Y. Lyubchik

Main Astronomical Observatory

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Ya. V. Pavlenko

Main Astronomical Observatory

H. R. A. Jones

University of Hertfordshire

B. Kaminsky

Main Astronomical Observatory

D. J. Pinfield

University of Hertfordshire

Kevin R. Covey

Western Washington University

Chien‐Hsiu Lee

W.M. Keck Observatory

M. Mugrauer

Friedrich Schiller University Jena

La. Yakovina

Main Astronomical Observatory

P. Afonso

American River College

N. Vogt

University of Valparaíso

Cooperative Institutions

Max Planck Society

Max Planck Institute for Extraterrestrial Physics

Main Astronomical Observatory

Centre National de la Recherche Scientifique

University of Chile

National Academy of Sciences of Ukraine

Optica

Ludwig-Maximilians-Universität München

Stuttgart Observatory

Russian Academy of Sciences

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A hot Jupiter transiting a mid-K dwarf found in the pre-OmegaCam Transit Survey

Monthly Notices of the Royal Astronomical Society (2013)

J. Koppenhoefer R. P. Saglia L. Fossati Y. Lyubchik M. Mugrauer

We describe the pre-OmegaTranS project, a deep survey for transiting extra-solar planets in the Carina region of the Galactic disc. In 2006–2008, we observed a single dense stellar field with a very high cadence of ∼2 min using the European Southern Observatory Wide Field Imager at the La Silla Observatory. Using the Astronomical Wide-field Imaging System for Europe environment and the Munich Difference Imaging Analysis pipeline, a module that has been developed for this project, we created the light curves of 16 000 stars with more than 4000 data points which we searched for periodic transit signals using a box-fitting least-squares detection algorithm. All light curves are publicly available. In the course of the pre-OmegaTranS project, we identified two planet candidates – POTS-1b and POTS-C2b – which we present in this work. With extensive follow-up observations we were able to confirm one of them, POTS-1b, a hot Jupiter transiting a mid-K dwarf. The planet has a mass of 2.31 ± 0.77 MJup, a radius of 0.94 ± 0.04 RJup and a period of P = 3.16 d. The host star POTS-1 has a radius of 0.59 ± 0.02 R⊙ and a mass of 0.70 ± 0.05 M⊙. Due to its low apparent brightness of I = 16.1 mag, the follow-up and confirmation of POTS-1b was particularly challenging and costly.

Hot Jupiter

Jupiter (rocket family)

10.1093/mnras/stt1512

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IRON ABUNDANCES IN THE ATMOSPHERES OF HD10700 and HD146233

DOAJ (DOAJ: Directory of Open Access Journals) (2010)

O. N. Ivanyuk Ya. V. Pavlenko J. S. Jenkins H. R. A. Jones Y. Lyubchik

There are many different means to determine physical parameters of stars and their abundances by spectral analysis. In our work we draw our attention to the rotational and microturbulenc velocities as well as metallicities for the stars of known effective temperature and surface gravity. We carried fits of LTE synthetic spectra to the observed spectra of HD10700 and HD146233. These stars are knows aa solar-twins except slightly higher rotational velocities in both cases and higher magnetical activity i of HD10700. We adopted ABEL software (Pavlenko Ya.V.) to fit to HD10700, HD146233 spectra obtained on Camino Observatory, Chilie. Selected stars looks like. We compare our results with previous work of Valenti and Fischer (2005).

10.18524/1810-4215.2010.23.84651

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A blue depression in the optical spectra of M dwarfs

Monthly Notices of the Royal Astronomical Society (2023)

H. R. A. Jones Ya. V. Pavlenko Y. Lyubchik M. S. Bessell N. F. Allard

A blue depression is found in the spectra of M dwarfs from 4000 to 4500A. This depression shows an increase toward lower temperatures though is particularly sensitive to gravity and metallicity. It is the single most sensitive feature in the optical spectra of M dwarfs. The depression appears as centered on the neutral calcium resonance line at 4227A and leads to nearby features being weaker by about two orders of magnitude than predicted. We consider a variety of possible causes for the depression including temperature, gravity, metallicity, dust, damping constants, and atmospheric stratification. We also consider relevant molecular opacities which might be the cause identifying AlH, SiH, and NaH in the spectral region. However, none of these solutions are satisfactory. In the absence of a more accurate determination of the broadening of the calcium line perturbed by molecular hydrogen, we find a promising empirical fit using a modified Lorentzian line profile for the calcium resonance line. Such fits provide a simplistic line-broadening description for this calcium resonance line and potentially other un-modelled resonance lines in cool high-pressure atmospheres. Thus we claim the most plausible cause of the blue depression in the optical spectra of M dwarfs is a lack of appropriate treatment of line broadening for atomic calcium. The broad wings of the calcium resonance line develop at temperatures below about 4000K and are analogous to the neutral sodium and potassium features which dominate the red optical spectra of L dwarfs.

