Search Publications
Analysis of Galactic late-type O dwarfs: more constraints on the weak wind problem
Bouret, J. -C.; Martins, F.; Hillier, D. J. +3 more
Aims: We investigate the stellar and wind properties of a sample of late-type O dwarfs. Previous analyses of such stars have found very low mass-loss rates; rates much lower than predicted by theory (the weak wind problem).
Methods: Far-UV to optical spectra of five Galactic O stars were analyzed: HD 216898 (O9IV/O8.5V), HD 326329 (O9V), HD 66…
Parameters of Herbig Ae/Be and Vega-type stars
Eiroa, C.; Montesinos, B.; Mora, A. +1 more
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 wo…
Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars and stars with debris disks
Hamaguchi, K.; Hubrig, S.; Stelzer, B. +6 more
Context: Recently, evidence for the presence of weak magnetic fields in Herbig Ae/Be stars has been found in several studies.
Aims: We seek to expand the sample of intermediate-mass pre-main sequence stars with circular polarization data to measure their magnetic fields, and to determine whether magnetic field properties in these stars are cor…
Empirical estimate of Lyα escape fraction in a statistical sample of Lyα emitters
Schaerer, D.; Östlin, G.; Hayes, M. +4 more
Context: The Lyman-alpha (Lyα) recombination line is a fundamental tool for galaxy evolution studies and modern observational cosmology. However, subsequent interpretations are still prone to a number of uncertainties. Besides numerical efforts, empirical data are urgently needed for a better understanding of the Lyα escape process.
Aims: We e…
The chemical abundance analysis of normal early A- and late B-type stars
Ryabchikova, T.; Fossati, L.; Alecian, E. +4 more
Context: Modern spectroscopy of early-type stars often aims at studying complex physical phenomena such as stellar pulsation, the peculiarity of the composition of the photosphere, chemical stratification, the presence of a magnetic field, and its interplay with the stellar atmosphere and the circumstellar environment. Comparatively less attention…
A self-consistent stellar and 3D nebular model of planetary nebula IC 418
Morisset, C.; Georgiev, L.
Aims: We present a coherent stellar and nebular model that reproduces observations of the planetary nebula IC 418. We aim to test whether a stellar model found to provide an optimal description of the stellar observations is able to satisfactory ionize the nebula and reproduce the nebular observations, a finding that is by no mean evident. This al…
Properties of WNh stars in the Small Magellanic Cloud: evidence for homogeneous evolution
Martins, F.; Hillier, D. J.; Foellmi, C. +4 more
Aims: We aim to assess the nature of three WNh stars in the SMC, to constrain stellar evolution beyond the main sequence at low metallicity, and to investigate the metallicity dependence of the clumping properties of massive stars.
Methods: We compute atmosphere models to derive the stellar and wind properties of the three WNh targets. A FUV/U…
Absorption line indices in the UV. I. Empirical and theoretical stellar population models
Thomas, D.; Bender, R.; Maraston, C. +1 more
Aims: Stellar absorption lines in the optical (e.g. the Lick system) have been extensively studied and constitute an important stellar population diagnostic for galaxies in the local universe and up to moderate redshifts. Proceeding towards higher look-back times, galaxies are younger and the ultraviolet becomes the relevant spectral region where …
Faint recombination lines in Galactic PNe with a [WC] nucleus
García-Rojas, J.; Peña, M.; Peimbert, A.
Aims: We present spatially resolved high-resolution spectrophotometric data for the planetary nebulae PB 8, NGC 2867, and PB 6. We have analyzed two knots in NGC 2867 and PB 6 and one in PB 8. The three nebulae are ionized by [WC] type nuclei: early [WO] for PB 6 and NGC 2867 and [WC 5-6] in the case of PB 8. Our aim is to study the behavior of th…
Model atmospheres of chemically peculiar stars. Self-consistent empirical stratified model of HD 24712
Shulyak, D.; Ryabchikova, T.; Kochukhov, O. +1 more
Context: High-resolution spectra of some chemically peculiar stars clearly demonstrate the presence of strong abundance gradients in their atmospheres. However, these inhomogeneities are usually ignored in the standard scheme of model atmosphere calculations, breaking the consistency between model structure and spectroscopically derived abundance …