A Survey of Nearby Very Low Mass Star-Brown Dwarf Spectral Binaries

University Of California-San Diego, La Jolla CA

Investigators

Abstract

The coolest stars and brown dwarfs, with mass less than 10% that of the Sun, compose the majority population in the Milky Way Galaxy. It is not yet clear how these objects were formed. An accurate measurement of the fraction of low-mass stars that are actually systems of two or more stars can constrain or rule out several currently proposed theories. The proposal team has developed a method to identify short-period, low-mass multiple systems. They will determine the low-mass multiple frequency, and for some binary systems they will measure their orbital properties and masses. The program will specifically engage students historically underrepresented in science fields. Analysis tools will be constructed in a manner that facilitates participation by high school and undergraduate research students in stellar research, with a focus on engaging students from historically underrepresented groups in science. The program's primary goal is to measure the very low mass (M < 0.1 Msun) binary fraction by determining a volume-limited and bias-corrected multiplicity fraction of "spectral blend" binaries, systems identified by their combined-light spectroscopy. It involves four primary investigations: (1) a near-infrared spectral survey of M7-L5 dwarfs within 25 pc of the Sun, (2) analysis of these spectra to identify and characterize blended light pairs; (3) numerical simulations to determine the selection function and its dependence on population age and mass distributions; and (4) multi-component radial and astrometric monitoring observations, with full orbital coverage of five previously identified binaries, to measure orbits, individual component masses and spin-orbit alignment. The data collected and analysis tools developed in this program willm be made publicly available through the SpeX Prism Library and Virtual Observatory frameworks for scientific investigations by the larger community.