Rediscussion of eclipsing binaries. Paper VII. Delta Scuti, gamma Doradus and tidally-perturbed pulsations in RR Lyncis

John Southworth

Published 2021-09-21Version 1

RR Lyn is a detached eclipsing binary with a 9.95 d orbit containing two A-stars: one metallic-lined and one possibly metal-poor. We use the light curve from the TESS satellite and two sets of published radial velocity measurements to determine the properties of the system to high precision. We find masses of 1.939 +/- 0.007 and 1.510 +/- 0.003 Msun, and radii of 2.564 +/- 0.019 and 1.613 +/- 0.013 Rsun. After adjusting published effective temperatures upwards by 200 K we find a good agreement with theoretical models for a solar chemical composition and an age of 1 Gyr, and a distance slightly shorter than expected from the Gaia EDR3 parallax. The light curve of RR Lyn shows clear evidence for pulsations. We measure 35 pulsation frequencies and attribute the higher frequencies to delta Scuti-type pulsations, and the intermediate frequencies to gamma Doradus-type pulsations (some of which may be tidally perturbed). The lower frequencies may be tidally excited pulsations in RR Lyn or alternatively of instrumental origin. Most or all of these pulsations are likely to arise in the secondary star. RR Lyn is one of the few eclipsing binaries known to have well-established properties and to exhibit multiple types of pulsations.