A tidally tilted sectoral dipole pulsation mode in the eclipsing binary TIC 63328020

TL;DR

This paper reports the discovery of a new tidally tilted pulsator in an eclipsing binary, revealing a sectoral dipole mode with unique properties and evidence of past mass transfer, expanding understanding of stellar pulsations influenced by tidal forces.

Contribution

The study identifies and characterizes a third tidally tilted pulsator, providing detailed mode analysis and binary evolution context, which differs from previously known systems.

Findings

Discovery of a third tidally tilted pulsator, TIC 63328020.

Identification of a sectoral dipole pulsation mode with orbital sidelobes.

Evidence of extensive past mass transfer in the binary system.

Abstract

We report the discovery of the third tidally tilted pulsator, TIC 63328020. Observations with the TESS satellite reveal binary eclipses with an orbital period of 1.1057 d, and $\delta$ Scuti-type pulsations with a mode frequency of 21.09533 d$^{-1}$. This pulsation exhibits a septuplet of orbital sidelobes as well as a harmonic quintuplet. Using the oblique pulsator model, the primary oscillation is identified as a sectoral dipole mode with $l = 1, |m| = 1$. We find the pulsating star to have $M_1 \simeq 2.5\, {\rm M}_\odot$, $R_1 \simeq 3 \, {\rm R}_\odot$, and $T_{\rm eff,1} \simeq 8000$ K, while the secondary has $M_2 \simeq 1.1 \, {\rm M}_\odot$, $R_2 \simeq 2 \, {\rm R}_\odot$, and $T_{\rm eff,2} \simeq 5600$ K. Both stars appear to be close to filling their respective Roche lobes. The properties of this binary as well as the tidally tilted pulsations differ from the previous two tidally tilted pulsators, HD74423 and CO Cam, in important ways. We also study the prior history of this system with binary evolution models and conclude that extensive mass transfer has occurred from the current secondary to the primary.