GCN Circular 9067
Subject
Swift/UVOT detection of GRB090401B
Date
2009-04-01T09:39:08Z (16 years ago)
From
Patricia Schady at MSSL/Swift <ps@mssl.ucl.ac.uk>
P.Schady (MSSL-UCL) and S.R.Oates report on behalf of the Swift/UVOT
team
Following from the tentative UVOT afterglow detection of GRB090401B
reported in Schady et al. (GCN 9066), we here report a fading by over
two magnitudes between the two UVOT white finding charts, taken 792s
apart at the following position
RA (J2000) = 06:20:21.11 (95.08775deg)
Dec (J2000) = -08:58:19.5 (-8.97199deg)
with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence),
suggesting this to be the optical afterglow of GRB090401B. This
position falls on a known source, making absolute magnitudes and a
precise localisation difficult at this stage, and further data will be
required in order to carry out source subtraction.
The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.67 in the direction of the burst
(Schlegel et al. 1998). All photometry is on the UVOT photometry
system described in Poole et al. (2008, MNRAS, 383, 627).