arXiv subjects

Igor Zaznobin

Publications and source records attributed to Igor Zaznobin.

4 recordsLinked to original sources

arXiv2026

New galaxy cluster in the Zone of Avoidance SRGe CL0512.7+3712. Discovery and multi-wavelength characterization

The census of massive clusters of galaxies in the local Universe is almost complete, thanks to their prominent observational signatures at X-ray, optical, and sub-mm wavelengths. Nevertheless, a number of such systems are likely to be missing and hidden behind the plane of our Galaxy, where high interstellar absorption as well as strong contamination by foreground stellar and diffuse sources prevent detection of even the brightest and the most massive ones. Here we report the discovery and multiwavelength characterization of such a cluster in the zone of avoidance (ZoA) SRGe CL0512.7+3712 in the data of SRG/eROSITA all-sky survey. Combining the data of radio, optical, and infrared surveys, we identify overdensity of possible red sequence galaxies, as well as the candidate brightest cluster galaxy. Follow-up optical and X-ray observations confirm that the newly found object is a massive ($M_{500c}=(4-5)\cdot 10^{14}M_{\odot}$, $kT\approx 5 $ keV) galaxy cluster at redshift $z=0.0745$ with possible indications of unrelaxed dynamical scale. Location and elongation of this cluster is consistent with an expectation from the large-scale structure at this redshift, and it might be a part of an extended overdensity of such objects in the Galactic Anticenter direction. Examination of X-ray, radio, and infrared data in the locations of ZoA, where similar objects are expected to be found based on the large-scale structure properties, might reveal another $\sim10$ clusters at this redshift in future.

astro-ph.HE↗

arXiv2025

New Active Galactic Nuclei Detected by the ART-XC and eROSITA Telescopes during the First Five SRG All-Sky X-ray Surveys. Part 2

We present the results of our identification of 11 X-ray sources detected on the half of the sky $0^\circ<l<180^\circ$ in the 4-12 keV energy band on the combined map of the first five all-sky surveys with the Mikhail Pavlinsky ART-XC telescope onboard the SRG observatory. All these sources were also detected by the SRG/eROSITA telescope in the 0.2-8 keV energy band, whose data have allowed us to improve their positions and to investigate their X-ray spectra. Five of them have been detected in X-rays for the first time, while the remaining ones have already been known previously, but their nature has remained unknown. We have taken optical spectra for nine sources 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); for two more objects we have analyzed the archival spectra from SDSS and the 6dF survey. The objects are classified as Seyfert galaxies (seven Sy1, three Sy1.9, and one Sy2) at redshifts $z$=0.029-0.258. Our analysis of the X-ray spectra has revealed a noticeable intrinsic absorption ($N_{\rm H} \sim 10^{22}$ cm$^{-2}$) in two of the four Seyfert 2 galaxies (Sy1.9-2). The spectrum of one more of them (SRGA J000132.9+240237) cannot be described within the model of an absorbed Comptonization continuum, which may point to a strong absorption and a significant contribution of the reflected radiation. However, the available SRG all-sky survey data are not enough to obtain reliable constraints on the absorption column density in this object, which is also interesting in that it is radio loud. Longer X-ray observations are required to refine the physical properties of this active galactic nucleus.

astro-ph.HE↗

arXiv2023

New Active Galactic Nuclei Detected by the ART-XC and eROSITA Telescopes during the First Five SRG All-Sky X-ray Surveys

We present the results of our identification of 14 X-ray sources detected in the eastern Galactic sky ($0 10^{22}$ cm$^{-2}$ at a 90% confidence level, with one of them being probably heavily obscured ($N_{\rm H}>5\times 10^{22}$ cm$^{-2}$ with 90% confidence). This paper continues our series of publications on the identification of hard X-ray sources detected during the all-sky survey with the SRG orbital X-ray observatory.

astro-ph.HE↗

arXiv2022

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 $δ> -20$ deg 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 TUBITAK 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 $z\approx 0.15$. 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 ($N_H > 10^{22}$ cm$^{-2}$) has been detected in three of them, with two of them being probably strongly absorbed ($N_H \sim 10^{23}$ 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.

astro-ph.GA↗