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Report on (non-)activity in the Galactic bulge region as seen by INTEGRAL

ATel #5332; E. Kuulkers (ESA/ESAC, Spain), J. Chenevez (DTU Space, Denmark), R. Wijnands (UvA, The Netherlands), J. Alfonso-Garzon (CAB/INTA-CSIC, Spain), V. Beckmann (APC, France), A. J. Bird (Southampton, UK), S. Brandt (DTU Space, Denmark), T. J.-L Courvoisier (ISDC, Switzerland), 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)
on 28 Aug 2013; 09:13 UT
Credential Certification: Erik Kuulkers (ekuulker@rssd.esa.int)

Subjects: X-ray, Binary, Black Hole, Neutron Star, Transient, Variables, Pulsar

We report on observations on (UT) 25 August 2013 04:42-08:23 as part of a new season of our INTEGRAL Galactic bulge monitoring (see ATel #438).

The neutron-star X-ray transient GRS 1741-2853, in X-ray outburst from the beginning of August 2013 (ATel #5246), is still active within the JEM-X instruments with fluxes of 16+/-3 mCrab (3-10 keV) and 7+/-3 (10-25 keV). The IBIS/ISGRI hard X-ray 3-sigma flux limits are about 4 mCrab (18-40 keV) and 10 mCrab (40-100 keV). A Type I X-ray burst from GRS 1741-2853 was recorded at UT 06:47:23.

The new outburst of the black hole X-ray transient H1732-322 (ATel #5241) is clearly seen by both JEM-X and IBIS/ISGRI at fluxes of 75+/-5 mCrab (3-10 keV), 43+/-4 mCrab (10-25 keV), 34+/-2 mCrab (18-40 keV), and 34+/-2 mCrab (40-100 keV).

The recently active (ATels #5222, #5226, #5246) neutron-star X-ray transient AX J1745.6-2901 (or Swift J174535.5-2901, CXOGC J174535.6-290133, see, e.g., ATels #753, #1513) is seen by JEM-X at flux levels of 20+/-5 mCrab (3-10 keV) and 12+/-4 mCrab (10-25 keV). We do not see the recently active magnetar SGR J1745-29 with JEM-X, about 1.5 arcmin from AX J1745.6-2901 (e.g, ATels #5006, #5008, #5009), with 6-sigma upper limits of about 6 mCrab (3-10 keV) and 4 mCrab (10-25 keV). The IBIS/ISGRI fluxes from the direction of both sources is about 6+/-1.5 mCrab in the 18-40 keV band, with a detection significance of 4.4.

IBIS/ISGRI does not detect the recently active neutron-star X-ray transients 1A 1744-361 (ATel #5301) and XTE J1709-267 (Atel #5319) in hard X-rays, with upper limits of about 7 mCrab (18-40 keV) and 10 mCrab (40-100 keV).

The neutron-star X-ray transient KS 1741-293, which started its outburst about half a year ago (see ATel #4840), is now below the IBIS/ISGRI and JEM-X detection limits. The JEM-X 6-sigma upper limits are about 6 mCrab (3-10 keV) and 4 mCrab (10-25 keV); the IBIS/ISGRI 3-sigma upper limits are about 4 mCrab (18-40 keV) and 10 mCrab (40-100 keV). The hard X-ray monitoring by the Swift/BAT (e.g., ATel #904; see http://swift.gsfc.nasa.gov/results/transients/weak/AXJ1744.8-2921/ ) indicates the hard X-ray outburst lasted up to this month. We note that KS 1741-293 was seen near the edge of the field with the Swift/XRT on 26 April 2013, confirming that it was indeed KS 1741-293 that was active.

The black-hole X-ray binary 1E 1740.7-2942 (the Great Annihilator) is seen to be still below INTEGRAL's monitoring detection limits (see ATels #4804, #4471). We derive JEM-X 6-sigma upper limits of about 6 mCrab (3-10 keV) and 4 mCrab (10-25 keV)mCrab, and IBIS/ISGRI 3-sigma upper limits of about 4 mCrab (18-40 keV) and 10 mCrab (40-100 keV).

The next monitoring observation of the Galactic bulge region will be in about a week, starting on September 3 20:43.