INTEGRAL observations confirm renewed activity of the black-hole X-ray binary V4641 Sgr

Following the MAXI/GSC announce of renewed activity of the black hole X-ray binary V4641 Sgr (AteL #16804), INTEGRAL performed a target-of-opportunity observation (TOO) of this source from 2024-09-07 at 16:44 until 2024-09-08 at 22:16 UTC. Additionally, V4641 Sgr was also in the field of view of a Galactic Center observation performed from 2024-09-05 at 16:58 until 2024-09-06 at 07:43 UTC, when it was detected in the 3-10 keV band at 3σ level, with a flux compatible with the subsequent TOO observation.

By combining data from the two observations, the source is well detected at the expected position at a significance level of 25 sigma for a total (JEM-X1+2) effective exposure time of 96.5 ks (3-10 keV). However, it is only marginally detected in mosaic images above 10 keV.

The average intensities measured over the ToO observation are:
12 ±1 mCrab (3-10 keV) and 3.5 ±1.5 mCrab (10-25 keV). The lightcurve shows pronounced variability on the scale of thousands of seconds. From IBIS/ISGRI, we obtain a 3σ upper limit of 3 mCrab in the 28-40 keV band.

Further observations in the direction of the source will be executed in the coming weeks.

All preliminary and consolidated results are available at this URL.