How many λ Bootis stars are binaries ? ?
نویسنده
چکیده
In the attempt to shed new light on the λ Boo phenomenon we analyzed the astrometric, photometric and spectroscopic characteristics of stars out of a list of recently selected λ Boo candidates. We show that the class is still ill-defined and discuss the possibility that some, if not most stars presently classified as λ Boo, are in fact binary pairs and that peculiar abundances may not correspond to actual values if the average values of the atmospheric parameters Teff and log g are assumed and the effect of veiling is not taken into account.
منابع مشابه
Identification of λ Bootis stars using IUE spectra II. High resolution data
Stars included in the catalogue of λ Bootis stars by Paunzen et al. (1997) with high resolution spectra (FWHM: 0.10–0.25 Å) in the INES Archive of the International Ultraviolet Explorer satellite (IUE) are analyzed here in order to establish membership criteria for the λ Bootis group. Line-ratios of carbon to heavier elements (Si, Al, Ca) were adopted as criteria in the SWP range (1150–1980 Å)....
متن کاملar X iv : a st ro - p h / 98 05 05 1 v 1 6 M ay 1 99 8 The λ Bootis stars
In this article the current knowledge of the group of λ Bootis stars is reviewed. These metal poor objects are quite outstanding compared to other chemically peculiar stars of the upper main sequence. Up to now no theory has been developed which is able to explain the majority of observational results. This article is mainly focused on the work which needs to be done in the future in order to c...
متن کاملThe λ Bootis phenomenon: interaction between a star and a diffuse interstellar cloud
The λ Bootis stars, a group of late B to early F-type population I stars, have surface abundances that resemble the general metal depletion pattern found in the interstellar medium. Inspired by the recent result that the fundamental parameters of these peculiar stars differ in no respect from a comparison sample of normal stars, the hypothesis of an interaction between a star and a diffuse inte...
متن کاملForty Years of X-Ray Binaries
In 2012 it was forty years ago that the discovery of the first X-ray binary Centaurus X-3 became known. That same year it was discovered that apart from the High-Mass X-ray Binaries (HMXBs) there are also Low-Mass X-ray Binaries (LMXBs), and that Cygnus X-1 is most probably a black hole. By 1975 also the new class of Be/X-ray binaries was discovered. After this it took 28 years before ESAs INTE...
متن کاملLight element non - LTE abundances of λ Bootis stars I . Carbon and oxygen ?
Abundances for the light elements of λ Bootis stars are a main key to understand the astrophysical processes behind the so-called λ Bootis phenomenon. These stars are characterized by a typical abundance pattern (strong underabundances of the Fe-peak elements whereas the light elements have apparently solar abundances) which is still based mainly on LTEcalculations. Therefore we started an inve...
متن کامل