Stellar Archaeology as a Time Machine to the First Stars

The binarity of dwarf carbon stars and their possible role as main sequence counterparts to CEMP stars

6 Dec 2018, 16:50

10m

Lecture Hall (Kavli IPMU)

Carbon enhanced metal-poor stars CEMP Stars: Observation

Speaker

Mr Lewis Whitehouse (University College London)

Description

Contrary to expectations, the most abundant carbon stars in the Galaxy are long-lived,
main-sequence stars. The origin of these dwarf carbon (dC) stars is an astrophysical
curiosity that is 40 years(!) old, and the mechanisms for enhancing their observed C/O
above unity are poorly constrained. Intriguingly, a significant fraction of the dC stars
have clear halo kinematics, and are thus almost certainly related to the carbon enhanced,
metal-poor (CEMP) stars observed in the Galactic halo.

We will present a search for evolved binary companions via radial velocity
measurements of these chemically peculiar dwarf stars, all of which are currently in the
solar neighbourhood. Over several years, we observed a few dozen dC stars with the
ISIS spectrograph on the WHT, and 22 stars with sufficient data are consistent with a
100% binary fraction. We hypothesise these main-sequence stars are essentially
CEMP-r or CEMP-s stars of relatively low mass, and are ancient and relatively pristine sites for stellar archaeology.

Affiliation

University College London