- ID:
- ivo://CDS.VizieR/J/other/AstBu/69.296
- Title:
- Speckle interferometry of Ap stars. II.
- Short Name:
- J/other/AstBu/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of speckle interferometric observations of 156 stars possessing global magnetic fields, carried out with the 6-m BTA telescope of the Special Astrophysical Observatory. Virtually all stars were observed between 2010 and 2012. Thirty-four stars were resolved into individual components (31 double and 3 triple), of which 14 binary systems (BD+41 43, HD2887, HD30466, HD36540, HD36955, HD37479, HD61045, HD89069, HD144334, HD164258, HD349321, HD343872, HD184471, HD196691) and 2 triple systems (HD37140, HD338226) were for the first time resolved by the astrometric method.
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- ID:
- ivo://CDS.VizieR/J/AJ/140/1758
- Title:
- Spectral atlas of peculiar stars
- Short Name:
- J/AJ/140/1758
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an Echelle+CCD, high S/N, high resolution (R=20000) spectroscopic atlas of 108 well-known objects representative of the most common types of peculiar and variable stars. The wavelength interval extends from 4600 to 9400{AA}, and includes the RAVE, Gaia and HERMES wavelength ranges. Multi-epoch spectra are provided for the majority of observed stars. A total of 425 spectra of peculiar stars are presented, which have been collected during 56 observing nights between November 1998 and August 2002. The spectra are given in FITS format and heliocentric wavelengths, with accurate subtraction of both the sky background and the scattered light. Auxiliary material useful for custom applications (telluric dividers, spectro-photometric stars, flat-field tracings) is also provided. The atlas aims to provide a homogeneous database of the spectral appearance of stellar peculiarities, a tool useful both for classification purposes and inter-comparison studies. It could also serve the planning for and training of automated classification algorithms designed for RAVE, Gaia, HERMES and other large scale spectral surveys. The spectrum of XX Oph is discussed in some detail as an example of the content of the present atlas.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/2764
- Title:
- Spectroscopic survey of Kepler stars. I.
- Short Name:
- J/MNRAS/450/2764
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kepler space mission provided near-continuous and high-precision photometry of about 207000 stars, which can be used for asteroseismology. However, for successful seismic modeling it is equally important to have accurate stellar physical parameters. Therefore, supplementary ground-based data are needed. We report the results of the analysis of high-resolution spectroscopic data of A- and F-type stars from the Kepler field, which were obtained with the HERMES spectrograph on the Mercator telescope. We determined spectral types, atmospheric parameters and chemical abundances for a sample of 117 stars. Hydrogen Balmer, FeI, and FeII lines were used to derive effective temperatures, surface gravities, and microturbulent velocities. We determined chemical abundances and projected rotational velocities using a spectrum synthesis technique. The atmospheric parameters obtained were compared with those from the Kepler Input Catalogue (KIC), confirming that the KIC effective temperatures are underestimated for A stars. Effective temperatures calculated by spectral energy distribution fitting are in good agreement with those determined from the spectral line analysis. The analysed sample comprises stars with approximately solar chemical abundances, as well as chemically peculiar stars of the Am, Ap, and {lambda} Boo types. The distribution of the projected rotational velocity, vsini, is typical for A and F stars and ranges from 8 to about 280km/s, with a mean of 134km/s.
- ID:
- ivo://CDS.VizieR/J/MNRAS/394/1338
- Title:
- Stellar effective magnetic fields. II.
- Short Name:
- J/MNRAS/394/1338
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the second catalog of averaged quadratic effective magnetic fields <B_e_> of 1212 main sequence and giant stars, and 11 white dwarfs. Our sample includes a subset of 610 chemically peculiar early-type stars. Some stars in the sample are members of several open clusters. The catalog was derived from measurements of the longitudinal magnetic field strength B_e_ for stars, which were scattered in the published sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/420/757
- Title:
- STEREO magnetic chemically peculiar stars
- Short Name:
- J/MNRAS/420/757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- About 10% of upper main-sequence stars are characterized by the presence of chemical peculiarities, often found together with a structured magnetic field. The atmospheres of most of those chemically peculiar stars present surface spots, leading to photometric variability caused by rotational modulation. The study of the light curves of those stars therefore permits a precise measurement of their rotational period, which is important to study stellar evolution and to plan further detailed observations. We analysed the light curves of 1028 chemically peculiar stars obtained with the STEREO spacecraft. We present here the results obtained for the 337 magnetic chemically peculiar stars in our sample.
- ID:
- ivo://CDS.VizieR/J/MNRAS/429/119
- Title:
- STEREO non-magnetic chemically peculiar stars
- Short Name:
- J/MNRAS/429/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analysed the photometric data obtained with the STEREO spacecraft for 558 non-magnetic chemically peculiar (CP) stars to search for rotational and pulsational variability. Applying the Lomb-Scargle and the phase dispersion minimization methods, we have detected photometric variability for 44 objects from which 35 were previously unknown. The new objects are all bright stars on the ecliptic plane (magnitude range 4.7<V<11.7) and will therefore be of great interest to studies of stellar structure and evolution. In particular, several show multiple signals consistent with hybrid {delta} Scuti and {gamma} Doradus pulsation, with different periodicities allowing very different regions of the stellar interior to be studied. There are two subgroups of stars in our sample: the cool metallic line Am (CP1) and the hot HgMn (CP3) stars. These objects fall well inside the classical instability strip where {delta} Scuti, {gamma} Doradus and slowly pulsating B-type stars are located. We also expect to find periods correlated to the orbital period for CP1 objects as they are mostly members of binary systems. For CP3 stars, rotationally induced variability is still a matter of debate. Although surface spots were detected, they are believed to produce only marginal photometric amplitudes. So, periods from several hours to a few days were expected for these two star groups. The STEREO/HI-1 data are well matched to studies of this frequency domain, owing to the cadence of approximately 40-min and multiple epochs over four and a half years. The remaining 514 stars are likely to be constant in the investigated range from 0.1 to 10d. In some cases, the presence of blending or systematic effects prevented us from detecting any reliable variability and in those cases we classified the star as constant. We discuss our results in comparison to already published ones and find a very good agreement. Finally, we have calibrated the variable stars in terms of the effective temperature and luminosity in order to estimate masses and ages. For this purpose, we used specifically developed calibrations for CP stars and, when available, Hipparcos parallaxes. All but two objects cover the stellar mass range from 1.5 to 5M_{sun}_ and are located between the zero- and terminal-age main sequence.
