GCN Circular 7580

A. Block (Seeing In The Dark Internet Telescope, and Steward
Observatory, Tucson, AZ) and M. Templeton (AAVSO) report on behalf of
the AAVSO International High Energy Network the following observations
and analysis of the optical afterglow of GRB 080330 (Mao et al., GCN
Circular #7537; Klotz, Boer, and Atteia, GCN #7536):

Adam Block reports unfiltered photometry of the GRB 080330 afterglow
spanning 2008 March 30.1675 UT to 2008 March 30.3273, taken with the
Seeing In The Dark Internet Telescope 14-inch Celestron SCT, using an
SBIG ST1001 camera, located near Mayhill, New Mexico.  Forty-seven,
300-second unfiltered exposures were obtained beginning 20 minutes
post-burst, and continuing through t0 + 0.1736 days. Data acquisition
began after the reported peak (D'Avanzo, et al., GCN #7554), but during
the early decay epoch.  A break in the light curve is apparent at
approximately 25 minutes after the trigger; only one data point was
obtained prior to this point, and so a slope cannot be reliably derived. 
After t0 + 25 minutes, the data are reasonably well fit with a power law
index of -1.104 +/- 0.001, with a zero point unfiltered magnitude of
22.65 (m = m(t+1day)).  However, the light curve appeared to briefly
rebrighten by more than 0.2 magnitudes (1-sigma error = 0.09 mag)
approximately 70 minutes post-burst, suggesting a late-time
manifestation of the rebrightening seen during early light (Schaefer and
Guver, GCN #7538).  These observations are consistent with other
optical observations taken during this time frame; observations through
t0 + 250 minutes do not show evidence for the steeper slope described by
Sergeev et al (GCN #7556) for data taken at t > t0 + 0.5 days,
suggesting this break occurred between the end of these observations and
the start of observations by Sergeev et al.

A report detailing these observations is available at the following URL:

ftp://ftp.aavso.org/grb/AdamBlock_GRB080330_2454558.33910_.txt

The initial image of the GRB field is available at the following URL:

ftp://ftp.aavso.org/grb/AdamBlock_GRB080330_2454558.33910_.fits

A light curve of the unfiltered photometry is available at the following
URL:

http://www.caelumobservatory.com/outgoing/grb080330LOG.jpg

Photometry and a full description of the observations will appear in the
Journal of the AAVSO, and are available from A. Block upon request to
ngc1535@caelumobservatory.com.

The AAVSO thanks the Curry Foundation for their continued support of the
AAVSO International High Energy Network.