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INTEGRAL observation of GRS 1739-278 in outburst

ATel #5991; E. Filippova (ISDC, Switzerland), E. Kuulkers (ESAC, Spain), N. M. Skødt (DTU Space, Denmark), J. Alfonso-Garzon (CAB/INTA-CSIC, Spain), V. Beckmann (APC, France), A. J. Bird (Southampton, UK), S. Brandt, J. Chenevez (DTU Space, Denmark), M. Del Santo (INAF/IAPS Roma, Italy), A. Domingo (CAB/INTA-CSIC, Spain), K. Ebisawa (U of Tokyo, JAXA/ISAS, Japan), P. G. Jonker (SRON/CfA/RU), P. Kretschmar (ESA/ESAC, Spain), C. B. Markwardt (NASA/GSFC, USA), T. Oosterbroek (ESA/ESTEC, The Netherlands), A. Paizis (INAF-IASF Milano, Italy), K. Pottschmidt (CRESST/UMBC, NASA/GSFC, USA), C. Sanchez-Fernandez (ESA/ESAC, Spain) & R. Wijnands (UvA, The Netherlands), E. Bozzo, C. Ferrigno (ISDC, Switzerland)
on 20 Mar 2014; 18:05 UT
Credential Certification: E. Bozzo (enrico.bozzo@unige.ch)

Subjects: X-ray, Black Hole, Transient

Referred to by ATel #: 9517

During the Galactic bulge monitoring observation (Atel #438) performed on 2014 March 19 from 11.00 to 14:42 (UTC), the black-hole candidate GRS 1739-278 (ATel #5986) was also seen by INTEGRAL.

The source is detected by IBIS/ISGRI up to an energy of about 200 keV. The estimated ISGRI flux is 143+/-2 mCrab in the 18-40 keV energy band and 166+/-2 mCrab in the 40-100 keV energy band. The fluxes estimated from JEM-X are 60+/-4 mCrab in the 3-10 keV energy band and 104+/-8 mCrab in the 10-20 keV energy band.

Its averaged broad-band (3-200 keV) spectrum, extracted by using all available ISGRI and JEM-X data (total exposure time 12.6 ks), could be roughly described with a cut-off power-law model. The measured photon index is 1.4+/-0.2 and the energy cut-off is 90(-20+40) keV (we fixed the absorption column density to the Galactic value expected in the direction of the source, i.e. 0.8E22 cm^-2). The 3-200 keV X-ray flux derived from the spectral fit is 5E-9 ergs/cm^2/s (not corrected for absorption).

This spectral shape is reminiscent of that displayed by black-hole candidates in the canonical hard state.

Further observations of the source with INTEGRAL are planned for March 28.

INTEGRAL Galactic bulge monitoring web-page