arXiv subjects

Ilya Mereminskiy

Publications and source records attributed to Ilya Mereminskiy.

7 recordsLinked to original sources

arXiv2025

SRGAJ230631.0+155633: an extremely X-ray luminous, heavily obscured, radio-loud quasar at z=0.44 discovered by SRG/ART-XC

We report on a detailed study of a luminous, heavily obscured ($N_{\rm H} \sim 2 \times 10^{23}$ cm$^{-2}$), radio-loud quasar SRGAJ230631.0+155633, discovered in the 4--12 keV energy band by the Mikhail Pavlinsky ART-XC telescope aboard the SRG observatory during the first two years of its all-sky X-ray survey in 2020--2021. The object is located at $z=0.4389$ and is a type 2 AGN according to optical spectroscopy (SDSS, confirmed by DESI). We combine radio-to-X-ray data, including near-simultaneous ART-XC and Swift/XRT observations conducted in June 2023. During these follow-up observations, the source was found in a significantly fainter but still very luminous state ($L_{\rm X}=1.0^{+0.8}_{-0.3} \times 10^{45}$ erg s$^{-1}$, absorption corrected, 2--10 keV) compared to its discovery during the all-sky survey ($L_{\rm X}=6^{+6}_{-3}\times10^{45}$ erg s$^{-1}$), which indicates significant intrinsic variability on a rest-frame time scale of $\sim 1$ year. The radio data show a complex morphology with a core and two extended radio lobes, indicating a giant FRII radio galaxy. From multi-wavelength photometry and the black hole-bulge relation we infer a bolometric luminosity of $\sim 6\times10^{46}$ erg s$^{-1}$ and a black hole mass of $\sim1.4\times10^{9}\,M_\odot$, implying accretion at $\sim30$\% of the Eddington limit. SRGAJ230631.0+155633 proves to be one of the most luminous obscured quasars out to $z=0.5$. As such, it can serve as a valuable testbed for in-depth exploration of the physics of such objects, which were much more abundant in the younger Universe.

astro-ph.HE↗

arXiv2023

Spectral and temporal analysis of the Supergiant Fast X-ray Transient IGR J16195-4945 with SRG/ART-XC

We present the results of the analysis of the SRG/ART-XC observation of the Supergiant Fast X-ray Transient IGR J16195-4545 performed on March 3, 2021. Six bright flares are present in the light curve, with no significant change in hardness occuring during these flares. The spectrum is described with an absorbed power law model with a high energy exponential cutoff showing heavy absorption, with $N_H=(12\pm2)\times 10^{22}\text{ cm}^{-2}$ and $Γ=0.56\pm 0.15$, $E_{cut}=13\pm 2$ keV. Adopting the Bayesian block decomposition of the light curve, we measured the properties of the observed flares (duration, rise time, waiting time, released energy and pre-flare luminosity), which are consistent with the quasi-spherical subsonic accretion model. The stellar wind velocity of the supergiant is estimated to be $v_{w} \approx 500$ km s$^{-1}$. Additionally, the system was found to have an unusual near-IR variability.

astro-ph.HE↗

arXiv2022

SRGA J181414.6-225604: A new Galactic symbiotic X-ray binary outburst triggered by an intense mass loss episode of a heavily obscured Mira variable

We present the discovery and multi-wavelength characterization of SRGA J181414.6-225604, a Galactic hard X-ray transient discovered during the ongoing SRG/ART-XC sky survey. Using data from the Palomar Gattini-IR survey, we identify a spatially and temporally coincident variable infrared (IR) source, IRAS 18111-2257, and classify it as a very late-type (M7-M8), long period ($1502 \pm 24$ days) and luminous ($M_K\approx -9.9 \pm 0.2$) O-rich Mira donor star located at a distance of $\approx 14.6^{+2.9}_{-2.3}$ kpc. Combining multi-color photometric data over the last $\approx 25$ years, we show that the IR counterpart underwent a recent (starting $\approx 800$ days before the X-ray flare) enhanced mass loss (reaching $\approx 2.1 \times 10^{-5}$ M$_\odot$ yr$^{-1}$) episode resulting in an expanding dust shell obscuring the underlying star. Multi-epoch follow-up from Swift, NICER and NuSTAR reveal a $\approx 200$ day long X-ray outburst reaching a peak luminosity of $L_X \approx 2.5 \times 10^{36}$ erg s$^{-1}$, characterized by a heavily absorbed ($N_{\rm H} \approx 6\times 10^{22}$ cm$^{-2}$) X-ray spectrum consistent with an optically thick Comptonized plasma. The X-ray spectral and timing behavior suggest the presence of clumpy wind accretion together with a dense ionized nebula overabundant in silicate material surrounding the compact object. Together, we show that SRGA J181414.6-225604 is a new symbiotic X-ray binary in outburst, triggered by an intense dust formation episode of a highly evolved donor. Our results offer the first direct confirmation for the speculated connection between enhanced late-stage donor mass loss and active lifetimes of the symbiotic X-ray binaries.

