Y. Pavlenko

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I was born in Ukraine, graduated Kiev University in 1976, in 1984 defended PhD Thesis (Astrophysics anf Radioastronomy) in Tartu Observatory (Estonia) , in 1996 defended Dr Sci Thesis in MAO (Kyiv), more on www.mao.kiev.ua/staff/yp

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James Elkins

School of the Art Institute of Chicago

Estela Blaisten-Barojas

George Mason University

David Seamon

Kansas State University

Armando Marques-Guedes

UNL - New University of Lisbon

Adam M Croom

Case Western Reserve University

John Sutton

Macquarie University

Michael Kirchhoff

University of Wollongong

Alhussein Adham Basheer

Helwan University

Viacheslav Kuleshov

Stockholm University

Colm Bracken

National University of Ireland, Maynooth

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Papers by Y. Pavlenko

Determination of abundances in atmospheres of F-, G-, K-dwarfs

Kinematika i fizika nebesnyh tel (Online), 2017

Model Atmospheres and Spectra for Cool Hydrogen-Deficient Stars and Peculiar Giants

Hydrogen-Deficient Stars, Jul 1, 2008

New model atmospheres, spectra and spectral energy distributions of hydrogen-deficient chemically... more New model atmospheres, spectra and spectral energy distributions of hydrogen-deficient chemically peculiar stars are presented. The methods used in the computation of these models are discussed, with special consideration given to the treatment of opacity. Some of the model atmospheres have been computed for R CrB stars with different H/He ratios and carbon abundances. In order to test these models the observed spectra of Sakurai’s object and some carbon-rich giants are fit with the newly computed spectral energy distributions.

Atmosphere of the K2III-STAR Alpha-Arietis

Determination of C N and O Abundances in the Atmospheres of Late Type Stars - Extreme Value Problem

Soviet Astronomy, Apr 1, 1991

Quantitative analysis of the spectrum of HD 108564

Kinematika i fizika nebesnyh tel (Online)

Ultraviolet NH bands as indicators of nitrogen abundance in the atmospheres of cool stars

KPCB, 1998

VizieR Online Data Catalog: HARPS and X-shooter spectra of Souhern M dwarfs (Kuznetsov+, 2019)

VizieR Online Data Catalog, Nov 1, 2020

The determination of physical parameters of the atmosphere of the primary star of the system V367 Cygni with the method of atmosphere models

VizieR Online Data Catalog: Luhman 16AB X-shooter spectra (Lodieu+, 2015)

Improving the quality of HCN/HNC and (HCN)-C-13 data

The HCN/HNC linelist of Harris et al. (2002) ApJ, 578, 657, is the most accurate and extensive ab... more The HCN/HNC linelist of Harris et al. (2002) ApJ, 578, 657, is the most accurate and extensive ab initio linelist in existence. It has been used to identify HNC in a carbon star for the first time (Harris et al. 2003, MN-RAS, 344, 1107). However, it suffers from the inherent accuracy problems of ab initio data. The band centres of some overtone bands deviate by up to 10 cm(-1) from experimental values. To improve the quality of many of our line frequencies we have substituted the available experimentally determined HCN energy levels for their ab initio counterparts, thus improving the accuracy of many of the strongest HCN/HNC line frequencies. We are currently repeating this process for (HCN)-C-13 in order to create a (HCN)-C-13 linelist.

E P ] 1 3 D ec 2 01 2 A hot Uranus orbiting the super metal-rich star HD 77338 and the Metallicity-Mass Connection 1

We announce the discovery of a low-mass planet orbiting the super metal-rich K0V star HD77338 as ... more We announce the discovery of a low-mass planet orbiting the super metal-rich K0V star HD77338 as part of our on-going Calan-Hertfordshire Extrasolar Planet Search. The best fit planet solution has an orbital period of 5.7361±0.0015 days and with a radial velocity semiamplitude of only 5.96±1.74 ms, we find a minimum mass of 15.9 −5.3 M⊕. The best fit eccentricity from this solution is 0.09 −0.09, and we find agreement for this data set using a Bayesian analysis and a periodogram analysis. We measure a metallicity for the star of +0.35±0.06 dex, whereas another recent work (Trevisan et al. 2011) finds +0.47±0.05 dex. Thus HD77338b is one of the most metal-rich planet host stars known and the most metal-rich star hosting a subNeptune mass planet. We searched for a transit signature of HD77338b but none was detected. We also highlight an emerging trend where metallicity and mass seem to correlate at very low masses, a discovery that would be in agreement with the core accretion model o...

