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

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, $\delta$ Sct pulsations in Am stars are mostly confined to the effective temperature range 6900 $<$ $T_{\mathrm{eff}}$ $<$ 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 $\kappa$-mechanism, which is expected to be suppressed by gravitational settling in these stars.

arXiv commentAccepted for publication in MNRAS. 10 pages, 10 figures, 1 table

References in corpus (20)

• Low Temperature Opacities
• The WASP Project and the SuperWASP Cameras
• The First Data Release (DR1) of the LAMOST general survey
• Overview of the Kepler Science Processing Pipeline
• Correcting systematic effects in a large set of photometric lightcurves
• Hybrid gamma Doradus - delta Scuti pulsators: New insights into the physics of the oscillations from Kepler observations
• Automatic Determination of Stellar Atmospheric Parameters and Construction of Stellar Spectral Templates of the Guoshoujing Telescope (LAMOST)
• LAMOST observations in the Kepler field. Database of low-resolution spectra
• On the relationship between the Delta Scuti and Gamma Doradus pulsators
• Global stellar variability study in the field-of-view of the Kepler satellite
• Pulsation frequency distribution in Delta Scuti stars
• K2P${}^2$ $-$ A photometry pipeline for the K2 mission
• The role of turbulent pressure as a coherent pulsational driving mechanism: the case of the delta Scuti star HD 187547
• High frequency A-type pulsators discovered using SuperWASP
• SuperWASP observations of pulsating Am stars
• On the incidence of eclipsing Am binary systems in the SuperWASP survey
• Spots on Am stars
• The new Toulouse-Geneva Stellar Evolution Code including radiative accelerations of heavy elements
• Hydrodynamical instabilities induced by atomic diffusion in A stars and their consequences
• A Large Sample of Am Candidates from LAMOST Data Release 1

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