Pulsation versus metallicism in Am stars as revealed by LAMOST and WASP
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We present the results of a study of a large sample of A and Am stars with spectral types from Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and light curves from Wide Area Search for Planets (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.
Smalley , B , Antoci , V , Holdsworth , D L , Kurtz , D W , Murphy , S J , De Cat , P , Anderson , D R , Catanzaro , G , Collier Cameron , A , Hellier , C , Maxted , P F L , Norton , A J , Pollacco , D , Ripepi , V , West , R G & Wheatley , P J 2017 , ' Pulsation versus metallicism in Am stars as revealed by LAMOST and WASP ' Monthly Notices of the Royal Astronomical Society , vol 465 , no. 3 , pp. 2662-2670 . DOI: 10.1093/mnras/stw2903
Monthly Notices of the Royal Astronomical Society
© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. This work is made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at: https://dx.doi.org/10.1093/mnras/stw2903
The WASP project is funded and operated by Queen’s University Belfast, the Universities of Keele, St Andrews and Leicester, the Open University, the Isaac Newton Group, the Instituto de Astrofisica de Canarias, the South African Astronomical Observatory and by the UK Science and Technology Facilities Council (STFC). Funding for the Stellar Astrophysics Centre was provided by the Danish National Research Foundation (grant no. DNRF106). The research is supported by the ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) funded by the European Research Council (grant agreement no. 267864). DWK is supported by the STFC.DLH acknowledges support from the STFC via grant number ST/M000877/1. SJM was supported by the Australian Research Council.
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