A candidate near-infrared counterpart to IGRJ 17511-3057

ATel #2216; M. A.P. Torres (CfA), P. G. Jonker (SRON/CfA), D. Steeghs (Warwick/CfA), J. D. Simon (OCIW), G. Gutowski (Haverford College)
on 25 Sep 2009; 16:30 UT
Credential Certification: P.G. Jonker (pjonker@cfa.harvard.edu)

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We report on near-infrared follow-up observations of the field containing the currently active accreting millisecond pulsar IGR J17511-3057 (ATels #2196, #2197, #2198, #2199).

Our observations consist of a series of 15s Ks-band images totaling 225s on source. They were acquired on 2009 Sep 22 23:46 - 23:52 UT with the PANIC camera mounted on the 6.5m Baade telescope at Las Campanas Observatory. Sky conditions were good with a seeing of 0.5". Additional 3s exposures were obtained to obtain the astrometric and absolute flux calibration of the data using 2MASS objects in the field of view. This delivered a positional rms < 0.1' and a zero-point accuracy < 0.15 mag.

Our mosaic image shows a faint point-like source at R.A (J2000)=17:51:08.64, Dec (J2000)=-30:57:40.70 consistent with the 0.6" Chandra position reported by Nowak et al. (2009, ATel #2215). Preliminary PSF-fitting photometry of the PANIC images yields Ks=18.0 +/- 0.1.

This source does not appear to be present in UKIDSS GPS frames obtained in 2007, although the image quality and depth is significantly worse than our PANIC epoch. The positional match and apparent variability does point towards a viable counterpart for the millisecond pulsar.

We would like to thank Mike Nowak, Ada Paizis and Joern Wilms for sharing the Chandra X-ray position prior to publication.