In search of RR Lyrae type stars in eclipsing binary systems. OGLE052218.07-692827.4: an optical blend

TL;DR

This study investigates the candidate RR Lyrae star in an eclipsing binary system, revealing it is actually an optical blend of multiple sources and not a true binary, highlighting challenges in identifying RR Lyrae binaries.

Contribution

The paper demonstrates that the previously identified RR Lyrae candidate in an eclipsing binary is an optical blend, not a genuine binary system, using high-resolution HST imaging.

Findings

The candidate is an optical blend of five sources.

The supposed eclipsing binary signature is from a background RR Lyr star.

No confirmed RR Lyr stars are known in eclipsing binary systems.

Abstract

During the OGLE-2 operation, Soszynski et al. (2003) found 3 LMC candidates for an RR Lyr-type component in an eclipsing binary system. Two of those have orbital periods that are too short to be physically plausible and hence have to be optical blends. For the third, OGLE052218.07-692827.4, we developed a model of the binary that could host the observed RR Lyr star. After being granted HST/WFPC2 time, however, we were able to resolve 5 distinct sources within a 1.3" region that is typical of OGLE resolution, proving that OGLE052218.07-692827.4 is also an optical blend. Moreover, the putative eclipsing binary signature found in the OGLE data does not seem to correspond to a physically plausible system; the source is likely another background RR Lyr star. There are still no RR Lyr stars discovered so far in an eclipsing binary system.