The PMS Eclipsing Binary RXJ 0529.4+0041

Abstract

Abstract. We report the discovery of the first low-mass pre-main sequence eclipsing binary among a sample of double-lined spectroscopic binaries in the Orion star forming region found in a previous high-resolution spectroscopic investigation on ROSAT-discovered weak-T Tauri stars. Here we present the preliminary results from the combined analysis of the spectroscopic orbit and B and V light-curves, using data available till spring 2000. We then compare the fundamental stellar parameters derived from the orbital solution with those inferred from some widely used theoretical evolutionary models.

First Results on Pre–Main-Sequence Evolution, Including a Magnetic Field

“…In Figure 2, we show the H-R diagram of our tracks and compare it with RX J0529.4ϩ0041 as given by Covino et al (2000). The secondary of RX J0529.4ϩ0041, which is just in the phase where lithium burning takes place, is consistent with our CSR models for a surface field of Ӎ35-45 G. In the SRS hypothesis, the location is consistent with a larger B surf (Ӎ60-80 G).…”

“…We are motivated by the determination of masses and physical parameters for some PMS stars (Dutrey et al 1998;Melo et al 2000) and in particular for the weak T Tauri star RX J0529.4ϩ0041, a double-lined eclipsing binary (Covino et al 2000). The H-R diagram location of some of these stars is in fact difficult to reconcile with the "standard" tracks.…”

Rotational Velocities and Radii of Pre–Main-Sequence Stars in the Orion Nebula Cluster

“…Furthermore, for objects with measured rotation periods, we can use their v sin(i) values to obtain statistical estimates of their radii. With the exception of four known pre-main-sequence eclipsing binaries (Popper 1987;Casey et al 1995Casey et al , 1998Andersen 1991;Mamajek et al 2000;Covino et al 2000), we have no direct measurements of the sizes of pre-main-sequence stars. Since P v sin(i) = 2πR sin(i), combining the stellar rotation period P with v sin(i) can constrain the stellar radius R to within a factor of sin(i).…”

“…With enough data, the rotational velocities and periods can provide statistical estimates of radii (without the sin(i) ambiguity) for stars grouped by their similar characteristics. Direct measurements of the radii of pre-main-sequence stars are hard to come by, since so far only four pre-main-sequence eclipsing binaries have been discovered (Popper 1987;Casey et al 1995Casey et al , 1998Andersen 1991;Mamajek et al 2000;Covino et al 2000). Therefore other methods for independently estimating stellar radii can be valuable tests of the reliability of the radii of pre-main-sequence stars and hence the accuracy with which they can be placed on the theoretical H-R diagram.…”

Principles of Star Formation

“…Two types of T Tauri stars are recognized, the classical or CTTS, which have an equivalent width (in emission) of H˛> 10Å, and the weak-lined or WTTS, which have an equivalent width in H˛< 10Å. The particular objects shown [122] are the components of a pre-main-sequence double-lined eclipsing spectroscopic binary in the post-T Tauri phase, whose masses can be directly measured and compared with those obtained from the tracks, for example those calculated by [30]. Both types have X-ray emission.…”