The pre-main-sequence eclipsing binary ASAS J052821+0338.5

Aims. In this paper we present the first results of a detailed spectroscopic and photometric analysis of the V = 11.7(m) eclipsing binary ASAS J052821+0338.5.

Methods. With the FIES spectrograph at the Nordic Optical Telescope, we obtained a series of high-resolution spectra (R approximate to 47 000) covering the entire orbit of the system. In addition we obtained simultaneous broadband photometry from three small aperture telescopes. From these spectroscopic and photometric data we have derived the system's orbital parameters and determined the fundamental stellar parameters of the two components.

Results. Our results indicate that ASAS J052821+ 0338.5 is a K1/K3 pre-main-sequence eclipsing binary, with component masses of 1.38 M-circle dot and 1.33 M-circle dot and a period of 3.87 days, located at a distance of 280 +/- 30 pc. The kinematics, physical location, and the evolutionary status of the two stars suggest that ASAS J052821+ 0338.5 is a member of the similar to 11 Myr old Orion OB1a subassociation. The systems also exhibits smooth similar to 0.15(m) out-of-eclipse variations that are similar to those found in RS CVn binaries. Furthermore, the parameters we derived are consistent with the 10-13 Myr isochrones of the popular Baraffe stellar evolutionary models.