Related papers: An abundance analysis for Vega: Is it a lambda Boo…
Vega's photospheric abundances of Li, Na, and K were determined by using considerably weak lines measured on the very high-S/N spectrum, while the non-LTE correction and the gravity-darkening correction were adequately taken into account.…
In the attempt to shed new light on the lambda Boo phenomenon we analyzed the astrometric, photometric and spectroscopic characteristics of stars out of a list of recently selected lambda Boo candidates. We show that the class is still…
Vega, the second brightest star in the northern hemisphere, serves as a primary spectral type standard. While its spectrum is dominated by broad hydrogen lines, the narrower lines of the heavy elements suggested slow to moderate rotation,…
Aims: To determine the metallicities of 113 Southern Hemisphere Vega-like candidate stars in relation to the Exoplanet host group and field stars. Methods: We applied two spectroscopic methods of abundance determinations: equivalent width…
We examine the large sample of lambda Boo candidates collected in Table 1 of Gerbaldi et al. (2003) to see how many of them show composite spectra. Of the 132 lambda Boo candidates we identify 22 which definitely show composite spectra and…
Seven high-resolution and high S/N CCD spectra were used to derive elemental abundances in the atmosphere of VW Ari A (T_eff=7200, log g=3.7) which is the primary component of a visual binary system. The synthetic spectrum technique applied…
Context: Recent attention has been directed to abundance variations among very young stars. Aims: To perform a detailed abundance study of the Herbig Ae star HD 101412, taking advantage of its unusually sharp spectral lines. Methods:…
The selective abundance of C, N, O (almost solar) with respect to that of other elements (underabundant) in lambda Boo stars has been interpreted as a characteristic peculiarity of these objects, when considered as single stars. We show…
The $\lambda$ Boo stars are chemically peculiar A-type stars whose abundance anomalies are associated with the accretion of metal-poor material. We searched for $\lambda$ Boo stars in the southern hemisphere in a targeted spectroscopic…
Very weak magnetic fields (with a longitudinal component below 1 Gauss) have recently been discovered in the A star Vega as well as in a few Am stars. According to fossil field scenarios, such weak fields should also exist in more massive…
The abundance anomalies in lambda Boo stars are popularly explained by element-specific mass inflows at rates that are much greater than empirically-inferred bounds for interstellar accretion. Therefore, a lambda Boo star's thin outer…
High-resolution and high S/N CCD spectra were analyzed to determine accurate LTE abundances in four lambda Boo stars: pi^1 Ori, 29 Cyg, HR 8203 and 15 And. In general, 14 chemical elements were investigated. The main results are the…
The discovery that Vega is a rapidly rotating pole-on star has raised a number of questions about this fundamental standard, including such issues as its composition, and in turn its mass and age. We report here a reanalysis of Vega's…
We carried out a search for M-type Vega-like stars by correlating the IRAS Faint Source Catalog with Hipparcos selected M-type stars. Three stars with apparent IRAS 25mu excess emission are shown instead to be non-IR-excess stars from…
Optical linear polarization measurements are presented for about 30 Vega-like stars. These are then compared with the polarization observed for normal field stars. A significant fraction of the Vega-like stars are found to show polarization…
We show that the UV spectrum (1280-3200 A) of the "superficially normal" A-star Vega, as observed by the IUE satellite at a resolution comparable to the star's rotational broadening width, can be fit remarkably well by a single-temperature…
Lambda Boo stars are predominately A-type stars with solar abundant C, N, O, and S, but up to 2 dex underabundances of refractory elements. The stars' unusual surface abundances could be due to a selective accretion of volatile gas over…
We present preliminary abundance analyses of a group of high-velocity metal-poor stars. This report describes our work in progress. We examine the derived abundances in the context of previous studies of metal-poor stars with unusual…
The recent discovery of a weak surface magnetic field on the normal intermediate-mass star Vega raises the question of the origin of this magnetism in a class of stars that was not known to host magnetic fields. We aim to confirm the field…
We take advantage of the Gaia-ESO Survey iDR4 bulge data to search for abundance anomalies that could shed light on the composite nature of the Milky Way bulge. The alpha-elements (Mg, Si, and whenever available, Ca) abundances, and their…