[vsnet-grb-info 1978] GRB050815: Optical afterglow detection by Swift
UVOT
GCN Circulars
gcncirc at capella.gsfc.nasa.gov
Tue Aug 16 12:23:37 JST 2005
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 3817
SUBJECT: GRB050815: Optical afterglow detection by Swift UVOT
DATE: 05/08/16 03:21:26 GMT
FROM: Patricia Schady at MSSL/Swift <ps at mssl.ucl.ac.uk>
P. Schady (MSSL/PSU), D. Fox (PSU), P. Roming (PSU), A. Cucchiara (PSU),
M. Still (GSFC), S.T. Holland (GSFC/USRA) K. Mason (MSSL), A. Blustin
(MSSL), N. Gehrels (GSFC), on behalf of the Swift UVOT team
The Swift Ultra-Violet Telescope (UVOT) began observations of GRB050815 on
August 15th, 2005 at 17:26:25.6 UT, 67s after the BAT trigger. The UVOT
took a 100s exposure in the V band and two 10s exposures in the M1 and W2
UV filters before the source was occulted by the Earth. The next set of
observations were made ~1hr after the BAT trigger.
Anylsis of the early time data reveals an uncatalogued source in the V
band at position
Ra, Dec = 19:34:23.147, +09:08:47.47
with an estimated uncertainty of 0.5". Astrometry was performed using
stars from the USNO-catalogue. The source is no longer detected in the
second epoch of V band images, confirming it's fading nature, and leading
us to conclude this to be the afterglow. No detections are made in any
other of the UVOT filters at the 3-sigma significance level.
Photometry carried out on this source requires additional care due to the
proximity ofvarious bright stars (~16-18mag). We estimate the afterglow to
have decayed by about 1 magnitude in 1 hour. Further analysis is still
undergoing.
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