GCN Circular 9265

Subject
GRB090426 Swift/UVOT observations
Event
Date
2009-04-26T22:13:22Z (17 years ago)
From
Samantha Oates at MSSL <sro@mssl.ucl.ac.uk>
S. R. Oates (MSSL/UCL) and J. R. Cummings (NASA/UMBC) report on behalf of 
the
Swift/UVOT team:

The Swift/UVOT started settled observations of the burst GRB090426
(Cummings et al. GCN Circ. 9254Loading...
 
 ) with the finding chart (fc) exposure in
white, 89s after the BAT trigger. The afterglow is detected in the white,
b, u and filters and marginally in the v filter at the refined UVOT 
position:

     RA (J2000)  12:36:18.07
    Dec (J2000)  32:59:09.6

with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence).
The lack of detection in the UV filters is consistent with a redshift
of 2.609, which was reported by Chornock et al. (GCN Circ. 9264Loading...
 
 ).

The UVOT magnitudes and upper limits our reported below:

Filter    Tstart(s) Tstop(s)  Exp(s)       Magnitude/3sig UL
###################################################
white (fc)   89      239      147          17.52 +/- 0.03
u (fc)       301     551      246          18.11 +/- 0.08

white        581     600      19           19.10 +/- 0.22
v            630     650      19           19.04 +/- 0.86 (1.3-sigma)
u            556     576      19           18.59 +/- 0.38
b            706     726      19           18.92 +/- 0.36
uvw1         680     2164     175          > 19.92
uvm2         655     2139     175          > 19.63
uvw2         606     2090     136          > 19.82

The values quoted above are in the UVOT photometric system (Poole et al.
2008, MNRAS, 383, 627) and are not corrected for the expected Galactic
extinction corresponding to a reddening of E(B-V)=0.02 mag in the
direction of the burst (Schlegel et al. 1998).