Eclipse time variations and the continued search for companions to short period eclipsing binary systems

TL;DR

This study analyzes eclipse time variations in four binary systems to evaluate the presence of circumbinary companions, providing new observational data and testing existing hypotheses about their existence.

Contribution

It offers new eclipse timing data and critically assesses previous claims of circumbinary objects in four specific binary systems.

Findings

Departure from early predictions in three systems

No definitive proof of circumbinary objects yet

Potential for detecting close-in transiting circumbinary objects

Abstract

Eclipse time variations have been detected in a number of post common envelope binary systems consisting of a subdwarf B star or white dwarf primary star and cool M type or brown dwarf secondary. In this paper we consider circumbinary hypotheses of two sdB systems, HS 0705+6700 (also known as V470 Cam) and NSVS 14256825 and one white dwarf system, NN Ser. In addition, and for comparison purposes, we investigate the eclipse time variations of the W UMa system NSVS 01286630 with its stellar circumbinary companion. All four systems have claims of circumbinary objects with computed physical and orbital parameters. We report 108 new observations of minima for these four eclipsing systems observed between 2017 May and 2019 September and combining these with all published data, we investigate how well the published circumbinary object hypotheses fit with our new data. Our new data has shown departure from early predictions for three of the four systems, but it is premature to conclude that these results rule out the presence of circumbinary objects. There is also the possibility (but with no observational proof so far) of detecting close-in transiting circumbinary objects around these systems but these are likely to have periods of days rather than years.