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arXiv · 1807.07977

The GALAH survey: a catalogue of carbon-enhanced stars and CEMP candidates

Klemen Čotar·Tomaž Zwitter·Janez Kos·Ulisse Munari·Sarah L. Martell·Martin Asplund·Joss Bland-Hawthorn·Sven Buder·Gayandhi M. De Silva·Kenneth C. Freeman·Sanjib Sharma·Borja Anguiano·Daniela Carollo·Jonathan Horner·Geraint F. Lewis·David M. Nataf·Thomas Nordlander·Denis Stello·Yuan-Sen Ting·Chris Tinney·Gregor Traven·Rob A. Wittenmyer
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Abstract

Swan bands - characteristic molecular absorption features of the C$_2$ 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.

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Klemen Čotar, Tomaž Zwitter, Janez Kos, Ulisse Munari, Sarah L. Martell, Martin Asplund, Joss Bland-Hawthorn, Sven Buder, Gayandhi M. De Silva, Kenneth C. Freeman, Sanjib Sharma, Borja Anguiano, Daniela Carollo, Jonathan Horner, Geraint F. Lewis, David M. Nataf, Thomas Nordlander, Denis Stello, Yuan-Sen Ting, Chris Tinney, Gregor Traven, Rob A. Wittenmyer. 2018-07-20. The GALAH survey: a catalogue of carbon-enhanced stars and CEMP candidates. https://doi.org/10.1093/mnras/sty3155

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