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Start Over Subject stellar mass loss
41. Modelisation of AGB stars in the LMC
ID:
ivo://CDS.VizieR/J/A+A/537/A105
Title:
Modelisation of AGB stars in the LMC
Short Name:
J/A+A/537/A105
Date:
21 Oct 2021
Publisher:
CDS
Description:
Asymptotic giant branch (AGB) stars are major contributors to both the chemical enrichment of the interstellar medium and the integrated light of galaxies. Despite its importance, the AGB is one of the least understood phases of stellar evolution. The main difficulties associated with detailed modelling of the AGB are related to the mass-loss process and the 3rd dredge-up efficiency. We provide direct measures of mass-loss rates and luminosities for a complete sample of AGB stars in the Large Magellanic Cloud, disentangling the C- and O-rich stellar populations.
42. Modelisation of Magellanic Cloud C/O stars
ID:
ivo://CDS.VizieR/J/A+A/506/1277
Title:
Modelisation of Magellanic Cloud C/O stars
Short Name:
J/A+A/506/1277
Date:
21 Oct 2021
Publisher:
CDS
Description:
Mass loss is one of the fundamental properties of Asymptotic Giant Branch (AGB) stars, and through the enrichment of the interstellar medium, AGB stars are key players in the life cycle of dust and gas in the universe. However, a quantitative understanding of the mass-loss process is still largely lacking, particularly its dependence on metallicity. To investigate the relation between mass loss, luminosity and pulsation period for a large sample of evolved stars in the Small and Large Magellanic Cloud.
43. Models for rotating stars
ID:
ivo://CDS.VizieR/J/A+A/553/A24
Title:
Models for rotating stars
Short Name:
J/A+A/553/A24
Date:
21 Oct 2021
Publisher:
CDS
Description:
B-type stars are known to rotate at various velocities, including very fast rotators near the critical velocity as the Be stars. In this paper, we provide stellar models covering the mass range between 1.7 to 15M_{sun}_, which includes the typical mass of known Be stars, at Z=0.014, 0.006 and 0.002 and for an extended range of initial velocities on the zero-age main sequence. We use the Geneva stellar-evolution code including the effects of shellular rotation and with a numerical treatment that has been improved in order for the code to track in a precise way the variation of the angular momentum content of the star as it changes under the influence of radiative winds and/or mechanical mass loss. We discuss the impact of the initial rotation rate on the tracks in the Hertzsprung-Russell diagram, the main-sequence (MS) lifetimes, the evolution of the surface rotation and abundances, as well as on the ejected masses of various isotopes. Among the new results obtained from the present grid we have that: 1) fast rotating stars with initial masses around 1.7M_{sun}_ present at the beginning of the core hydrogen-burning phase quite small convective cores with respect to their slowly rotating counterparts. This fact may be interesting to keep in mind in the frame of the asteroseismic studies of such stars; 2) the contrast between the core and surface angular velocity is higher in slower rotating stars. The values presently obtained are quite in the range of the very few values obtained for B-type stars from asteroseismology; 3) at Z=0.002, the stars in the mass range of 1.7 to 3M_{sun}_ with a mean velocity on the MS of the order of 150km/s show N/H enhancement superior to 0.2dex at mid-MS, and superior to 0.4dex at the end of the MS phase. At solar metallicity the corresponding values are below 0.2dex at any time in the MS. An extended database of stellar models containing 270 evolutionary tracks is provided to the community.
44. Models of a young star cluster ejecta
ID:
ivo://CDS.VizieR/J/MNRAS/425/1696
Title:
Models of a young star cluster ejecta
Short Name:
J/MNRAS/425/1696
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have computed with a fine time grid the evolution of the elemental abundances of He, C, N and O ejected by young (t<20Myr) and massive (M=10^6^M_{sun}_) coeval stellar cluster with a Salpeter initial mass function (IMF) over a wide range of initial abundances. Our computations incorporate the mass loss from massive stars (M>=30M_{sun}_) during their wind phase including the Wolf-Rayet phase and the ejecta from the core-collapse supernovae. We find that during the Wolf-Rayet phase (t<5Myr) the cluster ejecta composition suddenly becomes vastly overabundant in N for all initial abundances and in He, C and O for initial abundances higher than one-fifth of the solar. The C and O abundances in the cluster ejecta can reach over 50 times the solar value with important consequences for the chemical and hydrodynamical evolution of the surrounding interstellar medium.
45. Near IR Photometry of a Sample of IRAS Point Sources
ID:
ivo://CDS.VizieR/II/177
Title:
Near IR Photometry of a Sample of IRAS Point Sources
Short Name:
II/177
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results are given for the 516 sources that we have observed from La Silla (452 in the southern hemisphere, plus 64 in the range 0 to 20deg). For each source, the IRAS name is given followed by the epoch of observation (with the convention given in Table 1), the J, H, K, L', M magnitudes that we have obtained, then three classifications based on IRAS Low Resolution Spectra (LRS), IRAS broad-band photometry (VH) and the combination of IRAS broad-band photometry with our near-infrared photometry (Val), and, finally, one association.
