- ID:
- ivo://CDS.VizieR/J/A+A/462/683
- Title:
- Velocities in SMC field of NGC 330
- Short Name:
- J/A+A/462/683
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search for the effects of metallicity on B and Be stars in the Small and Large Magellanic Clouds (SMC and LMC) and in the Milky Way (MW), by extending our previous analysis of B and Be star populations in the LMC to the SMC. The rotational velocities of massive stars and the evolutionary status of Be stars are examined with respect to their environments. Spectroscopic observations of hot stars belonging to the young cluster SMC-NGC 330 and its surrounding region were obtained with the VLT-GIRAFFE facilities in MEDUSA mode. We determined fundamental parameters for B and Be stars with the GIRFIT code, taking the effect of fast rotation and the age of observed clusters into account. We compared the mean vsini obtained by spectral type- and mass-selection for field and cluster B and Be stars in the SMC with the one in the LMC and MW.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/156/300
- Title:
- Velocity and light curve analysis of three PPNe
- Short Name:
- J/AJ/156/300
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained contemporaneous light, color, and radial velocity data for three proto-planetary nebulae (PPNe) over the years 2007 to 2015. The light and velocity curves of each show similar periods of pulsation, with photometric periods of 42 and 50 days for IRAS 17436+5003, 102 days for IRAS 18095+2704, and 35 days for IRAS 19475+3119. The light and velocity curves are complex with multiple periods and small, variable amplitudes. Nevertheless, at least over limited time intervals, we were able to identify dominant periods in the light, color, and velocity curves and compare the phasing of each. The color curves appear to peak with or slightly after the light curves while the radial velocity curves peak about a quarter of a cycle before the light curves. Similar results were found previously for two other PPNe, although for them the light and color appeared to be in phase. Thus, it appears that PPNe are brightest when smallest and hottest. These phase results differ from those found for classical Cepheid variables, where the light and velocity differ by half a cycle, and are hottest at about average size and expanding. However, they do appear to have similar phasing to the larger-amplitude pulsations seen in RV Tauri variables. Presently, few pulsation models exist for PPNe, and these do not fit the observations well, especially the longer periods observed. Model fits to these new light and velocity curves would allow masses to be determined for these post-AGB objects, and thereby provide important constraints to post-AGB stellar evolution models of low- and intermediate-mass stars.
- ID:
- ivo://CDS.VizieR/J/A+A/398/141
- Title:
- Vertical distribution of galactic disk stars
- Short Name:
- J/A+A/398/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nearly 400 Tycho-2 (Cat. <I/259>) stars have been observed in a 720 square degree field in the direction of the North Galactic Pole with the high resolution echelle spectrograph ELODIE. Absolute magnitudes, effective temperatures, gravities and metallicities have been estimated, as well as distances and 3D velocities. Most of these stars are clump giants and span typical distances from 200pc to 800pc to the galactic mid-plane. This new sample, free of any kinematical and metallicity bias, is used to investigate the vertical distribution of disk stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/180
- Title:
- Very metal-poor stars in the Milky Way's halo
- Short Name:
- J/ApJ/788/180
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the kinematics and orbital properties of a sample of 323 very metal-poor stars in the halo system of the Milky Way, selected from the high-resolution spectroscopic follow-up studies of Aoki et al. (2013, J/AJ/145/13) and Yong et al (2013, J/ApJ/762/26). The combined sample contains a significant fraction of carbon-enhanced metal-poor (CEMP) stars (22% or 29%, depending on whether a strict or relaxed criterion is applied for this definition). Barium abundances (or upper limits) are available for the great majority of the CEMP stars, allowing for their separation into the CEMP-s and CEMP-no subclasses. A new method to assign membership to the inner- and outer-halo populations of the Milky Way is developed, making use of the integrals of motion, and applied to determine the relative fractions of CEMP stars in these two subclasses for each halo component. Although limited by small-number statistics, the data suggest that the inner halo of the Milky Way exhibits a somewhat higher relative number of CEMP-s stars than CEMP-no stars (57% versus 43%), while the outer halo possesses a clearly higher fraction of CEMP-no stars than CEMP-s stars (70% versus 30%). Although larger samples of CEMP stars with known Ba abundances are required, this result suggests that the dominant progenitors of CEMP stars in the two halo components were different; massive stars for the outer halo, and intermediate-mass stars in the case of the inner halo.
- ID:
- ivo://CDS.VizieR/J/AJ/157/171
- Title:
- Visual analysis and demographics of Kepler TTVs
- Short Name:
- J/AJ/157/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We visually analyzed the transit timing variation (TTV) data of 5930 Kepler Objects of Interest (KOIs) homogeneously. Using data from Rowe et al. (2014, J/ApJ/784/45) and Holczer et al. (2015, J/ApJ/807/170; 2016, J/ApJS/225/9), we investigated TTVs for nearly all KOIs in Kepler's Data Release 24 catalog. Using TTV plots, periodograms, and phase-folded quadratic plus sinusoid fits, we visually rated each KOI's TTV data in five categories. Our ratings emphasize the hundreds of planets with TTVs that are weaker than the ~200 that have been studied in detail. Our findings are consistent with statistical methods for identifying strong TTVs, though we found some additional systems worth investigation. Between about 3-50 days and 1.3-6 Earth radii, the frequency of strong TTVs increases with period and radius. As expected, strong TTVs are very common when period ratios are near a resonance, but there is not a one-to-one correspondence. The observed planet-by-planet frequency of strong TTVs is only somewhat lower in systems with one or two known planets (7%+/-1%) than in systems with three or more known planets (11%+/-2%). We attribute TTVs to known planets in multitransiting systems but find ~30 cases where the perturbing planet is unknown. Our conclusions are valuable as an ensemble for learning about planetary system architectures and individually as stepping stones toward more-detailed mass-radius constraints. We also discuss Data Release 25 TTVs, investigate ~100 KOIs with transit duration and/or depth variations, and estimate that the Transiting Exoplanet Survey Satellite will likely find only ~10 planets with strong TTVs.
