The ART-XC telescope onboard Spektr-RG space observatory continues to monitor the Galactic center region after reports on Sgr A* flaring activity (ATel #13007, #12768).
Recent ART-XC observations of Sgr A* on August 15-16 (2019-08-14T23:40 – 2019-08-15T14:00 and 2019-08-15T23:40 – 2019-08-16T14:00, UTC) with total exposure of 50 ks each, demonstrate source average 5-16 keV flux at the level of 1.6×10-11 erg cm-2 s-1, which corresponds to the luminosity of 1.4×1035 erg s-1 , assuming a distance of 8.5 kpc. This measurement of the source luminosity is comparable to that observed with ART-XC on August 12 (ATel #13023). We also see a small flux variability at the level of 15% on the timescale of a few hours. More detailed information will be provided in the corresponding publication, which is under preparation.
Multi-wavelength observations are encouraged; next time when ART-XC will observe Sgr A* is between 2019-08-22T05:46 and 2019-08-22T15:20 UTC.
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
One of the most exciting times in the life of any astronomical observatory is achieving “first light“, the first time a telescope produces an image of an astronomical object. For space-based observatories, this can be a time that’s especially nerve-wracking, given the remote nature of the science and the fact that it can be difficult to address problems in deep space. As capabilities grow, and observatories are placed farther from earth, problems encountered are ever harder to resolve. The Spektr-RG observatory (or SRG as it’s more commonly known) is a Russian-German X-ray observatory, launched on July 13, and currently on a journey to its final staging point, a region of precarious orbital stability in the earth-Sun system called “L2”, about a million miles from earth along the earth-Sun line. Once it arrives at L2, SRG will survey the entire sky every six months over the next four years. SRG consists of two observing instruments. The Astronomical Roentgen Telescope X-ray Concentrator (ART-XC) instrument consists of 7 individual telescopes whichwill generate images of the X-ray sky in the energy band from 5 kilo-electronvolts up to 30 kilo-electronvolts, which is about 3 times higher in energy than most other imaging X-ray observatories, like Chandra, XMM-Newton and Swift. ART-XC was developed by the Russian Academy of Sciences’ Space Research Institute, in cooperation with the Russian Federal Nuclear Centre; NASA’s Marshall Space Flight Center provided ART-XC’s X-Ray mirrors. The image above is the first light image from the 7 ART-XC telescopes, obtained on July 30, 2019. This image shows the well-known X-ray pulsar Cen X-3, a binary system in which a spinning neutron star (rotating once every 4.8 seconds) is in a 2-day orbit around Krzeminski’s star, a massive star about 20 times the mass of the Sun. ART-XC can also measure the time variation of the observed X-rays, and the plot on the bottom of the image clearly shows the 4.8 second X-ray variation of the pulsar as measured by ART-XC. eROSITA, developed by Germany’s Max Planck Institute, is the second instrument on SRG, and is expected to achieve first light in the coming weeks.
During the ART-XC calibration observations on August 3, the collaboration received a new scientific image:
As of August 7, 2019, the Spektr-RG spacecraft was continuing its flight to the L2 Sun – Earth system libration point area, the onboard equipment being adjusted. The ART-XC telescope creators expect to receive the images from the second telescope, eROSITA, to collate the fields of view of both telescopes.
eROSITA, the second telescope of the project was created in Germany. The spacecraft has already opened the lid used to cover the mirror systems entrance openings. eROSITA is expected to send its first images in mid-September.
Spektr-RG is a Russian-German joint project to create a space astrophysical observatory aimed to explore the Universe in the X-Ray electromagnetic radiation spectrum around the Sun – Earth system L2 point. The spacecraft was launched on July 13 2019 from the Baikonur Cosmodrome.