Infrared observations of IGR J17497-2821: new position, new candidate counterparts

ATel #906; Chaty, S. (AIM CEA Saclay/University Paris 7, France), Hatano, H. (Dept. Astrophysics, Nagoya Univ., Japan), Matsuoka, Y. (Inst. Astronomy, Univ. Tokyo, Japan), Nagata, T. (Dept. Astronomy, Kyoto Univ., Japan)
on 2 Oct 2006; 23:20 UT
Credential Certification: Sylvain Chaty (S.Chaty@open.ac.uk)

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Following the report by Kennea et al. (Atel #900) of a new Swift/XRT position for the recently discovered source IGR J17497-2821 (see Soldi et al., atel #885), we inspected our infrared (IR) images obtained in J, H and Ks bands of the field of IGR J17497-2821 at 1.4m IRSF at South African Astronomical Observatory (details on the observations and reduction are given in Chaty et al., atel #897).

Inside the new Swift/XRT error circle (5.3" radius), there are 3 2MASS catalogued sources:

2MASS 17493780-2821181 at 4.0" from the centre of the error circle

2MASS 17493774-2821173 at 4.7" from the centre

2MASS 17493798-2821120 at 5.1" from the centre

In addition, there are 6 other detected objects inside the new error circle, 3 of them are closer to the centre of the error circle than the 2MASS objects. The astrometry (J2000) and magnitudes of these objects are:

Candidate 1 RA=17 49 38.08, DEC=-28 21 17.6, at 0.7" from the centre; J=16.6+/-0.06, H=14.2+/-0.3, K=13.1+/-0.4

Candidate 2 RA=17 49 38.16, DEC=-28 21 19.1, at 2.35" from the centre; J=16.8+/-0.08, H=14.1+/-0.2, K=12.9+/-0.2

Candidate 3 RA=17 49 37.87, DEC=-28 21 18.6, at 3.3" from the centre; J>18.8+/-0.5, H=13.4+/-0.4, K=12.9+/-0.3 (Candidate 3 is the same as described in Chaty et al. Atel #897).

Candidate 4 RA=17:49:37.89, DEC=-28:21:14.9, at 3.4" from the centre; J=15.3+/-0.3, H=14.3+/-0.3, K=12.8+/-0.3

Candidate 5 RA=17:49:38.18, DEC=-28:21:13.2, at 4.0" from the centre; J>18.8, H=15.6+/-0.3, 13.7+/-0.3

Candidate 6 RA=17:49:38.34, DEC=-28:21:14.6, at 4.0" from the centre; J>18.8, H=14.9+/-0.4, 14.3+/-0.4

The astrometry has been computed with all 2MASS stars located in a radius of 1' from the centre of the error circle, the error on the astrometry is +/-0.4" because of the blending of some of the 2MASS sources (see Chaty et al., atel #897), and the magnitudes are given for the date of 22nd of September 2006. Some candidates exhibit variations, but none is strong enough yet to pinpoint any counterpart.

We have observed the field of the source every night since 22nd of September 2006, and we will continue to observe it in order to look for variations of the candidate counterparts and 2MASS objects. We also encourage observations of the field at all wavelengths, to try to detect the real counterpart of IGR J17497-2821.