Swift/XRT imaging of XTE J1812-182 (=XMMU J181227.8-181234?)
ATel #1696; M. A.P. Torres (CfA), D. Steeghs (Warwick/CfA), J. A. Kennea (PSU), J. Homan (MIT) and J. M. Miller (Michigan)
on 4 Sep 2008; 13:21 UT
Credential Certification: Manuel Torres (mtorres@cfa.harvard.edu)
Subjects: X-ray, Black Hole, Neutron Star, Transient
Referred to by ATel #: 10567
We report on target of opportunity observations of XTE J1812-182 taken
by Swift/XRT starting on 2008-09-03 13:12 UT and performed in Photon
Counting (PC) and Window Timing (WT) modes for 257 and 387
seconds, respectively.
PC mode data were taken to ensure an accurate localization of this
transient and determine whether this source is a new transient or
renewed activity from XMMU J181227.8-181234 (Markwardt, Pereira &
Swank 2008, ATEL #1685). Analysis of the data reveals a single bright
(2.0 cts/s) point source at R.A. (J2000) = 18:12:28.37, Dec(J2000) =
-18:12:36.0, with an estimated uncertainty of 3.7 arcseconds radius
(90% confidence). These coordinates lie 8.3 arcseconds away from the
position of XMMU J181227.8-181234 reported in Cackett, Wijnands &
Remillard,2006,MNRAS,369,1965.
The WT mode observation with 4.1 cts/s provided data free of
pile-up. As in Cackett et al, (2008), the X-ray spectrum can be
described by 1) an absorbed power-law model with N_H = (11.3 +/-
1.0)e22 cm^-2 and a photon index of 2.2 +/- 0.2 (reduced chi**2 =
0.96) and by 2) an absorbed multi-color disk blackbody model with N_H
= (9.0 +/- 0.7)e22 cm^-2 and kT_in = 2.3 +/- 0.2 keV (reduced chi**2 =
0.95). Uncertainties are at the 68% level confidence. From the above
fits we derive an unabsorved 0.5 - 10 keV flux of (1.1-2.3)e-09
ergs/cm^2/s (range depending on the model used). The above fit
parameters and flux are in line with those reported for XMMU
J181227.8-181234 during the 2003 discovery outburst.
We therefore conclude that the X-ray source detected by RXTE is
likely due to renewed activity of XMMU J181227.8-181234.
