GCN Circular 9210
Subject
GRB090423 - Swift/UVOT upper limits.
Event
Date
2009-04-23T17:06:23Z (17 years ago)
From
Massimiliano de Pasquale at MSSL-UCL <mdp@mssl.ucl.ac.uk>
M. De Pasquale (MSSL/UCL) and H. Krimm (GSFC/GWU) report on
behalf of the Swift UVOT team:
The Swift/UVOT took the first settled exposure of GRB 090423 starting
77 s after the BAT trigger (Krimm, et al., 2009, GCN Circ. 9198) in the
white filter. We do not find any new source, at the enhanced position of
the XRT afterglow (Evans, et al. 2009, GCN Circ. 9205) nor at the
position of the K band candidate found by UKIRT (Tanvir,
et al. 2009, GCN Circ. 9206). No source is detected even when all
the images of all filters are summed. The 3-sigma upper limits for
detecting a source in the white and u band first exposures, and
subsequent co-added images in all filters are:
Filter T_start T_stop Exp(s) Mag
----------------------------------------------------------
white 77 227 147 >20.7
u 290 540 246 >20.0
v 619 6162 413 >19.6
b 545 5497 413 >20.2
u 290 5342 462 >20.4
uvw1 668 6503 344 >20.1
uvm2 644 6367 413 >20.1
uvw2 594 5958 412 >20.5
white 77 5752 560 >21.3
---------------------------------------------------------
The quoted upper limits have not been corrected for the expected
modest Galactic extinction along the line of sight corresponding to a
reddening of E_{B-V} = 0.03 mag (Schlegel, et al., 1998, ApJS, 500,
525). All photometry is on the UVOT photometry system described in
Poole et al. (2008, MNRAS, 383, 627).