XMM-Newton Observation of IGR J18538-0102 and an Optical/IR Candidate
ATel #2445; J. P. Halpern, E. V. Gotthelf
on 18 Feb 2010; 07:40 UT
Credential Certification: Jules Halpern (jules@astro.columbia.edu)
Subjects: Infra-Red, Optical, X-ray, Gamma Ray, Request for Observations
We observed the X-ray counterpart of IGR J18538-0102
(Stephen et al., ATel #2441) in a pointed observation
with XMM-Newton on 2004 October 8. This apparently
steady source (in an 8 ks exposure) can be fitted with a power-law model
of photon index 1.7+/-0.1, NH = (1.5+/-0.2)e22 cm-2,
and unabsorbed 1-10 keV flux 5.6e-12 erg cm-2 s-1. Its
coordinates 18h53m48.50s, -01d02'30.0" (J2000), with
90% confidence error radius of 3.2", coincide
with an object in the 2MASS Point Source Catalog at
18h53m48.48s, -01d02'29.6" of magnitudes
H=14.00+/-0.05 and K=12.50+/-0.05. On 2006 June 29,
we obtained a 60 s uncalibrated exposure in the
I-band on the 2.4m Hiltner telescope of the MDM Observatory
under partly cloudy conditions, that
shows a faint object at 18h53m48.49s, -01d02'29.2",
consistent with the XMM-Newton and 2MASS coordinates.
As argued previously, IGR J18538-0102
is unlikely to be a compact object in the supernova
remnant G32.1-0.9. Deeper images and
red or near-IR spectra of our candidate are desired
to ascertain its nature. We have already obtained
optical spectra that rule out a brighter star
in the X-ray error circle.
IR and Optical Finding Charts