.