46. Neptune-like planets low-density overabundance
ID:
ivo://CDS.VizieR/J/MNRAS/466/1868
Title:
Neptune-like planets low-density overabundance
Short Name:
J/MNRAS/466/1868
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a uniform analysis of the atmospheric escape rate of Neptune-like planets with estimated radius and mass (restricted to M_p_<30M_{Earth}_). For each planet, we compute the restricted Jeans escape parameter, {Lambda}, for a hydrogen atom evaluated at the planetary mass, radius, and equilibrium temperature. Values of {Lambda}<=20 suggest extremely high mass-loss rates. We identify 27 planets (out of 167) that are simultaneously consistent with hydrogen-dominated atmospheres and are expected to exhibit extreme mass-loss rates. We further estimate the mass-loss rates (L_hy_) of these planets with tailored atmospheric hydrodynamic models. We compare L_hy_ to the energy-limited (maximum-possible high-energy driven) mass-loss rates. We confirm that 25 planets (15 per cent of the sample) exhibit extremely high mass-loss rates (L_hy_>0.1M_{Earth}_/Gyr), well in excess of the energy-limited mass-loss rates. This constitutes a contradiction, since the hydrogen envelopes cannot be retained given the high mass-loss rates. We hypothesize that these planets are not truly under such high mass-loss rates. Instead, either hydrodynamic models overestimate the mass-loss rates, transit-timing-variation measurements underestimate the planetary masses, optical transit observations overestimate the planetary radii (due to high-altitude clouds), or Neptunes have consistently higher albedos than Jupiter planets. We conclude that at least one of these established estimations/techniques is consistently producing biased values for Neptune planets. Such an important fraction of exoplanets with misinterpreted parameters can significantly bias our view of populations studies, like the observed mass-radius distribution of exoplanets for example.
47. Photometry and spectroscopy of SN 2010jl
ID:
ivo://CDS.VizieR/J/AJ/144/131
Title:
Photometry and spectroscopy of SN 2010jl
Short Name:
J/AJ/144/131
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present extensive optical observations of a Type IIn supernova (SN IIn) 2010jl for the first 1.5years after its discovery. The UBVRI light curves demonstrated an interesting two-stage evolution during the nebular phase, which almost flatten out after about 90days from the optical maximum. SN 2010jl has one of the highest intrinsic H{alpha} luminosities ever recorded for an SN IIn, especially at late phase, suggesting a strong interaction of SN ejecta with the dense circumstellar material (CSM) ejected by the progenitor. This is also indicated by the remarkably strong Balmer lines persisting in the optical spectra. One interesting spectral evolution about SN 2010jl is the appearance of asymmetry of the Balmer lines. These lines can be well decomposed into a narrow component and an intermediate-width component. The intermediate-width component showed a steady increase in both strength and blueshift with time until t~400days after maximum, but it became less blueshifted at t~500days, when the line profile appeared relatively symmetric again. Owing to the fact that a pure reddening effect will lead to a sudden decline of the light curves and a progressive blueshift of the spectral lines, we therefore propose that the asymmetric profiles of H lines seen in SN 2010jl are unlikely due to the extinction by newly formed dust inside the ejecta, contrary to the explanation by some early studies. Based on a simple CSM-interaction model, we speculate that the progenitor of SN 2010jl may suffer a gigantic mass loss (~30-50M_{sun}_) a few decades before explosion. Considering a slow-moving stellar wind (e.g.,~28km/s) inferred for the preexisting, dense CSM shell and the extremely high mass-loss rate (1-2M_{sun}_/yr), we suggest that the progenitor of SN 2010jl might have experienced a red supergiant stage and may explode finally as a post-red supergiant star with an initial mass above 30-40M_{sun}_.
48. Post-AGB evolution
ID:
ivo://CDS.VizieR/J/ApJS/92/125
Title:
Post-AGB evolution
Short Name:
J/ApJS/92/125
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, we present the results for the post-AGB phases of stellar evolutionary sequences, complete from the main-sequence phase, through the AGB phase, and on into the planetary nebula and white dwarf regimes. Mass loss has been included using an empirical formalism derived from observed mass-loss rates of planetary nebula nuclei available in the literature and from radiation-pressure-driven stellar wind theory. Models are calculated for initial masses 0.89, 0.95, 1.0, 1.5, 2.0, 2.5, 3.5, and 5.0M_{sun}_, and metallicities 0.016, 0.008, 0.004, and 0.001. These abundance and mass values were chosen to allow comparison with Galactic, and Magellanic Cloud planetary nebulae and their nuclei. The post-AGB evolutionary sequences fall into two distinct groups depending on when the planetary nebula nuclei leave the AGB: one group where helium-shell burning is dominant, and the other group where hydrogen-shell burning is dominant. Of the 27 computed sequences: 17 are hydrogen-burners, and 10 are helium-burners. In only five cases was any effort made to control the phase of departure from the AGB. Lower mass models are more likely to leave the AGB burning helium, as the preceding AGB evolution has a mass-loss rate which is greatest immediately prior to a helium-shell flash. The calculations are compared with the large observational database that has developed over recent years for the Large Magellanic Cloud. These calculations will be useful for determining the planetary nebula luminosity function, and for the study of the ultraviolet excess observed in elliptical galaxies.
