Early optical and millimeter observations of GRB 030226 afterglow

Abstract

Abstract. The CCD magnitudes in Johnson UBV and Cousins RI photometric passbands for the afterglow of the long duration GRB 030226 are presented. Upper limits of a few mJy to millimeter wave emission at the location of optical are obtained over the first two weeks. The optical data presented here, in combination with other published data on this afterglow, show an early R band flux decay slope of 0.77 ± 0.04, steepening to 2.05 ± 0.04 about 0.65 ± 0.03 day after the burst. Interpreted as the "jet break", this indicates a half opening angle of ∼3.2 degree for the initial ejection, for an assumed ambient density of ∼1 cm −3 . Broadband spectra show no appreciable evolution during the observations, and indicate the presence of synchrotron cooling frequency ν c near the upper edge of the optical band. From the broadband spectra we derive an electron energy distribution index p = 2.07 ± 0.06 and an intrinsic extinction E(B − V) ∼ 0.17. Millimeter upper limits are consistent with these derived parameters.

SCUBA sub-millimeter observations of gamma-ray bursts

“…Millimeter observations with the Plateau de Bure Interferometer did not detect the source (Pandey et al 2004), but these did not start until 1.8 days after the burst. From the radio catalog of Frail et al (2003b), VLA observations 0.12 days after the burst did not detect the source, with a flux density of −0.058 ± 0.074 mJy at 8.46 GHz.…”

Indian Astronomical Observatory, Leh-Hanle

“…The afterglows monitored in detail include GRB 010222 (Cowsik et al, 2001a), GRB 021004 (Pandey et al, 2003a), GRB 021211 (Pandey et al, 2003c), GRB 030226 (Pandey et al, 2004) and GRB 030329 (Resmi et al, 2005), all observed during the science verification phase. Subsequent to regular allotment of time, monitoring the GRB afterglows is being conducted as a Target of Opportunity programme and the data is published.…”

Core-Collapse Supernovae and Gamma-Ray Bursts in TMT Era

“…Ashok B N et al 1987;Sahu et al 2006;Roy et al 2008;Brajesh et al 2013) and afterglows of GRBs (e.g. Sagar et al 1999;Bhattacharya 2003;Pandey et al , 2004Resmi et al 2013) in detail.…”

“…The afterglow light curves generally show a power-law behavior. In general the flux f ν from the afterglow follows a power law decay with time, a combination of several characteristic properties of the ejecta, represented as f (ν, t) ∝ ν β t −α where t is the time since the burst and α is the temporal flux decay index, ν is the frequency of observations and β is the spectral index (Sari, Piran & Narayan 1998, Wijers & Galama 1999Pandey et al 2004). In case of most of the afterglows, generally the optical-IR emission is very faint (V ∼ 23 mag, 1-2 day after the burst) and only 8-10m class telescopes could monitor the emission to observe the characteristic jet break time and other possible light curve features at late epochs (Sari, Piran & Halpern 1999;;Castro-Tirado et al 1999;Mészáros 2002).…”