scholarly journals Evolution of O stars and the WR connection

1979 ◽  
Vol 83 ◽  
pp. 431-445 ◽  
Author(s):  
Peter S. Conti
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
High Luminosity ◽  
Loss Mechanism ◽  
Evolutionary Scenario ◽  
Processed Material ◽  
Dominant Process ◽  
Highly Evolved ◽  
Loss Rates ◽  
Enriched Composition

The stellar wind mass loss rates of at least some single Of type stars appear to be sufficient to remove much if not all of the hydrogen-rich envelope such that nuclear processed material is observed at the surface. This highly evolved state can then be naturally associated with classic Population I WR stars that have properties of high luminosity for their mass, helium enriched composition, and nitrogen or carbon enhanced abundances. If stellar wind mass loss is the dominant process involved in this evolutionary scenario, then stars with properties intermediate between Of and WR types should exist. The stellar parameters of luminosity, temperature, mass and composition are briefly reviewed for both types. All late WN stars so far observed are relatively luminous like Of stars, and also contain hydrogen. All early WN stars, and WC stars, are relatively faint and contain little or no hydrogen. The late WN stars seem to have the intermediate properties required if a stellar wind is the dominant mass loss mechanism that transforms an Of star to a WR type.

scholarly journals On the evolutionary time scale of the accreting component in massive close binaries: consequences for the supernova event

1981 ◽  
Vol 59 ◽  
pp. 465-468
Author(s):  
C. Doom ◽  
J.P. De Grève
Keyword(s):  
Mass Loss ◽  
Mass Exchange ◽  
Stellar Wind ◽  
Time Scale ◽  
Roche Lobe ◽  
Close Binaries ◽  
Evolutionary Time ◽  
Hydrogen Burning ◽  
Evolutionary Time Scale ◽  
Evolutionary Scenario

AbstractThe remaining core hydrogen burning lifetime after a case B of mass exchange is computed for the mass gaining component in massive close binaries. Effects of stellar wind mass loss and mass loss during Roche Lobe OverFlow (RLOF) are included. Consequences for the evolutionary scenario are discussed.

Mass Loss and Stellar Wind in Massive X-Ray Binaries

1980 ◽  
Vol 5 ◽  
pp. 541-547
Author(s):  
H. F. Henrichs
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Binary Systems ◽  
Massive Stars ◽  
Compact Star ◽  
X Rays ◽  
Early Type ◽  
X Ray ◽  
X Ray Binaries ◽  
Loss Rates

A number of massive stars of early type is found in X-ray binary systems. The catalog of Bradt et al. (1979) contains 21 sources optically identified with massive stars ranging in spectral type from 06 to B5 out of which 13 are (nearly) unevolved stars and 8 are supergiants. Single stars of this type generally show moderate to strong stellar winds. The X-rays in these binaries originate from accretion onto a compact companion (we restrict the discussion to this type of X-rays).We consider the compact star as a probe traveling through the stellar wind. This probe enables us to derive useful information about the mass outflow of massive stars.After presenting the basic data we derive an upper limit to mass loss rates of unevolved early type stars by studying X-ray pulsars. Next we consider theoretical predictions concerning the influence of X-rays on the stellar wind and compare these with the observations. Finally, using new data from IUE, we draw some conclusions about mass loss rates and velocity laws as derived from X-ray binaries.

scholarly journals Corrections for Hydrostatic Atmospheric Models: Radii and Effective Temperatures of Wolf Rayet Stars

1982 ◽  
Vol 99 ◽  
pp. 53-56 ◽  
Author(s):  
C. De Loore ◽  
P. Hellings ◽  
H.J.G.L.M. Lamers
Keyword(s):  
Mass Loss ◽  
Optical Depth ◽  
Stellar Wind ◽  
Theoretical Models ◽  
Roche Lobe ◽  
Evolutionary Models ◽  
Atmospheric Models ◽  
Helium Burning ◽  
Effective Temperatures ◽  
Loss Rates

