arXiv subjects

M. Demianenko

Publications and source records attributed to M. Demianenko.

3 recordsLinked to original sources

arXiv2026

Website with interactive visualization of multivariate astronomical time series

Light curves represent astronomical time series of flux measured across one or more photometric bands. With the rapid growth of large-scale sky surveys, time-domain astronomy has become an essential area of modern astrophysical research. Interactive visualization of extensive light-curve datasets plays a key role in exploring transient phenomena and in planning large follow-up campaigns. In this work, we introduce two web-based platforms designed for interactive light-curve visualization: Fulu, for transient event studies, and VALC, for investigations of low-mass active galactic nuclei (AGNs). These tools provide a user-friendly interface for examining, comparing, and interpreting vast collections of astronomical light curves, supporting scientific discovery.

astro-ph.IM↗

arXiv2024

Optical spectroscopy of host-galaxies of intermediate mass black holes: evolution of central black holes

Intermediate-mass black holes (IMBHs) with masses below ($2 \times 10^5 M_{\odot}$) are pivotal in understanding the origin and growth mechanisms of supermassive black holes (SMBHs) in galactic nuclei. This study focuses on the search and detailed analysis of central lightweight black holes in various galaxies. An expanded sample of IMBH candidates was selected from the RCSED optical spectral catalog, followed by refined spectral observations using large telescopes, including the Magellan, SALT, Keck and CMO telescopes. Analyzing over 70 spectra, we obtained accurate virial masses, stellar population parameters, and kinematics. One significant finding includes the detection of a binary black hole system with masses ($1.7 \times 10^5 M_{\odot})$ and $(1.4 \times 10^6 M_{\odot}$). Our results indicate that IMBHs and their low-mass SMBH counterparts do not necessarily co-evolve with their host galaxies, suggesting super-Eddington accretion as a dominant growth mechanism. This research enhances the precision of virial mass estimates and offers new insights into the $M_{BH} - \sigma_{bulge}$ relation, potentially impacting future high-redshift SMBH observations using next-generation facilities.

astro-ph.GA↗

arXiv2024

What excites the optical emission in X-ray-selected galaxies?

We present a study of $1347$ galaxies at $z<0.35$ with detected nuclear X-ray emission and optical emission line diagnostics in the Baldwin-Phillips-Terlevich (BPT) diagram. This sample was obtained by cross-matching the X-ray Multi-Mirror Mission Observatory - Newton (XMM-Newton) DR10 catalogue with Sloan Digital Sky Survey (SDSS) DR17 galaxies with well-measured line ratios. The distribution of these sources in the BPT diagram covers all three excitation regimes: Ionized Hydrogen (HII) regions (23\%), `composites' (30\%), and Seyfert galaxies with the low ionization nuclear emission line regions (LINERs) (47\%). In contrast, the fraction of objects classified as active galactic nuclei (AGN) in the SDSS subsample selected for cross-match with XMM-Newton is only 13\%. This fact illustrates that X-ray emission from galaxies commonly points towards the presence of AGN. Our data show, for the first time, a clear dependence of the BPT position on the ratio of the X-ray to $H\alpha$ fluxes. Sources dominated by X-ray emission lie in the Seyfert and LINER regimes of the BPT diagram. Most sources with a low X-ray-to-$H\alpha$-luminosity ratio, $log_{10}(L_X/L_{H\alpha}) < 1.0$, lie in the HII regime. In our sample, there are even 45 galaxies that have $L^{Star}_{XR}/L^{Total}_{Xray}>0.5$. In contrast, the positions of the sample members in the BPT diagram exhibit {no} dependence on the X-ray hardness ratio. Our finding suggests that the X-ray-to-$H\alpha$ ratio can help us to differentiate galaxies whose X-ray flux is dominated by an AGN {from galaxies with} central X-ray binaries and other stellar X-ray sources.

astro-ph.GA↗