First tidal disruption events discovered by SRG/eROSITA: X-ray/optical properties and X-ray luminosity function at z < 0.6

High Energy Astrophysic

Spectroscopic redshift measurements for galaxy clusters detected in the Planck all-sky survey

We present the results of spectroscopic redshift measurements for galaxy clusters from the catalogue compiled previously from Planck all-sky survey data in combination with Sloan Digital Sky Survey (SDSS) and WISE data in the optical and infrared ranges. Most of these clusters are massive objects that will also be detected in future all-sky surveys, such as the eROSITA all-sky X-ray survey onboard the Spectrum–Roentgen–Gamma (SRG) space observatory. The spectroscopic observations of these galaxy clusters have been carried out with the 1.5-m Russian–Turkish telescope (RTT150), the 1.6-m Sayan Observatory AZT-33IK telescope, and the 6-m SAO RAS telescope (Bolshoi Teleskop Azimutalnyi, BTA). The spectroscopic redshift measurements have been obtained for 67 galaxy clusters, including 12 galaxy clusters from the second Planck catalogue of Sunyaev–Zeldovich sources

Spectroscopic Redshift measurements for galaxy clusters from the Planck Survey and observations of these clusters in the SRG/eROSITA Survey

We present the results of our spectroscopic redshift measurements for galaxy clusters detected previously from Planck all-sky survey data as well as Sloan Digital Sky Survey and WISE all-sky survey data. The redshifts have been measured for 23 clusters, including four galaxy clusters from the second Planck catalogue of Sunyaev–Zeldovich sources. The main spectroscopic observations were carried out during 2019–early 2020 at the 1.6-m AZT-33IK telescope of the Sayan Observatory and the 1.5-m Russian–Turkish telescope (RTT-150). Some of the data have been obtained previously at the 3.5-m Calar Alto telescope. Out of the 23 clusters in this sample, 14 objects are located in the half of the sky where the rights to the data from the eROSITA sky survey onboard the SRG orbital X-ray observatory belong to the Russian side. All these clusters were detected with the eROSITA telescope in the course of the sky survey during 2020. On the whole, we have measured the spectroscopic redshifts for 220 galaxy clusters within our program of optical identifications of galaxy clusters from the Planck catalogue during several years. Many of them have already been detected in the SRG/eROSITA survey; a significant fraction of these objects are among the most massive galaxy clusters of the eROSITA sky survey and will most likely enter into cosmological samples of clusters from this survey

Identification of three cataclysmic variables detected by the ART-XC and eROSITA telescopes on board the SRG during the all-sky X-ray survey

We report the discovery of three previously unknown cataclysmic variables in the data of the first year of the all-sky X-ray survey by the SRG orbital observatory. The sources were selected due to their brightness in the 4--12 keV band in the data of the Mikhail Pavlinsky ART-XC telescope. They are also detected by the eROSITA telescope, which provided accurate localizations and spectral data for broad-band spectral analysis. All three objects had been previously known as X-ray sources from the ROSAT all-sky survey and XMM-Newton slew survey, but their nature remained unknown. The X-ray spectra obtained by eROSITA and ART-XC are consistent with optically thin thermal emission with a temperature kT>~15 keV for SRGAJ194638.9+704552 and SRGAJ225412.8+690658 and kT>~5 keV for SRGAJ204547.8+672642. This, together with the inferred high X-ray luminosities ($2\times 10^{32}$-$3\times 10^{33}$ erg s$^{-1}$), strongly suggests that all three sources are CVs. We have obtained optical photometry and spectroscopy for these objects using the AZT-33IK 1.6-m telescope of the Sayan Observatory. The optical properties confirm the CV nature of the objects. We conclude that SRGAJ194638.9+704552 is an intermediate polar, SRGAJ204547.8+672642 is most likely a polar or an intermediate polar, and SRGAJ225412.8+690658 can be either a magnetic or a non-magnetic CV. We also measured an orbital period of 2.98~hours for SRGAJ204547.8+672642, based on TESS data. Three out of the planned eight SRG all-sky surveys have now been completed. We expect to find plenty of new CVs during the survey and to continue our optical follow-up program.Comment: Accepted for publication in A&A Special Issue: The Early Data Release of eROSITA and Mikhail Pavlinsky ART-XC on the SRG Mission. 9 pages, 5 figure

Optical identifications of galaxy clusters among objects from the second Planck catalogue of Sunyaev–Zeldovich sources

