Pulsation versus metallicism in Am stars as revealed by LAMOST and WASP

Smalley, B.; Antoci, V.; Holdsworth, D. L.; Kurtz, D. W.; Murphy, S. J.; De Cat, P.; Anderson, D. R.; Catanzaro, G.; Cameron, A. Collier; Hellier, C.; Maxted, P. F. L.; Norton, A. J.; Pollacco, D.; Ripepi, V.; West, R. G. and Wheatley, P. J. (2017). Pulsation versus metallicism in Am stars as revealed by LAMOST and WASP. Monthly Notices of the Royal Astronomical Society, 465(3) pp. 2662–2670.

DOI: https://doi.org/10.1093/mnras/stw2903

Abstract

We present the results of a study of a large sample of A and Am stars with spectral types from LAMOST and light curves from WASP. We find that, unlike normal A stars, δ Sct pulsations in Am stars are mostly confined to the effective temperature range 6900 <Teff <7600 K. We find evidence that the incidence of pulsations in Am stars decreases with increasing metallicism (degree of chemical peculiarity). The maximum amplitude of the pulsations in Am stars does not appear to vary significantly with metallicism. The amplitude distributions of the principal pulsation frequencies for both A and Am stars appear very similar and agree with results obtained from Kepler photometry. We present evidence that suggests turbulent pressure is the main driving mechanism in pulsating Am stars, rather than the κ-mechanism, which is expected to be suppressed by gravitational settling in these stars.

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About

  • Item ORO ID
  • 48826
  • Item Type
  • Journal Item
  • ISSN
  • 1365-2966
  • Keywords
  • asteroseismology – techniques; photometric – stars; chemically peculiar – stars; oscillations – stars; variables: δ Scuti
  • Academic Unit or School
  • Other Departments > Other Departments
  • Copyright Holders
  • © 2016 The Authors
  • Depositing User
  • Andrew Norton

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