- ID:
- ivo://CDS.VizieR/J/A+A/537/A146
- Title:
- Stellar models with rotation. 0.8<M<120, Z=0.014
- Short Name:
- J/A+A/537/A146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Many topical astrophysical research areas, such as the properties of planet host stars, the nature of the progenitors of different types of supernovae and gamma ray bursts, and the evolution of galaxies, require complete and homogeneous sets of stellar models at different metallicities in order to be studied during the whole of cosmic history. We present here a first set of models for solar metallicity, where the effects of rotation are accounted for in a homogeneous way. We computed a grid of 48 different stellar evolutionary tracks, both rotating and non-rotating, at Z=0.014, spanning a wide mass range from 0.8 to 120M_{sun}_. For each of the stellar masses considered, electronic tables provide data for 400 stages along the evolutionary track and at each stage, a set of 43 physical data are given. These grids thus provide an extensive and detailed data basis for comparisons with the observations. The rotating models start on the ZAMS with a rotation rate v_ini_/v_crit_=0.4. The evolution is computed until the end of the central carbon-burning phase, the early AGB phase, or the core helium-flash for, respectively, the massive, intermediate, and both low and very low mass stars. The initial abundances are those deduced by Asplund et collaborators, which best fit the observed abundances of massive stars in the solar neighbourhood. We update both the opacities and nuclear reaction rates, and introduce new prescriptions for the mass-loss rates as stars approach the Eddington and/or the critical velocity. We account for both atomic diffusion and magnetic braking in our low-mass star models. The present rotating models provide a good description of the average evolution of non-interacting stars. In particular, they reproduce the observed MS width, the positions of the red giant and supergiant stars in the HR diagram, the observed surface compositions and rotational velocities. Very interestingly, the enhancement of the mass loss during the RSG stage, when the luminosity becomes supra-Eddington in some outer layers, help models above 15-20 Msun to lose a significant part of their hydrogen envelope and evolve back into the blue part of the HR diagram. This result has interesting consequences for the blue to red supergiant ratio, the minimum mass for stars to become WR stars, and the maximum initial mass of stars that explode as type II-P supernovae.
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- ID:
- ivo://CDS.VizieR/J/A+A/637/A6
- Title:
- Stripped-envelope stars Binary Evolution Models
- Short Name:
- J/A+A/637/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive binaries that merge as compact objects are the progenitors of gravitational-wave sources. Most of these binaries experience one or more phases of mass transfer, during which one of the stars loses part or all of its outer envelope and becomes a stripped-envelope star. The evolution of the size of these stripped stars is crucial in determining whether they experience further interactions and their final fate. We present new calculations of stripped-envelope stars based on binary evolution models computed with the MESA stellar evolution code. We use these to investigate their radius evolution as a function of mass and metallicity. We further discuss their pre- supernova observable characteristics and potential consequences of their evolution on the properties of supernovae from stripped stars. At high metallicity we find that practically all of the hydrogen-rich envelope is removed, in agreement with earlier findings. Only progenitors with initial masses below 10\Msun expand to large radii (up to 100R_{sun}_), while more massive progenitors stay compact. At low metallicity, a substantial amount of hydrogen remains and the progenitors can, in principle, expand to giant sizes (>400R_{sun}_), for all masses we consider. This implies that they can fill their Roche lobe anew. We show that the prescriptions commonly used in population synthesis models underestimate the stellar radii by up to two orders of magnitude. We expect that this has consequences for the predictions for gravitational-wave sources from double neutron star mergers, in particular for their metallicity dependence.
