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N. A. Gorynya

Publications and source records attributed to N. A. Gorynya.

8 recordsLinked to original sources
arXiv2023

Precise Fourier parameters of Cepheid Radial Velocity Curves

The primary goal of this paper is to derive precise Fourier parameters of the radial velocity (RV) curves for fundamental and first-overtone Galactic Cepheids. For each star, we carefully selected RV measurements available in the literature which yield the highest precision of Fourier parameters. We performed a Fourier decomposition of the RV curves. We subtracted RV modulations caused by binary motion and have removed other residual trends. Finally, we have displayed and analyzed qualitatively the progressions found for Fourier parameters. We applied a standard identification of their pulsation mode based on their Fourier phase $ϕ_{21}$. Our final sample includes 178 fundamental-mode and 33 first overtone pulsators, as well as 7 additional Cepheids whose pulsation mode is uncertain or undetermined according to our criteria. For the fundamental-mode Cepheids, we improved the precision of Fourier parameters in comparison of previous results from the literature. We are able to firmly identify V495 Cyg as a new first-overtone Cepheid. We confirm first-overtone nature of several other stars. We also show that $α$ UMi should be definitely classified as a first-overtone pulsator. In 3 objects (VY Per, AQ Pup and QZ Nor) we found significant $γ$-velocity variations that we attribute to spectroscopic binarity. Finally, the analysis of the F-mode Fourier parameters up to 7th order reveals tight progression of Fourier phases. For $P<10\,$day we find a well defined upper limit for the Fourier amplitude $A_1$. The pulsation period coverage and the precision obtained, in particular for Fourier phase $ϕ_{21}$, will be useful for studying the dynamics of Cepheid pulsations with the help of hydrodynamical models. Further radial velocity measurements from modern high-resolution spectroscopic instruments will be important to improve these results.

astro-ph.SR↗
arXiv2018

Spectroscopic orbits of nearby solar-type dwarfs. II

Several nearby solar-type dwarfs with variable radial velocity were monitored to find their spectroscopic orbits. First orbital elements of 15 binaries (HIP 12144, 17895, 27970, 32329, 38636, 39072, 40479, 43004, 73700, 79234, 84696, 92140, 88656, 104514, and 112222) are determined. The previously known orbits of HIP 5276, 21443, 28678, and 41214 are confirmed and updated. The orbital periods range from 2 days to 4 years. There are 8 hierarchical systems with additional distant companions among those 19 stars. The outer visual orbit of the triple system HIP 17895 is updated and the masses of all its components are estimated. We provide radial velocities of another 16 Hipparcos stars without orbital solutions, some of those with long periods or false claims of variability.

astro-ph.SR↗
arXiv2015

PZ Mon is a new synchronous binary with low mass ratio

Analysis of new radial velocity measurements of the active giant PZ Mon is presented. Only in 2015 was reported that PZ Mon may be classified as RS CVn giant. At the same time was discovered the variability of radial velocity. However, lack of the data is not allowed to determine parameters of the system. The measurements of radial velocity were performed using Radial Velocity Meter installed at the Simeiz 1-m telescope of the Crimean Astrophysical Observatory and using echelle spectrographs installed at the 2-m Zeiss telescope of the Terskol Observatory and the 6-m telescope BTA of the Special Astrophysical Observatory of the Russian Academy of Sciences. We estimated parameters of this binary system including the $γ$-velocity 25.5$\pm$0.3 kms, the period on the circular orbit $P=34.15\pm0.02$ days, the mass of the secondary component $M_2$=0.14 \Mo, and the mass ratio $q=0.09$ The mass ratio is a smallest value among known RS CVn type giants. Combined with photometric data we conclude that PZ Mon is a system with synchronous rotation, and there is a big cool spotted area on the stellar surface towards to the secondary component that provides the optical variability.

astro-ph.SR↗
arXiv2014

Evolutionary status of the active star PZ Mon

We use original spectra and available photometric data to recover parameters of the stellar atmosphere of PZ Mon, formerly referred as an active red dwarf. The derived effective temperature Teff=4700K and gravity lgg=2.8 suggest that PZ Mon is a K2III giant. Stellar atmosphere parameters (Teff and lgg) alongside with the evolutionary tracks are used to estimate the stellar mass of ~1.5Mo and the radius of ~7.7Ro. The angular radius derived by the infrared flux method when combined with the linear radius suggests the distance of 250+/-70 pc, a factor 2.5 smaller than that suggested by the Hipparcos parallax. The red giant status of PZ Mon is confirmed by the carbon and nitrogen abundance. The spectrum reveals pronounced HeI 5876 A absorption and Halpha emission indicating the robust chromosphere. The IUE spectrum is found to contain transition layer emission line of CIV 1550 A. The CIV and X-ray luminosities turn out typical of RS CVn stars. The extended set of available photometric data confirms the period of 34.14 days presumably related to the stellar rotation. We found variations of the radial velocity with the amplitude of ~8 kms which could be caused by the orbital motion.

astro-ph.SR↗
arXiv2014

Spectroscopic orbits of ten nearby solar-type dwarfs

Several nearby solar-type dwarfs with variable radial velocity were monitored to find their spectroscopic orbits. Orbital elements of HIP 179, 1989, 2981, 5276, 6439, 11218, 21443, 96434 are determined, as well as tentative orbits for HIP 28678 and 41214. We discuss each of those objects. Three of the four double-lined binaries are twins with nearly equal components. All four orbits with periods shorter than 10 days are circular, the remaining orbits are eccentric.

astro-ph.SR↗
arXiv2011

Cepheid investigations using the Kepler space telescope

We report results of initial work done on selected candidate Cepheids to be observed with the Kepler space telescope. Prior to the launch 40 candidates were selected from previous surveys and databases. The analysis of the first 322 days of Kepler photometry, and recent ground-based follow-up multicolour photometry and spectroscopy allowed us to confirm that one of these stars, V1154 Cyg (KIC 7548061), is indeed a 4.9-d Cepheid. Using the phase lag method we show that this star pulsates in the fundamental mode. New radial velocity data are consistent with previous measurements, suggesting that a long-period binary component is unlikely. No evidence is seen in the ultra-precise, nearly uninterrupted Kepler photometry for nonradial or stochastically excited modes at the micromagnitude level. The other candidates are not Cepheids but an interesting mix of possible spotted stars, eclipsing systems and flare stars.

astro-ph.SR↗
arXiv2005

Angular Diameter Amplitudes of Bright Cepheids

Expected mean angular diameters and amplitudes of angular diameter variations are estimated for all monoperiodic Classical Cepheids brighter than = 8.0mag. The catalog is intended to help selecting best Cepheid targets for interferometric observations.

astro-ph↗