Dynamic masses for the close PG1159 binary SDSSJ212531.92-010745.9

TL;DR

This study presents the first dynamical mass determination of a PG1159 star in a close binary system, combining spectroscopic and photometric data to analyze the system's properties and constrain stellar parameters.

Contribution

It provides a detailed analysis of the first known PG1159 star in a close binary, including spectroscopic and photometric observations, and derives constraints on the star's mass and system parameters.

Findings

Confirmed PG1159 spectral features and emission lines from the companion.

Obtained radial velocity curves for both binary components.

Estimated the possible mass range for the PG1159 star.

Abstract

SDSSJ212531.92-010745.9 is the first known PG1159 star in a close binary with a late main sequence companion allowing a dynamical mass determination. The system shows flux variations with a peak-to-peak amplitude of about 0.7 mag and a period of about 6.96h. In August 2007, 13 spectra of SDSSJ212531.92-010745.9 covering the full orbital phase range were taken at the TWIN 3.5m telescope at the Calar Alto Observatory (Alm\'{e}ria, Spain). These confirm the typical PG1159 features seen in the SDSS discovery spectrum, together with the Balmer series of hydrogen in emission (plus other emission lines), interpreted as signature of the companion's irradiated side. A radial velocity curve was obtained for both components. Using co-added radial-velocity-corrected spectra, the spectral analysis of the PG1159 star is being refined. The system's lightcurve, obtained during three seasons of photometry with the G\"ottingen 50cm and T\"ubingen 80cm telescopes, was fitted with both the NIGHTFALL and PHOEBE binary simulation programs. An accurate mass determination of the PG1159 component from the radial velocity measurements requires to first derive the inclination, which requires light curve modelling and yields further constraints on radii, effective temperature and separation of the system's components. From the analysis of all data available so far, we present the possible mass range for the PG1159 component of SDSSJ212531.92-010745.9.