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New X-ray transient IGR J17507-2856 discovered with INTEGRAL

ATel #342; S. A. Grebenev (IKI, Moscow), R. A. Sunyaev (IKI, Moscow; MPA, Garching)
on 11 Oct 2004; 11:11 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: S.A.Grebenev (sergei@hea.iki.rssi.ru)

Subjects: Radio, Far-Infra-Red, Infra-Red, X-ray, Black Hole, Neutron Star, Transient

Referred to by ATel #: 3181

We report on the discovery with INTEGRAL of a new X-ray source 1.3 deg off the Galactic center. This source, IGR J17507-2856, was detected with IBIS/ISGRI on Sept. 18-23, 2004, during Open Program observations of the region. The S/N ratio was 6.9 in the 18-45 keV mosaic image, the corresponding average flux was 2.98+/-0.43 mCrab. The source was also seen during individual revolutions (on a scale of 3 days) at the S/N ratio level of 4.5-5.0

The best fit position, R.A.= 17h50m44s, Dec.= -28d56m17s (equinox 2000.0, error radius 2') keeps the source outside error boxes of the nearby known sources: the transient X-ray burster SAX J1750.8-2900 (R.A.=17h50m24s, Dec.=-29d02m18s, 90%-error radius 1', Natalucci et al., ApJ, 1999, 523, L45; offset 7.5') and the soft X-ray source 1RXP J175029-2859.9 = AX J1750.5-2900 (error radius 0.1'; offset 4.9')

. The source was marginally detected again on Oct. 3-5 during next INTEGRAL observations (dedicated to the Galactic Center Deep Exposure). We encourage follow-up observations of this source at all wavelengths.