GCN Circular 1921
Subject
GRB 030226: Ic Observations
Event
Date
2003-03-04T20:18:06Z (23 years ago)
From
Melissa Nysewander at UNC,Chapel Hill <mnysewan@astro.unc.edu>
M. C. Nysewander, J. Moran, D. Reichart (U. North Carolina), A. Henden
(USRA/USNO), and M. Schwartz (Tenagra Observatories) report on the behalf
of a larger collaboration:
We observed the the optical afterglow (Fox et al., GCN 1879) of GRB 030226
(Suzuki et al., GCN 1888) with the 32-inch Tenagra II telescope at a mean
time of 27.357 UT. In a stacked series of 14 x 300 second images we find
the source magnitude to be Ic = 20.52 +- 0.10 based on 5 stars from the
calibration of Henden (GCN 1916).
Recalibrating the 27.261 UT Rc magnitude of Covino et al. (GCN 1909) and
transforming it to the time of our observation using the post-break
temporal index of Zeh et al. (GCN 1898) we find the spectral slope at this
time to be -0.99 +- 0.42.
Pre- and post-break temporal indexes of -0.62 +- 0.19 and -1.95 +- 0.26
(Zeh et al., GCN 1898) and a spectral index of -0.99 +- 0.42 suggest, at
least prior to two days (see Kulkarni et al., GCN 1911), that the afterglow
is probably expanding into a constant density medium of non-negligible
extinction and that the cooling break is blueward of the observations.
However, ISM and WIND models with negligible extinction and the cooling
break redward of the observations are also possible (e.g., Sari, Piran &
Narayan 1998; Chevalier & Li 2000).
Chevalier, R. A., and Li, Z. 2000, ApJ, 536, 195
Sari, R., Piran, T., and Narayan, R. 1998, ApJ, 497, L17