Empirical ionization fractions in the winds and the determination of mass-loss rates for early-type stars

1980 ◽  
Vol 242 ◽  
pp. L33 ◽  
Author(s):  
H. J. G. L. M. Lamers ◽  
R. Gathier ◽  
T. P. Snow
Keyword(s):  
Mass Loss ◽  
Early Type ◽  
Early Type Stars ◽  
Loss Rates

scholarly journals The theory of winds in early type stars

1981 ◽  
Vol 59 ◽  
pp. 125-130 ◽  
Author(s):  
A.G. Hearn
Keyword(s):  
Mass Loss ◽  
Spectral Type ◽  
Stellar Evolution ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Optical Measurements ◽  
Early Type ◽  
Large Uncertainty ◽  
Early Type Stars ◽  
Loss Rates

I assume that the purpose of this review of the theory of winds from early type stars is to summarize the way in which the mass loss rate of a star may be included in a calculation of stellar evolution. Let me summarize my conclusions. It is not possible. One can only use estimates of mass loss rates obtained from the observations. Even these give a large uncertainty. The observed mass loss rates for different stars of the same spectral type vary. Further the mass loss rates obtained by different methods for the same star differ. An extreme example of this is 9 Sgr. The mass loss rate derived from the radio observations is forty times greater than that derived from the U.V. and optical measurements (Abbott et al. 1980).

scholarly journals Mass loss rates of OB stars derived from infrared observations

1981 ◽  
Vol 59 ◽  
pp. 51-56 ◽  
Author(s):  
E.G. Tanzi ◽  
M. Tarenghi ◽  
N. Panagia
Keyword(s):  
Mass Loss ◽  
Near Infrared ◽  
Broad Band ◽  
Early Type ◽  
Model Calculations ◽  
Infrared Observations ◽  
Ob Stars ◽  
Wide Range ◽  
Early Type Stars ◽  
Loss Rates

In this paper we report briefly on a study of the mass loss of early type stars in the infrared. Up to now near infrared (1.25 - 4.8 μ ) broad band photometry of 70 southern OB stars of various luminosity class has been secured. Program stars have been selected, among those bright enough in the infrared to give a suitable photometric accuracy, in order to cover a wide range of spectral types (Fig. 1).37 stars are found to exhibit emission in excess over a blackbody photospheric continuum, which is interpreted in terms of gas ejected in the form of an accelerated wind. By means of model calculations the corresponding mass loss rates are derived. The obtained values compare well with those determined indipendently by various Authors for stars in common. Our data show that mass loss rates increase with luminosity and are a decreasing function of surface gravity.

scholarly journals Supernovae and their Evolution in a Low Metallicity ISM

2008 ◽  
Vol 4 (S255) ◽  
pp. 175-181
Author(s):  
Roger A. Chevalier
Keyword(s):  
Mass Loss ◽  
Interaction Region ◽  
High Mass ◽  
Initial Mass ◽  
Dust Formation ◽  
Core Collapse ◽  
Early Type ◽  
Low Metallicity ◽  
Early Type Stars ◽  
Loss Rates

AbstractObservations of core collapse supernovae and their progenitors generally support expectations of increasing mass loss with increasing initial mass. Mass loss rates are expected to decline at lower metallicity, and there are prospects for directly testing this for the red supergiant progenitors of Type IIP supernovae. However, there are indications that mass loss rates for high mass early type stars may be overestimated and that there are mass loss mechanisms that do not decline at lower metallicity. In this case, there may be supernova emission from strong circumstellar interaction even at low metallicity. Although there is evidence for dust formation in freely expanding ejecta of supernovae, the quantities are relatively small. Another promising site of dust formation is the circumstellar interaction region, but this should occur in only a fraction of supernovae.

scholarly journals The properties of early-type stars in the Magellanic Clouds

2008 ◽  
Vol 4 (S256) ◽  
pp. 325-336
Author(s):  
Christopher J. Evans
Keyword(s):  
Physical Properties ◽  
Mass Loss ◽  
Temperature Scale ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Early Type ◽  
The Past ◽  
The Galaxy ◽  
Stellar Temperature ◽  
Early Type Stars

AbstractThe past decade has witnessed impressive progress in our understanding of the physical properties of massive stars in the Magellanic Clouds, and how they compare to their cousins in the Galaxy. I summarise new results in this field, including evidence for reduced mass-loss rates and faster stellar rotational velocities in the Clouds, and their present-day compositions. I also discuss the stellar temperature scale, emphasizing its dependence on metallicity across the entire upper-part of the Hertzsprung-Russell diagram.

scholarly journals The VLT-FLAMES survey of massive stars: mass loss and rotation of early-type stars in the SMC

2006 ◽  
Vol 456 (3) ◽  
pp. 1131-1151 ◽  
Author(s):  
M. R. Mokiem ◽  
A. de Koter ◽  
C. J. Evans ◽  
J. Puls ◽  
S. J. Smartt ◽  
...  
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Early Type ◽  
Early Type Stars

scholarly journals Terminal Velocities for a Large Sample of O Stars, B Supergiants, and Wolf-Rayet Stars

1991 ◽  
Vol 143 ◽  
pp. 317-317
Author(s):  
R. K. Prinja ◽  
M. J. Barlow ◽  
I. D. Howarth
Keyword(s):  
High Resolution ◽  
Mass Loss ◽  
Early Type ◽  
Nuclear Mass ◽  
Ob Stars ◽  
Residual Intensity ◽  
The Mean ◽  
Effective Temperatures ◽  
Early Type Stars ◽  
Absorption Features

We argue that easily measured, reliable estimates of terminal velocities for early-type stars are provided (1) by the central velocity asymptotically approached by narrow absorption features in unsaturated UV P Cygni profiles, and (2) by the violet limit of zero residual intensity in saturated P Cygni profiles. We use these estimators and high resolution IUE data to determine terminal velocities, v∞, for 181 O stars, 70 early B supergiants, and 35 Wolf-Rayet stars. For OB stars our values are typically 15-20% smaller than the extreme violet edge velocities, vedge, while for WR stars v∞ = 0.76vedge on average. We give new mass-loss rates for WR stars which are thermal radio emitters, taking into account our new terminal velocities and recent revisions to estimates of distances and to the mean nuclear mass per electron. We examine the relationships between v∞, the surface escape velocities, and effective temperatures.

scholarly journals Mass loss from early-type stars

1970 ◽  
Vol 36 ◽  
pp. 209-212
Author(s):  
J. B. Hutchings
Keyword(s):  
Mass Loss ◽  
Spectral Type ◽  
Stellar Evolution ◽  
Early Type ◽  
High Luminosity ◽  
Spectroscopic Evidence ◽  
Ob Stars ◽  
Early Type Stars ◽  
Very High ◽  
Hr Diagram

Following the detailed study of four very high luminosity OB stars, a survey has been made for spectroscopic evidence of mass loss in a number of early-type supergiants. A list of spectroscopic criteria is given and the mass loss estimates for 24 stars plotted on the HR diagram. The dependence of the phenomenon on spectral type and luminosity is discussed as well as its significance in terms of stellar evolution.

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