- ID:
- ivo://CDS.VizieR/III/215
- Title:
- 7th Catalog of Galactic Wolf-Rayet stars
- Short Name:
- III/215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VIIth catalogue of galactic Population I Wolf Rayet stars provides improved coordinates, spectral types and bv photometry of known WR stars and adds 71 new WR stars to the previous WR catalogue. This census of galactic WR stars reaches 227 stars, comprising 127 WN stars, 87 WC stars, 10 WN/WC stars and 3 WO stars. This includes 15 WNL and 11 WCL stars within 30 pc of the Galactic Center. We compile and discuss WR spectral classification, variability, periodicity, binarity, terminal wind velocities, correlation with open clusters and OB associations, and correlation with H I bubbles, H II regions and ring nebulae. Intrinsic colours and absolute visual magnitudes per subtype are re-assessed for a re-determination of optical photometric distances and galactic distribution of WR stars. In the solar neighbourhood we find projected on the galactic plane a surface density of 3.3 WR stars per kpc^2^, with a WC/WN number ratio of 1.5, and a WR binary frequency (including probable binaries) of 39%. The galactocentric distance (R_WR_) distribution per subtype shows R_WR_ increasing with decreasing WR subtype, both for the WN and WC subtypes. This R_WR_ distribution allows for the possibility of WNE->WCE and WNL->WCL subtype evolution. The successive catalogues of galactic WR stars are: I 55 stars Campbell, 1884 Astronomy and Astrophysics 13, 448 (Northfield, Minn: Goodsell Observatory) II 108 stars Fleming, 1912 Harvard College Obs. Ann. 56, 165 III 92 stars Payne, 1930 The Stars of High Luminosity, Harvard Obs. Monographs No. 3, p. 19 IV 123 stars Roberts, 1962AJ.....67...79R V 127 stars Smith, 1968MNRAS.138..109S VI 157 stars van der Hucht et al., 1981SSRv...28..227V VII 227 stars van der Hucht, 2001NewAR..45..135V, this paper
- ID:
- ivo://CDS.VizieR/J/ApJ/863/181
- Title:
- The fifth catalog of LMC Wolf-Rayet stars
- Short Name:
- J/ApJ/863/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We summarize the results of our 4yr survey searching for Wolf-Rayet (WR) stars in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud. Over the course of this survey we have discovered 15 new WR stars and 12 Of-type stars. In this last year we discovered two rare Of-type stars: an O6.5f?p and an O6nfp, in addition to the two new Of?p stars discovered in our first year and the three Onfp stars discovered in our second and third years. However, even more exciting was our discovery of a new type of WR star, ones we are calling WN3/O3s owing to their spectroscopic signatures. We describe the completeness limits of our survey and demonstrate that we are sensitive to weak-lined WRs several magnitudes fainter than any we have discovered, arguing that there is not a population of fainter WRs waiting to be discovered. We discuss the nature of the WN3/O3s, summarizing the results of our extensive spectroscopy and modeling. We also examine the important claim made by others that the WN3/O3s are isolated compared to other massive stars. We find that if we use a more complete sample of reference massive stars, the WN3/O3s show the same spatial distribution as other early WNs, consistent with a common origin. Finally, we use this opportunity to present the "Fifth Catalog of LMC Wolf-Rayet Stars," which includes revised coordinates and updated spectral types for all 154 known LMC WRs.
- ID:
- ivo://CDS.VizieR/J/ApJ/733/123
- Title:
- The Wolf-Rayet content of M33 (NGC 598)
- Short Name:
- J/ApJ/733/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Wolf-Rayet (WR) stars are evolved massive stars, and the relative number of WC-type and WN-type WRs should vary with metallicity, providing a sensitive test of stellar evolutionary theory. The observed WC/WN ratio is much higher than that predicted by theory in some galaxies but this could be due to observational incompleteness for WN types, which have weaker lines. Previous studies of M33's WR content show a galactocentric gradient in the relative numbers of WCs and WNs, but only small regions have been surveyed with sufficient sensitivity to detect all of the WNs. Here, we present a sensitive survey for WRs covering all of M33, finding 55 new WRs, mostly of WN type. Our spectroscopy also improves the spectral types of many previously known WRs, establishing in one case that the star is actually a background quasar. The total number of spectroscopically confirmed WRs in M33 is 206, a number we argue is complete to ~5%, with most WRs residing in OB associations, although ~2% are truly isolated.