- ID:
- ivo://CDS.VizieR/J/A+A/479/541
- Title:
- VLT-FLAMES survey of massive stars
- Short Name:
- J/A+A/479/541
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to provide the atmospheric parameters and rotational velocities for a large sample of O- and early B-type stars, analysed in a homogeneous and consistent manner, for use in constraining theoretical models. Atmospheric parameters, stellar masses, and rotational velocities have been estimated for approximately 250 early B-type stars in the Large (LMC) and Small (SMC) Magellanic Clouds from high-resolution VLT-FLAMES data using the non-LTE TLUSTY model atmosphere code. This data set has been supplemented with our previous analyses of some 50 O-type stars (Mokiem et al., 2006A&A...456.1131M, 2007A&A...465.1003M) and 100 narrow-lined early B-type stars (Hunter et al., 2006, Cat. <J/A+A/466/277>, Trundle et al., 2007, Cat. <J/A+A/471/625>) from the same survey, providing a sample of ~400 early-type objects.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A79
- Title:
- VLTS. Properties of O dwarf in 30 Dor
- Short Name:
- J/A+A/601/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VLT-FLAMES Tarantula Survey has observed hundreds of O-type stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). We study the properties of 105 apparently single O-type dwarfs. To determine stellar and wind parameters, we used the IACOB-GBAT package, an automatic procedure based on a large grid of atmospheric models calculated with the FASTWIND code. In addition to classical techniques, we applied the Bayesian BONNSAI tool to estimate evolutionary masses. We provide a new calibration of effective temperature vs. spectral type for O-type dwarfs in the LMC, based on our homogeneous analysis of the largest sample of such objects to date and including all spectral subtypes. Good agreement with previous results is found, although the sampling at the earliest subtypes could be improved. Rotation rates and helium abundances are studied in an evolutionary context. We find that most of the rapid rotators (vsini higher than 300km/s) in our sample have masses below 25 MSun and intermediate rotation-corrected gravities (logg_c_ between 3.9 and 4.1). Such rapid rotators are scarce at higher gravities (i.e. younger ages) and absent at lower gravities (larger ages). This is not expected from theoretical evolutionary models, and does not appear to be due to a selection bias in our sample. We compare the estimated evolutionary and spectroscopic masses, finding a trend that the former is higher for masses below 20M_{sun}_. This can be explained as a consequence of limiting our sample to the O-type stars, and we see no compelling evidence for a systematic mass discrepancy. For most of the stars in the sample we were unable to estimate the wind-strength parameter (hence mass-loss rates) reliably, particularly for objects with luminosity lower than logL/L_{sun}_ about 5.1. Ultraviolet spectroscopy is needed to undertake a detailed investigation of the wind properties of these dwarfs.
- ID:
- ivo://CDS.VizieR/J/AJ/158/51
- Title:
- VR CCD photometry of variable stars in the GC NGC 4147
- Short Name:
- J/AJ/158/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a search for variable stars in a region of the globular cluster NGC 4147 based on photometric observations with a 4Kx4K CCD imager mounted at the axial port of the recently installed 3.6 m Devasthal optical telescope (DOT) at Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India. We performed time series photometry of NGC 4147 in the V and R bands, and identified 42 periodic variables in the region of NGC 4147, 28 of which have been detected for the first time. Seventeen variable stars are located within the half-light radius ~<0.48', of which 10 stars are newly identified variables. Two of the 10 variables are located within the core radius ~<0.09'. Based on their location in the V/(V-R) color-magnitude diagram and variability characteristics, seven, eight, five, and one newly identified probable member variables are classified as RRc, EA/E, EW, and SX Phe, respectively. The metallicity of NGC 4147 estimated from the light curves of RRab and RRc stars with the help of Fourier decomposition is found to be characteristic of Oosterhoff II. The distance derived using the light curves of RRab stars is consistent with that obtained from the observed V/(V-R) color-magnitude diagram.
- ID:
- ivo://CDS.VizieR/J/ApJS/176/262
- Title:
- VRI photometry and theta values in open clusters
- Short Name:
- J/ApJS/176/262
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, new Cousins VRI data are presented for NGC 752 and Praesepe, and new and extant data are combined into an augmented database for M67. For those three clusters, catalogs containing Cousins VRI photometry, reddening-corrected values of (V-K)J, and temperatures are produced. The same is done for Coma by using both previously published and newly derived Cousins photometry. An extant set of catalogs for the Hyades is updated to include V magnitudes and values of (R-I)C that were published after the original catalogs appeared. Finally, M67 V magnitudes published previously by Sandquist are corrected for an effect that depends on location on the face of the cluster. The corrected data and values of (V-I)C given by Sandquist are then set out in a supplementary catalog.
- ID:
- ivo://CDS.VizieR/J/A+A/458/895
- Title:
- vsini of evolved metal-poor stars
- Short Name:
- J/A+A/458/895
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Precise rotational velocities vsini are presented for a large sample of 100 metal-poor stars, most of them evolving off the main-sequence. The survey was carried out with the FEROS and CORALIE spectrometers. For the vsini measurements, obtained from spectral synthesis, we estimate an uncertainty of about 2.0km/s. For the large majority of the stars composing the present sample rotational velocities have been measured for the first time.
