- ID:
- ivo://CDS.VizieR/J/AJ/130/1880
- Title:
- Cepheids with periods between 3 and 6 days
- Short Name:
- J/AJ/130/1880
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a detailed multiphase spectroscopic analysis of six classical Cepheids with pulsation periods between 3 and 6 days. For each star we have derived phased values of effective temperature, surface gravity, microturbulent velocity, and elemental abundances. We show that the elemental abundance results for these Cepheids are consistent for all pulsational phases.
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262. Cetus dSph RR Lyrae
- ID:
- ivo://CDS.VizieR/J/MNRAS/422/89
- Title:
- Cetus dSph RR Lyrae
- Short Name:
- J/MNRAS/422/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the variable star content of the isolated, Local Group, dwarf spheroidal (dSph) galaxy Cetus. Multi-epoch, wide-field images collected with the Very Large Telescope/Visible Multiobject Spectrograph camera allowed us to detect 638 variable stars (630 RR Lyrae stars and eight anomalous Cepheids), 475 of which are new detections. We present a full catalogue of periods, amplitudes and mean magnitudes.
- ID:
- ivo://CDS.VizieR/J/ApJ/770/98
- Title:
- Chandra study of NGC 6791
- Short Name:
- J/ApJ/770/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first X-ray study of NGC 6791, one of the oldest open clusters known (8Gyr). Our Chandra observation is aimed at uncovering the population of close interacting binaries down to L_X_~1x10^30^erg/s (0.3-7keV). We detect 86 sources within 8' of the cluster center, including 59 inside the half-mass radius. We identify 20 sources with proper-motion cluster members, which are a mix of cataclysmic variables (CVs), active binaries (ABs), and binaries containing sub-subgiants. With follow-up optical spectroscopy, we confirm the nature of one CV. We discover one new, X-ray variable candidate CV with Balmer and He II emission lines in its optical spectrum; this is the first X-ray-selected CV in an open cluster. The number of CVs per unit mass is consistent with the field, suggesting that the 3-4 CVs observed in NGC 6791 are primordial. We compare the X-ray properties of NGC 6791 with those of a few old open (NGC 6819, M67) and globular clusters (47 Tuc, NGC 6397). It is puzzling that the number of ABs brighter than 1x10^30^erg/s normalized by cluster mass is lower in NGC 6791 than in M 67 by a factor ~3-7. CVs, ABs, and sub-subgiants brighter than 1x10^30^erg/s are under-represented per unit mass in the globular clusters compared to the oldest open clusters, and this accounts for the lower total X-ray luminosity per unit mass of the former. This indicates that the net effect of dynamical encounters may be the destruction of even some of the hardest (i.e., X-ray-emitting) binaries.
- ID:
- ivo://CDS.VizieR/J/ApJS/188/473
- Title:
- Chandra variable guide star catalog
- Short Name:
- J/ApJS/188/473
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Variable stars have been identified among the optical-wavelength light curves of guide stars used for pointing control of the Chandra X-ray Observatory. We present a catalog of these variable stars along with their light curves and ancillary data. Variability was detected to a lower limit of 0.02mag amplitude in the 4000-10000{AA} range using the photometrically stable Aspect Camera on board the Chandra spacecraft. The Chandra Variable Guide Star Catalog (VGUIDE) contains 827 stars, of which 586 are classified as definitely variable and 241 are identified as possibly variable. Of the 586 definite variable stars, we believe 319 are new variable star identifications. Types of variables in the catalog include eclipsing binaries, pulsating stars, and rotating stars. The variability was detected during the course of normal verification of each Chandra pointing and results from analysis of over 75000 guide star light curves from the Chandra mission. The VGUIDE catalog represents data from only about 9 years of the Chandra mission. Also, guide stars were often used multiple times for Chandra observations, so many of the stars in the VGUIDE catalog have multiple light curves available from various times in the mission. The catalog is presented as both online data associated with this paper and as a public Web interface. The stars available for use as Chandra guide stars are generally 6-11mag and are commonly spectral types A and later. Statistics of variability compared to spectral type indicate the expected dominance of A-F stars as pulsators. Eclipsing binaries are consistently 20%-30% of the detected variables across all spectral types.