With the assumption of planparallel hydrostatic atmospheres, used generally for the computation of evolutionary models, the radii of WR stars are seriously underestimated. The true atmospheres may be very extended, due to the effect of the stellar wind. Instead of these hydrostatic atmospheres we consider dynamical atmospheres adopting a velocity law. The equation of the optical depth is integrated outwards using the equation of continuity.The “hydrostatic” radii are to be multiplied with a factor 2 to 8, and the effective temperatures with a factor 0.8 to 0.35 when Wolf Rayet characteristics for the wind are considered, and WR mass loss rates are used. With these corrections the effective temperatures of the theoretical models, which are helium burning Roche lobe overflow remnants, range between 30 000 K and 50 000 K. Effective temperatures calculated in the hydrostatic hypothesis can be as high as 150 000 K for helium burning RLOF-remnants with WR mass loss rates.

scholarly journals A radio census of the massive stellar cluster Westerlund 1

2019 ◽  
Vol 632 ◽  
pp. A38
Author(s):  
H. Andrews ◽  
D. Fenech ◽  
R. K. Prinja ◽  
J. S. Clark ◽  
L. Hindson
Keyword(s):  
Radio Emission ◽  
Mass Loss ◽  
Stellar Wind ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Evolutionary Stage ◽  
Spectral Indices ◽  
Stellar Cluster ◽  
The Impact ◽  
Loss Rates

Context. Massive stars and their stellar winds are important for a number of feedback processes. The mass lost in the stellar wind can help determine the end-point of the star as a neutron star (NS) or a black hole (BH). However, the impact of mass loss on the post-main sequence evolutionary stage of massive stars is not well understood. Westerlund 1 is an ideal astrophysical laboratory in which to study massive stars and their winds in great detail over a large range of different evolutionary phases. Aims. We aim to study the radio emission from Westerlund 1, in order to measure radio fluxes from the population of massive stars, and determine mass-loss rates and spectral indices where possible. Methods. Observations were carried out in 2015 and 2016 with the Australia Telescope Compact Array (ATCA) at 5.5 and 9 GHz using multiple configurations, with maximum baselines ranging from 750 m to 6 km. Results. Thirty stars are detected in the radio from the fully concatenated dataset, ten of which are Wolf-Rayet stars (WRs) (predominantly late type WN stars), five yellow hypergiants (YHGs), four red supergiants (RSGs), one luminous blue variable (LBV), the sgB[e] star W9, and several OB supergiants. New source detections in the radio are found for five WR stars, and five OB supergiants. These detections lead to evidence for three new OB supergiant binary candidates, which is inferred from derived spectral index limits. Conclusions. Spectral indices and index limits were determined for massive stars in Westerlund 1. For cluster members found to have partially optically thick emission, mass-loss rates were calculated. Under the approximation of a thermally emitting stellar wind and a steady mass-loss rate, clumping ratios were then estimated for eight WRs. Diffuse radio emission was detected throughout the cluster. Detections of knots of radio emission with no known stellar counterparts indicate the highly clumped structure of this intra-cluster medium, likely shaped by a dense cluster wind.

scholarly journals The dependence of mass loss on the basic stellar parameters

1981 ◽  
Vol 59 ◽  
pp. 19-25
Author(s):  
Henny J.G.L.M. Lamers
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Radio Flux ◽  
Wind Model ◽  
Infrared Excess ◽  
B Stars ◽  
Radio Data ◽  
Hα Emission ◽  
Loss Rates

We determined the dependence of mass loss on the stellar parameters for O and B stars of various luminosities. We used four homogenous sets of mass loss rates derived by different authors from the radioflux, the infrared excess, the UV lines and Hα emission. As the rates derived from the radio flux are the least dependent on model assumptions for the stellar wind, these will be adopted as our standards. The others sets of mass loss rates will be corrected for the differences in the adopted wind model, especially in the velocity law, by scaling the rates to those derived from radio data, using the stars which the different sets have in common.

