GCN Circular 9450
Subject
GRB090530: Swift/UVOT afterglow detection
Event
Date
2009-05-30T17:08:39Z (16 years ago)
From
Patricia Schady at MSSL/Swift <ps@mssl.ucl.ac.uk>
P. Schady (MSSL-UCL) and J. K. Cannizzo (NASA/UMBC) report on behalf of
the Swift UVOT team:
The Swift/UVOT began settled observations of the field of GRB 090530 158s
after the BAT trigger (Cannizzo et al., GCN Circ. 9438) and a decaying
source is detected in all UVOT filters within the XRT error circle
(Beardmore et al., GCN Circ. 9445), putting an upper limit on the redshift
of z < 1.7. The source initially rises, and at around 100s after the BAT
trigger decays at a constant rate of 0.73+/-0.03 for the duration of
intial UVOT observations, out to ~20ks after the BAT trigger. The best
UVOT position determined from a co-added white band exposure is
RA (J2000) 11:57:40.50 = 179.41873 (deg)
Dec (J2000) +26:35:38.4 = +26.59400 (deg)
with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence,
statistical + systematic), consistent with the ROTSE-IIIb afterglow
position (Flewelling et al., GCN Circ. 9439).
The magnitudes for the observations currently available are as follows:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 83 233 147 17.43 +/- 0.03
v 624 644 19 17.69 +/- 0.29
b 550 570 19 18.60 +/- 0.27
u 295 545 246 17.46 +/- 0.05
uvw1 5735 5935 197 20.15 +/- 0.37
uvm2 5530 11687 1082 20.31 +/- 0.22
uvw2 5121 17468 1279 21.31 +/- 0.32
The values quoted above are not corrected for the Galactic extinction due
to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel
et al. 1998). The photometry is on the UVOT photometric system described
in Poole et al. (2008, MNRAS, 383, 627).