2000/10/31 by R. Sagar, S. B. Pandey, V. Mohan +2
Physics and Astronomy · #astro-ph
published as Bull. Astr. Soc. India, vol. 29, pp. 1-13 (2001) · 13 pages, 3 figures, accepted for publication in Bull. Astr. Soc. India
arxiv created 2001/01/25 · arxiv updated 2009/12/01
CCD Johnsons BV and Cousins RI photometric magnitudes are determined for 20 stars in the field of GRB 000926. Using them as calibrators, B and R band light curves are constructed of the afterglow from ours and other published observations. They show a steepening of the flux decay, from a decay constant of 1.4+/-0.1 to 2.6+/-0.06 at about 1.7 days after the burst. Attributing this break to the onset of sideways expansion of a jet-like ejecta, we estimate an initial jet opening angle of ~0.14 radian, and a burst energy of ~1051 erg. We construct the X-ray-optical-near infrared spectrum of the afterglow and derive a spectral index of ~ -0.9. From the spectrum we also estimate that the source has a rather large intrinsic extinction, amounting to E(B-V)=0.36+/-0.02.