GCN Circular 9840
Subject
GRB 090823: Swift XRT possible detection of the X-ray afterglow
Event
Date
2009-08-25T19:20:00Z (17 years ago)
From
Dirk Grupe at PSU/Swift-XRT <grupe@astro.psu.edu>
D. Grupe (PSU), E. Hoversten (PSU) and Jay Cummings (NASA/GSFC)
report on behalf of the Swift team:
We have analysed the XRT and UVOT data of the IPN burst GRB090823
(Cummings et al. GCN Circ. 9835), beginning on 2009-08-24 at
22:17, 30 hours after the Suzaku WAM trigger. The data contain 4.7
ks in XRT photon counting mode. We clearly detect a possible X-ray
afterglow within the 4' BAT error circle given by Cummings and Copete
et al. (GCN circs. 9838 and 9839, respectively) at
RA-2000,Dec-2000=128.67676, +60.65169 which corresponds to
RA-2000 = 08h 34m 42.42s
Dec-2000 = +60d 39' 06.1"
with an uncertainty of 5.5"
During the 4.7 ks observation on 2009-08-24 the X-ray source had a
count rate of (5.7+/-1.1)e-3 counts s-1 in the XRT which converts
to an observed flux in the 0.3-10 keV band of (2.9+/-0.5)e-13
ergs s-1 cm-2 assuming a typical GRB afterglow spectrum.
The Swift/UVOT began settled observations of the field of GRB 090823
108380 s after the BAT trigger (Cummings, et al., GCN Circ. 9835).
No optical afterglow consistent with the XRT position
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627) for the initial exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 109194 115699 1464 >21.8
v 110009 116640 1680 >20.1
u 108380 114954 1597 >20.7
The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.06 in the direction of the burst
(Schlegel et al. 1998).
Swift is planning to re-observe the field of GRB 090823 on
2009-08-27 for 10 ks in order to see if the X-ray source has faded.
This circular is an official product of the Swift team.