Research Note

In search of RR Lyrae type stars in eclipsing binary systems^*

OGLE052218.07-692827.4: an optical blend

¹ Villanova University, Department of Astronomy, 800 Lancaster Ave, Villanova, PA 19085, USA e-mail: andrej.prsa@villanova.edu
² University of Ljubljana, Dept. of Physics, Jadranska 19, SI-1000 Ljubljana, EU
³ James Cook University, Centre for Astronomy, Townsville QLD 4811, Australia

Received: 30 June 2008
Accepted: 23 August 2008

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.