- ID:
- ivo://CDS.VizieR/J/AJ/159/214
- Title:
- UBVRI linear polarisation in Wolf-Rayet winds
- Short Name:
- J/AJ/159/214
- Date:
- 09 Dec 2021
- Publisher:
- CDS
- Description:
- Wolf-Rayet (WR) stars have strong, hot winds, with mass-loss rates at least a factor of 10 greater than their O-star progenitors, although their terminal wind speeds are similar. In this paper, we use the technique of multiband linear polarimetry to extract information on the global asymmetry of the wind in a sample of 47 bright Galactic WR stars. Our observations also include time-dependent observations of 17 stars in the sample. The path to our goal includes removing the dominating component of wavelength-dependent InterStellar Polarization (ISP), which normally follows the well-known Serkowski law. We include a wavelength-dependent ISP position angle parameter in our ISP law and find that 15 stars show significant results for this parameter. We detect a significant component of wavelength-independent polarization due to electron scattering in the wind for 10 cases, with most WR stars showing none at the ~0.05% level precision of our data. The intrinsically polarized stars can be explained with binary interaction, large-scale wind structure, and clumping. We also found that 5 stars out of 19 observed with the Stromgren b filter (probing the complex {lambda}4600-4700{AA} emission-line region) have significant residuals from the ISP law and propose that this is due to wind asymmetries. We provide a useful catalog of ISP for 47 bright Galactic WR stars and upper limits on the possible level of intrinsic polarization.
- ID:
- ivo://CDS.VizieR/J/A+A/404/L29
- Title:
- VB differential photometry of WR30a
- Short Name:
- J/A+A/404/L29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new photometric observations in Johnson V and B of WR30a, revealing relative dramatic changes in brightness of 0.2mag. These variations occur on a time scale of hours, and are only seen in V. We argue that they are not caused by dust extinction, but either by a dramatic change in the strength of the C IV 5801-12{AA} emission line doublet due to a de-excitation process, or by some unknown continuum effect.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A151
- Title:
- V light curve of WR 123
- Short Name:
- J/A+A/530/A151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- What is the origin of the large-amplitude variability in Wolf-Rayet WN8 stars in general and WR123 in particular? A dedicated spectroscopic campaign targets the ten-hour period previously found in the high-precision photometric data obtained by the MOST satellite. In June-August 2003 we obtained a series of high signal-to-noise, mid-resolution spectra from several sites in the {lambda}{lambda}4000-6940{AA} domain. We also followed the star with occasional broadband (Johnson V) photometry. The acquired spectroscopy allowed a detailed study of spectral variability on timescales from ~5 minutes to months.
- ID:
- ivo://CDS.VizieR/J/ApJ/697/1741
- Title:
- Warped disks of YSOs in Galactic center
- Short Name:
- J/ApJ/697/1741
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The central parsec around the supermassive black hole in the Galactic center (GC) hosts more than 100 young and massive stars. Outside the central cusp (R~1") the majority of these O and Wolf-Rayet (W-R) stars reside in a main clockwise system, plus a second, less prominent disk or streamer system at large angles with respect to the main system. Here we present the results from new observations of the GC with the AO-assisted near-infrared imager NACO and the integral field spectrograph SINFONI on the ESO/VLT. These include the detection of 27 new reliably measured W-R/O stars in the central 12" and improved measurements of 63 previously detected stars, with proper motion uncertainties reduced by a factor of 4 compared to our earlier work. Based on the sample of 90 well measured W-R/O stars, we develop a detailed statistical analysis of their orbital properties and orientations. We show that half of the W-R/O stars are compatible with being members of a clockwise rotating system.
- ID:
- ivo://CDS.VizieR/J/A+A/331/949
- Title:
- Wolf-Rayet and O-star runaways kinematics
- Short Name:
- J/A+A/331/949
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Reliable systemic radial velocities are almost impossible to secure for Wolf-Rayet stars, difficult for O stars. Therefore, to study the motions - both systematic in the Galaxy and peculiar - of these two related types of hot, luminous star, we have examined the Hipparcos proper motions of some 70 stars of each type. We find that (a) both groups follow Galactic rotation in the same way, (b) both have a similar fraction of ``runaways'', (c) mean kinetic ages based on displacement and motion away from the Galactic plane tend to slightly favour the cluster ejection over the the binary supernova hypothesis for their formation, and (d) those with significant peculiar supersonic motion relative to the ambient ISM, tend to form bow shocks in the direction of the motion.
