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ATEL # 1319; S.A. Grebenev (IKI, Moscow), M.G. Revnivtsev (IKI; MPA, Garching), R.A. Sunyaev (IKI; MPA)
on 4 Dec 2007; 16:13 UT
Distributed as an Instant Email Notice (Transients)
Password Certification: S.A.Grebenev (firstname.lastname@example.org)
Subjects: Radio, Far-Infra-Red, Infra-Red, Optical, X-ray, Request for Observations, Transients
This new X-ray source was discovered by the IBIS/ISGRI telescope of the INTEGRAL observatory on October 12, 2007 when INTEGRAL carried out the latitude dissection of the Galaxy at the Sgr Arm tangent region.
The source was variable but sufficiently bright during all 7 hours when it was in the field-of-view (between 15h and 23h UTC). The source position was R.A.=18h46m16s, Decl.=-02d23m12s (equinox 2000.0, uncertainty 2 arcmin). The flux in the 18-45 keV band was equal to 17+/-2 mCrab on the average, reaching in a peak 35+/-6 mCrab. There are some signatures of its decay during the observation. The source's spectrum could be described by a power law with the photon index of -2.7 up to ~70 keV. It was not confidently detected at higher energies. The source was not observed in the standard X-ray band being outside the JEM-X field-of-view.
Two our subsequent observations of the region (on October 13 and 15) indicated that the source switched off. The 3-sigma upper limits on its flux were 8.7 and 6.5 mCrab, respectively.
An apparent short duration of the outburst, a hard power law spectrum of the source and its location in the Galactic plane and in the Galactic arm tangent region allow us to suggest that it could be another fast X-ray transient with a high mass or may be even supergiant companion.
We encourage follow-up observations of the source in soft X-rays and infrared/radio bands.