Line (geometry)

Surface gravity

10.1093/mnras/stad1391

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Citations (21)

AlH lines in the blue spectrum of Proxima Centauri

Monthly Notices of the Royal Astronomical Society (2022)

Ya. V. Pavlenko Jonathan Tennyson S. N. Yurchenko M. Schmidt H. R. A. Jones

The recently-computed ExoMol line lists for isotopologues of AlH are used to analyse the blue spectrum (4000-4500 {\AA}) of Proxima Cen (M5.5 V). Comparison of the observed and computed spectra enables the identification of a large number of 27AlH lines of the A1{\Pi} - X1{\Sigma}+ band system: the spectral range covering 1-0, 0-0 and 1-1 bands is dominated by clearly resolved AlH lines. We reveal the diffuse nature of transitions close to the dissociation limit which appears in the form of increasingly wider(up to 5 {\AA}) and shallower (up to the continuum confusion limit) AlH line profiles. The predicted wavelengths of AlH diffuse lines are systematically displaced. The effect broadening by pre-dissociation states on the line profiles is included by increasing the radiative damping rate by up to 5 orders of magnitude. We determine empirical values of damping rates for a number of the clean 0-0 Q-branch transitions by comparing the observed and synthetic stellar spectra. We find excellent agreement between our damping rates and lifetimes available in the literature. A comparison of 27Al1H ExoMol and REALH spectra shows that the observed spectrum is better described by the ExoMol line list. A search for 26Al1H lines in the Proxima Cen spectrum does not reveal any notable features; giving an upper limit of 27Al1H/26Al1H {>} 100.

10.1093/mnras/stac2588

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Values of v sin i for late-type stars from spectral synthesis in the K-band region

Monthly Notices of the Royal Astronomical Society (2012)

Y. Lyubchik H. R. A. Jones Ya. V. Pavlenko D. J. Pinfield Kevin R. Covey

We analyse medium-resolution spectra (R∼ 18 000) of 19 late type dwarfs in order to determine v sin i values using synthetic rather than observational template spectra. For this purpose, observational data around 2.2 μm for stars with spectral classes from G8V to M9.5V were modelled. We find that the Na i (2.2062- and 2.2090-μm) and 12CO 2–0 band features are modelled well enough to use for v sin i determination without the need for suitable observational template spectra. Within the limit of the resolution of our spectra, we use synthetic spectra templates to derive v sin i values consistent with those derived in the optical regime using observed templates. We quantify the errors in our v sin i determination due to incorrect choice of model parameters Teff, log g, vmicro, [Fe/H] or full width at half-maximum and show that they are typically less than 10 percent. We note that the spectral resolution of our data (∼16 km s−1) limited this study to relatively fast rotators and that a resolution of 60 000 will be required to access most late-type dwarfs.

Spectral resolution

10.1111/j.1365-2966.2012.20762.x

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Experimental Ti i oscillator strengths and their application to cool star analysis

Monthly Notices of the Royal Astronomical Society (2006)

R. Blackwell-Whitehead H. Lundberg Gillian Nave Juliet C. Pickering H. R. A. Jones

We report experimental oscillator strengths for 88 Ti I transitions covering the wavelength range 465 to 3892 nm, 67 of which had no previous experimental values. Radiative lifetimes for thirteen energy levels, including the low energy levels 3d2 (3F) 4s4p (3P) z5Dj, have been measured using time resolved laser induced fluorescence. Intensity calibrated Ti I spectra have been measured using Fourier transform spectroscopy to determine branching fractions for the decay channels of these levels. The branching fractions are combined with the radiative lifetimes to yield absolute transition probabilities and oscillator strengths. Our measurements include 50 transitions in the previously unobserved infrared region lambda > 1000 nm, a region of particular interest to the analysis of cool stars and brown dwarfs.

Branching fraction

Branching (polymer chemistry)

10.1111/j.1365-2966.2006.11161.x

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Citations (28)

Modelling the spectrum and SED of V838 Mon

arXiv (Cornell University) (2006)

Ya. V. Pavlenko B. Kaminsky Y. Lyubchik La. Yakovina

We model the spectra and spectral energy distribution of V838 Mon which were observed in February, March, and November, 2002. Theoretical spectra are calculated using the classical model atmospheres taking into account absorption of atomic and molecular lines. By fitting the observed spectra we determine the physical parameters of the atmosphere of V838 Mon. These parameters are determined to be Teff = 5330 +/- 300 K, 5540 +/- 270 K, 4960 +/- 190 K, and 2000 +/- 200 K for February 25, March 2, March 26, and November 6, respectively.

Spectral energy distribution

10.48550/arxiv.astro-ph/0609604

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Pulsational variability of Li I 6708 Åline profile in the spectra of roAp star gamma Equ

Memorie della Societa Astronomica Italiana (2006)

А. В. Шаврина N. S. Polosukhina S. Khan Ya. V. Pavlenko D. O. Kudryavtsev

Line (geometry)

Star (game theory)

Source

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