HERMES spectroscopy of normal A and Am stars

Abstract :

The nominal Kepler mission provided very high-precision photometric data. Using these data, interesting phenomena such as spots, and "hump and spike" features were observed in the light curves of some normal A and metallic lined A stars (Am stars). However, the connection between such phenomena and the chemical peculiarity of the Am stars is still unclear. In order to make progress on these issues, its important to collect high-resolution spectroscopic data to determine their fundamental parameters and individual chemical abundances. In this paper, we present a spectroscopic study of a sample of "hump and spike" stars in the nominal Kepler field. We used data collected with the High Efficiency and Resolution Mercator Échelle Spectrograph (HERMES). We determined the spectral type of these stars and obtained the atmospheric stellar parameters such as effective temperatures, surface gravities, projected rotational, microturbulent and radial velocities. We also performed a detailed individual chemical abundance analysis for each target. We confirmed KIC 3459226 and KIC 6266219 as Am stars, KIC 9349245 as a marginal Am star, while KIC 4567097, KIC 4818496, KIC 5524045, KIC 5650229, KIC 7667560, and KIC 9272082 are non-Am stars. To estimate their evolutionary phases, all the stars were placed in the Hertzsprung-Russell (HR) diagram. Based on their spectral classification and chemical abundance pattern, we reclassified KIC 6266219 (previously treated as chemically normal) as an Am star (kA3hA7mF1) and KIC 9272082 (previously treated as Am) as non-Am.

Publication : Monthly Notices of the Royal Astronomical Society, Advance Access
DOI : 10.1093/mnras/stab1149 
Bibcode : 2021MNRAS.tmp.1130T 
Keywords : stars: chemically peculiar; stars: rotation; stars: starspots; stars: general; techniques: spectroscopic; Astrophysics - Solar and Stellar Astrophysics