Kepler observations of Am stars★

Monthly Notices of the Royal Astronomical Society (Impact Factor: 5.23). 06/2011; 414(1):792 - 800. DOI: 10.1111/j.1365-2966.2011.18454.x

ABSTRACT We present an analysis of high-resolution spectra for two pulsating Am stars in the Kepler field. The stellar parameters derived in this way are important because parameters derived from narrow-band photometry may be affected by the strong metal lines in these stars. We analyse the Kepler time series of ten known Am stars and find that six of them clearly show δ Scuti pulsations. The other four appear to be non-pulsating. We derive fundamental parameters for all known pulsating Am stars from ground-based observations and also for the Kepler Am stars to investigate the location of the instability strip for pulsating Am stars. We find that there is not much difference between the Am-star instability strip and the δ Scuti instability strip. We find that the observed location of pulsating Am stars in the HR diagram does not agree with the location predicted from diffusion calculations.


Available from: L. A. Balona, May 29, 2015
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    ABSTRACT: In this paper we present a detailed analysis of a sample of eight Am stars, four of them are in the {\it Kepler} field of view. We derive fundamental parameters for all observed stars, effective temperature, gravity, rotational and radial velocities, and chemical abundances by spectral synthesis method. Further, to place these stars in the HR diagram, we computed their luminosity. Two objects among our sample, namely HD\,114839 and HD\,179458 do not present the typical characteristic of Am stars, while for the others six we confirm their nature. The behavior of lithium abundance as a function of the temperature with respect the normal A-type stars has been also investigated, we do not find any difference between metallic and normal A stars. All the pulsating Am stars present in our sample (five out of eight) lies in the $\delta$~Sct instability strip, close to the red edge.
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