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Title:
Looking for a Connection between the Am Phenomenon and Hybrid δ Sct -γ Dor Pulsation: Determination of the Fundamental Parameters and Abundances of HD 114839 and BD +18 4914
Authors:
Hareter, M.; Fossati, L.; Weiss, W.; Suárez, J. C.; Uytterhoeven, K.; Rainer, M.; Poretti, E.
Affiliation:
AA(Department of Astronomy, University of Vienna, Türkenschanzstrasse 17, A-1180 Wien, Austria ), AB(Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes MK6 7AA, UK ), AC(Department of Astronomy, University of Vienna, Türkenschanzstrasse 17, A-1180 Wien, Austria ), AD(Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía S/N, 18008, Granada, Spain ), AE(Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg, Germany ; Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain ; Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain ), AF(INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807, Merate (LC), Italy), AG(INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807, Merate (LC), Italy)
Publication:
The Astrophysical Journal, Volume 743, Issue 2, article id. 153 (2011). (ApJ Homepage)
Publication Date:
12/2011
Origin:
IOP
Astronomy Keywords:
stars: abundances, stars: individual: BD +18 4914 HD 114839, stars: variables: delta Scuti, techniques: spectroscopic
DOI:
10.1088/0004-637X/743/2/153
Bibliographic Code:
2011ApJ...743..153H

Abstract

δ Sct-γ Dor hybrids pulsate simultaneously in p- and g-modes, which carry information on the structure of the envelope as well as to the core. Hence, they are key objects for investigating A and F type stars with asteroseismic techniques. An important requirement for seismic modeling is small errors in temperature, gravity, and chemical composition. Furthermore, we want to investigate the existence of an abundance indicator typical for hybrids, something that is well established for the roAp stars. Previous to the present investigation, the abundance pattern of only one hybrid and another hybrid candidate has been published. We obtained high-resolution spectra of HD 114839 and BD +18 4914 using the SOPHIE spectrograph of the Observatoire de Haute-Provence and the HARPS spectrograph at ESO La Silla. For each star we determined fundamental parameters and photospheric abundances of 16 chemical elements by comparing synthetic spectra with the observations. We compare our results to that of seven δ Sct and nine γ Dor stars. For the evolved BD +18 4914 we found an abundance pattern typical for an Am star, but could not confirm this peculiarity for the less evolved star HD 114839, which is classified in the literature as uncertain Am star. Our result supports the concept of evolved Am stars being unstable. With our investigation we nearly doubled the number of spectroscopically analyzed δ Sct-γ Dor hybrid stars, but did not yet succeed in identifying a spectroscopic signature for this group of pulsating stars. A statistically significant spectroscopic investigation of δ Sct- γ Dor hybrid stars is still missing, but would be rewarding considering the asteroseismological potential of this group.

Based on observations made at the Observatoire de Haute-Provence and with HARPS at the 3.6 m ESO telescope under the Large Programme LP185.D-0056.

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