astro-ph.HE↗

arXiv2022

INTEGRAL/IBIS 17-yr hard X-ray all-sky survey

The International Gamma-Ray Astrophysics Laboratory (INTEGRAL), launched in 2002, continues its successful work in observing the sky at energies E>20 keV. The legacy of the mission already includes a large number of discovered or previously poorly studied hard X-ray sources. The growing INTEGRAL archive allows one to conduct an all-sky survey including a number of deep extragalactic fields and the deepest ever hard X-ray survey of the Galaxy. Taking advantage of the data gathered over 17 years with the IBIS coded-mask telescope of INTEGRAL, we conducted survey of hard X-ray sources, providing flux information from 17 to 290 keV. The catalog includes 929 objects, 890 of which exceed a detection threshold of 4.5 sigma and the rest are detected at 4.0-4.5 sigma and belong to known cataloged hard X-ray sources. Among the identified sources of known or suspected nature, 376 are associated with the Galaxy and Magellanic clouds, including 145 low-mass and 115 high-mass X-ray binaries, 79 cataclysmic variables, and 37 of other types; and 440 are extragalactic, including 429 active galactic nuclei (AGNs), 2 ultra-luminous sources, one supernova (AT2018cow) and 8 galaxy clusters. 113 sources remain unclassified. 46 objects are detected in the hard X-ray band for the first time. The LogN-LogS distribution of 356 non-blazar AGNs is measured down to a flux of 2E-12 erg/s/cm2 and can be described by a power law with a slope of 1.44 +/- 0.09 and normalization 8E-3/deg2 at 1E-11 erg/s/cm2. The LogN-LogS distribution of unclassified sources indicates that the majority of them are of extragalactic origin.

astro-ph.HE↗

arXiv2021

Identification of SRGt 062340.2-265715 as a bright, strongly variable, novalike cataclysmic variable

We report the identification and follow-up of the transient SRG 062340.2-265715 detected with both instruments on board the Spektrum-Roentgen-Gamma mission. Optical spectroscopy of the G=12.5 counterpart firmly classifies the object as a novalike cataclysmic variable (CV) at a distance of 495 pc. A highly significant TESS period of 3.941 hours, tentatively identified with the orbital period of the binary, could not be found when the object was reobserved with TESS two years later. The newer high-cadence TESS data revealed quasi-periodic oscillations around 25 min, while ground-based photometry indicated periodic variability at 32 min. Located in very sparsely populated regions of color-magnitude diagrams involving X-ray and optical magnitudes and colors, the new object could be an X-ray underluminous magnetic CV, an intermediate polar, or an overluminous nonmagnetic CV. The lack of uniquely identified spin and orbital periods prevents a final classification. The site of X-ray production in the system, L(X, bol) = 4.8 x 10^{32} erg/s, remains to be understood given its high variability on long and short timescales.

astro-ph.SR↗

arXiv2020

INTEGRAL view of AGN

AGN are among the most energetic phenomena in the Universe and in the last two decades INTEGRAL's contribution in their study has had a significant impact. Thanks to the INTEGRAL extragalactic sky surveys, all classes of soft X-ray detected (in the 2-10 keV band) AGN have been observed at higher energies as well. Up to now, around 450 AGN have been catalogued and a conspicuous part of them are either objects observed at high-energies for the first time or newly discovered AGN. The high-energy domain (20-200 keV) represents an important window for spectral studies of AGN and it is also the most appropriate for AGN population studies, since it is almost unbiased against obscuration and therefore free of the limitations which affect surveys at other frequencies. Over the years, INTEGRAL data have allowed to characterise AGN spectra at high energies, to investigate their absorption properties, to test the AGN unification scheme and to perform population studies. In this review the main results are reported and INTEGRAL's contribution to AGN science is highlighted for each class of AGN. Finally, new perspectives are provided, connecting INTEGRAL's science with that at other wavelengths and in particular to the GeV/TeV regime which is still poorly explored.

astro-ph.HE↗

arXiv2017

New hard X-ray sources discovered in the ongoing INTEGRAL Galactic Plane survey after 14 years of observations

The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) continues to successfully work in orbit after its launch in 2002. The mission provides the deepest ever survey of hard X-ray sources throughout the Galaxy at energies above 20 keV. We report on a catalogue of new hard X-ray source candidates based on the latest sky maps comprising 14 years of data acquired with the IBIS telescope onboard INTEGRAL in the Galactic Plane (|b|<17.5 deg). The current catalogue includes in total 72 hard X-ray sources detected at S/N>4.7 sigma and not known to previous INTEGRAL surveys. Among them, 31 objects have also been detected in the on-going all-sky survey by the BAT telescope of the Swift observatory. For 26 sources on the list, we suggest possible identifications: 21 active galactic nuclei, two cataclysmic variables, two isolated pulsars or pulsar wind nebulae, and one supernova remnant; 46 sources from the catalogue remain unclassified.

astro-ph.HE↗