- ID:
- ivo://CDS.VizieR/J/AJ/159/281
- Title:
- Characteristics of 335 KOI stars
- Short Name:
- J/AJ/159/281
- Date:
- 09 Dec 2021
- Publisher:
- CDS
- Description:
- We propose several descriptive measures to characterize the arrangements of planetary masses, periods, and mutual inclinations within exoplanetary systems. These measures are based on complexity theory and capture the global, system-level trends of each architecture. Our approach considers all planets in a system simultaneously, facilitating both intrasystem and intersystem analysis. We find that based on these measures, Kepler's high-multiplicity (N>=3) systems can be explained if most systems belong to a single intrinsic population, with a subset of high-multiplicity systems (~20%) hosting additional, undetected planets intermediate in period between the known planets. We confirm prior findings that planets within a system tend to be roughly the same size and approximately coplanar. We find that forward modeling has not yet reproduced the high degree of spacing similarity (in log- period) actually seen in the Kepler data. Although our classification scheme was developed using compact Kepler multis as a test sample, our methods can be immediately applied to any other population of exoplanetary systems. We apply this classification scheme to 1- quantify the similarity between systems, 2- resolve observational biases from physical trends, 3- identify which systems to search for additional planets and where to look for these planets.
- ID:
- ivo://CDS.VizieR/J/A+A/281/465
- Title:
- Chemical Composition of alf UMi and V473 Lyr
- Short Name:
- J/A+A/281/465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectrograms of the s-Cepheids alpha-UMi and HR 7308, taken at reciprocal dispersion of 9 A/mm with the Main Stellar Spectrograph at the Special Astrophysical Observatory's 6-m telescope, were analysed for determining chemical elements abundance. The results include the equivalent width, and the abundances in the two stars.
- ID:
- ivo://CDS.VizieR/J/PASP/124/401
- Title:
- Chemical composition of BE Lyn
- Short Name:
- J/PASP/124/401
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution spectroscopic observation was carried out to find the chemical composition of BE Lyn. The abundances of 25 chemical elements from carbon to neodymium were found. The deficiency of iron appeared to be equal to {DELTA}logN(Fe)=-0.26+/-0.08 with respect to the solar metallicity, and the abundances of other elements were mainly undersolar. Only nitrogen, sodium, aluminium, and sulfur showed overabundances near 0.2-0.3dex. The abundance pattern showed no clear signs of accretion or mass transfer events. It is not possible to exclude the classification of BE Lyn as a SX Phe-type star with slightly undersolar abundances of chemical elements. In addition, new differential time-series observations of BE Lyn were secured using V filters, and seven new times of light maximum were identified. We collected 162 times of light maximum from the literature, unpublished data, and an open database, and we proceeded to investigate the pulsational properties of BE Lyn. All five harmonic frequencies were identified using the Fourier decomposition method.
- ID:
- ivo://CDS.VizieR/J/MNRAS/359/865
- Title:
- Chemical composition of delta Sct
- Short Name:
- J/MNRAS/359/865
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present chemical abundances in the photosphere of delta Scuti (delta Sct) - a prototype of the class of pulsating variables - determined from the analysis of a spectrum obtained by using the 2-m telescope at the Peak Terskol Observatory and a high-resolution spectrometer with R=52000, a signal-to-noise ratio 250 and from International Ultraviolet Explorer spectra. The abundance pattern of delta Sct consists of 49 chemical elements. The abundances of 19 elements have not been investigated previously. The abundances of Pr and Nd obtained from the lines of the second and third spectra are equal. The abundances of heavy elements indicate the overabundances with respect to the solar system values up to 1dex. The abundance pattern of delta Sct is similar to the abundance patterns of Am-Fm or delta Del type stars. A splitting of the cores of all clean lines is observed for the spectra of Sct and HD 57749. This can signify evidence of non-radial pulsations in these stars
- ID:
- ivo://CDS.VizieR/J/A+A/305/551
- Title:
- Chemical composition of the s-Cepheids
- Short Name:
- J/A+A/305/551
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the base of photographic, Reticon and CCD spectra analysis we have derived the abundances for 8 s-Cepheids and V1162 Aql (before classified as s-Cepheid). The following results have been obtained: 1) all Cepheids (excluding only EU Tau) have solar-like abundances of {alpha}- and iron-group elements, 2) Na is over abundant for all program stars, 3) the carbon deficiency found for EU Tau, DT Cyg, V440 Per and nitrogen overabundance (DT Cyg), show that these s-Cepheids are not crossing the instability strip for first time, 4) s-process elements are slightly enhanced in the program stars, 5) V1162 Aql does not show any changes in C and N abundances. The most plausible explanation is that this star is a normal Cepheid (C{delta}), but it is firstly crossing the instability strip toward the giant branch. This conclusion is also confirmed by its position on the evolutionary diagram.
- ID:
- ivo://CDS.VizieR/J/AJ/134/926
- Title:
- Chemical composition of V2314 Oph
- Short Name:
- J/AJ/134/926
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigated V2314 Oph using high-resolution (R=45000) spectral observations. The atmospheric parameters were determined using iron-line abundance analysis. We derived a mean effective temperature of Teff=7510K, mean surface gravity of logg=3.30, metallicity of [Fe/H]=-0.59, and rotation velocity of vsini=38km/s. The abundances of 19 chemical elements were determined.
