GCN Circular 8544
Subject
GRB081121: Refined Swift/UVOT observations
Date
2008-11-22T12:13:02Z (15 years ago)
From
Samantha Oates at MSSL <sro@mssl.ucl.ac.uk>
S. R. Oates (MSSL-UCL) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 081121,
2816s after the BAT trigger (Oates et al., GCN Circ. 8537). We detect the
optical afterglow in the white, v, b, u filters and marginally in the
uvw1 filter at the position:
RA(J2000.0) = 5:57:06.15
DEC(J2000.0) = -60:36:10.0
with an estimated uncertainty of 0.6 arcsec (radius, 90% confidence).
This position is consistent with the UVOT-enhanced XRT position
and the position reported by ROTSE-IIIC (Yuan et al., GCN Circ. 8536).
The marginal detection of the optical afterglow in uvw1, and the lack
of a detection in the uvm2 and uvw2 filters is consistent with a redshift
of z=2.512 reported by Magellan (Berger and Rauch, GCN Circ. 8542).
The magnitudes and 3 sigma upper limits are reported below:
Filter T_start (s) T_stop Exposure Mag/3sig UL
---------------------------------------------------------
white 2816 2965 147 17.93 +/- 0.04
v 2972 3172 197 17.58 +/- 0.08
b 3792 3992 197 18.26 +/- 0.07
u 3587 3787 197 17.62 +/- 0.06
uvw1 3383 3582 197 20.60 +/- 0.48 (2.3-sigma)
uvm2 3177 4813 393 > 20.09
uvw2 4203 11200 790 > 20.78
---------------------------------------------------------
The above magnitudes are not corrected for the Galactic extinction
corresponding to a reddening of E_{B-V} = 0.05 mag (Schlegel et al.,
1998, ApJS, 500, 525). The photometry is on the UVOT flight system
described in Poole et al. (2008, MNRAS, 383,627).