scholarly journals Evolution of massive stars with mass loss: Surface abundances

1984 ◽  
Vol 105 ◽  
pp. 329-332
Author(s):  
Laura Greggio
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
The Other ◽  
Surface Chemical ◽  
Theoretical Formulation ◽  
Surface Chemical Composition ◽  
Evolutionary Scenario ◽  
Processed Material ◽  
Theoretical Predictions ◽  
Convective Overshoot

The location of theoretical stellar models in the upper part of the HR Diagram (HRD) depends on a variety of poorly understood physical proc esses which may occur during the evolution of massive stars. Among the most important we find: mass loss, convective overshoot and opacity enhancement for temperatures around 106 °K. The effects of these phenomena have been recently investigated by several authors (Bertelli et al. 1983 and references therein), but, due to the large uncertainties still present in the theoretical formulation of these processes, only parametrized formulae are avaliable for model computations. Since the theoretical dis tribution of massive stars in the HRD turns out to be fairly sensitive to these parameters, the evolutionary scenario for massive stars is still far from being satisfactorily settled. On the other hand, due to mass loss, nuclear processed material is expected to be exposed at the surface of massive stars and then, the comparison between theoretical predictions and observations of the surface chemical composition of these objects can help in understanding their evolution and to set more stringent limits to the mentioned parameters.

Mass Loss from Stars

1970 ◽  
Vol 39 ◽  
pp. 272-280
Author(s):  
S. R. Pottasch
Keyword(s):  
Interstellar Medium ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Stellar Mass ◽  
High Luminosity ◽  
Similar Extent ◽  
Probable Loss ◽  
Loss Rates

In this summary we shall attempt to evaluate the mass loss from several kinds of high luminosity stars, especially planetary nebulae, OB supergiants and M giants and supergiants. The purpose is to give an observational basis for the discussion of the mechanism of mass loss and of the consequences of stellar mass loss for the interstellar medium and for stellar evolution. For reasons which will presently be discussed, we are now certain that mass loss is occurring in all the objects mentioned, and probably to a similar extent in all high luminosity stars as well. The precise values of the mass loss rate are uncertain at present; for some objects the uncertainty will be large (two orders of magnitude) and have important influence on the consequences of the mass loss. Therefore we shall discuss in some detail how the different loss rates quoted in the literature have been obtained and what assumptions have been made (see also the Report by Boyarchuk, p. 281). On the basis of this discussion we will indicate the most probable loss rates and their consequences, always remembering the possible influence of the uncertainties.

scholarly journals Evolutionary effects of stellar rotation of massive stars in their pre-supernova environments

2010 ◽  
Vol 6 (S272) ◽  
pp. 99-100
Author(s):  
Brenda Pérez-Rendón ◽  
Horacio Pineda-León ◽  
Alfredo Santillán ◽  
Liliana Hernández-Cervantes
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Main Sequence ◽  
Massive Stars ◽  
Stellar Winds ◽  
Stellar Rotation ◽  
Main Sequence Stars ◽  
Mixing Processes ◽  
Circumstellar Medium ◽  
Loss Rates

AbstractMassive main sequence stars are fast rotators. Stellar rotation affects massive stellar rotation due to rotationally induced mixing processes, the increase of mass loss rates, etc. and also affects the circumstellar medium due to their interaction with the stellar wind. The parameters of stellar winds depends on stellar parameters so the wind parameters change as the star evolves, coupling the evolution of circumstellar medium to the star itself. In this work we used a stellar code to build models of two massive stars (30 and 40 M⊙) and we used their wind parameters to simulate the hydrodynamics of their surrounding gas with the ZEUS-3D code in order to explore the effects of stellar rotation in the pre-supernova environments.

Sign in / Sign up

Export Citation Format

Share Document