49. Red supergiant stars in the LMC. II.
ID:
ivo://CDS.VizieR/J/A+A/616/A175
Title:
Red supergiant stars in the LMC. II.
Short Name:
J/A+A/616/A175
Date:
21 Oct 2021
Publisher:
CDS
Description:
The characteristics of infrared properties and mid-infrared (MIR) variability of red supergiant (RSG) stars in the Large Magellanic Cloud (LMC) are analyzed based on 12 bands of near-infrared (NIR) to MIR co-added data from 2MASS, Spitzer and WISE, and ~6.6 years of MIR time-series data collected by the ALLWISE and NEOWISE-R projects. 773 RSGs candidates are compiled from the literature and verified by using the color-magnitude diagram (CMD), spectral energy distribution (SED) and MIR variability. About 15% of valid targets in the IRAC1-IRAC2/IRAC2-IRAC3 diagram may show Polycyclic Aromatic Hydrocarbon (PAH) emission. We show that arbitrary dereddening Q parameters related to the IRAC4, S9W, WISE3, WISE4 and MIPS24 bands could be constructed based on a precise measurement of MIR interstellar extinction law. Several peculiar outliers in our sample are discussed, in which one outlier might be a RSG right before the explosion or an extreme asymptotic giant branch (AGB) star in the very late evolutionary stage based on the MIR spectrum and photometry. There are 744 identified RSGs in the final sample having both the WISE1- and WISE2-band time-series data. The results show that the MIR variability is increasing along with the increasing of brightness. There is a relatively tight correlation between the MIR variability, mass loss rate (MLR; in terms of K_S-WISE3 color) and the warm dust/continuum (in terms of WISE4 magnitude/flux), where the MIR variability is evident for the targets with K_S-WISE3>1.0mag and WISE4<6.5mag, while the rest of the targets show much smaller MIR variability. The MIR variability is also correlated with the MLR for which targets with larger variability also show larger MLR with an approximate upper limit of -6.1M_{sun}_/yr. The variability and luminosity may both be important for the MLR since the WISE4-band flux is increasing exponentially along with the degeneracy of luminosity and variability. The identified RSG sample has been compared with the theoretical evolutionary models and shown that the discrepancy between observation and evolutionary models can be mitigated by considering both variability and extinction.
50. RS Cnc IRAM NOEMA interferometric data
ID:
ivo://CDS.VizieR/J/A+A/658/A135
Title:
RS Cnc IRAM NOEMA interferometric data
Short Name:
J/A+A/658/A135
Date:
22 Feb 2022
Publisher:
CDS
Description:
The latest evolutionary phases of low- and intermediate mass stars are characterized by complex physical processes like turbulence, convection, stellar pulsations, magnetic fields, condensation of solid particles, and the formation of massive outflows that inject freshly produced heavy elements and dust particles into the interstellar medium. By investigating individual objects in detail we wish to analyze and disentangle the effects of the interrelated physical processes on the structure of the wind forming region around these objects. We use the Northern Extended Millimeter Array (NOEMA) to obtain spatially and spectrally resolved observations of the semi-regular Asymptotic Giant Branch star RS Cancri to shed light on the morpho-kinematic structure of its inner, wind forming environment by applying detailed 3-D reconstruction modeling and LTE radiative transfer calculations. We detect 32 lines of 13 molecules and isotopologs (CO, SiO, SO, SO_2_, H_2_O, HCN, PN), including several transitions from vibrationally excited states. HCN, H^13^CN, millimeter vibrationally excited H_2_O, SO, ^34^SO, SO_2_, and PN are detected for the first time in RS Cnc. Evidence for rotation is seen in HCN, SO, SO_2_, and SiO(v=1). From CO and SiO channel maps, we find an inner, equatorial density enhancement, and a bipolar outflow structure with a mass loss rate of 1x10^-7^M_{sun}_/yr for the equatorial region and of 2x10^-7^M_{sun}_/yr for the polar outflows. The ^12^CO/^13^CO ratio is measured to be ~20 on average, 24+/-2 in the polar outflows and 19+/-3 in the equatorial region. We do not find direct evidence of a companion that might explain this kind of kinematic structure, and explore the possibility that a magnetic field might be the cause of it. The innermost molecular gas is influenced by stellar pulsation and possibly by convective cells that leave their imprint on broad wings of certain molecular lines, such as SiO and SO. RS Cnc is one of the few nearby, low mass-loss-rate, oxygen-rich AGB stars with a wind displaying both an equatorial disk and bipolar outflows. Its orientation with respect to the line of sight is particularly favorable for a reliable study of its morpho-kinematics. The mechanism causing early spherical symmetry breaking remains however uncertain, calling for additional high spatial and spectral resolution observations of the emission of different molecules in different transitions, along with a deeper investigation of the coupling among the different physical processes at play.

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