[vsnet-grb-info 8324] GRB 090827: Swift XRT and UVOT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9847
SUBJECT: GRB 090827: Swift XRT and UVOT observations
DATE:    09/08/29 09:38:48 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at star.le.ac.uk>

P.A. Evans (U. Leicester) and S.R. Oates (MSSL-UCL) report on behalf of
the Swift team:

The Swift-XRT observed the field of GRB 090827 (Cummings et al. GCN
Circ. 9846), gathering 7.1 ks of Photon Counting (PC) mode data from
T0+92 ks to T0+122 ks. Inside the BAT error circle we find a single,
uncatalogued source at a location of RA,Dec = 18.4495, -50.8957 which is
equivalent to:

RA (J2000)  = 01h 13m 47.88s
Dec (J2000) = -50d 53' 44.0"

with an uncertainty of 6.4 arcsec (radius, 90% condfidence).
There are only 14 counts detected from this source, giving it a count
rate of (3+/-1) x 10^-3 ct/sec. It is impossible to say whether this
source is fading.

A spectrum formed from all available data can be well fitted using an
absorbed power law, with a photon index of 1.6 (+0.9, -0.8) and  an
absorption column density consistent with the Galactic value of 1.6 x
10^20 cm^-2 (Kalberla et al. 2005).

The Swift-UVOT began settled observations of the field 91.6 ks after the
BAT trigger. We do not detect any source at the XRT position.

The 3-sigma upper limits for the finding chart exposure is:

Filter   T_start(s)   T_stop(s)   Exp(s)  Mag (3-sigma upper limit)
-------------------------------------------------------------
U         91644        120333      5671        > 21.94
-------------------------------------------------------------

The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight of E_(B-V) = 0.01 mag.
All photometry is on the UVOT photometric system described in Poole et
al. (2008, MNRAS, 383, 627).

This circular is an official product of the Swift team.