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Activity from SAX J1747.0-2853 and KS 1741-293 detected by INTEGRAL Galactic Bulge Monitoring

ATel #9387; J. Chenevez (DTU Space, Denmark), E. Kuulkers (ESA/ESAC, Spain), R. Wijnands (UvA, The Netherlands), A. Bazzano (INAF/IAPS, Italy) , V. Beckmann (APC, France), T. Bird (Southampton, UK), A. Bodaghee (GCSU, USA), M. Del Santo (INAF/IASF-Pa, Italy), A. Domingo (CAB/INTA-CSIC, Spain), P. Jonker (SRON, The Netherlands), P. Kretschmar (ESA/ESAC, Spain), C. Markwardt (GSFC, USA), A. Paizis (INAF/IASF-Mi, Italy), K. Pottschmidt (UMBC/NASA GSFC, USA), C. Sanchez-Fernandez (ESA/ESAC, Spain)
on 19 Aug 2016; 14:00 UT
Credential Certification: Jerome CHENEVEZ (jerome@space.dtu.dk)

Subjects: X-ray, Gamma Ray, Neutron Star, Transient, Variables

Referred to by ATel #: 10265

A new season of observations has started for the INTEGRAL Galactic Bulge Monitoring Program (ATel #438; Kuulkers et al. 2007, A&A, 466, 595; see also: http://integral.esac.esa.int/BULGE ).
During the observation performed on August 17, 2016, between UTC 17:20 and 21:01, the neutron star low-mass X-ray binary (NS-LMXB) SAX J1747.0-2853 (aka 1A 1743-288) is detected by the twin JEM-X cameras with an effective exposure time of ∼15 ks. The highest pixels on the combined JEM-X1+2 significance mosaics between 3-10 keV and 10-25 keV reach 6 and 3 σ, respectively. The corresponding fluxes are measured at 8 +/-2 mCrab (3-10 keV) and 6 +/-4 mCrab (10-25 keV). The source does not appear in the 18-40 keV and 40-100 keV mosaics of the IBIS/ISGRI camera, and we estimate the 5-σ upper limits at 18 mCrab and 21 mCrab, respectively.
We note that SAX J1747.0-2853 was already reported in outburst during a Chandra observation on May 17, 2016 (ATel #9115). It appears from the MAXI 2-20 keV light curve ( http://maxi.riken.jp/top/index.php?cid=1&jname=J1747-288#lc ) that the outburst has declined and stabilized at the current level since the end of June 2016.

During the same observation, a typical type-I X-ray burst from the NS-LMXB KS 1741-293 was detected by JEM-X on MJD 57617.8233 (UTC 19:45:30 on August 17, 2016). The burst light curves reveal this event is likely a photospheric radius expansion burst.
This source is also detected by ISGRI, and we measure the following average fluxes: 9 +/-2 mCrab (3-10 keV), 11.5 +/-4 mCrab (10-25 keV), 18 +/-2 mCrab (18-40 keV), and 19 +/-3 mCrab (40-100 keV).

INTEGRAL will continue to monitor the Galactic Bulge (next time on August 21st) at a rough cadence of an observation every satellite revolution (2.7 days) until October 24th. Near-Real-Time data are publicly available from the ISDC ( http://www.isdc.unige.ch/integral/archive#DataRelease ).