Further improved X-ray position and possible optical/nIR counterpart for XTE J1637-489
ATel #1704; R. Starling, P. Evans (University of Leicester) and R. Wijnands (University of Amsterdam)
on 8 Sep 2008; 15:07 UT
Credential Certification: Rhaana Starling (rlcs1@star.le.ac.uk)
Subjects: Infra-Red, Optical, X-ray, Transient
We report a further refinement of the position of the recently discovered
X-ray transient XTE J1637-498 (Markwardt, Pereira and Swank, ATEL #1699).
Using 1 ks of Swift XRT Photon Counting mode data and 3 Swift UVOT v band
images from the observation described in Wijnands et al. (ATEL #1700), we find an astrometrically corrected X-ray position (using the
XRT-UVOT alignment and matching UVOT field sources to the USNO-B1
catalogue) of RA, Dec = 249.26112, -49.86128 deg which is equivalent to:
RA (J2000): 16 37 2.67
Dec (J2000): -49 51 40.6
with an uncertainty of 1.8 arcsec (radius, 90% confidence).
This is 4.8 arcseconds from the centre of the previous X-ray position reported
by Wijnands et al. (ATEL #1700).
Position enhancement is described by Goad et al. (2007, A&A, 476, 1401), the current algorithm is an
extension of this method.
This new position coincides with a single optical source clearly detected in
each of the UVOT v band images of exposure times 76, 760 and 93 seconds
respectively. We measure a preliminary v band magnitude of 18.4+/-0.3, which
has a larger than typical error associated with it due to the presence of a
nearby brighter star and a generally crowded field.
This magnitude has not been corrected for the unknown but likely high expected
Galactic extinction in this direction.
We also note that the 2MASS source 16370267-4951401 lies at this
position with the following magnitudes: J=14.556+/-0.156,
H=13.848+/-0.269 and K=13.372+/-0.116.
The optical and nIR fields can be seen at
http://www.star.le.ac.uk/~rlcs1/XTEJ1637/finder.html.
Further optical and IR observations are encouraged to determine the
variability of the possible counterpart.
