SRG X-ray orbital observatory

Abstract

The orbital observatory Spectrum-Roentgen-Gamma (SRG), equipped with the grazing-incidence X-ray telescopes Mikhail Pavlinsky ART-XC and eROSITA, was launched by Roscosmos to the Lagrange L2 point of the Sun-Earth system on July 13, 2019. The launch was carried out from the Baikonur Cosmodrome by a Proton-M rocket with a DM-03 upper stage. The German telescope eROSITA was installed on SRG under an agreement between Roskosmos and the DLR, the German Aerospace Agency. In December 2019, SRG started to perform its main scientific task: scanning the celestial sphere to obtain X-ray maps of the entire sky in several energy ranges (from 0.3 to 8 keV with eROSITA, and from 4 to 30 keV with ART-XC). By mid-June 2021, the third six-month all-sky survey had been completed. Over a period of four years, it is planned to obtain eight independent maps of the entire sky in each of the energy ranges. The sum of these maps will provide high sensitivity and reveal more than three million quasars and over one hundred thousand massive galaxy clusters and galaxy groups. The availability of eight sky maps will enable monitoring of long-term variability (every six months) of a huge number of extragalactic and Galactic X-ray sources, including hundreds of thousands of stars with hot coronae. In addition, the rotation of the satellite around the axis directed toward the Sun with a period of four hours enables tracking the faster variability of bright X-ray sources during one day every half year. The chosen strategy of scanning the sky leads to the formation of deep survey zones near both ecliptic poles. The paper presents sky maps obtained by the telescopes on board SRG during the first survey of the entire sky and a number of results of deep observations performed during the flight to the L2 point in the frame of the performance verification program, demonstrating the capabilities of the observatory in imaging, spectroscopy, and timing of X-ray sources. It is planned that in December 2023, the observatory will for at least two years switch to observations of the most interesting sources in the sky in triaxial orientation mode and deep scanning of selected celestial fields with an area of up to 150 square degrees. These modes of operation were tested during the performance verification phase. Every day, data from the SRG observatory are dumped onto the largest antennas of the Russian Deep Space Network in Bear Lakes and near Ussuriysk.

Host galaxy properties of quasi-periodically erupting X-ray sources

“…These large amplitude (in excess of an order of magnitude), short (duration of several tens of minutes to hours) eruptions recur on timescales of hours to approximately a day (Miniutti et al 2019;Giustini et al 2020;Arcodia et al 2021). They were first discovered serendipitously in pointed (Miniutti et al 2019) and archival (Giustini et al 2020) XMM-Newton observations, and more recently they were also discovered in a blind X-ray survey (Arcodia et al 2021) performed by the eROSITA instrument (Predehl et al 2021) aboard the Spectrum-Roentgen-Gamma telescope (Sunyaev et al 2021) as well as targeted searches in X-ray archives (Chakraborty et al 2021).…”

Constraints on the X-ray Luminosity Function of AGN at z=5.7-6.4 with the Extragalactic Serendipitous Swift Survey

“…Our source can be seen to be the highest redshift source identified serendipitously by X-ray surveys with a well-defined area coverage, from which an XLF can be determined. The sensitivity limits of eROSITA, for the equatorial region after 6 months (eRASS:1), after 4 years (eRASS:8) and the Polar region after 4 years of the survey are shown by the dashed line, the dot-dashed line and the dotted line respectively, with our ExSeSS 𝑧 > 6 quasar lying along the limit of greatest sensitivity possible with eROSITA(Predehl et al 2021;Sunyaev et al 2021) and at the highest redshift of all serendipitously detected AGN.…”

The eROSITA extragalactic CalPV serendipitous catalog

“…The Russian-German "Spectrum-Roentgen-Gamma" (SRG) observatory (Sunyaev et al 2021) was successfully launched on 13 July 2019, and subsequently brought into a large halo orbit around the Lagrangian point L2 of the Sun-Earth system. SRG largest instrument is the eROSITA X-ray telescope (Predehl et al 2021), the main mission of which, i.e., a deep all-sky survey, started in December 2019 and will take four years to scan the full sky eight times.…”