arXiv subjects

Dmitry Chulkov

Publications and source records attributed to Dmitry Chulkov.

7 recordsLinked to original sources

arXiv2025

Pleiades Binary Fraction Revisited

One of the nearest and best studied open clusters, Pleiades is an important cornerstone of stellar astrophysics. Despite its role as reference coeval stellar population, its multiplicity properties remain vaguely determined. The combined use of Gaia DR3 multiband photometry, astrometric parameter RUWE, non-single star solutions along with available ground-based spectroscopic, high angular resolution, and polarimetric observations enable more robust constraints on the binary star population in the cluster. Several conclusions may have broader implications for other stellar populations. Twin binaries, with mass ratio close to $q\sim 1$, tend to have lower RUWE, increasing their membership selection probability, relative to $q\sim 0.5$ systems that are disfavored. The frequently observed peak in mass ratio distribution for $q\sim 1$ binaries may be partially attributed to this bias. Photometrically fitted mass ratio is underestimated for double-lined spectroscopic binaries in agreement with other authors. Differential extinction photometrically mimics stellar binarity. An area of enlarged absorption is traced by increased polarization south of the Merope star and excluded from the analysis to avoid this bias. The fraction of systems with $q>0.6$ companions is measured to be $f=16.4\%^{+2.6}_{-0.6}$ for $m>0.5~M_\odot$ stars, which is larger than recent Gaia-based estimates, but compatible with the pre-Gaia values for Pleiades and the field population. Binary fraction shows no steady increase with stellar mass in the 0.5 $-$ 1.2 $M_\odot$ range, while mass ratio has a bimodal distribution with a minimum near $q\sim 0.7$.

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arXiv2024

Resolving Pleiades binary stars with Gaia and speckle interferometric observations

The Pleiades is the most prominent open star cluster visible from Earth and an important benchmark for simple stellar populations, unified by common origin, age, and distance. Binary stars are its essential ingredient, yet their contribution remains uncertain due to heavy observational biases. A resolved multiplicity survey was conducted for a magnitude-limited G < 15mag sample of 423 potential cluster members, including sources with poorly fitted astrometric solutions in Gaia DR3. Speckle interferometric observations at the 2.5 meter telescope of SAI MSU observatory were combined with Gaia data, enabling the identification of 61 resolved binary or multiple systems within the 0.04 - 10 arcsec (5 - 1350 au) separation range. With speckle observations, we discovered 21 components in 20 systems. The existence of a Merope (23 Tau) companion is confirmed after several previous unsuccessful attempts. We show that the Gaia multipeak fraction is a strong predictor of subarcsecond multiplicity, as all sources with ipd_frac_multi_peak > 4% are successfully resolved. We found that 10% of Pleiades stars have a companion with a mass ratio q > 0.5 within projected separation of 27 < s < 1350 au, and confirm a deficit of wide binaries with s > 300 au. An observed dearth of wide pairs with large mass ratio (q > 0.55) may imprint the transition from hard to soft binaries regime at the early stages of cluster evolution. The total binary fraction for q > 0.5 systems is extrapolated to be around 25%.

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arXiv2024

Unveiling subarcsecond multiplicity in the Pleiades with Gaia multicolor photometry

The list of 409 probable cluster members down to $G=15^{\rm mag}$ ($m \gtrsim 0.5M_\odot$) is compiled for the two degree radius of the Pleiades, based on astrometric data from Gaia DR3 and the PPMXL catalog, along with several radial velocity surveys, including APOGEE and LAMOST. This approach allows for the inclusion of binary stars with unreliable Gaia solutions, thereby eliminating associated bias. Thus, the often-neglected 14 sources with Gaia two-parameter solutions are included. The subsequent analysis of color-magnitude and color-color diagrams exploits artifacts in Gaia photometric data, caused by the different field sizes used to measure fluxes in the $G$, $B_p$, and $R_p$ passbands, to reveal binary stars with subarcsecond angular separation. The findings are validated with prior high-resolution observations. Overall, $24 \pm 3$ cluster members with angular separation between 0.1 and 1 arcsec (13.5 to 135 AU projected distance) and mass ratio $q>0.5$ are deemed binary, indicating a binarity fraction of $6 \pm 1$\%.

