Young Star Dynamical Mass Ratios and Masses

Lowell Observatory, Flagstaff AZ

Investigators

Abstract

Although Earth orbits a single star, most stars in our Galaxy are located in binary or multiple systems - groups of two or more stars that are gravitationally bound to each other. The time it takes the two stars in a binary to complete one full orbit around each other can be anywhere from hours to days, weeks, month, years, or millennia. The stars in the closest pairs with orbits that take months or less, comprise a special category called "spectroscopic binaries". They move so rapidly that it is possible to measure the velocities of each star, and from the velocities we can determine the ratio of their masses. Among very young, newly formed stars, these spectroscopic binaries provide a way to measure the most fundamental stellar property, mass, during a poorly understood period in the life-cycle of stars. This can help us calibrate the relationships between fundamental stellar properties at a key epoch: the onset of planet formation. In this program, the PI will observe a sample of 140 candidate young spectroscopic binaries to confirm their multiplicity and to measure the mass ratios of the bona fide pairs. This research will be carried out by the PI in collaboration with undergraduate and junior graduate students, some of them from groups traditionally underrepresented in astronomy. Measuring the mass ratios and masses of young stars is important for understanding the physical processes of star and binary formation. Usually, this is accomplished by comparing the locations of stars on an H-R diagram to theoretical tracks of young star evolution. However, the wide variety of available calculations predict a large range of possible stellar masses at young ages. The PI's work in this area has helped to renew interest in improving these models. In this program, she will observe a sample of 140 candidate young spectroscopic binaries to confirm their multiplicity with multi-object visible light spectroscopy on the MMT Telescope and to measure the mass ratios of the bona fide pairs with 3 epochs of infrared spectroscopy using the Discovery Channel Telescope.