scholarly journals Dust formation in M-stars

1987 ◽  
Vol 122 ◽  
pp. 533-534
Author(s):  
H.-P. Gail
Keyword(s):  
Homogeneous Nucleation ◽  
Stellar Winds ◽  
Dust Formation ◽  
M Stars

A mechanism is proposed for the initiation of dust formation in stellar winds of M-type giants and supergiants. If Mg and Fe are ionized (M0…M4) dust formation is initiated by homogeneous nucleation of SiO, otherwise (later ≍ M2) by homogeneous nucleation of MgS. The condensation temperatures for these mechanisms agree well with observations.

Dust Formation in, and the Structure of Wolf-Rayet Stellar Winds

1987 ◽  
pp. 455-456
Author(s):  
P. M. Williams ◽  
K. A. van der Hucht ◽  
P. S. Thé
Keyword(s):  
Stellar Winds ◽  
Dust Formation

scholarly journals Dust Driven Winds from Pulsating Stars

1993 ◽  
Vol 137 ◽  
pp. 572-574 ◽  
Author(s):  
E.A. Dorfi ◽  
M.U. Feuchtinger ◽  
S. Höfner
Keyword(s):  
The Self ◽  
Time Dependent ◽  
Full Description ◽  
Stellar Winds ◽  
Dust Formation ◽  
Radiation Hydrodynamics ◽  
Simple Description ◽  
Pulsating Stars ◽  
Self Consistent ◽  
Different Parts

The cool extended atmospheres of late type giants are sites where dust formation takes place. Radiation pressure on the dust grains is an important force for driving the slow but massive winds observed in such objects. Existing calculations of dust driven stellar winds (e.g. Bowen 1988, Fleischer et al. 1991) suffer from the fact that they include approximations at various levels for different parts of the problem like the hydrodynamics or the dust formation. Furthermore they do not include time-dependent radiative transfer.In order to overcome these insufficiencies we plan to calculate self-consistent models of dust driven winds with a full description of both the radiation hydrodynamics and the time-dependent dust formation. As a first step, however, we concentrate our investigations on the self-consistent description of the radiation hydrodynamics adopting only a simple description of the dust opacities.

scholarly journals The Environments of Cool Stars

1988 ◽  
Vol 103 ◽  
pp. 57-64
Author(s):  
Robert E. Stencel
Keyword(s):  
Boundary Conditions ◽  
Physical Environment ◽  
Binary Star ◽  
Stellar Winds ◽  
Dust Formation ◽  
Tidal Forces ◽  
Cool Stars ◽  
Red Giant

AbstractThis review describes recent conclusions about the physical environment of red giant and supergiant stars. This includes coronae, chromospheres, dust formation and stellar winds. This knowledge can provide the boundary conditions for considering what role such objects play as members of binary star systems, where tidal forces and companion behavior alter observed characteristics.

scholarly journals Interacting stellar winds in a binary system

1981 ◽  
Vol 59 ◽  
pp. 499-502
Author(s):  
Sun Kwok
Keyword(s):  
Binary System ◽  
Mass Loss ◽  
Stellar Winds ◽  
Long Time ◽  
Wind Velocities ◽  
M Stars ◽  
Hr Diagram ◽  
Loss Rates

It is now known that strong stellar winds develop in stars mostly at the red and blue sides of the HR diagram. However, although the mass loss rates observed in O and M stars are comparable, the corresponding wind velocities are vastly different. It would thus be of great interest to find a binary system, containing both a cool and a hot star each with its own wind, and observe the resultant interaction. For a long time, α Sco (M1.5 Iab + B2.5 V) was the only known example (Kudritzki and Reimers 1978, van der Hucht et al. 1980). The situation in this case is best illustrated by a VLA map made by Gibson (1979) who finds that a shock develops at the surface of interaction of the two winds. In this paper I shall describe another binary system in which two stellar winds are interacting with dramatic effects.

scholarly journals Maximum black hole mass across cosmic time

2021 ◽  
Vol 504 (1) ◽  
pp. 146-154
Author(s):  
Jorick S Vink ◽  
Erin R Higgins ◽  
Andreas A C Sander ◽  
Gautham N Sabhahit
Keyword(s):  
Black Hole ◽  
Massive Star ◽  
Fundamental Problem ◽  
Cosmic Time ◽  
Host Galaxy ◽  
Stellar Winds ◽  
Key Points ◽  
Wave Event ◽  
M Stars ◽  
Proper Consideration

ABSTRACT At the end of its life, a very massive star is expected to collapse into a black hole (BH). The recent detection of an 85  M⊙ BH from the gravitational wave event GW 190521 appears to present a fundamental problem as to how such heavy BHs exist above the approximately 50  M⊙ pair-instability (PI) limit where stars are expected to be blown to pieces with no remnant left. Using mesa, we show that for stellar models with non-extreme assumptions, 90–100  M⊙ stars at reduced metallicity ($Z/\mbox{ $\mathrm{Z}_{\odot }$}\le 0.1$) can produce blue supergiant progenitors with core masses sufficiently small to remain below the fundamental PI limit, yet at the same time lose an amount of mass via stellar winds that is small enough to end up in the range of an ‘impossible’ 85  M⊙ BH. The two key points are the proper consideration of core overshooting and stellar wind physics with an improved scaling of mass-loss with iron (Fe) contents characteristic for the host galaxy metallicity. Our modelling provides a robust scenario that not only doubles the maximum BH mass set by PI, but also allows us to probe the maximum stellar BH mass as a function of metallicity and cosmic time in a physically sound framework.

scholarly journals Recurrent Dust Formation by Wolf-Rayet Stars

1991 ◽  
Vol 143 ◽  
pp. 417-420
Author(s):  
P.M. Williams ◽  
K.A. Van Der Hucht ◽  
P.S. Thé ◽  
P. Bouchet ◽  
G. Roberts
Keyword(s):  
Dust Emission ◽  
Infrared Emission ◽  
Circumstellar Dust ◽  
Stellar Winds ◽  
Dust Formation ◽  
Dust Grains

A number of Wolf-Rayet stars show variations of up to a factor of ten in their infrared emission on timescales of months to years while their photospheric luminosities remain unchanged. This can be interpreted in terms of variation in the rates at which dust grains form in their stellar winds. Our data show variable circumstellar dust emission from WR 70 (HD 137603), with an episode of enhanced dust formation in early 1989, and fading of emission by dust formed around WR 48a (in 1979) and WR 19 some time before our first observation in 1988. We consider their relation to WR 140 (HD 193793), which forms dust in its wind for a few months at intervals of 7.94 years.

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