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arXiv2022

Visual binary stars with known orbits in Gaia EDR3

3350 objects from the Sixth catalog of orbits of visual binary stars (ORB6) are investigated to validate Gaia EDR3 parallaxes and provide mass estimates for the systems. We show that 2/3 of binaries with 0.2 - 0.5 arcsec separation are left without a parallax solution in EDR3. A special attention is paid to 521 pairs with parallax known separately for both components. We find 16 entries that are deemed to be chance alignments of unrelated stars. At once we show examples of high-confidence binary systems with significant differences in the reported parallaxes of their components. Next we conclude that the reported Gaia EDR3 parallax errors are underestimated, at least by a factor of 3 for sources with large RUWE. Parallaxes are needed to estimate stellar masses. Since nearly 30\% of ORB6 entries lack 5 or 6-parameter solution in EDR3, we attempt to enrich the astrometric data. Distant companions of ORB6 entries are revealed in EDR3 by analysis of stellar proper motions and Hipparcos parallaxes. Notably, in 28 cases intrinsic EDR3 parallaxes of the binary components appear to be less reliable than the parallax of the outer companions. Gaia DR2, TGAS and Hipparcos parallaxes are used when EDR3 data is unavailable. Synthetic mass-luminosity relation in the G band for main sequence stars is obtained to provide mass estimates along with dynamical masses calculated via Kepler's Third Law.

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arXiv2020

Pairing function of visual binary stars

An all-sky sample of 1227 visual binaries based on Washington Double Star catalogue is constructed to infer the IMF, mass ratio, and projected distance distribution with a dedicated population synthesis model. Parallaxes from Gaia DR2 and Hipparcos are used to verify the distance distribution. The model is validated on the single-star Tycho-2 sample and successfully reproduces the observed magnitudes and angular separations. The projected separation distribution follows $f(s)\sim s^{-1.2}$ in $10^2 - 2\cdot10^3$ AU range for 1--4.5 $m_{\odot}$ primary stars. Several algorithms are explored as pairing functions. Random pairing is confidently rejected. Primary-constrained (PCP) and split-core pairing (SCP), the scenarios adopting primary component's or total system's mass as fundamental, are considered. The preferred IMF slope is $α\sim 2.8$ either way. A simple power-law mass ratio distribution is unlikely, but the introduction of a twin excess provides a favourable result. PCP with $f(q) \sim q^{-1}$ is preferred with a tiny twin fraction, models with $f(q) \sim q^{-1.5}$ are acceptable when a larger twin excess is allowed. SCP is similar to PCP when a larger slope of the power law is adopted: $f(q)\sim q^{β+0.7}$.

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arXiv2018

Verification of Photometric Parallaxes with Gaia DR2 Data

Results of comparison of Gaia DR2 parallaxes with data derived from a combined analysis of 2MASS (Two Micron All-Sky Survey), SDSS (Sloan Digital Sky Survey), GALEX (Galaxy Evolution Explorer), and UKIDSS (UKIRT Infrared Deep Sky Survey) surveys in four selected high-latitude $|b|>48^{\circ}$ sky areas are presented. It is shown that multicolor photometric data from large modern surveys can be used for parameterization of stars closer than 4400 pc and brighter than $g_{SDSS} = 19.^m6$, including estimation of parallax and interstellar extinction value. However, the stellar luminosity class should be properly determined.

astro-ph.SR↗

arXiv2017

Catalogues, parameters and distributions of orbital binaries

The most complete list of visual binary systems with known orbital elements is compiled. It is based on OARMAC and ORB6 data and contains 3139 orbits for 2278 pairs. A refined subset of high quality orbits with available distance was also compiled. Relations between and distributions along different observational parameters are constructed, and an analysis of selection effects is made. Dynamical, photometric and spectral masses of systems are estimated, and reasons for discrepancies between them are discussed.

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