Looking for a connection between the Am phenomenon and hybrid delta Sct - gamma Dor pulsation: a determination of the fundamental parameters and abundances of HD 114839 and BD +18 4914

Abstract

Delta Sct - gamma 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 are 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 delta Sct and nine gamma 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 delta Sct - gamma 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 delta Sct - gamma Dor hybrid stars still is missing, but would be rewarding considering the asteroseismological potential of this group.

20 pages, 8 figures, accepted for publication in APJ

References in corpus (13)

• The effect of rotation on the abundances of the chemical elements of the A-type stars in the Praesepe cluster
• A spectroscopic study of southern (candidate) gamma Doradus stars. II. Detailed abundance analysis and fundamental parameters
• Late stages of the evolution of A-type stars on the main sequence: comparison between observed chemical abundances and diffusion models for 8 Am stars of the Praesepe cluster
• No detection of large-scale magnetic fields at the surfaces of Am and HgMn stars
• The gamma Dor CoRoT target HD49434. I-Results from the ground-based campaign
• Inter-comparison of the g-, f- and p-modes calculated using different oscillation codes for a given stellar model
• A comprehensive asteroseismic modelling of the high-amplitude delta Scuti star RV Arietis
• Discovery of hybrid $\gamma$ Dor and $\delta$ Sct pulsations in BD+18 4914 through MOST spacebased photometry
• Asteroseismology with the WIRE satellite. I. Combining Ground- and Space-based Photometry of the Delta Scuti Star Epsilon Cephei
• Abundance analysis of seven delta Scuti Stars
• DDO spectroscopic survey of MOST variable stars
• Gamma Dor and Gamma Dor - Delta Sct Hybrid Stars In The CoRoT LRa01
• Am stars in binary systems

Cited by in corpus (11)

• Spectroscopic survey of Kepler stars. I. HERMES/Mercator observations of A- and F-type stars
• KIC 3858884: a hybrid δ Sct pulsator in a highly eccentric eclipsing binary
• Spectroscopic Survey of γ Doradus Stars I. Comprehensive atmospheric parameters and abundance analysis of γ Doradus stars
• Statistical Properties of Galactic δ Scuti Stars: Revisited
• Fundamental parameters of 8 Am stars: comparing observations with theory
• Unveiling $\delta$ Scuti and $\gamma$ Doradus Hybrid Pulsation of HD 53166 and HD 53349 Plus Rich Frequencies in HD 52788 -- Catalogs of 70552 $\delta$ Sct and 8080 $\gamma$ Dor
• Spectroscopy of hot Gamma Doradus and A-F hybrid Kepler candidates close to the hot border of the Delta Scuti instability strip
• An Investigation of Four Chemically Peculiar Stars with Photometric Periods below 12 Hours
• Gaia/GSP-spec spectroscopic properties of gamma Doradus pulsators
• Abundance analysis of the Gamma Doradus - Delta Scuti hybrid metallic line (Am) star HD 8801
• STEREO Observations of Hybrid Stars V775 Tau and V483 Tau