With observations at the Canada-France-Hawaii telescope, photospheric abundances of two evolved field Am stars, t UMa and HR 178, have been determined for Li, Al, Si, S, Fe, Ni, and Eu by model ...abundance analysis. Thanks to these new determined abundances and the HIPPARCOS mission, making it possible to better estimate the evolutionary stage of field stars, one can consider the influence of evolution on the abundances of Am stars. No abundance trend for Al, Si, S, and Fe is found during Main Sequence evolution, up to its very last phases. The abundance of Li is, generally, cosmic. Large Li deficiencies may be observed in the very last phases (the "hook" region of the H-R diagram) and, too, on the red side of the Am phenomenon region where the r Puppis-like stars lie.
l Bootis stars with composite spectra Faraggiana, R; Bonifacio, P; Caffau, E ...
Astronomy and astrophysics (Berlin),
10/2004, Letnik:
425, Številka:
2
Journal Article
Recenzirano
We examine the large sample of l Boo candidates collected of Gerbaldi et al. (2003) to see how many of them show composite spectra. Of the 132 l Boo candidates we identify 22 which definitely show ...composite spectra and 15 more for which there are good reasons to suspect a composite spectrum. The percentage of l Boo candidates with composite spectra is therefore > 17% and possibly considerably higher. For such stars the l Boo classification should be reconsidered taking into account the fact that their spectra are composite. We argue that some of the underabundances reported in the literature may simply be the result of the failure to consider the composite nature of the spectra. This leads to the legitimate suspicion that some, if not all, the l Boo candidates are not chemically peculiar at all. A thorough analysis of even a single one of the l Boo candidates with composite spectra, in which the composite nature of the spectrum is duly considered, which would demonstrate that the chemical peculiarities persist, would clear the doubt we presently have that the stars with composite spectra may not be l Boo stars at all.
We examine the large sample of λ Boo candidates collected in Table 1 of Gerbaldi et al. (CITE) to see how many of them show composite spectra. Of the 132 λ Boo candidates we identify 22 which ...definitely show composite spectra and 15 more for which there are good reasons to suspect a composite spectrum. The percentage of λ Boo candidates with composite spectra is therefore >17% and possibly considerably higher. For such stars the λ Boo classification should be reconsidered taking into account the fact that their spectra are composite. We argue that some of the underabundances reported in the literature may simply be the result of the failure to consider the composite nature of the spectra. This leads to the legitimate suspicion that some, if not all, the λ Boo candidates are not chemically peculiar at all. A thorough analysis of even a single one of the λ Boo candidates with composite spectra, in which the composite nature of the spectrum is duly considered, which would demonstrate that the chemical peculiarities persist, would clear the doubt we presently have that the stars with composite spectra may not be λ Boo stars at all.
Rotational velocities of A-type stars Royer, F.; Gerbaldi, M.; Faraggiana, R. ...
Astronomy and astrophysics (Berlin),
01/2002, Letnik:
381, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Within the scope of a Key Programme determining fundamental parameters of stars observed by HIPPARCOS, spectra of 525 B8 to F2-type stars brighter than $V=8$ have been collected at ESO. Fourier ...transforms of several line profiles in the range 4200–4500 Å are used to derive $v\sin i$ from the frequency of the first zero. Statistical analysis of the sample indicates that measurement error is a function of $v\sin i$ and this relative error of the rotational velocity is found to be about 6% on average. The results obtained are compared with data from the literature. There is a systematic shift from standard values from CITE, which are 10 to 12% lower than our findings. Comparisons with other independent $v\sin i$ values tend to prove that those from Slettebak et al. are underestimated. This effect is attributed to the presence of binaries in the standard sample of Slettebak et al., and to the model atmosphere they used.
The high-resolution ultraviolet spectrum of Procyon (F5 IV-V) in the range 2030-2371 A is analyzed by using BUSS VIII and IUE data. A detailed identification is performed with the synthetic spectrum ...method. The theoretical spectrum has been computed with a Kurucz blanketed model, and using an extended and updated version of the Kurucz and Peytremann log gf tables. The convolution of the computed spectrum with a Gaussian broadening function shows that the observations are well reproduced with a total broadening velocity (stellar plus instrumental) of 10.8 km/s. An atlas of the spectrum observed by BUSS VIII is given. The IUE and BUSS VIII observations are compared with each other, and the overlapping spectra are displayed. An estimate of the quality of the line list, of the atomic data, and of the abundances used for the computations has been derived. Elements predicted as being present in the region studied, but not observed in the visual range, are discussed.
The ultraviolet spectrum of Alpha Lyrae Faraggiana, R.; Hack, M.; Leckrone, D. S.
The Astrophysical journal. Supplement series,
11/1976, Letnik:
32
Journal Article
We present a detailed analysis of seven young stars observed with the spectrograph SOPHIE at the Observatoire de Haute-Provence for which the chemical composition was incomplete or absent in the ...literature. For five stars, we derived the stellar parameters and chemical compositions using our automatic pipeline optimized for F, G, and K stars, while for the other two stars with high rotational velocity, we derived the stellar parameters by using other information (parallax), and performed a line-by-line analysis. Chromospheric emission-line fluxes from CaII are obtained for all targets. The stellar parameters we derive are generally in good agreement with what is available in the literature. We provide a chemical analysis of two of the stars for the first time. The star HIP 80124 shows a strong Li feature at 670.8 nm implying a high lithium abundance. Its chemical pattern is not consistent with it being a solar sibling, as has been suggested.
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