NOAO >   Observing Info >   Approved Programs >   2015B-0125

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Program Information for 2015B-0125


PI: Jay Farihi, University College London, j.farihi@ucl.ac.uk
Address: Physics Department, Gower Place, London WC1E 6BT UK

CoI: Hugh C Harris, US Naval Observatory
CoI: John P Subasavage, US Naval Observatory, Flagstaff
CoI: Carolina Bergfors, University College London
CoI: Paul J Green, Harvard-Smithsonian Center for Astrophysics
CoI: Boris Gansicke, University of Warwick

Title: An Ongoing Study of Dwarf Carbon Stars: Binary Fraction, Orbital Period Constraints

Abstract: We are currently monitoring the radial velocities of low-mass, main- sequence stars with C/O $>$1. The dwarf carbon (dC) star conundrum is nearly 40 years old as only giant stars dredge up interior carbon, and similar to the C-enhanced metal-poor, halo stars the bulk of dC stars show no obvious sign of evolved companions necessary to externally- pollute their atmospheres. These stars are sensitive tracers of Galactic chemical evolution and star formation, and provide strong constraints on the potential for C-dominated (single star) planetary systems. Our data hint at orbital periods of hours to days for some targets, and longer time scale variations (months to years) for others, and here we propose to continue RV monitoring to constrain their orbits. The monitoring will confirm or refute the hypothetical binary nature of all dwarf carbon stars, and the orbital period measurements will determine the physical separation and mass-transfer mechanism (Roche lobe overflow vs.\ AGB wind capture) in all binaries.

Program Type: Standard/Galactic

Scheduled Nights:
Run 1 (2015B):  KP-4m/KOSMOS -- 2n on Dec 16 - Dec 17 2015


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NOAO >   Observing Info >   Approved Programs >   2015B-0125

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