We present the results of optical identifications and spectroscopic redshift measurements for galaxy clusters from the second Planck catalogue of Sunyaev-Zeldovich sources. We used the data of observations with the 1.5-m Russian-Turkish telescope (RTT150), the 1.6-m Sayan Observatory AZT-33IK telescope, the 3.5-m Calar Alto telescope, and the 6-m SAO RAS telescope (Bolshoi Teleskop Azimutalnyi, BTA). For the observations we selected Sunyaev-Zeldovich sources unidentified with galaxy clusters with known redshifts. The observations have been carried out for three years, as a result of which we obtained direct images in various filters for a set of galaxy clusters and spectra for the brightest red-sequence galaxies of these clusters. For 38 galaxy clusters we obtained spectroscopic redshift measurements

Optical Identifications of Galaxy Clusters Among Objects from the Second Planck Catalogue of Sunyaev–Zeldovich Sources

© 2019, Pleiades Publishing, Inc. We present the results of optical identifications and spectroscopic redshift measurements for galaxy clusters from the second Planck catalogue of Sunyaev-Zeldovich sources. We used the data of observations with the 1.5-m Russian-Turkish telescope (RTT150), the 1.6-m Sayan Observatory AZT-33IK telescope, the 3.5-m Calar Alto telescope, and the 6-m SAO RAS telescope (Bolshoi Teleskop Azimutalnyi, BTA). For the observations we selected Sunyaev-Zeldovich sources unidentified with galaxy clusters with known redshifts. The observations have been carried out for three years, as a result of which we obtained direct images in various filters for a set of galaxy clusters and spectra for the brightest red-sequence galaxies of these clusters. For 38 galaxy clusters we obtained spectroscopic redshift measurements

Optical Identifications of Galaxy Clusters Among Objects from the Second Planck Catalogue of Sunyaev–Zeldovich Sources

© 2019, Pleiades Publishing, Inc. We present the results of optical identifications and spectroscopic redshift measurements for galaxy clusters from the second Planck catalogue of Sunyaev-Zeldovich sources. We used the data of observations with the 1.5-m Russian-Turkish telescope (RTT150), the 1.6-m Sayan Observatory AZT-33IK telescope, the 3.5-m Calar Alto telescope, and the 6-m SAO RAS telescope (Bolshoi Teleskop Azimutalnyi, BTA). For the observations we selected Sunyaev-Zeldovich sources unidentified with galaxy clusters with known redshifts. The observations have been carried out for three years, as a result of which we obtained direct images in various filters for a set of galaxy clusters and spectra for the brightest red-sequence galaxies of these clusters. For 38 galaxy clusters we obtained spectroscopic redshift measurements

Spectroscopic redshift measurements for galaxy clusters from the Lockman Hole survey with the eROSITA telescope onboard the SRG observatory

We present the first results of our program of optical observations for galaxy clusters from the Lockman Hole X-ray survey with the eROSITA telescope onboard the SRG space observatory. We present the results of spectroscopic redshift measurements for 11 galaxy clusters that have been identified optically among the extended X-ray sources of the SRG/eROSITA survey using data from optical and infrared sky surveys. The spectroscopic observations were carried out in late 2019–early 2020 with the 1.6-m AZT-33IK telescope of the Sayan Observatory and the 6-m SAO RAS telescope (Bolshoi Teleskop Azimutalnyi, BTA)

New active galactic nuclei detected by the ART-XC and eROSITA telescopes onboard the SRG observatory during an All-Sky X-ray Survey

We present the results of our identification of 17 X-ray sources detected in the 4–12 keV energy range by the Mikhail Pavlinsky ART-XC telescope during the first year of the SRG all-sky survey. Three of them have been discovered by the ART-XC telescopes, while the remaining ones have already been known previously as X-ray sources, but their nature has remained unknown. We took optical spectra for nine sources located in the northern sky (δ>−20∘) with the 1.6-m AZT-33IK telescope at the Sayan Observatory (the Institute of Solar–Terrestrial Physics, the Siberian Branch of the Russian Academy of Sciences) and the 1.5-m Russian–Turkish telescope at the TÜBITAK National Observatory. For the remaining objects we have analyzed the archival optical spectra taken during the 6dF survey. All of the investigated objects have turned out to be Seyfert galaxies (eight of type 1, seven of type 2, and two of intermediate type 1.8) at redshifts up to z≈0.15. Based on data from the eROSITA and ART-XC telescopes onboard the SRG observatory, we have obtained X-ray spectra in the energy range 0.2–20 keV for eight sources. A significant intrinsic absorption (NH>1022 cm−2) has been detected in three of them, with two of them being probably strongly absorbed (NH∼1023 cm−2). This paper is a continuation of the series of publications on the optical identification of active galactic nuclei detected by the ART-XC telescope