event
Friday 22 Jun 2012: The Mass-Luminosity Relation for Pre-Main Sequence Stars with Aperture Mask Interferometry
Dr Mike Ireland - Macquarie University, Sydney
Physics, 4th floor 14:00-14:30
The fundamental properties of young stars (masses, luminosities, and temperatures) are poorly understood in comparison to their older field counterparts. The standard method for calibrating these properties is to monitor the orbits of binary systems and measure their dynamical masses, but only a handful of well-determined dynamical masses are known for low-mass stars. Placing these systems in context is difficult both because of the uncertain ages of young associations, age spreads and uncertain membership. Therefore, a large number of well-characterised systems are needed to calibrate PMS models. We are conducting an ongoing monitoring campaign to expand the sample of precise young star masses from $\sim$5 to $\sim$50, using nonredundant aperture-mask interferometry behind adaptive optics. We are able to monitor extremely short-period systems that are unresolved in traditional AO imaging (often less than 20 milli-arcsec separation) and generally too faint for long baseline interferometry (K magnitudes fainter than ~8). I will present our initial results, encompassing 12 binary systems in the Taurus and Upper Scorpius star-forming regions. These systems present a serious challenge to existing stellar evolutionary models, as the dynamical masses of some purported "solar analogs" disagree with theoretical predictions by as much as 50%. Finally, I will discuss plans including detailed SED modelling to determine how to disentangle age uncertainties and modelling calibration issues from interesting irreducible scatter in stellar properties due to e.g. differing accretion history and age spreads.
