scholarly journals Shear-turbulence in rotating massive stars

1999 ◽  
Vol 193 ◽  
pp. 260-260
Author(s):  
Eugene Staritsin
Keyword(s):  
Angular Momentum ◽  
Main Sequence ◽  
Massive Stars ◽  
Stellar Surface ◽  
Stellar Radius ◽  
Shear Turbulence

Shear-turbulence in a radiative envelopes of rotating main sequence massive stars transports angular momentum from the deeper layers to the stellar surface. This process enlarges the influence of rotation on the stellar radius. As a result, the width of the main sequence increases.

scholarly journals Mass loss and evolution of hot massive stars

2008 ◽  
Vol 4 (S252) ◽  
pp. 271-281 ◽  
Author(s):  
Jorick S. Vink
Keyword(s):  
Angular Momentum ◽  
Mass Loss ◽  
Main Sequence ◽  
Gamma Ray ◽  
Massive Stars ◽  
Gamma Ray Bursts ◽  
Absorption Profile ◽  
Luminous Blue Variables ◽  
Progenitor Stars

AbstractWe discuss the role of mass loss for the evolution of the most massive stars, highlighting the role of the predicted bi-stability jump that might be relevant for the evolution of rotational velocities during or just after the main sequence. This mechanism is also proposed as an explanation for the mass-loss variations seen in the winds from Luminous Blue Variables (LBVs). These might be relevant for the quasi-sinusoidal modulations seen in a number of recent transitional supernovae (SNe), as well as for the double-throughed absorption profile recently discovered in the Hα line of SN 2005gj. Finally, we discuss the role of metallicity via the Z-dependent character of their winds, during both the initial and final (Wolf-Rayet) phases of evolution, with implications for the angular momentum evolution of the progenitor stars of long gamma-ray bursts (GRBs).

scholarly journals Evolution of rotation in rapidly rotating early-type stars during the main sequence with 2D models

2019 ◽  
Vol 625 ◽  
pp. A89 ◽  
Author(s):  
D. Gagnier ◽  
M. Rieutord ◽  
C. Charbonnel ◽  
B. Putigny ◽  
F. Espinosa Lara
Keyword(s):  
Angular Momentum ◽  
Mass Loss ◽  
Main Sequence ◽  
Massive Stars ◽  
Early Type ◽  
Wind Regime ◽  
Momentum Loss ◽  
Angular Momentum Loss ◽  
Rotational Evolution ◽  
Early Type Stars

The understanding of the rotational evolution of early-type stars is deeply related to that of anisotropic mass and angular momentum loss. In this paper, we aim to clarify the rotational evolution of rapidly rotating early-type stars along the main sequence (MS). We have used the 2D ESTER code to compute and evolve isolated rapidly rotating early-type stellar models along the MS, with and without anisotropic mass loss. We show that stars with Z = 0.02 and masses between 5 and 7 M⊙ reach criticality during the main sequence provided their initial angular velocity is larger than 50% of the Keplerian one. More massive stars are subject to radiation-driven winds and to an associated loss of mass and angular momentum. We find that this angular momentum extraction from the outer layers can prevent massive stars from reaching critical rotation and greatly reduce the degree of criticality at the end of the MS. Our model includes the so-called bi-stability jump of the Ṁ − Teff relation of 1D-models. This discontinuity now shows up in the latitude variations of the mass-flux surface density, endowing rotating massive stars with either a single-wind regime (no discontinuity) or a two-wind regime (a discontinuity). In the two-wind regime, mass loss and angular momentum loss are strongly increased at low latitudes inducing a faster slow-down of the rotation. However, predicting the rotational fate of a massive star is difficult, mainly because of the non-linearity of the phenomena involved and their strong dependence on uncertain prescriptions. Moreover, the very existence of the bi-stability jump in mass-loss rate remains to be substantiated by observations.

scholarly journals Rotation rates of massive stars in the Magellanic Clouds

2010 ◽  
Vol 6 (S272) ◽  
pp. 38-43
Author(s):  
Laura R. Penny ◽  
Douglas R. Gies
Keyword(s):  
Angular Momentum ◽  
Main Sequence ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Evolutionary Models ◽  
Rotation Rates ◽  
Angular Momentum Loss ◽  
Kolmogorov Smirnov ◽  
Statistical Results ◽  
Smirnov Test

AbstractWe present the results of our survey of the projected rotational velocities of 161 O-type stars in the Magellanic Clouds from archival FUSE observations. The evolved and unevolved samples from each environment are compared through the Kolmogorov-Smirnov test to determine if the distribution of equatorial rotational velocities is metallicity dependent for these massive objects. Stellar interior models predict that massive stars with SMC metallicity will have significantly reduced angular momentum loss on the main sequence compared to their Galactic counterparts. Our statistical results find some support for this prediction but also show that even at Galactic metallicity, evolved and unevolved massive stars have fairly similar fractions of stars with large V sin i. What is more compelling are the few evolved objects in the Magellanic Clouds with rotational velocities that approach or even exceed those predicted from the evolutionary models.

