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Program Information for 2020B-0030


PI: Eliot Halley Vrijmoet, RECONS Institute & Georgia State University, vrijmoet@astro.gsu.edu
Address: Physics Department, 25 Park Place, Suite 605, Atlanta, GA 30303 USA

CoI: Todd Henry, Georgia State U.
CoI: Elliott P Horch, SCSU
CoI: Jao Wei-Chun, Georgia State U.
CoI: Andrei Tokovinin, NOIRLab
CoI: Jennifer Winters, Harvard-Smithsonian Center for Astrophysics

Title: Orbital Architectures of M Dwarf Binaries

Abstract: M dwarfs account for three of every four stars in the solar neighborhood. These are key stars to study not only because of their ubiquity, but because they span broad ranges in age (none have evolved significantly since the Big Bang), metallicity (all stages of Galactic recycling of metals are represented), mass (a factor of 8 from the largest to smallest), and structure (some are partially radiative, while others are fully convective). Here we propose an aggressive effort to understand two particular aspects of binary M dwarfs --- their orbital architectures and their masses. The orbits reveal critical information about their formation, while the masses will be used as the fundamental attribute for investigations into ages and metallicities. These M dwarf binaries are especially attractive because their low masses result in shorter orbital periods than their more massive stellar counterparts. By characterizing orbits as long as 30 years in period and as large as 6 AU in semimajor axis, we will establish the distribution of periods vs.~eccentricities from which specific aspects of binary formation and evolution can be constrained. Our approach combines data from two distinct observational programs: astrometry from the 20-year RECONS program at the CTIO/SMARTS 0.9m, and speckle interferometry from SOAR with HRCam+SAM. These efforts are augmented with data from {it Gaia} and the literature. The first two semesters allocated for this project at SOAR have been an unquestionable success, as most (77%) of the targets already observed at least once, with companions detected for 53% of them, and many already showing clear orbital motion. In this proposal we request long-term status to continue this program for 1.5 nights/semester for 4 more semesters. This will bring the total observed baseline to 3 years for our binaries, complementing our 20-year coverage of astrometric binaries and thus opening the door to a wider view of the stellar dynamics of M dwarf systems.

Program Type: Long Term/Galactic

Scheduled Nights:
Run 1 (2020B):  SOAR/HRCam -- 1n on Oct 27 2020, Dec 03 2020
Run 1 (2021A):  SOAR/HRCam -- 1.5n on Feb 27 2021, Apr 26 2021, Jul 25 2021
Run 1 (2021B):  SOAR/HRCam -- 1.5n on Sep 23 2021, Nov 20 2021, Jan 15 2022


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