The first eclipsing B-shell + sdO binary discovered in HD 328058

TL;DR

This paper reports the discovery and detailed analysis of the first known eclipsing binary system consisting of a B-shell star and a hot subdwarf (sdO), providing insights into mass transfer and stellar evolution.

Contribution

It presents the first discovery of an eclipsing B-shell + sdO binary and estimates the physical parameters of both components through combined photometry and stellar modeling.

Findings

Primary star: 6.9 Msun, 5.2 Rsun, 17600 K

Companion: 0.78 Msun, 1.20 Rsun, 56000 K

Binary formed by mass transfer from sdO progenitor

Abstract

An eclipsing binary with an orbital period of 62 days has been discovered in HD 328058 and studied by UBVIcHalpha photometry. Combining the results of light curve modelling with existing stellar models and known B3-shell spectral type of the primary star then allowed a reliable estimation of the mass, radius and effective temperature of both components: about 6.9 Msun, 5.2 Rsun and 17600 K for the primary star, and about 0.78 Msun, 1.20 Rsun and 56000 K for the hot subdwarf companion of type sdO. Obviously, this binary has been created by mass transfer of the envelope of the sdO progenitor to our primary star, now being a rapidly rotating shell star. Its spheroidal distortion and its decretion disk can be studied here unusually well.