Helium abundance in a sample of cool stars: measurements from asteroseismology

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  • Kuldeep Verma
  • Keyuri Raodeo, Homi Bhabha Centre for Science Education, TIFR, V. N. Purav Marg, Mankhurd, Mumbai 400088, India 0000-0003-2409-2942
  • ,
  • Sarbani Basu, Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 065208101, USA
  • ,
  • Víctor Silva Aguirre
  • Anwesh Mazumdar, Homi Bhabha Centre for Science Education, TIFR, V. N. Purav Marg, Mankhurd, Mumbai 400088, India 0000-0003-2409-2942
  • ,
  • Jakob Rørsted Mosumgaard
  • Mikkel N. Lund
  • Pritesh Ranadive, Homi Bhabha Centre for Science Education, TIFR, V. N. Purav Marg, Mankhurd, Mumbai 400088, India 0000-0003-2409-2942
The structural stratification of a solar-type main sequence star primarily depends on its mass and chemical composition. The surface heavy element abundances of the solar-type stars are reasonably well determined using conventional spectroscopy, however the second most abundant element helium is not. This is due to the fact that the envelope temperature of such stars is not high enough to excite helium. Since the helium abundance of a star affects its structure and subsequent evolution, the uncertainty in the helium abundance of a star makes estimates of its global properties (mass, radius, age etc.) uncertain as well. The detections of the signatures of the acoustic glitches from the precisely measured stellar oscillation frequencies provide an indirect way to estimate the envelope helium content. We use the glitch signature caused by the ionization of helium to determine the envelope helium abundance of 38 stars in the Kepler seismic LEGACY sample. Our results confirm that atomic diffusion does indeed take place in solar-type stars. We use the measured surface abundances in combination with the settling predicted by the stellar models to determine the initial abundances. The initial helium and metal mass fractions have subsequently been used to get the preliminary estimates of the primordial helium abundance, Yp = 0.244 ± 0.019, and the galactic enrichment ratio, ΔY/ΔZ = 1.226 ± 0.849. Although the current estimates have large errorbars due to the limited sample size, this method holds great promises to determine these parameters precisely in the era of upcoming space missions.
Original languageEnglish
JournalRoyal Astronomical Society. Monthly Notices
Volume483
Issue4
Pages (from-to)4678-4694
Number of pages17
ISSN0035-8711
DOIs
Publication statusPublished - Mar 2019

    Research areas

  • stars: abundances, stars: fundamental parameters, stars: interiors, stars: oscillations, stars: solar-type, MAIN-SEQUENCE STARS, S-FACTOR, REGULATING HYDRODYNAMICAL PROCESS, STELLAR EVOLUTION CODE, SLOWLY ROTATING STARS, ASTROPHYSICAL REACTION-RATE, OVERSHOOT, DIFFUSION, POSSIBLE EXISTENCE, OSCILLATIONS

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