Period spacings of γ Doradus pulsators in the Kepler field: Rossby and gravity modes in 82 stars
Abstract
Rossby modes are the oscillations in a rotating fluid, whose restoring force is the Coriolis force. They provide an additional diagnostic to understand the rotation of stars, which complicates asteroseismic modelling. We report 82 γ Doradus stars for which clear period spacing patterns of both gravity and Rossby modes have been detected. The period spacings of both show a quasilinear relation with the pulsation period, but the slope is negative for the gravity modes and positive for the Rossby modes. Most Rossby modes have k = 2, m = 1. For only one star, a series of k = 1, m = 1 modes is seen. For each pattern, the mean pulsation period, the mean period spacing, and the slope are measured. We find that the slope correlates with the mean period for Rossby mode patterns. The traditional approximation of rotation is used to measure the nearcore rotation rate, assuming the star rotates rigidly. We report the nearcore rotation rates, the asymptotic period spacings, and the radial orders of excited modes of these 82 mainsequence stars. The nearcore rotation rates lie between 0.6 and 2.3 d^{1}. Six stars show surface rotation modulations, among which only KIC 3341457 shows differential rotation, whilst the other five stars have uniform rotations. The radial orders of excited modes show different distributions for the dipole and quadrupole gravity modes versus the Rossby modes.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 July 2019
 DOI:
 10.1093/mnras/stz1171
 arXiv:
 arXiv:1904.12291
 Bibcode:
 2019MNRAS.487..782L
 Keywords:

 stars: oscillations;
 stars: rotation;
 stars: variables;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 Accepted by MNRAS. There is an onlineonly appendix. Please find it from MNRAS webpage