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INTEGRAL IBIS/ISGRI confirms renewed activity of V404 Cyg

ATel #8458; D. Malyshev (ISDC/University of Geneva, Switzerland), V. Savchenko (APC/FACe, Paris), C. Ferrigno, E. Bozzo (ISDC/University of Geneva, Switzerland), E. Kuulkers (ESA/ESAC, Spain), on behalf of a larger collaboration
on 23 Dec 2015; 22:11 UT
Credential Certification: E. Bozzo (enrico.bozzo@unige.ch)

Subjects: X-ray, Binary, Black Hole, Transient

Referred to by ATel #: 8494, 8499, 8501, 8507, 8512, 8520, 8531

During a recent public observation of the Cygnus region, performed between 2015-12-21 16:20 and 2015-12-23 04:21 UTC (revolution 1624), INTEGRAL detected a renewed activity from the black-hole X-ray transient V404 Cyg (GS 2023+338). This confirms the recent analogous detections reported by the Swift/BAT (Barthelmy et al 2015 GCN 18716, Beardmore et al 2015 ATel #8455), Fermi/GBM (Jenke at al 2015, GCN 18719, Atel #8457), and MASTER (Lipunov et al 2015 ATel #8453).

The source was detected by IBIS/ISGRI at a significance of 8 sigma in the 20-40 keV energy band and 7 sigma in the 40-80 keV energy band. The corresponding fluxes were 6.4 +/- 0.8 mCrab and 7.7 +/- 1.1 mCrab (effective exposure time 18 ksec). The source was not detected by JEM-X, and we estimated a 3 sigma upper limit on the source flux of 5 mCrab in the 3-10 keV energy band (effective exposure time 16 ks).

We note that the source was not significantly detected in the previous observations of the same region carried out by INTEGRAL from 2015-12-13 at 19:11 to 2015-12-15 at 04:48 (UTC). In this case, the 5 sigma upper limits on the source flux estimated from the IBIS/ISGRI mosaics in the 20-40 keV and 40-80 keV energy band were of 4 and 5 mCrab, respectively.

A public target of opportunity INTEGRAL observation of the source is planned for the satellite revolutions 1626 and 1627 (from 2015-12-26 07:59 to 2015-12-31 03:04 UTC).