Unresolved Rossby and gravity modes in 214 A and F stars showing rotational modulation

Andreea I. Henriksen*, Victoria Antoci*, Hideyuki Saio, Frank Grundahl, Hans Kjeldsen, Timothy Van Reeth, Dominic M. Bowman, Péter I. Pápics, Peter De Cat, Joachim Krüger, M. Fredslund Andersen, P. L. Pallé

*Corresponding author af dette arbejde

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avisTidsskriftartikelForskningpeer review

Abstract

Here, we report an ensemble study of 214 A- and F-type stars observed by Kepler, exhibiting the so-called hump and spike periodic signal, explained by Rossby modes (r modes) - the hump - and magnetic stellar spots or overstable convective (OsC) modes - the spike, respectively. We determine the power confined in the non-resolved hump features and find additional gravity-mode (g-mode) humps always occurring at higher frequencies than the spike. Furthermore, we derive projected rotational velocities from FIES, SONG, and HERMES spectra for 28 stars and the stellar inclination angle for 89 stars. We find a strong correlation between the spike amplitude and the power in the r and g modes, which suggests that both types of oscillations are mechanically excited by either stellar spots or OsC modes. Our analysis suggests that stars with a higher power in m = 1 r-mode humps are more likely to also exhibit humps at higher azimuthal orders (m = 2, 3, or 4). Interestingly, all stars that show g-mode humps are hotter and more luminous than the observed red edge of the δScuti instability strip, suggesting that either magnetic fields or convection in the outer layers could play an important role.

OriginalsprogEngelsk
TidsskriftMonthly Notices of the Royal Astronomical Society
Vol/bind524
Nummer3
Sider (fra-til)4196-4211
Antal sider16
ISSN0035-8711
DOI
StatusUdgivet - sep. 2023

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