IGR J18284-0345: a new hard X-ray transient detected by INTEGRAL

ATel #1981; T. Blanchard, V. Beckmann (ISDC), J. Chenevez (DTU/NSI), S. Corbel (CEA Saclay), M. Del Santo (INAF/IASF Roma), C. Ferrigno (ISDC), N. Gehrels (NASA/GSFC), D. Gotz (CEA Saclay), J. A. Kennea (PSU), F. Mattana (APC), S. Mereghetti, A. Paizis, L. Sidoli (INAF/IASF Milano), K. Watanabe (FGCU), G. Weidenspointner (MPI HLL), J. A. Zurita Heras (CEA Saclay), on behalf of a larger collaboration
on 21 Mar 2009; 17:57 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Volker Beckmann (Volker.Beckmann@obs.unige.ch)

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The IBIS/ISGRI and the JEM-X1 instrument aboard INTEGRAL discovered a new X-ray source during an observation of the inner Galactic disk conducted from 2009 March 18 at 18:37 UT to March 19, 6:22 UT. The new source, IGR J18284-0345 was detected at RA=277.114, DEC=-3.764 (J2000) in the 20-40 keV energy band by ISGRI with 6.3 sigma detection significance for 27 ksec on-source exposure time and about 3 sigma in JEM-X1 (3-10 keV; 8 ksec). The flux of the source was about 10 mCrab at 3-10 keV and 6 mCrab in the 10-25 keV and in the 20-40 keV energy band, respectively. No source had been reported in the X-rays at this position previous to this finding within the error circle of 4 arcmin. Analysis of 4.8 Msec of IBIS/ISGRI data on the source position gives a marginal detection of 3.9 sigma, indicating strong source variability.

Swift has performed a follow-up observation of the source, starting at 2009 March 20 at 15:58 UT for an effective on source time of 1.9 ksec. Swift/XRT detected one source within the INTEGRAL error circle at RA=277.125, DEC=-3.762 with an uncertainty of 4 arcsec. The spectrum can be fit together with the INTEGRAL data by a black body model with kT = 4.0±0.2 keV. The intrinsic absorption is not well constrained and has been fixed to the Galactic value of NH = 5.6e21 1/cm**2. The model flux of IGR J18284-0345 is 3.5e-11 erg/cm**2/sec and 1.4e-10 erg/cm**2/sec in the 2-10 keV and 2-30 keV band, respectively.
No source has been reported within the Swift/XRT error circle and no source is visible in the Swift U, V, and B filter image or on plates of the Second Palomar Observatory Sky Survey (POSS-II).

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