Y. Lyubchik

Publications (7)4.9 Total impact

• Source

  Available from: Yakiv V. Pavlenko

  Article: Metallicities & Activities of Southern Stars

  J. S. Jenkins, H. R. A. Jones, Y. Pavlenko, D. J. Pinfield, J. R. Barnes, Y. Lyubchik
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  ABSTRACT: We present the results from high-resolution spectroscopic measurements to determine metallicities and activities of bright stars in the southern hemisphere. We have measured the iron abundances ([Fe/H]) and chromospheric emission indices (logR'HK) of 353 solar-type stars with V=7.5-9.5. [Fe/H] abundances are determined using a custom chi^2 fitting procedure within a large grid of Kurucz model atmospheres. The chromospheric activities were determined by measuring the amount of emission in the cores of the strong CaII HK lines. The sample of metallicities has been compared to other [Fe/H] determinations and was found to agree with these at the +/-0.05 dex level for spectroscopic values and at the +/-0.1 dex level for photometric values. The distribution of chromospheric activities is found to be described by a bimodal distribution, agreeing well with the conclusions from other works. Also an analysis of Maunder Minimum status was attempted and it was found that 6+/-4 stars in the sample could be in a Maunder Minimum phase of their evolution and hence the Sun should only spend a few per cent of its main sequence lifetime in Maunder Minimum. Comment: 20 pages, 19 figures, 4 tables, accepted A&A (04/04/2008); New version has updated section references
  04/2008;
• Source

  Available from: Yakiv V. Pavlenko

  Article: Experimental Ti I oscillator strengths and their application to cool star analysis

  R.J. Blackwell-Whitehead, H. Lundberg, G. Nave, J. C. Pickering, H. R. A. Jones, Y. Lyubchik, Y. V. Pavlenko, S. Viti
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  ABSTRACT: 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.
  01/2007;
• Source

  Available from: Yakiv V. Pavlenko

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

  R. J. Blackwell-Whitehead, H. Lundberg, G. Nave, J. C. Pickering, H. R. A. Jones, Y. Lyubchik, Y. V. Pavlenko, S. Viti
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  ABSTRACT: We report experimental oscillator strengths for 88 Ti i transitions covering the wavelength range 465–3892 nm, 67 of which had no previous experimental values. Radiative lifetimes for 13 energy levels, including the low energy levels 3d2(3F) 4s4p (3P) z 5D°j, 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 λ > 1.0 μm, a region of particular interest to the analysis of cool stars and brown dwarfs.
  Monthly Notices of the Royal Astronomical Society 12/2006; 373(4):1603 - 1609. · 4.90 Impact Factor
• Article: Atomic lines in infrared spectra for ultracool dwarfs

  Y. Lyubchik, H. R. A. Jones, Y. V. Pavlenko, S. Viti, J. C. Pickering, R. Blackwell-Whitehead
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  ABSTRACT: We provide a set of atomic lines which are suitable for the description of ultracool dwarf spectra from 10 000 to 25 000 Å. This atomic linelist was made using both synthetic spectra calculations and existing atlases of infrared spectra of Arcturus and Sunspot umbra. We present plots which show the comparison of synthetic spectra and observed Arcturus and Sunspot umbral spectra for all atomic lines likely to be observable in high resolution infrared spectra.
  http://dx.doi.org/10.1051/0004-6361:20034419.
• Article: Spectral energy distribution for GJ406.

  Y. Pavlenko, H. R. A. Jones, Y. Lyubchik, J. Tennyson, D. J. Pinfield
• Article: Atomic lines in infrared spectra for ultracool dwarfs

  Y. Lyubchik, H. R. A. Jones, Y. Pavlenko, S. Viti, J. C. Pickering, R.J. Blackwell-Whitehead
• Article: Experimental Ti I oscillator strengths and their application to cool star analysis.

  R.J. Blackwell-Whitehead, H. Lundberg, G. Nave, J. C. Pickering, H. R. A. Jones, Y. Lyubchik, Y. Pavlenko, S. Viti