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IGR J16316-4028 a possible X-ray counterpart to 3EG J1631-4033 discovered by INTEGRAL

ATel #201; Jerome Rodriguez (CEA Saclay & ISDC) & Andrea Goldwurm (CEA Saclay)
on 24 Oct 2003; 08:12 UT
Credential Certification: Jerome Rodriguez (jrodriguez@cea.fr)

Subjects: X-ray, Gamma Ray, >GeV, AGN, Black Hole, Neutron Star, Quasar, Pulsar

Referred to by ATel #: 227, 253

We report the detection of a source, IGR J16316-4028, at RA=16h31.6m Dec=-40°28' (+-3 arcmin) with the IBIS/ISGRI telescope on board INTEGRAL. The source was detected during a ToO observation of the Galactic black hole candidate XTE J1720-318 performed on Feb. 28 2003. The source is detected at the 9 sigma level in the 20-40 keV range during a ~20 ks mosaic, with an average flux of ~25 mCrab. It is also detected between 40 and 80 keV, during the same time, with an average flux of ~19 mCrab. IGR J16316-4028 shows some variations on ~2000s time scales from just below the detection threshold (~20 mCrab) up to a flux of 45 mCrab in one occasion (4.5 sigma in ~2000s), in the 20-40 keV energy range.

IGR J16316-4028 lies at ~10 arcmin from the EGRET source 3EG 1631-4033, well within the 95% EGRET error box. This renders likely the identification of IGR J16316-4028 as the (hard) X-ray counterpart to 3EG J1631-4033. The ISGRI 20-40 keV (15*9 degrees) image is available (here). The closest known X-ray source, 1RXS J163336.7-404609, lies at 29 arcmin from the INTEGRAL position, which thus renders the identification of IGR J16316-4028 with 1RXS J163336.7-404609 very unlikely.

Observations at other wavelengths are strongly encouraged to better understand the nature of this (possible) EGRET source.