The NIR counterpart to XTE J1747-274(=IGR J17473-2721)
ATel #634; M. A.P. Torres, D. Steeghs, M. R.Garcia, J. E.McClintock (CfA), P. G.Jonker (SRON/CfA), P. J.Callanan (UCC)
on 18 Oct 2005; 19:47 UT
Credential Certification: Danny Steeghs (dsteeghs@cfa.harvard.edu)
Subjects: Infra-Red, X-ray, Binary, Black Hole, Neutron Star, Transient
We report follow-up observations confirming the near-infrared (NIR)
counterpart to the X-ray transient XTE J1747-274/IGR J17473-2721 (ATEL
#467, #498). A Ks=16.2 mag candidate was suggested in ATEL #521 on the
basis of its coincidence with the Chandra localization for the X-ray
source. The candidate appeared extended and/or blended with a nearby
NIR source to the south.
Our observations consist of a series of Ks-band images obtained with the
6.5m Magellan Baade telescope between 2005 Sep 13 02:06-02:26 UT using the
PANIC camera and totaling 375s on source. The frames were acquired with a
seeing of 0.8 arcsec and a projected pixel size of 0.125 arcsec on the
1024x1024 Hawaii detector. Photometric and astrometric scales were defined using
2MASS sources in the field of view.
Our images show a single point-like source 0.3-0.4 arcsec south from the
position reported for the NIR candidate (ATEL #521). This source is likely
associated with a field star and the cause of the reported extension of the
counterpart during outburst. The proposed counterpart candidate has thus faded
significantly and is not detected with a 3-sigma upper limit magnitude
of Ks>17.4.
This large decrease in brightness relative to the observations reported
when the transient was active confirms the candidate reported in ATEL #521
is indeed the NIR counterpart to XTE J1747-274/IGR J17473-2721.
