scholarly journals On possible mass loss from the supergiant RHO Cassiopeia

1981 ◽  
Vol 59 ◽  
pp. 117-118
Author(s):  
M. Boyarchuk
Keyword(s):  
Mass Loss ◽  
Crimean Astrophysical Observatory ◽  
High Luminosity ◽  
Very High

The supergiant Rho Cas F8Ia has a very high luminosity. Astronomers have payed attention to this star in August 1946, when its by its brightness had dropped from 4.2 to 6.2. The systematic spectrographic observations of Rho Cas are beeing carried out at the Crimean Astrophysical Observatory since 1965. No large light variations were observed during that time.

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.

Observational Evidence for Atmospheric Physical Characteristics Relevant to Stellar Evolution

1977 ◽  
Vol 4 (2) ◽  
pp. 105-114
Author(s):  
R. and G. Cayrel
Keyword(s):  
Mass Loss ◽  
Nuclear Fuel ◽  
Stellar Evolution ◽  
Effective Temperature ◽  
Time Scale ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Observational Evidence ◽  
High Luminosity ◽  
Very High

As a star burns its nuclear fuel, its radius R and its luminosity L are modified. Its mass may as well be affected if the mass loss rate has a time scale comparable to the nuclear time scale; this is likely to occur for stars of very high luminosity. Currently, the change in radius R and luminosity L of an evolving star is described in the socalled theoretical Herzsprung-Russel diagramme with in abscissa the logarithm of the effective temperature defined by:

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 Mass loss from Eta Carinae

1979 ◽  
Vol 83 ◽  
pp. 47-50
Author(s):  
C. D. Andriesse ◽  
R. Viotti
Keyword(s):  
Turbulent Flow ◽  
Mass Loss ◽  
Large Mass ◽  
Ultraviolet Spectrum ◽  
High Excitation ◽  
High Luminosity ◽  
Hydrogen Burning ◽  
Eta Carinae ◽  
Hot Zone

This high luminosity (5 × 106 L⊙) star since 1840 is losing mass at the rate of 7.5 × 10−2 M⊙ per year. The large mass loss could be the result of vibrational instabilities produced in the CNO hydrogen burning phase of a very massive (160 M⊙) star. The presence of high excitation lines in the ultraviolet spectrum of Eta Car suggests the idea of a hot zone excited by dissipation of the supersonic turbulent flow.

Very high energy y-rays from Cygnus X-3

1981 ◽  
Vol 301 (1462) ◽  
pp. 633-634 ◽  
Keyword(s):  
Light Curve ◽  
High Energy ◽  
Crimean Astrophysical Observatory ◽  
Sharp Peak ◽  
X Rays ◽  
Very High Energy ◽  
Time Variations ◽  
Comparison Of The Results ◽  
Very High

Very high energy y-rays (above 10 12 eV) from Cyg X-3 have been observed for 7 years at the Crimean Astrophysical Observatory by means of the Cherenkov technique. These observations enable us to find the derivative with time of the 4.8 hour periodicity. As is well known, the observations of X -rays have revealed time variations of the Cyg X-3 period (see, for instance, Eisner et al. 1979). The ‘light’ curve for very high energy y-rays has a sharp peak lasting 15 minutes and differs significantly from the ‘light’ curve for X-rays. For this reason the comparison of the results in these two regions is important.

scholarly journals Spectroscopic Investigations of Luminous Emission-Line Objects

1975 ◽  
Vol 67 ◽  
pp. 297-298
Author(s):  
Angelo Cassatella ◽  
Roberto Nesci ◽  
Roberto Viotti
Keyword(s):  
Mass Loss ◽  
Emission Line ◽  
Physical Characteristics ◽  
Emission Lines ◽  
Expansion Velocity ◽  
Evolutionary Stage ◽  
High Luminosity ◽  
Spectroscopic Investigations ◽  
Differential Expansion ◽  
Parent Star

Emission lines are frequently observed in the spectra of the high luminosity stars, indicating the presence of extended atmospheric envelopes. We are investigating the physical characteristics (differential expansion velocity, density, extension, mass loss) and the origin of these envelopes in relation to the high luminosity of the parent star, and its evolutionary stage. Some results are presented concerning Eta Car, S Dor, HD 34664, P Cyg, AG and HR Car, and two WR stars.

scholarly journals QU Car: a very high luminosity nova-like binary with a carbon-enriched companion

2003 ◽  
Vol 338 (2) ◽  
pp. 401-411 ◽  
Author(s):  
J. E. Drew ◽  
L. E. Hartley ◽  
K. S. Long ◽  
J. van der Walt
Keyword(s):  
High Luminosity ◽  
Very High

scholarly journals Episodic Mass Loss and Pre-SN Circumstellar Envelopes

2007 ◽  
Vol 3 (S250) ◽  
pp. 193-200 ◽  
Author(s):  
Nathan Smith
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Massive Stars ◽  
Supernova Explosion ◽  
Circumstellar Envelopes ◽  
Observational Fact ◽  
Solar Metallicity ◽  
The 19Th Century ◽  
Very High ◽  
Circumstellar Environment

AbstractI discuss observational clues concerning episodic mass-loss properties of massive stars in the time before the final supernova explosion. In particular, I will focus on the mounting evidence that LBVs and related stars are candidates for supernova progenitors, even though current paradigms place them at the end of core-H burning. Namely, conditions in the immediate circumstellar environment within a few 102 AU of Type IIn supernovae require very high progenitor mass-loss rates. Those rates are so high that the only known stars that come close are LBVs during rare giant eruptions. I will highlight evidence from observations of some recent extraordinary supernovae suggesting that explosive or episodic mass loss (a.k.a. LBV eruptions like the 19th century eruption of Eta Car) occur in the 5-10 years immediately preceding the SN. Finally, I will discuss some implications for stellar evolution from these SNe, the most important of which is the observational fact that the most massive stars can indeed make it to the ends of their lives with substantial H envelopes intact, even at Solar metallicity.

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