arXiv subjects

I. A. Shaposhnikov

Publications and source records attributed to I. A. Shaposhnikov.

6 recordsLinked to original sources

arXiv2026

Wolf-Rayet stars and black holes: mass distributions and evolutionary connection

The form and relationship between the mass distributions of Wolf-Rayet stars and black holes are analyzed using a direct method for estimating the distribution function from a sample of mass values with individual distributions obtained from current observations. It is shown that, taking into account the mass loss of WR stars by the end of this evolutionary stage, the mass distribution of black holes is close to that of the CO-cores of WR stars before gravitational collapse, $M_\mathrm{BH}\simeq M_\mathrm{CO}$.

astro-ph.HE↗

arXiv2026

Orbital Parameters of the Unusual WR + O Binary System LS III +44 21

We present the results of a spectroscopic study of the recently discovered WR + O binary system LS III +44 21. The system is unusual because, despite having characteristics similar to those of the classical WR + O system V444 Cyg, its X-ray emission is completely absent. We refined the spectral classification of the system components to WN4 + O7III?(f) and obtained their radial velocity curves for the first time. The solution of these curves reveals that the system has a circular orbit. Using photometric observations from ASAS-SN and TESS, we significantly refined the values of the initial epoch T_0 and the orbital period P. The radial velocity curve solution with the updated T_0 and P allowed us to determine the parameters of the orbit and the system components for the first time. A preliminary qualitative analysis of the light curves obtained by the TESS satellite and the ASAS-SN project, combined with the interesting variability of the N IV and N V ion line profiles with the orbital phase that we detected, suggests that the lack of X-ray emission from the system may be due to an unusually weak stellar wind from the WR star. The shape of the highly precise mean TESS light curve is extremely unusual, exhibiting non-monotonic behavior near the quadratures and an unusual morphology of the secondary minimum, which shows a nearly total eclipse yet with rounded edges. Such a shape cannot be modeled within the standard Roche geometry, which may provide a direct indication of the influence of the component stellar winds.

astro-ph.SR↗

arXiv2025

The jet and circumstellar environment of the young binary DF Tau

Jets and disc winds play an important role in the evolution of protoplanetary discs and the formation of planetary systems. However, there is still a lack of observational data regarding the presence and parameters of outflows, especially for close young binaries. In this study, we aim to find the HH flow near the young sub-arcsecond binary DF Tau and explore its morphology. Narrow-band H$α$ and H$_2$ 2.12 $μ$m imaging and spectroscopic observations of DF Tau and its vicinity were performed. We have discovered several emission nebulae near the binary, which likely result from the interaction of gas outflow from the binary components with the surrounding medium. The outflow appears to occur both in the form of jets, generating numerous Herbig-Haro objects (HH 1266 flow), and as a weakly collimated wind responsible for the formation of the ring-like nebula around the binary and the rim of the cometary globule. We have found that the angle between the jet and the counter-jet is $168^\circ$ and discuss the complex morphology of the HH flow.

astro-ph.SR↗

arXiv2024

High-resolution spectroscopy of the variable hot post-AGB star LS 4331 (IRAS 17381-1616)

An analysis of high-resolution ($R\sim48\,000$) optical spectrum of hot (B1Ibe) post-AGB star LS 4331 (IRAS 17381-1616) is presented. The detailed identification of the observed absorption and emission features in the wavelength range 3700-9200 Å is carried out for the first time. From non-LTE analysis of absorption lines the atmospheric parameters and chemical composition of the star are derived. We estimate $T_{\rm eff}=20~900\pm500$ K, $\log g=2.57\pm0.08$, $V_r=-51.7\pm0.8$ km s$^{-1}$, $ξ_{\rm t}=24\pm4$ km s$^{-1}$ and $v \sin i=30\pm5$ km s$^{-1}$. A abundance analysis for C, N, O, Mg, Al, S and Si reveals that the N and O abundance is close to solar while metal underabundances relative to the solar value (i.e. [Mg/H] = -1.04 dex, [Al/H] = -1.20 dex, [Si/H] = -0.46 dex) are found. We conclude that LS 4331 is a high galactic latitude metal-poor and carbon deficient hot post-AGB star. The underabundance of carbon ([C/H]= -0.64 dex) is similar to that found in other hot post-AGB stars and indicates that the star's AGB phase of evolution was terminated before the third dredge up. From the nebular emission lines the plasma diagnostics are derived. The presence of nebular emission lines in the spectrum of LS 4331 indicates that the photoionization of circumstellar envelope has already started. The nebular parameters and expansion velocity of the nebula is derived. Using the Gaia DR3 distance the absolute luminosity of the star is derived and the star's position on the post-AGB evolutionary tracks suggests that its initial main sequence mass is about 1.2$M_{\odot}$. It is also reported that fast irregular brightness variations with an amplitude of up to 0.3 mag in $V$ band have been found in the star, typical of hot post-AGB objects.

