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- ID:
- ivo://CDS.VizieR/J/MNRAS/468/2745
- Title:
- Rotational properties of mCP stars
- Short Name:
- J/MNRAS/468/2745
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The magnetic chemically peculiar (mCP) stars of the upper main sequence exhibit strong, globally organized magnetic fields that are inclined to the rotational axis and facilitate the development of surface abundance inhomogeneities resulting in photometric and spectroscopic variability. Therefore, mCP stars are perfectly suited for a direct measurement of the rotational period without the need for any additional calibrations. We have investigated the rotational properties of mCP stars based on an unprecedentedly large sample consisting of more than 500 objects with known rotational periods. Using precise parallaxes from the Hipparcos and Gaia satellite missions, well-established photometric calibrations and state-of-the-art evolutionary models, we have determined the location of our sample stars in the Hertzsprung-Russell diagram and derived astrophysical parameters such as stellar masses, effective temperature, radii, inclinations and critical rotational velocities. We have confirmed the conservation of angular momentum during the main sequence evolution; no signs of additional magnetic braking were found. The inclination angles of the rotational axes are randomly distributed, although an apparent excess of fast rotators with comparable inclination angles has been observed. We have found a rotation rate of v/v_crit_>=0.5 for several stars, whose characteristics cannot be explained by current models. For the first time, we have derived the relationship between mass and rotation rate of mCP stars, and provide an analysis that links mass and rotation with magnetic field strength. Our sample is unique and offers crucial input for forthcoming evolutionary models that include the effects of magnetic fields for upper main sequence stars.
- ID:
- ivo://CDS.VizieR/II/229
- Title:
- Sakurai's object (V4334 Sgr) in 1996-1998
- Short Name:
- II/229
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The photometric UBV observations of V4334 Sgr during 1996-1998 are presented. V4334 Sgr is the nucleus of a planetary nebula during the last helium flash of the shell source and it entered the R CrB phase.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A135
- Title:
- Sgr dSph CEMP-r/s star abundance analysis
- Short Name:
- J/A+A/641/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the discovery and chemical abundance analysis of the first CEMP-r/s star detected in the Sagittarius dwarf spheroidal galaxy (Sgr dSph) by means of UVES high-resolution spectra. The star, found in the outskirts of Sgr dSph, along the major axis of the main body, is a moderately metal-poor giant (Teff=4753K, logg=1.75, [Fe/H]=-1.55) with [C/Fe]=1.13, placing it in the so-called "high-carbon band", and strong s-process and r-process enrichment ([Ba/Fe]=1.4, [Eu/Fe]=1.01). Abundances of 29 elements from C to Dy were obtained. The chemical pattern appears to be best fitted by a scenario where an r-process pollution event pre-enriched the material out of which the star was born as secondary in a binary system whose primary evolved through the AGB phase, providing C- and s-process enrichment.
- ID:
- ivo://CDS.VizieR/J/other/Ap/46.234
- Title:
- Spatial distribution of magnetic CP stars
- Short Name:
- J/other/Ap/46.23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the basis of analysis of original publications and our own measurements a Cataloque of magnetic chemically peculiar (CP) upper-main sequence stars has been established. The sample includes 211 magnetic CP stars with magnetic fields ranging from hundreds of gauss to dozens of kilogauss, for 49 of them the surface magnetic field (B_e_) has been measured from the Zeeman splitting. The CP stars may be divided into 3 groups: reversing stars (table3, longitudinal field B_e_ changes its sign), non-reversing (table4, B_e_ keeps the same sign), and poorly studied stars.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/67.44
- Title:
- Speckle interferometry of Ap stars
- Short Name:
- J/other/AstBu/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of speckle interferometry of a sample of 117 chemically peculiar stars with global magnetic fields. The observations were made in December 2009 at the BTA with a spatial resolution of about 0.02 arcseconds in the visual spectral region. Twenty-nine stars were resolved into individual components, 14 of them for the first time (HD965, HD5797, HD8855, HD10783, HD16605, HD21699, HD35502, HD51418, HD64486, HD79158, HD103498, HD108651, HD213918, HD293764). In twelve cases a companion turned out to be 2-4 magnitudes fainter than the main component - a magnetic star. Young hot Bp stars HD35502 and HD213918 are exceptions, since their companions are fainter by about 1 magnitude. In all cases, the linear distance from a star to its companion at the epoch of observations in the picture plane exceeded 10^9^km. Eighty-eight magnetic CP stars revealed no secondary components within our study. Thus, the fraction of speckle interferometric binaries in our sample amounts to 25%.
- 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.
- 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/A+A/578/A75
- Title:
- Spectrum of V4332 Sgr in 2005
- Short Name:
- J/A+A/578/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- V4332 Sgr is a red transient (red nova) whose eruption was observed in 1994. The remnant of the eruption shows a unique optical spectrum: strong emission lines of atomes and molecules superimposed on a M-type stellar spectrum. The stellar-like remnant is presumably embedded in a disc-like dusty envelope orientated almost face-on. The observed optical spectrum is supposed to result from interactions of the central-star radiation with dust and gas in the disc and outflows initiated in 1994. We have reduced and measured a high-resolution (R~40000) spectrum of V4332 Sgr obtained with VLT/UVES in April/May 2005. The spectrum comes from the ESO archives and is the best quality spectrum of the object ever obtained. We have identified and measured over 200 emission features belonging to 11 elements and 6 molecules. The continuous, stellar-like component can be classified as ~M3. The radial velocity of the object, as derived from narrow atomic emission line, is -75km/s. The interstellar reddening was estimated as being 0.35<E(B-V)<0.75. From radial velocities of interstellar absorption features in the NaI D lines we have estimated a lower limit of ~5.5 kpc to the distance of V4332 Sgr. When compared to spectroscopic observations done in 2009, the spectrum of V4332 Sgr considerably evolved between 2005 and 2009. The object significantly faded in the optical (by ~2mag in the V band), which resulted from the main remnant cooled by 300-350K corresponding to its spectral type changed from M3 to M5-6. The object however increased in luminosity by ~50%, implying a significant expansion of its dimensions. Most of the emission features seen in 2005 significantly faded or even disappeared from the spectrum of V4332 Sgr in 2009.
