KIC 1718290: A helium-rich V1093-her-like pulsator on the blue horizontal branch

R. H. Østensen, P. Degroote, J. H. Telting, J. Vos, C. Aerts, C. S. Jeffery, E. M. Green, M. D. Reed, U. Heber

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

We introduce the first g-mode pulsator found to reside on the classical blue horizontal branch. One year of Kepler observations of KIC1718290 reveals a rich spectrum of low-amplitude modes with periods between 1 and 12 hr, most of which follow a regular spacing of 276.3s. This mode structure strongly resembles that of the V1093Her pulsators, with only a slight shift toward longer periods. Our spectroscopy, however, reveals KIC1718290 to be quite distinct from the sdB stars that show V1093Her pulsations, which all have surface gravities higher than log g= 5.1 and helium abundances depleted by at least an order of magnitude relative to the solar composition. We find that KIC1718290 has T eff= 22,100K, log g= 4.72, and a super-solar helium abundance (log N He/N H= -0.45). This places it well above the extreme horizontal branch, rather on the very blue end of the classical horizontal branch, where shell hydrogen burning is present. We conclude that KIC1718290 must have suffered extreme mass loss during its first giant stage, but not sufficient to reach the extreme horizontal branch.

Original languageEnglish (US)
Article numberL17
JournalAstrophysical Journal Letters
Volume753
Issue number1
DOIs
StatePublished - Jul 1 2012
Externally publishedYes

Keywords

  • stars: horizontal-branch
  • stars: individual (KIC 1718290)
  • stars: oscillations
  • stars: variables: general
  • subdwarfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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