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X-ray localization and possible IR counterpart of XTE J1747-274/IGR J17473-2721

ATel #521; A. M. Juett (Virginia), D. L. Kaplan (MIT), D. Chakrabarty (MIT), C. B. Markwardt (U. Maryland & NASA/GSFC), P. G. Jonker (SRON/CfA)
on 17 Jun 2005; 17:06 UT
Credential Certification: Adrienne M. Juett (ajuett@virginia.edu)

Subjects: Infra-Red, X-ray, Gamma Ray, Binary, Transient

Referred to by ATel #: 634, 1445, 1459

On 2005 June 6 23:56UT, we observed a field centered on the source XTE J1747-274 (Markwardt et al., ATEL #498) using the HRC-I on Chandra for 1.1 ks. With a 30' x 30' field of view, we were able to cover an area twice the error circle of the RXTE detection. We found only 1 source in the entire Chandra FOV at a position of

RA = 17 47 18.06
Dec. = -27 20 38.9

with an error radius of 0.8". This position is consistent with the source found in a Swift observation of the field (Kennea et al., ATEL #500). The Swift source was identified with the INTEGRAL detected transient IGR J17473-2721 (Grebenev et al., ATEL #467).

We find a source count rate of 5.37+/-0.07 cnts/s (1 sigma error). Using the Swift determined spectral parameters and PIMMS, we estimate the source flux at 7.77+/-0.10 x 10^-10 erg/cm^2/s (0.5-10 keV). This is consistent with the Swift determined flux for IGR J17473-2721 and the RXTE measured flux from XTE J1747-274. We therefore conclude that IGR J17473-2721 and XTE J1747-274 are the same source.

We also obtained an infrared image of the Swift position on 2005 May 26 04:38UT, using the PANIC camera at the 6.5-m Magellan I (Baade) telescope in Chile. The observation was a total of 270 sec in Ks-band only, under good seeing (0.4"-0.5") and with variable clouds. Astrometric and photometric calibration were done with respect to 2MASS. One infrared source was found in the Chandra error circle with a position of

RA = 17:47:18.08
Dec. = -27:20:38.7,

0.3" from the X-ray position. It has Ks=16.2 mag. The FWHM is approximately 4.8 pixels (or 0.6" FWHM), compared to most of the stars in the field that have FWHM = 3.8-4.1 pixels (~0.5" FWHM), so it appears slightly extended and/or blended with another object to the south. We identify this source as the possible infrared counterpart of XTE J1747-274/IGR J17473-2721. Taken together, the properties of the candidate counterpart and X-ray source are not consistent with those of the obscured high mass X-ray binaries that Integral is finding in large numbers.

PANIC Ks image of candidate counterpart with Swift and Chandra error circles