The rapidly pulsating sdO star, SDSS J160043.6+074802.9

TL;DR

This study analyzes a binary system with a pulsating sdO star, determining its physical parameters, comparing them with models, and exploring pulsation stability and mode variability through photometry and pulsation analysis.

Contribution

It provides detailed spectroscopic and photometric analysis of SDSS J160043.6+074802.9, including new data and insights into pulsation stability and mode variability in sdO stars.

Findings

Teff = 70,000 +/- 5,000 K and log g = 5.25 +/- 0.30 for the sdO star

Detection of variable pulsation modes with some amplitude changes

Models with log g > 5.3 are more likely to be pulsationally unstable

Abstract

A spectroscopic analysis of SDSS J160043.6+074802.9, a binary system containing a pulsating subdwarf-O (sdO) star with a late-type companion, yields Teff = 70 000 +/- 5000 K and log g = 5.25 +/- 0.30, together with a most likely type of K3V for the secondary star. We compare our results with atmospheric parameters derived by Fontaine et al. (2008) and in the context of existing evolution models for sdO stars. New and more extensive photometry is also presented which recovers most, but not all, frequencies found in an earlier paper. It therefore seems probable that some pulsation modes have variable amplitudes. A non-adiabatic pulsation analysis of uniform metallicity sdO models show those having log g > 5.3 to be more likely to be unstable and capable of driving pulsation in the observed frequency range.