Pulsation in extremely low-mass helium stars

C. S. Jeffery, H. Saio

Research output: Chapter in Book/Report/Conference proceedingConference contribution


We explore the stability of extremely low-mass stars (M < 0.25 M⊙ across a wide range of composition, effective temperature, and luminosity. We identify the instability boundaries associated with radial oscillations. These are a strong function of both composition and radial order (0 ≤ n ≤ 13). The classical blue edge shifts to higher effective temperature and luminosity with decreasing hydrogen abundance. Higher-order modes are more easily excited, and small islands of instability develop. Short-period oscillations have been discovered in the low-mass pre-white dwarf component of the eclipsing binary J0247-25. If its envelope is depleted in hydrogen, J0247-25B is unstable to intermediate-order p modes. Driving is by the classical κ mechanism operating in the second helium ionization zone. The observed periods, temperature and luminosity of J0247-25B require an envelope hydrogen abundance 0.2 ≤ X ≤ 0.3.

Original languageEnglish
Title of host publicationPrecision Asteroseismology
EditorsJoyce Guzik, William Chaplin, William Chaplin, Gerald Handler, Andrzej Pigulski
Number of pages2
Publication statusPublished - 2014

Publication series

NameProceedings of the International Astronomical Union
ISSN (Print)1743-9213
ISSN (Electronic)1743-9221


  • stars: early-type
  • stars: interiors
  • stars: oscillations
  • subdwarfs
  • white dwarfs

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Astronomy and Astrophysics
  • Nutrition and Dietetics
  • Public Health, Environmental and Occupational Health
  • Space and Planetary Science


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