scholarly journals Centrifugally driven mass-loss and outbursts of massive stars

2020 ◽  
Vol 495 (1) ◽  
pp. 249-265 ◽  
Author(s):  
Xihui Zhao ◽  
Jim Fuller
Keyword(s):  
Angular Momentum ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Main Sequence ◽  
Massive Stars ◽  
Variable Stars ◽  
Be Stars ◽  
Rotational Evolution ◽  
Break Up ◽  
Ultimate Fate

ABSTRACT Rotation and mass-loss are crucially interlinked properties of massive stars, strongly affecting their evolution and ultimate fate. Massive stars rotating near their break-up limit shed mass centrifugally, creating Be stars with circumstellar discs and possibly driving outbursts. Using the mesa stellar evolution code, we examine the effects of efficient angular momentum transport on the main-sequence and post-main-sequence rotational evolution of massive stars. In rapid rotators, angular momentum transported from the contracting core to the expanding envelope can spin-up the surface layers past the break-up rate, particularly for stars near (or beyond) the end of the main-sequence and in low-metallicity environments. We also demonstrate that centrifugal instabilities could arise in rapidly rotating massive stars, potentially triggering the S Doradus outbursts observed in luminous blue variable stars. Prior mass accretion from a binary companion increases both the likelihood and the intensity of centrifugal mass-loss. We discuss implications for massive stellar evolution, Be stars, and luminous blue variables.

SPECIFIC ANGULAR MOMENTUM DISTRIBUTION FOR SOLAR ANALOGS AND TWINS: WHERE IS THE SUN MISSING HIS ANGULAR MOMENTUM?

2012 ◽  
Vol 18 ◽  
pp. 58-62
Author(s):  
J. S. DA COSTA ◽  
J. D. DO NASCIMENTO
Keyword(s):  
Angular Momentum ◽  
Spectral Type ◽  
Momentum Distribution ◽  
Main Sequence ◽  
Mass Range ◽  
Large Mass ◽  
Global Behavior ◽  
The Sun ◽  
Stellar Radius ◽  
Solar Analogs

It is well established that there is a breakdown in the curve of specific angular momentum as a function of mass for stars on the main sequence Ref. 5. Stars earlier than F5 and more massive than the sun, rotate rapidly over a large mass range. For spectral type F5 and later, including the Sun, much smaller rotational velocities are found. We revisit this question from a new sample to shed a light on the basis of a sample solar twins and analogs recently observed by interferometric measurements of stellar radius. Our results clearly show that, as the Sun, the solar twins present similar global behavior from their specific angular momentum. 18 Sco and HIP 100963 have a specific angular momentum one order higher than the solar value, and HIP 55459 and HIP 56948 have a specific angular momentum one order lower than the solar value.

scholarly journals The pre-supernova evolution of rotating massive stars

2003 ◽  
Vol 212 ◽  
pp. 357-364 ◽  
Author(s):  
Alexander Heger ◽  
Stan E. Woosley ◽  
Norbert Langer
Keyword(s):  
Angular Momentum ◽  
Magnetic Fields ◽  
Main Sequence ◽  
Massive Stars ◽  
Iron Core ◽  
Core Collapse ◽  
Mode Instability ◽  
Angular Momentum Transport ◽  
Explosion Mechanism ◽  
Chemical Mixing

Massive stars are born rotating rigidly with a significant fraction of critical rotation at the surface. Consequently, rotationally-induced circulation and instabilities lead to chemical mixing in regions that would otherwise be stable, as well as a redistribution of angular momentum. Differential rotation also winds up magnetic fields, causing instabilities that can power a dynamo and magnetic stresses that lead to additional angular momentum transport. We follow the evolution of typical massive stars, their structure and angular momentum distribution, from the zero-age main sequence until iron core collapse. Without the action of magnetic fields, the resulting angular momentum is sufficiently large to significantly affect the explosion mechanism and neutron star formation. Sub-millisecond pulsars result that could encounter the r-mode instability. In helium cores massive enough, at least at low metalicity, the angular momentum is also sufficiently great to form a centrifugally supported accretion disk around a central black hole, powering the engine of the ‘collapsar’ model for GRBs. Including current estimates of the effect of magnetic fields still allows the formation of rapidly rotating (~ 5-10 ms) pulsars, but might leave too little angular momentum for collapsars.

scholarly journals Presupernova Evolution of Rotating Massive Stars and the Rotation Rate of Pulsars