astro-ph.SR↗

arXiv2024

Spectroscopic Searches for Evolutionary Orbital Period Changes in WR+OB Binaries: the Case of WR 127 (Hen 3-1772)

We aim at searching for secular evolution of the orbital period in the short-period binary system WR 127 (WN3b+O9.5V, $P = 9.555^d$). We performed new low-resolution spectroscopic observations of WR 127 on 2.5-m CMO SAI telescope to construct the radial velocity curves of the components suggesting the component masses $M_\mathrm{WR}\sin^3(i) = 11.8\pm1.4$ $M_{\odot}$, $M_\mathrm{O}\sin^3(i)=17.2\pm1.4$ $M_{\odot}$. The comparison with archival radial velocity curves enabled us to calculate the $(O-C)$ plot with accuracy sufficient to search for the orbital period change in WR 127. We report on the reliable detection of a secular increase in the orbital period of WR 127 at a rate of $\dot{P} = 0.83\pm0.14~\mbox{s~yr}^{-1}$ corresponding to the dynamical mass-loss rate from the WR star $\dot{M}_\mathrm{WR} = (2.6\pm0.5)\times 10^{-5}$ $M_{\odot}$ yr$^{-1}$. The mass-loss rate from WR stars in three WR+OB binaries (WR 127, CX Cep and V444 Cyg) as inferred from spectroscopic and photometric measurements suggests a preliminary empirical correlation between the WR star mass and the dynamical mass-loss rate $\dot M_\mathrm{WR}\sim M_\mathrm{WR}^{1.8}$. This relation is important for the understanding of the evolution of massive close binaries with WR stars -- precursors of gravitational-wave binary merging events with neutron stars and black holes.

astro-ph.SR↗

arXiv2021

Spectroscopic Variability of the Compact Planetary Nebula Hb 12

We present the results of our new low-resolution spectroscopic observations of the young compact planetary nebula Hb 12 performed in 2011-2020 with SAI MSU telescopes. We have measured the intensities of more than 50 nebular emission lines in the spectral range $λ$3687-9532, detected interstellar absorption features, and conducted a search for absorptions belonging to the possible secondary component of the central star. The extinction coefficient has been estimated from the Balmer decrement to be $c$(H$β$)=1.15$\pm$0.07. The distance has been found by analyzing the interstellar extinction maps to be $D\approx2400$ pc. We have traced the history of the spectroscopic observations of Hb 12, beginning with the first spectra taken by Aller (1951) in 1945. We have detected a systematic increase in the relative intensities of the nebular [O III] $λ$4959 and $λ$5007 lines and a decrease in the relative intensity of the auroral [O III] $λ$4363 line, which has led to an increase in the observed flux ratio $F(λ4959+λ5007)/F(λ4363)$ by a factor of $\sim$4 from 1945 to the present time. The [O III]/[O II] line ratio $F(λ4363)/F(λ3727+ \lambda3729)$ remains constant, suggesting that the degree of ionization, on average, for the nebula is invariable. The temperature of the exciting star has been estimated to be $T\approx41~000$ K. We conclude that a decrease in the electron temperature and, possibly, the electron density in the [O III] line formation region is mainly responsible for the spectroscopic variability.

astro-ph.SR↗