The SRG/ART-XC collaboration sent its first astronomic “telegram” on observing the supermassive black hole Sagittarius A* in the center of the Milky Way.
ATel #13023; M. Pavlinsky on behalf of ART-XC collaboration (IKI RAS, Moscow)
on 13 Aug 2019; 21:56 UT
Following the recent report on Sgr A* flaring activity (ATel #13007, #12768) ART-XC telescope onboard Spektr-RG observed the Galactic center region for 50 ks during the period between 2019-08-11 22:27:50 UTC and 2019-08-12 13:19:12 UTC
We found Sgr A* in unusually active state: using absorbed power-law spectral model (slope Γ=2, following Zhang+17) we estimated mean flux in 5-16 keV band as (1.6±0.2)x10-11 erg cm-2 s-1, which corresponds to the unabsorbed bolometric luminosity of 2×1035 erg s-1 (0.1-20 keV), assuming a distance of 8.5 kpc.
We also noticed variability on timescale of few kiloseconds.
Because of preliminary calibration status of ART-XC more accurate details will be provided in the following article.
Multi-wavelength observations are encouraged; ART-XC will observe Sgr A* between 14.08.2019 23:40 and 15.08.2019 15:20 UTC