AAS 200th meeting, Albuquerque, NM, June 2002
Session 71. Stellar Youth: Tomorrow's Degenerates
Display, Thursday, June 6, 2002, 9:20am-4:00pm, SW Exhibit Hall

## [71.09] Testing Pre-Main-Sequence Stellar Evolution Theory: Discovery and Analysis of a Young, Low-Mass Eclipsing Binary

K.G. Stassun, N. Stroud, R.D. Mathieu (University of Wisconsin)

We present a preliminary analysis of a previously unknown, low-mass, pre-main-sequence (PMS), double-lined spectroscopic, eclipsing binary system in Orion. Eclipsing binaries provide powerful tests of stellar evolutionary models because stellar masses and radii are determined in a distance-independent way. Only four other PMS eclipsing binaries are presently known.

We present WIYN and HET spectroscopy from which we determine a double-lined orbit solution. We also present multi-epoch, multi-band photometric light curves which we model to derive key system parameters such as inclination and the ratio of stellar effective temperatures. With the addition of T\rm eff for the primary (determined from our HET spectra), all system parameters are determined.

The primary and secondary masses are measured to be 1.0 M\odot and 0.7 M\odot, respectively. Thus the secondary in this system is the lowest mass star yet discovered in a PMS eclipsing binary.

We also give an update on our program to discover and analyze additional PMS eclipsing binaries as sensitive tests of PMS stellar evolution, particularly among very low-mass stars.

Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.