Spectroscopy of hot γ Doradus and A-F hybrid Kepler candidates close to the hot border of the δ Scuti instability strip
Abstract
If γ Dor-type pulsations are driven by the convective blocking mechanism, a convective envelope at a sufficient depth is essential. There are several hot γ Dor and hybrid star candidates in which there should not be an adequate convective envelope to excite the γ Dor-type oscillations. The existence of these hot objects needs an explanation. Therefore, we selected, observed, and studied 24 hot γ Dor and hybrid candidates to investigate their properties. The atmospheric parameters, chemical abundances, and vsin I values of the candidates were obtained using medium-resolution (R = 46 000) spectra taken with the Fibre-fed Échelle Spectrograph instrument mounted at the Nordic Optical Telescope. We also carried out frequency analyses of the Kepler long- and short-cadence data to determine the exact pulsation contents. We found only five bona fide hot γ Dor and three bona fide hot hybrid stars in our sample. The other 16 stars were found to be normal γ Dor, δ Sct, or hybrid variables. No chemical peculiarity was detected in the spectra of the bona fide hot γ Dor and hybrid stars. We investigated the interplay between rotation and pulsational modes. We also found that the hot γ Dor stars have higher Gaia luminosities and larger radii compared to main-sequence A-F stars.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- April 2020
- DOI:
- 10.1093/mnras/staa399
- arXiv:
- arXiv:2002.04669
- Bibcode:
- 2020MNRAS.493.4518K
- Keywords:
-
- stars: abundances;
- stars: atmospheres;
- stars: general;
- stars: oscillations;
- stars: rotation;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in Monthly Notices of the Royal Astronomical Society Letters