An Unusual Eclipsing Blue Straggler V8-NGC 6752

TL;DR

This paper analyzes a rare short-period binary blue straggler in NGC 6752, revealing an unusual configuration likely caused by significant mass exchange, and proposing a new perspective on W UMa-type secondary stars.

Contribution

It presents detailed photometric analysis of an unusual blue straggler binary, suggesting a novel evolutionary scenario involving shell-burning cores.

Findings

Mass ratio between 0.15 and 0.35

Luminosity ratio about 4.0

Components have nearly identical temperatures

Abstract

We report the analysis of a binary blue straggler in NGC 6752 with a short orbital period of 0.315 d and a W UMA-type light curve. We use photometric data spanning 13 years to place limits on the mass ratio (0.15<q<0.35), luminosity ratio (L1/L2 about 4.0) and the ratio of the radii of the components (r1/r2 about 2.0). The effective temperatures of the components are nearly identical, and the system is detached or semi-detached (in the latter case the component filling its Roche lobe is the secondary). Such a configuration is unusual given the shortness of the orbital period, and it must have resulted from substantial mass exchange. We suggest that some secondaries of W UMa-type stars, normally regarded as main sequence objects which fill their Roche lobes to different degrees, in fact may be shell-burning cores of originally more massive components.