- ID:
- ivo://CDS.VizieR/J/MNRAS/460/1912
- Title:
- The Catalog of HgMn Stars
- Short Name:
- J/MNRAS/460/1912
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To better understand the hot chemically peculiar group of HgMn stars, we have considered a compilation of a large number of recently published data obtained for these stars from spectroscopy. We compare these data to the previous compilation by Smith. We confirm the main trends of the abundance peculiarities, namely the increasing overabundances with increasing atomic number of heavy elements, and their large spread from star to star. For all the measured elements, we have looked for correlations between abundances and effective temperature (T_eff_). In addition to the known correlation for Mn, some other elements are found to show some connection between their abundances and T_eff_. We have also checked if multiplicity is a determinant parameter for abundance peculiarities determined for these stars. A statistical analysis using a Kolmogorov-Smirnov test shows that the abundances anomalies in the atmosphere of HgMn stars do not present significant dependence on the multiplicity.
- ID:
- ivo://CDS.VizieR/J/ApJS/123/639
- Title:
- UBV photometry of metal-weak candidates
- Short Name:
- J/ApJS/123/639
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photoelectric UBV photometry for some 2600 metal-poor dwarf and giant candidates selected from the HK objective-prism/interference-filter survey of Beers and colleagues. These data provide the basis for our ultraviolet-excess selection of objects having [Fe/H]{<~}-2.0 for a spectroscopic investigation in which we have obtained ~1-2{AA} resolution spectra of some 1000 objects. The present material may also prove useful for investigations of the metal-poor dwarfs and giants more metal-rich than [Fe/H]=-2.0, as well as the misclassified subdwarf O and B stars, white dwarfs, blue metal-poor stars, and field horizontal-branch stars which appear in the catalog.
- ID:
- ivo://CDS.VizieR/J/A+AS/128/265
- Title:
- ubvy-beta photometry of CP2 stars
- Short Name:
- J/A+AS/128/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this work is to study the capacity of the uvby H_{beta}_ system for detecting the chemically peculiar (CP) stars based on the effect that peculiar features in the flux distribution have on all the Stroemgren-Crawford indices. Our study focuses on the classical magnetic peculiar stars (CP2), though Am star s (CP1) are also included for comparison with cool CP2 stars. Satisfactory results were obtained for hot CP2 stars: the definition of a new index p, which is a linear combination of uvby H_{beta}_ colours, allowed us to separate a high percentage of hot CP2 stars from normal stars. According to this new index, 60 new CP2 candidates are proposed. The working sample was extracted from The General Catalogue of Ap and Am stars by Renson et al. (1991, Cat. <III/162>). Photometric observations to enlarge the sample of CP2 stars with complete uvby H_{beta}_ photometry were carried out. These observations are also reported in the present paper. The new index p is also used to correct the reddening of early CP2 stars computed as if they were normal stars.
- ID:
- ivo://CDS.VizieR/J/A+A/373/625
- Title:
- uvby{beta} photometry of lambda Bootis stars
- Short Name:
- J/A+A/373/625
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lambda Bootis stars comprise only a small number of all A-type stars and are characterized as nonmagnetic, Population I, late B to early F-type dwarfs which show significant underabundances of metals whereas the light elements (C, N, O and S) are almost normal abundant compared to the Sun. In the second paper on a spectroscopic survey for lambda Bootis stars, we present the spectral classifications of all program stars observed. These stars were selected on the basis of their Stromgren uvbybeta colors as lambda Bootis candidates. In total, 708 objects in six open clusters, the Orion OB1 association and the Galactic field were classified. In addition, nine serendipity non-candidates in the vicinity of our program stars as well as 15 Guide Star Catalogue stars were observed resulting in a total of 732 classified stars. The 15 objects from the Guide Star Catalogue are part of a program for the classification of apparent variable stars from the Fine Guidance Sensors of the Hubble Space Telescope. A grid of 105 MK standard as well as ``pathological'' stars guarantees a precise classification. A comparison of our spectral classification with the extensive work of Abt & Morrell (1995, Cat. <J/ApJS/99/135>) shows no significant differences. The derived types are 0.23+/-0.09 (rms error per measurement) subclasses later and 0.30+/-0.08 luminosity classes more luminous than those of Abt & Morrell (1995, Cat. <J/ApJS/99/135>)) based on a sample of 160 objects in common. The estimated errors of the means are +/-0.1 subclasses. The characteristics of our sample are discussed in respect to the distribution on the sky, apparent visual magnitudes and Stromgren uvbybeta colors. Table 2 lists all observed Galactic field stars.
