Dwarf carbon stars are likely metal-poor binaries and unlikely hosts to carbon planets

TL;DR

This study confirms that dwarf carbon stars are predominantly binary systems resulting from mass transfer, making them unlikely candidates for hosting carbon planets.

Contribution

The paper provides observational evidence supporting the binary nature of dwarf carbon stars through radial velocity monitoring and simulations.

Findings

21 out of 28 dwarf carbon stars show radial velocity variations

Detection fraction consistent with 100% binary population

Orbital periods are on the order of hundreds of days

Abstract

Dwarf carbon stars make up the largest fraction of carbon stars in the Galaxy with around 1200 candidates known to date primarily from the Sloan Digital Sky Survey. They either possess primordial carbon-enhancements, or are polluted by mass transfer from an evolved companion such that C/O is enhanced beyond unity. To directly test the binary hypothesis, a radial velocity monitoring survey has been carried out on 28 dwarf carbon stars, resulting in the detection of variations in 21 targets. Using Monte Carlo simulations, this detection fraction is found to be consistent with a 100% binary population and orbital periods on the order of hundreds of days. This result supports the post-mass transfer nature of dwarf carbon stars, and implies they are not likely hosts to carbon planets.