2004 ◽  
Vol 215 ◽  
pp. 591-600 ◽  
Author(s):  
A. Heger ◽  
S. E. Woosley ◽  
N. Langer ◽  
H. C. Spruit
Keyword(s):  
Angular Momentum ◽  
Neutron Stars ◽  
Rotation Rate ◽  
Main Sequence ◽  
Gamma Ray ◽  
Massive Stars ◽  
Hydrodynamic Instabilities ◽  
Order Of Magnitude ◽  
Advanced Stages ◽  
Explosion Mechanism

Rotation in massive stars has been studied on the main sequence and during helium burning for decades, but only recently have realistic numerical simulations followed the transport of angular momentum that occurs during more advanced stages of evolution. The results affect such interesting issues as whether rotation is important to the explosion mechanism, whether supernovae are strong sources of gravitational radiation, the star's nucleosynthesis, and the initial rotation rate of neutron stars and black holes. We find that when only hydrodynamic instabilities (shear, Eddington-Sweet, etc.) are included in the calculation, one obtains neutron stars spinning at close to critical rotation at their surface – or even formally in excess of critical. When recent estimates of magnetic torques (Spruit 2002) are added, however, the evolved cores spin about an order of magnitude slower. This is still more angular momentum than observed in young pulsars, but too slow for the collapsar model for gamma-ray bursts.

scholarly journals Angular momentum loss and stellar spin-down in magnetic massive stars

2008 ◽  
Vol 4 (S259) ◽  
pp. 423-424
Author(s):  
Asif ud-Doula ◽  
Stanley P. Owocki ◽  
Richard H.D. Townsend
Keyword(s):  
Angular Momentum ◽  
Massive Stars ◽  
Solid Angle ◽  
Magnetic Confinement ◽  
Dipole Field ◽  
Hot Stars ◽  
Momentum Loss ◽  
Dipole Magnetic Field ◽  
Angular Momentum Loss ◽  
Compare And Contrast

AbstractWe examine the angular momentum loss and associated rotational spin-down for magnetic hot stars with a line-driven stellar wind and a rotation-aligned dipole magnetic field. Our analysis here is based on our previous 2-D numerical MHD simulation study that examines the interplay among wind, field, and rotation as a function of two dimensionless parameters, W(=Vrot/Vorb) and ‘wind magnetic confinement’, η∗ defined below. We compare and contrast the 2-D, time variable angular momentum loss of this dipole model of a hot-star wind with the classical 1-D steady-state analysis by Weber and Davis (WD), who used an idealized monopole field to model the angular momentum loss in the solar wind. Despite the differences, we find that the total angular momentum loss averaged over both solid angle and time follows closely the general WD scaling ~ ṀΩR2A. The key distinction is that for a dipole field Alfvèn radius RA is significantly smaller than for the monopole field WD used in their analyses. This leads to a slower stellar spin-down for the dipole field with typical spin-down times of order 1 Myr for several known magnetic massive stars.

scholarly journals The VLT-FLAMES Tarantula Survey

2016 ◽  
Vol 12 (S329) ◽  
pp. 279-286
Author(s):  
Jorick S. Vink ◽  
C.J. Evans ◽  
J. Bestenlehner ◽  
C. McEvoy ◽  
O. Ramírez-Agudelo ◽  
...  
Keyword(s):  
Mass Loss ◽  
Main Sequence ◽  
Massive Stars ◽  
Mass Function ◽  
Large Magellanic Cloud ◽  
Initial Mass Function ◽  
Data Set ◽  
Large Program ◽  
Medium Resolution ◽  
Key Questions

AbstractWe present a number of notable results from the VLT-FLAMES Tarantula Survey (VFTS), an ESO Large Program during which we obtained multi-epoch medium-resolution optical spectroscopy of a very large sample of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). This unprecedented data-set has enabled us to address some key questions regarding atmospheres and winds, as well as the evolution of (very) massive stars. Here we focus on O-type runaways, the width of the main sequence, and the mass-loss rates for (very) massive stars. We also provide indications for the presence of a top-heavy initial mass function (IMF) in 30 Dor.

scholarly journals Radiative-transfer modelling of funnel flows

2007 ◽  
Vol 3 (S243) ◽  
pp. 83-94
Author(s):  
Tim J. Harries
Keyword(s):  
Numerical Methods ◽  
Radiative Transfer ◽  
Emission Line ◽  
Main Sequence ◽  
Line Profiles ◽  
Stellar Radius ◽  
Transfer Modelling ◽  
Synthetic Line ◽  
Made In ◽  
Geometry And Kinematics

AbstractEmission line profiles from pre-main-sequence objects accreting via magnetically-controlled funnel flows encode information on the geometry and kinematics of the material on stellar radius scales. In order to extract this information it is necessary to perform radiative-transfer modelling of the gas to produce synthetic line profiles. In this review I discuss the physics that needs to be included in such models, and the numerical methods and assumptions that are used to render the problem tractable. I review the progress made in the field over the last decade, and summarize the main successes and failures of the modelling work.

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