The GALAH survey: a catalogue of carbon-enhanced stars and CEMP candidates
Lewis, Geraint F.; Ting, Yuan-Sen; Buder, Sven; Nordlander, Thomas; Bland-Hawthorn, Joss; de Silva, Gayandhi M.; Kos, Janez; Martell, Sarah L.; Sharma, Sanjib; Zwitter, Tomaž; Horner, Jonathan; Anguiano, Borja; Freeman, Kenneth C.; Munari, Ulisse; Carollo, Daniela; Asplund, Martin; Čotar, Klemen; Nataf, David M.; Traven, Gregor; Wittenmyer, Rob A.; Galah Collaboration; Stello, Denis; Tinney, Chris
Slovenia, Australia, Italy, Germany, United States, Denmark, Sweden
Abstract
Swan bands - characteristic molecular absorption features of the C2 molecule - are a spectroscopic signature of carbon-enhanced stars. They can also be used to identify carbon-enhanced metal-poor (CEMP) stars. The GALAH (GALactic Archaeology with Hermes) is a magnitude-limited survey of stars producing high-resolution, high-signal-to-noise spectra. We used 627 708 GALAH spectra to search for carbon-enhanced stars with a supervised and unsupervised classification algorithm, relying on the imprint of the Swan bands. We identified 918 carbon-enhanced stars, including 12 already described in the literature. An unbiased selection function of the GALAH survey allows us to perform a population study of carbon-enhanced stars. Most of them are giants, out of which we find 28 CEMP candidates. A large fraction of our carbon-enhanced stars with repeated observations show variation in radial velocity, hinting that there is a large fraction of variables among them. 32 of the detected stars also show strong Lithium enhancement in their spectra.