INTEGRAL detects renewed activity from GRS 1736-297

ATel #8698; V. Esposito (ISDC, Switzerland), K. Watanabe (FGCU, USA), E. Kuulkers (ESA/ESAC, Spain), E. Bozzo, C. Ferrigno (ISDC, Switzerland)
on 15 Feb 2016; 18:04 UT
Distributed as an Instant Email Notice Transients
Credential Certification: E. Bozzo (enrico.bozzo@unige.ch)

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During the observations performed in the direction of the Galactic Center from 2016 February 14 at 22:52 to February 15 at 12:12 (UTC), the IBIS/ISGRI instrument on-board INTEGRAL detected a renewed activity of the LMXB GRS 1736-297.

By using data collected from February 14 at 22:52 to February 15 at 07:55 (UTC), the source is detected in the IBIS/ISGRI mosaic with a significance of 8 sigma in the 20-40 keV energy range and 6 sigma in the 40-80 keV energy band. The corresponding fluxes were 11+/-1 mCrab and 12+/-2 mCrab, respectively. The ISGRI spectrum (effective exposure time 24 ks) could be well fit (reduced chi^2/d.o.f.=1.1/6) with a power-law model with photon index 2.4+/-0.6. The estimated 20-100 keV X-ray flux from the spectral fit was 2.3E-10 erg/cm^2/s. When the remaining data are added (from February 15 at 07:55 to 12:12 UTC), we observe a decrease in the average flux of the source down to 10+/-1 mCrab in the 20-40 keV energy range and 9+/-2 mCrab in the 40-80 keV energy range.

The source was not detected by JEM-X. The estimated 3 sigma upper limit on the source X-ray flux is 6 mCrab in the 3-10 keV energy range (effective exposure time 7.6 ks).

Further INTEGRAL observations in the direction of the source are already planned for the next weeks.