Characterisation of red supergiants in the Gaia spectral range

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Título: Characterisation of red supergiants in the Gaia spectral range
Autor/es: Dorda Laforet, Ricardo | González-Fernández, Carlos | Negueruela, Ignacio
Grupo/s de investigación o GITE: Astrofísica Estelar (AE)
Centro, Departamento o Servicio: Universidad de Alicante. Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal
Palabras clave: Methods: data analysis | Stars: massive | Supergiants | Galaxy: stellar content | Magellanic Clouds
Área/s de conocimiento: Astronomía y Astrofísica
Fecha de publicación: 8-nov-2016
Editor: EDP Sciences
Cita bibliográfica: Astronomy & Astrophysics. 2016, 595: A105. doi:10.1051/0004-6361/201628422
Resumen: Context. The infrared calcium triplet and its nearby spectral region have been used for spectral and luminosity classification of late-type stars, but the samples of cool supergiants (CSGs) used have been very limited (in size, metallicity range, and spectral types covered). The spectral range of the Gaia Radial Velocity Spectrograph (RVS) covers most of this region but does not reach the main TiO bands in this region, whose depths define the M sequence. Aims. We study the behaviour of spectral features around the calcium triplet and develop effective criteria to identify and classify CSGs, comparing their efficiency with other methods previously proposed. Methods. We measure the main spectral features in a large sample (almost 600) of red supergiants (RSGs) from three different galaxies, and we analyse their behaviour through a principal component analysis. Using the principal components, we develop an automatised method to differentiate CSGs from other bright late-type stars, and to classify them. Results. The proposed method identifies a high fraction (0.98 ± 0.04) of the supergiants in our test sample, which cover a wide metallicity range (supergiants from the Magellanic Clouds and the Milky Way) and with spectral types from G0 up to late-M. In addition, it is capable to separate most of the non-supergiants in the sample, identifying as supergiants only a very small fraction of them (0.02 ± 0.04). A comparison of this method with other previously proposed shows that it is more efficient and selects less interlopers. A way to automatically assign a spectral type to the supergiants is also developed. We apply this study to spectra at the resolution and spectral range of the Gaia RVS, with a similar success rate. Conclusions. The method developed identifies and classifies CSGs in large samples, with high efficiency and low contamination, even in conditions of wide metallicity and spectral-type ranges. As this method uses the infrared calcium triplet spectral region, it is specially useful for surveys looking for CSGs in high-extinction regions. In addition the method is directly applicable to the Gaia spectra.
Patrocinador/es: This research is partially supported by the Spanish Ministerio de Economía y Competitividad (Mineco) under grants AYA2012-39364-C02-02, AYA2015-68012-C2-2-P (MINECO/FEDER), and FPI BES-2011-049345. The work reported in this publication has been partially supported by the European Science Foundation (ESF), in the framework of the GREAT Research Networking Programme.
URI: http://hdl.handle.net/10045/71808
ISSN: 0004-6361 (Print) | 1432-0746 (Online)
DOI: 10.1051/0004-6361/201628422
Idioma: eng
Tipo: info:eu-repo/semantics/article
Derechos: © ESO 2016
Revisión científica: si
Versión del editor: http://dx.doi.org/10.1051/0004-6361/201628422
Aparece en las colecciones:INV - Astrofísica Estelar - Artículos de Revistas

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