Examinando por Autor "Masseron, T."

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Acceso Abierto
Physical parameters of red supergiants in dwarf irregular galaxies in the Local Group
(EDP Sciences, 2019-10-28) Britavskiy, N.; Bonanos, A. Z.; Herrero, A.; Cerviño, M.; García Álvarez, D.; Boyer, M. L.; Masseron, T.; Mehner, A.; McQuinn, B. W.; Ministerio de Economía y Competitividad (MINECO); Agencia Estatal de Investigación (AEI); Cerviño, M. [0000-0001-8009-231X]; Bonanos, A. [0000-0003-2851-1905]; Mehner, A. [0000-0002-9564-3302]; Masseron, T. [0000-0002-6939-0831]; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFÍSICA DE CANARIAS (IAC), SEV-2015-0548; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. Increasing the statistics of evolved massive stars in the Local Group enables investigating their evolution at different metallicities. During the late stages of stellar evolution, the physics of some phenomena, such as episodic and systematic mass loss, are not well constrained. For example, the physical properties of red supergiants (RSGs) in different metallicity regimes remain poorly understood. Thus, we initiated a systematic study of RSGs in dwarf irregular galaxies (dIrrs) in the Local Group. Aims. We aim to derive the fundamental physical parameters of RSGs and characterize the RSG population in nearby dIrrs. Methods. The target selection is based on 3.6 μm and 4.5 μm photometry from archival Spitzer Space Telescope images of nearby galaxies. We selected 46 targets in the dIrrs IC 10, IC 1613, Sextans B, and the Wolf-Lundmark-Melotte (WLM) galaxy that we observed with the GTC–OSIRIS and VLT–FORS2 instruments. We used several photometric techniques together with a spectral energy distribution analysis to derive the luminosities and effective temperatures of known and newly discovered RSGs. Results. We identified and spectroscopically confirmed 4 new RSGs, 5 previously known RSGs, and 5 massive asymptotic giant branch (AGB) stars. We added known objects from previous observations. In total, we present spectral classification and fundamental physical parameters of 25 late-type massive stars in the following dIrrs: Sextans A, Sextans B, IC 10, IC 1613, Pegasus, Phoenix, and WLM. This includes 17 RSGs and 8 AGB stars that have been identified here and previously. Conclusions. Based on our observational results and PARSEC evolutionary models, we draw the following conclusions: (i) a trend to higher minimum effective temperatures at lower metallicities and (ii) the maximum luminosity of RSGs appears to be constant at log(L/L⊙)≈5.5, independent of the metallicity of the host environment (up to [Fe/H] ≈ −1 dex).
Acceso Abierto
The Gaia -ESO Survey: Calibrating the lithium-age relation with open clusters and associations: I. Cluster age range and initial membership selections
(EDP Sciences, 2020-11-05) Gutiérrez Albarrán, M. L.; Montes, D.; Gómez Garrido, M.; Tabernero, H. M.; Marfil, E.; Frasca, A.; Lanzafame, A. C.; Klutsch, A.; Franciosini, E.; Randich, S.; Smiljanic, R.; Korn, A. J.; Gilmore, G.; Alfaro, E. J.; Baratella, M.; Bayo, A.; Bensby, T.; Bonito, R.; Carraro, G.; Delgado Mena, E.; Feltzing, S.; Gonneau, A.; Heiter, U.; Hourihane, A.; Jiménez Esteban, F. M.; Jofre, P.; Masseron, T.; Monaco, L.; Morbidelli, L.; Prisinzano, L.; Roccatagliata, V.; Sousa, S.; Van der Swaelmen, M.; Worley, Charlotte C.; Zaggia, S.; González Hernández, Carmen; Ministerio de Economía y Competitividad (MINECO); European Commission (EC); Istituto Nazionale di Astrofisica (INAF); Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR); Agencia Estatal de Investigación (AEI); Fundação para a Ciência e a Tecnologia (FCT); Leverhulme Trust; 0000-0002-7569-3513; 0000-0002-7779-238X; 0000-0002-8087-4298; 0000-0002-0264-7356; 0000-0001-8907-4775; 0000-0002-0474-0896; 0000-0001-7869-3888; 0000-0003-3969-0232; 0000-0003-2438-0899; 0000-0003-0942-7855; 0000-0003-3978-1409; 0000-0001-9297-7748; 0000-0002-0155-9434; 0000-0002-3148-9836
Context. Previous studies of open clusters have shown that lithium depletion is not only strongly age dependent but also shows a complex pattern with other parameters that is not yet understood. For pre- and main-sequence late-type stars, these parameters include metallicity, mixing mechanisms, convection structure, rotation, and magnetic activity. Aims. We perform a thorough membership analysis for a large number of stars observed within the Gaia-ESO survey (GES) in the field of 20 open clusters, ranging in age from young clusters and associations, to intermediate-age and old open clusters. Methods. Based on the parameters derived from the GES spectroscopic observations, we obtained lists of candidate members for each of the clusters in the sample by deriving radial velocity distributions and studying the position of the kinematic selections in the EW(Li)-versus-Teff plane to obtain lithium members. We used gravity indicators to discard field contaminants and studied [Fe/H] metallicity to further confirm the membership of the candidates. We also made use of studies using recent data from the Gaia DR1 and DR2 releases to assess our member selections. Results. We identified likely member candidates for the sample of 20 clusters observed in GES (iDR4) with UVES and GIRAFFE, and conducted a comparative study that allowed us to characterize the properties of these members as well as identify field contaminant stars, both lithium-rich giants and non-giant outliers. Conclusions. This work is the first step towards the calibration of the lithium-age relation and its dependence on other GES parameters. During this project we aim to use this relation to infer the ages of GES field stars, and identify their potential membership to young associations and stellar kinematic groups of different ages. © ESO 2020.