The Curve of Growth and Radiation Diffusion in the Case of a Hydrogen Multilevel Atom in Prominences

Nonlte Effects and Strong Lii Lines in the Spectra of the K Giants HD9746 and HD112127

Spectral Features in the Circumstellar Envelope of the Close Binary System V367-CYGNI

The statistical equilibrium and the 670.776- and 670.791-nm absorption lines of Li I in red-giant spectra - Methodology

The solution of the NLTE problem for lithium in atmospheres of K and M giants are presented. The ... more The solution of the NLTE problem for lithium in atmospheres of K and M giants are presented. The opacity at lithium bound-bound and bound-free Li I transition frequencies is due to continuum sources, molecular bands, and atomic lines. The LTE and NLTE growth curves for the Li I doublet synthetic spectra in the lambda 670.8-nm region are obtained. The results show that NLTE effects are significant in red-giant atmospheres.

VizieR Online Data Catalog: Carbon and oxygen in 107 dwarf stars (Pavlenko+, 2019)

Modelling the spectral energy distribution of the red giant in RS Ophiuchi: evidence for irradiation

Monthly Notices of the Royal Astronomical Society, 2015

We present an analysis of optical and infrared spectra of the recurrent nova RS Oph obtained duri... more We present an analysis of optical and infrared spectra of the recurrent nova RS Oph obtained during between 2006 and 2009. The best fit to the optical spectrum for 2006 September 28 gives T eff = 3900 K for log g = 2.0, while for log g = 0.0 we find T eff = 4700 K, and a comparison with template stellar spectra provides T eff ∼ 4500 K. The observed spectral energy distribution (SED), and the intensities of the emission lines, vary on short (1 d) timescales , due to disc variability. We invoke a simple one-component model for the accretion disc, and a model with a hot boundary layer, with high (∼3.9 × 10 −6 M yr −1) and low (∼2 × 10 −8 M yr −1) accretion rates, respectively. Fits to the accretion disc-extracted infrared spectrum (2008 July 15) yield effective temperatures for the red giant of T eff = 3800 ± 100 K (log g = 2.0) and T eff = 3700 ± 100 K (log g = 0.0). Furthermore, using a more sophisticated approach, we reproduced the optical and infrared SEDs of the red giant in the RS Oph system with a twocomponent model atmosphere, in which 90 per cent of the surface has T eff = 3600 K and 10 per cent has T eff = 5000 K. Such structure could be due to irradiation of the red giant by the white dwarf.

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Spectral Investigations of CM Dra

Odessa astronomical publications, Dec 1, 2010

We present an analysis of a high resolution (R=47000) echelle spectra of the low-mass eclipsing b... more We present an analysis of a high resolution (R=47000) echelle spectra of the low-mass eclipsing binary CM Draconis, which were obtained on the 4.2-m William Herschel Telescope. Spectra were obtained for various phases of the orbit. There are some difficulties in echelle spectra processing of cool stars, since it is hard to get energy distribution in a large scale in such spectra. We proposed an efficient method for making the continuum of spectrum of cool stars. We refined the parameters (effective temperature, rotational velocity and metallicity) of the components of the system CM Dra using the method of stellar atmospheres. The data that we obtained are in good agreement with the results obtained by other authors. It is indicate on efficiency of our technique. The errors of temperature and metallicity determinations is about 100 K and 0.3 dex respectively.

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Statistical Equilibrium and the Lii 670.766-NM and 670.791-NM Absorption Lines in the Spectrum of Red Giants - Results

Soviet Astronomy, Dec 1, 1991

New exocomets of β Pic

Astronomy & Astrophysics, 2022

Aims. The aim of our work is to analyze the light curves of β Pic which were recently observed by... more Aims. The aim of our work is to analyze the light curves of β Pic which were recently observed by the Transiting Exoplanet Survey Satellite (TESS) in sectors 32, 33, and 34 by searching for the signatures of exocomet transits. Methods. We processed the β Pic light curves from the Mikulski Archive for Space Telescopes database, applying the frequency analysis to remove harmonic signals due to the star’s pulsations, and we used a simple 1D model to fit the profiles of the events that were found. Results. We recovered events previously found by other authors in sectors 5 and 6 and found five new distinct aperiodic dipping events with asymmetric shapes resembling the expected profiles due to the passage of a comet-like body across the star disk. These dips are rather shallow, with the flux drop at a level of 0.03% and a duration of less than 1 day. No periodic transits were found in the sectors investigated. Conclusions. The depth and duration of the identified dips are similar to the r...

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Determination of abundances in atmospheres of F-, G-, K-dwarfs

Kinematika i fizika nebesnyh tel (Online), 2017