Volume 495, Number 3, March I 2009
|Page(s)||901 - 917|
|Section||Stellar structure and evolution|
|Published online||14 January 2009|
Parameters of Herbig Ae/Be and Vega-type stars*
LAEX, Centro de Astrobiología (CAB, CSIC-INTA). Postal address: LAEFF, European Space Astronomy Centre, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain e-mail: Benjamin.Montesinos@laeff.inta.es
2 Universidad Autónoma de Madrid, Departamento de Física Teórica C-XI, 28049 Madrid, Spain
3 Herschel Science Centre, European Space Astronomy Centre, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
Accepted: 13 November 2008
Context. This work presents the characterization of 27 young early-type stars, most of them in the age range 1–10 Myr, and three suspected hot companions of post-T Tauri stars belonging to the Lindroos binary sample. Most of these objects show IR excesses in their spectral energy distributions, which are indicative of the presence of disks. The work is relevant in the fields of stellar physics, physics of disks and formation of planetary systems.
Aims. The aim of the work is the determination of the effective temperature, gravity, metallicity, mass, luminosity and age of these stars. An accurate modelling of their disks requires the knowledge of most of these parameters, since they will determine the energy input received by the disk and hence, its geometry and global properties.
Methods. Spectral energy distributions and mid-resolution spectra were used to estimate Teff, the effective temperature. The comparison of the profiles of the Balmer lines with synthetic profiles provides the value of the stellar gravity, . High-resolution optical observations and synthetic spectra are used to estimate the metallicity, [M/H]. Once , and [M/H] are known for each star, evolutionary tracks and isochrones provide estimations of the mass, luminosity, age and distances (or upper limits in some cases). The method is original in the sense that it is distance-independent, i.e. the estimation of the stellar parameters does not require the knowledge of the distance to the object.
Results. Stellar parameters (effective temperature, gravity, metallicity, mass, luminosity, age and distances – or upper limits) are obtained for the sample of stars mentioned above. A detailed discussion of some individual objects, in particular VV Ser, RR Tau, 49 Cet and the three suspected hot companions of post-T Tauris, is presented.
Conclusions. These results, apart from their intrinsic interest, would be extremely valuable to model the disks surrounding the stars. The paper also shows the difficulty posed by the morphology and behaviour of the system star+disk in the computation of the stellar parameters.
Key words: stars: pre-main sequence / stars: fundamental parameters / stars: abundances / stars: evolution / stars: circumstellar matter / stars: planetary systems: protoplanetary disks
Based on observations collected at the German-Spanish Astronomical Centre, Calar Alto, jointly operated by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC), and on observations made with the WHT telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.
© ESO, 2009
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