Mass transfer and tidally tilted pulsation in the Algol-type system TZ Dra

TL;DR

This study investigates the pulsations and mass transfer in the Algol-type system TZ Dra, revealing tidally tilted pulsations, mass loss through stellar winds, and detailed stellar parameters using photometric and spectroscopic data.

Contribution

It provides the first detailed analysis of pulsations and mass transfer in TZ Dra, identifying tidally tilted pulsations and quantifying mass loss in an Algol-type system.

Findings

Detection of mass transfer via Hα line profiles.

Identification of tidally tilted pulsations with harmonic frequency spacing.

Quantification of mass loss rate as 3.52 x 10^-9 M_sun/year.

Abstract

Oscillating eclipsing Algols (oEAs) are remarkable systems which allow us to determine accurate fundamental stellar parameters (mass, radius) and probe the stellar interiors through pulsations. TZ\,Dra is an oEA system containing a $\delta$ Scuti component. To examine particular characteristics of such close systems including pulsations and mass transfer, we present a detailed photometric and spectroscopic study of TZ\,Dra. With the analysis of high-resolution spectra, the orbital parameters were determined by the radial velocity analysis and the atmospheric parameters were derived for the primary component. The binary modelling and the pulsational frequency analysis was carried out using the TESS data set. The H$\alpha$ line profiles show the signature of mass transfer from the cool to the hot binary component. The conclusion of mass transfer/mass loss in the system was supported by the analysis of the orbital period changes. As a result, it was found that there is $3.52 \times 10^{-9}$ $M_\odot$/year mass loss from the system most probably through the hotspot and stellar winds. Additionally, most pulsation frequencies originating from the primary component were found to be spaced by harmonics of the orbital frequencies in particular, twelve doublets spaced by $2f_{\rm orb}$ were detected from which we infer that this star a tidally tilted pulsator. A mean p-mode frequency spacing of $\approx 7.2 $d$^{-1}$ was found as well.