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IGR J17361-4441: ~200 days of monitoring with Swift/XRT

ATel #3958; E. Bozzo, C. Ferrigno, L. Gibaud (ISDC, Switzerland), T. M. Belloni (INAF - Brera Observatory, Italy), P. R. den Hartog (Stanford University HEPL, USA), F. Fontani (INAF - Arcetri Observatory, Italy), I. Kreykenbohm (Dr. Karl Remeis-Sternwarte & ECAP, Germany), A. Papitto (University of Cagliari, Italy), J. Rodriguez (CEA, France)
on 8 Mar 2012; 22:59 UT
Credential Certification: E. Bozzo (enrico.bozzo@unige.ch)

Subjects: X-ray, Transient

The hard X-ray transient IGR J17361-4441 was discovered by INTEGRAL on 2011 August 11 (Atel #3565) in the Globular Cluster NGC6388 (Atel #3566, #3627) and classified as a possible low mass X-ray binary (Bozzo et al. 2011, A&A, 535, 1; Nucita et al. 2012, arXiv:1203.0965).

After the discovery, Swift/XRT regularly followed the outburst of the source up to 5 November 2011, when the source could no longer be observed due to Sun constraints. The source was again visible and observed on 29 January 2012. At this stage, XRT still measured some residual X-ray emission from a position consistent with that of the source. The estimated (absorbed) 1-10 keV X-ray flux was 5.3(+0.15,-0.25)E-13 erg/cm^2/s, corresponding to a luminosity of ~1E34 erg/s at 13.2 kpc. A compatible value was measured also during the latest observations performed from 2012 February 25 to 2012 March 2 and during an archival XRT observation carried out previous to the outburst on 2010 May 17.

While the quiescent X-ray luminosity of IGRJ17361-4441 was estimated to be ~1E31 erg/s (Atel #3627), a number of faint X-ray sources located inside the XRT spectral extraction region (circle with a radius of ~47 arcsec) are known to contribute ~1E34 erg/s to the total luminosity (Nucita et al. 2008, A&A, 478, 763; Cseh et al. 2010, MNRAS, 406, 1049). At this stage we are thus no longer able to distinguish between the different contributions and determine if IGRJ1736.1-4441 is back into its real quiescent state or if it is still active at a very low level.

A table containing the summary of all the Swift/XRT observations performed in the direction of the source to date is available below.

We thank the Swift Team for the support during the observational campaign of IGR J17361-4441.

Results of the Swift/XRT monitoring