An analysis of spectroscopic, seismological, astrometric, and photometric masses of pulsating white dwarf stars

TL;DR

This study compares multiple methods for determining the masses of pulsating white dwarf stars, revealing general agreement for certain types but notable disparities for others, especially massive or chemically distinct stars.

Contribution

It provides a comprehensive comparison of spectroscopic, seismological, astrometric, and photometric mass estimates for pulsating white dwarfs using consistent models and tracks.

Findings

Consensus among methods for H-rich atmosphere WDs below 0.75 M_sun

Astrometric masses tend to be higher for He-rich atmosphere WDs

Discrepancies observed in mass estimates for massive and chemically peculiar WDs

Abstract

A central challenge in the field of stellar astrophysics lies in accurately determining the mass of isolated stars. However, for pulsating white dwarf (WD) stars, the task becomes more tractable due to the availability of multiple approaches such as spectroscopy, asteroseismology, astrometry, and photometry. The objective of this work is to compare the asteroseismological and spectroscopic mass values of WDs in detail and, in turn, to compare them with the masses derived using astrometric parallaxes/distances and photometry. Our analysis encompasses a selection of pulsating WDs with different surface chemical abundances that define the main classes of variable WDs. We calculated their spectroscopic masses, compiled seismological masses, and determined astrometric masses. We also derived photometric masses, when possible. Subsequently, we compared all the sets of stellar masses obtained through these different methods. To ensure consistency and robustness in our comparisons, we used identical WD models and evolutionary tracks across all four methods. The analysis suggests a general consensus among the these methods regarding the masses of pulsating WD with H-rich atmospheres, known as DAV or ZZ Ceti stars, especially for objects with masses below approximately $0.75 M_{\sun}$, although notable disparities emerge for certain massive stars. For pulsating WD stars with He-rich atmospheres, called DBV or V777 Her stars, we find that astrometric masses generally exceed seismological, spectroscopic, and photometric masses. Finally, while there is agreement among the sets of stellar masses for pulsating WDs with C-, O-, and He-rich atmospheres (designated as GW Vir stars), outliers exist where mass determinations by various methods show significant discrepancies.