- ID:
- ivo://CDS.VizieR/J/A+A/622/A50
- Title:
- Calibrated grid of rotating single star models
- Short Name:
- J/A+A/622/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive star evolution is dominated by various physical effects, including mass loss, overshooting, and rotation, but the prescriptions of their effects are poorly constrained, even affecting our understanding of the main sequence. We aim to constrain massive star evolution models using the unique testbed eclipsing binary HD166734 with new grids of MESA stellar evolution models, adopting calibrated prescriptions of overshooting, mass loss, and rotation. We introduce a novel tool: the "mass-luminosity plane" or "M-L plane", as an equivalent to the traditional HR diagram, utilising it to reproduce the testbed binary HD166734 with newly calibrated MESA stellar evolution models for single stars. We can only reproduce the Galactic binary system with an enhanced amount of core overshooting (alpha_ov_=0.5), mass loss, and rotational mixing. We can utilise the gradient in the M-L plane to constrain the amount of mass loss to 0.5-1.5 times the standard Vink et al. (2001A&A...369..574V) prescriptions, and we can exclude extreme reduction or multiplication factors. The extent of the vectors in the M-L plane leads us to conclude that the amount of core overshooting is larger than is normally adopted in contemporary massive star evolution models. We furthermore conclude that rotational mixing is mandatory to get the nitrogen abundance ratios between the primary and secondary components to be correct (3:1) in our testbed binary system. Our calibrated grid of models, alongside our new M-L plane approach, present the possibility of a widened main sequence due to an increased demand for core overshooting. The increased amount of core overshooting is not only needed to explain the extended main sequence, but the enhanced overshooting is also needed to explain the location of the upper-luminosity limit of the red supergiants. Finally, the increased amount of core overshooting has - via the compactness parameter - implications for supernova explodibility.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/606/A67
- Title:
- Circumstellar envelopes CO photodissociation
- Short Name:
- J/A+A/606/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon monoxide is the most abundant molecule after H_2_ and is important for chemistry in circumstellar envelopes around late-type stars. The size of the envelope is important when modelling low-J transition lines and deriving mass-loss rates from such lines. Now that ALMA is coming to full power the extent of the CO emitting region can be measured directly for nearby asymptotic giant branch (AGB) stars. In parallel, it has become obvious in the past few years that the strength of the interstellar radiation field (ISRF) can have a significant impact on the interpretation of the emission lines. In this paper an update and extension of the classical Mamon et al. (1988ApJ...328..797M) paper is presented; these authors provided the CO abundance profile, described by two parameters, as a function of mass-loss rate and expansion velocity. Following recent work an improved numerical method and updated H_2_ and CO shielding functions are used and a larger grid is calculated that covers more parameter space, including the strength of the ISRF. The effect of changing the photodissociation radius on the low-J CO line intensities is illustrated in two cases.
- ID:
- ivo://CDS.VizieR/J/A+AS/99/291
- Title:
- CO and HCN observations of circumstellar envelopes
- Short Name:
- J/A+AS/99/291
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have searched the literature for all observations of the ^12^CO(1-0), ^12^CO(2-1), and HCN(1-0) lines in circumstellar envelopes of late type stars published between January 1985 and September 1992. We report data for 1361 observations (stellar velocity, expansion velocity, peak intensity, integrated area, noise level). This CO-HCN sample now contains 444 sources. 184 are identified as oxygen-rich, 205 as carbon-rich, and there are 9 S stars. About 85% of the sources are AGB stars. There are 32 planetary nebulae and about thirty post-AGB stars candidates. Besides results of millimeter observations, we also list identifications, coordinates, IRAS data, chemical and spectral types for every source. For AGB stars, we have estimated (or compiled) bolometric fluxes and distances for 349 sources, and mass loss rates deduced from CO results for 324 sources, taking into account the influence of the CO photodissociation radius. We also list mass loss rates derived from detailed models of CO emission which we could find in the literature.
- ID:
- ivo://CDS.VizieR/J/A+AS/93/121
- Title:
- CO emission from a sample of IRAS sources
- Short Name:
- J/A+AS/93/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first results from a survey of circumstellar CO(1-0) emission are presented. The sources were selected from the IRAS point source catalog according to the IRAS color criteria described in van der Veen and Habing (1988A&A...194..125V). The sources have good quality fluxes at 12, 25, and 60 microns, flux densities larger than 20Jy at 25{mu}m, and are situated more than 5{deg} away from the Galactic plane. The survey is undertaken to study the relationship between mass loss rates, dust properties, and the evolution along the AGB. The sample consists of 787 sources and contains both oxygen and carbon-rich stars, including Mira variables, OH/IR objects, protoplanetary nebulae, planetary nebulae, and 60-micron excess sources. So far, 519 objects, situated on both the northern and the southern sky, have been observed; 163 sources were found to have circumstellar CO emission, and in 58 of these CO emission has not previously been detected.
