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ATEL # 1437; R. Landi, N. Masetti, A. Malizia (INAF/IASF Bologna), A. Bazzano, M. Fiocchi (IASF/INAF Rome), A.J. Bird, A.J. Dean (Univ. Southampton)
on 20 Mar 2008; 15:41 UT
Password Certification: Raffaella Landi (email@example.com)
Subjects: X-ray, Gamma Ray, Request for Observations
We report the results of an X-ray follow-up observation performed with Swift/XRT of the unidentified INTEGRAL source IGR J18173-2509 in the 3rd IBIS Survey Catalogue (Bird et al. 2007, ApJS, 170, 175) and recently associated to the XMM-Newton slew source XMMLS1 J181722.2-250838 (Ibarra et al. 2008, Atel #1397).
The Swift/XRT telescope pointed at the source region on 2008, March 5 and 8 for 5.8 and 7.9 respectively. Within the IBIS error box, we find only one source detected with a confidence level of 24.4 sigma and located at RA(J2000) = 18h 17m 22.06s and Dec(J2000) = -25d 08m 40.47s (3.7 arcsec, 90% error radius). This position is compatible with that of the XMM-Newton and the faint ROSAT sources (see attached figure). The XRT uncertainty circle contains at least two optical objects on the DSS red plate. The X-ray data are well described by an absorbed (6.7 x 1022 cm-2) power law having a flat photon index (Gamma ~0.6) plus an additional power law having the same photon index but absorbed only by the Galactic column density (2.31 x 1021 cm-2). The 2-10 keV flux is 1.3 x 10-11 erg cm-2 s-1.
Swift/XRT image of the IGR J18173-2509 field