- ID:
- ivo://CDS.VizieR/J/A+A/560/A16
- Title:
- Comparison of evolutionary tracks
- Short Name:
- J/A+A/560/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution of massive stars is not fully understood. The relation between different types of evolved massive stars is not clear, and the role of factors such as binarity, rotation or magnetism needs to be quantified. Several groups make available the results of 1D single stellar evolution calculations in the form of evolutionary tracks and isochrones. They use different stellar evolution codes for which the input physics and its implementation varies. In this paper, we aim at comparing the currently available evolutionary tracks for massive stars. We focus on calculations aiming at reproducing the evolution of Galactic stars. Our main goal is to highlight the uncertainties on the predicted evolutionary paths. We compute stellar evolution models with the codes MESA and STAREVOL. We compare our results with those of four published grids of massive stellar evolution models (Geneva, STERN, Padova and FRANEC codes). We first investigate the effects of overshooting, mass loss, metallicity, chemical composition. We subsequently focus on rotation. Finally, we compare the predictions of published evolutionary models with the observed properties of a large sample of Galactic stars.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A143
- Title:
- Cool, evolved stars PACS and SPIRE spectroscopy
- Short Name:
- J/A+A/618/A143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- At the end of their lives AGB stars are prolific producers of dust and gas. The details of this mass-loss process are still not understood very well. Herschel PACS and SPIRE spectra which cover the wavelength range from ~55 to 670um almost continuously, offer a unique way of investigating properties of AGB stars in general and the mass-loss process in particular as this is the wavelength region where dust emission is prominent and molecules have many emission lines. We present the community with a catalogue of AGB stars and red supergiants (RSGs) with PACS and/or SPIRE spectra reduced according to the current state of the art. The Herschel Interactive Processing Environment (HIPE) software with the latest calibration is used to process the available PACS and SPIRE spectra of 40 evolved stars. The SPIRE spectra of some objects close to the Galactic plane require special treatment because of the weaker fluxes in combination with the strong and complex background emission at those wavelengths. The spectra are convolved with the response curves of the PACS and SPIRE bolometers and compared to the fluxes measured in imaging data of these sources. Custom software is used to identify lines in the spectra, and to determine the central wavelengths and line intensities. Standard molecular line databases are used to associate the observed lines. Because of the limited spectral resolution of the PACS and SPIRE spectrometers (~1500), several known lines are typically potential counterparts to any observed line. To help identifications in follow-up studies the relative contributions in line intensity of the potential counterpart lines are listed for three characteristic temperatures based on local thermodynamic equilibrium (LTE) calculations and assuming optically thin emission. The following data products are released: the reduced spectra, the lines that are measured in the spectra with wavelength, intensity, potential identifications, and the continuum spectra, i.e. the full spectra with all identified lines removed. As simple examples of how this data can be used in future studies we have fitted the continuum spectra with three power laws (two wavelength regimes covering PACS, and one covering SPIRE) and find that the few OH/IR stars seem to have significantly steeper slopes than the other oxygen- and carbon-rich objects in the sample, possibly related to a recent increase in mass-loss rate. As another example we constructed rotational diagrams for CO (and HCN for the carbon stars) and fitted a two-component model to derive rotational temperatures.
- ID:
- ivo://CDS.VizieR/J/A+A/382/184
- Title:
- Crystalline silicates around evolved stars
- Short Name:
- J/A+A/382/184
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first paper in a series of three where we present the first comprehensive inventory of solid state emission bands observed in a sample of 17 oxygen-rich circumstellar dust shells surrounding evolved stars. The data were taken with the Short and Long Wavelength Spectrographs on board of the Infrared Space Observatory (ISO) and cover the 2.4 to 195{mu}m wavelength range. The spectra show the presence of broad 10 and 18{mu}m bands that can be attributed to amorphous silicates. In addition, at least 49 narrow bands are found whose position and width indicate they can be attributed to crystalline silicates. Almost all of these bands were not known before ISO.
- ID:
- ivo://CDS.VizieR/J/ApJ/642/1140
- Title:
- Disk mass loss in the Orion Nebula Cluster
- Short Name:
- J/ApJ/642/1140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relevance of encounters on the destruction of protoplanetary disks in the Orion Nebula cluster (ONC) is investigated by combining two different types of numerical simulation. First, star-cluster simulations are performed to model the stellar dynamics of the ONC, the results of which are used to investigate the frequency of encounters, the mass ratio and separation of the stars involved, and the eccentricity of the encounter orbits.
- ID:
- ivo://CDS.VizieR/J/A+A/429/235
- Title:
- Effective temperatures of 119 C-rich giants
- Short Name:
- J/A+A/429/235
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass loss rates, expansion velocities and dust-to-gas density ratios from millimetric observations of 119 carbon-rich giants are compared, as functions of stellar parameters, to the predictions of recent hydrodynamical models. Distances and luminosities previously estimated from HIPPARCOS data, masses from pulsations and C/O abundance ratios from spectroscopy, and effective temperatures from a new homogeneous scale, are used.
- ID:
- ivo://CDS.VizieR/J/A+A/376/997
- Title:
- Galactic mass-losing AGB stars
- Short Name:
- J/A+A/376/997
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AGB mass-losing sources are easy to identify and to characterize in the near-infrared range (1-5{mu}m). We make use of the near-infrared data acquired by the Japanese space experiment IRTS to study a sample of sources detected in the 2 celestial strips surveyed by the IRTS. Mass-loss rates and distances are estimated for 40 carbon-rich sources and 86 oxygen-rich sources of which 8 are probably of S-type. Although the sample is small, one sees a dependence of the relative contribution of the two kinds of sources to the replenishment of the interstellar medium (ISM) on the galactocentric distance. E.g. from 6 to 8kpc, oxygen-rich sources in our sample contribute 10-12 times as much as carbon rich sources, whereas from 10 to 12kpc, the latters contribute 3-4 times as much as the formers. Therefore, one would expect a gradient in the composition of the ISM between 6 and 12kpc from the Galactic Centre, especially in its dust component. Most of the replenishment (>50%) by AGB stars is due to sources with mass-loss rate larger than 10^-6^M_{sun}_/yr.
