scholarly journals Wind anisotropy and stellar evolution

2008 ◽  
Vol 4 (S255) ◽  
pp. 199-203
Author(s):  
Cyril Georgy ◽  
Georges Meynet ◽  
André Maeder
Keyword(s):  
Angular Momentum ◽  
Massive Star ◽  
Gamma Ray ◽  
Massive Stars ◽  
Gamma Ray Bursts ◽  
Surface Velocity ◽  
Hot Stars ◽  
Low Metallicity ◽  
Determinant Factor ◽  
Fast Rotating

AbstractMass loss is a determinant factor which strongly affects the evolution and the fate of massive stars. At low metallicity, stars are supposed to rotate faster than at the solar one. This favors the existence of stars near the critical velocity. In this rotation regime, the deformation of the stellar surface becomes important, and wind anisotropy develops. Polar winds are expected to be dominant for fast rotating hot stars.These polar winds allow the star to lose large quantities of mass and still retain a high angular momentum, and they modify the evolution of the surface velocity and the final angular momentum retained in the star's core. We show here how these winds affect the final stages of massive stars, according to our knowledge about Gamma Ray Bursts. Computation of theoretical Gamma Ray Bursts rate indicates that our models have too fast rotating cores, and that we need to include an additional effect to spin them down. Magnetic fields in stars act in this direction, and we show how they modify the evolution of massive star up to the final stages.

scholarly journals Supernovae and Gamma-ray Bursts

2011 ◽  
Vol 7 (S279) ◽  
pp. 75-82
Author(s):  
Paolo A. Mazzali
Keyword(s):  
Black Hole ◽  
Massive Star ◽  
Gamma Ray ◽  
Massive Stars ◽  
Observational Evidence ◽  
Gamma Ray Bursts ◽  
Core Collapse ◽  
Broad Absorption ◽  
X Ray ◽  
Long Duration

AbstractThe properties of the Supernovae discovered in coincidence with long-duration Gamma-ray Bursts and X-Ray Flashes are reviewed, and compared to those of SNe for which GRBs are not observed. The SNe associated with GRBs are of Type Ic, they are brighter than the norm, and show very broad absorption lines in their spectra, indicative of high expansion velocities and hence of large explosion kinetic energies. This points to a massive star origin, and to the birth of a black hole at the time of core collapse. There is strong evidence for gross asymmetries in the SN ejecta. The observational evidence seems to suggest that GRB/SNe are more massive and energetic than XRF/SNe, and come from more massive stars. While for GRB/SNe the collapsar model is favoured, XRF/SNe may host magnetars.

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 DIVISION IV / WORKING GROUP MASSIVE STARS

2008 ◽  
Vol 4 (T27A) ◽  
pp. 236-239
Author(s):  
Stanley P. Owocki ◽  
Paul A. Crowther ◽  
Alexander W. Fullerton ◽  
Gloria Koenigsberger ◽  
Norbert Langer ◽  
...  
Keyword(s):  
Working Group ◽  
Gamma Ray ◽  
Massive Stars ◽  
Gamma Ray Bursts ◽  
Core Collapse ◽  
Hot Stars ◽  
First Stars ◽  
Ob Stars ◽  
Red Supergiants

Our Working Group studies massive, luminous stars, with historical focus on early-type (OB) stars, but extending in recent years to include massive red supergiants that evolve from hot stars. There is also emphasis on the role of massive stars in other branches of astrophysics, particularly regarding starburst galaxies, the first stars, core-collapse gamma-ray bursts, and formation of massive stars.

scholarly journals Supernovae, Gamma-Ray Bursts and Stellar Rotation

2004 ◽  
Vol 215 ◽  
pp. 601-612 ◽  
Author(s):  
S. E. Woosley ◽  
A. Heger
Keyword(s):  
Angular Momentum ◽  
Neutron Star ◽  
Gamma Ray ◽  
Massive Stars ◽  
Supernova Explosion ◽  
Gamma Ray Bursts ◽  
Iron Core ◽  
Stellar Rotation ◽  
Explosion Mechanism ◽  
Stellar Mergers

One of the most dramatic possible consequences of stellar rotation is its influence on stellar death, particularly of massive stars. If the angular momentum of the iron core when it collapses is such as to produce a neutron star with a period of 5 ms or less, rotation will have important consequences for the supernova explosion mechanism. Still shorter periods, corresponding to a neutron star rotating at break up, are required for the progenitors of gamma-ray bursts (GRBs). Current stellar models, while providing an excess of angular momentum to pulsars, still fall short of what is needed to make GRBs. The possibility of slowing young neutron stars in ordinary supernovae by a combination of neutrino-powered winds and the propeller mechanism is discussed. The fall back of slowly moving ejecta during the first day of the supernova may be critical. GRBs, on the other hand, probably require stellar mergers for their production and perhaps less efficient mass loss and magnetic torques than estimated thus far.

scholarly journals Explosions from stellar collapse

2003 ◽  
Vol 212 ◽  
pp. 377-386
Author(s):  
Chris L. Fryer
Keyword(s):  
Potential Energy ◽  
Gravitational Potential ◽  
Massive Star ◽  
Gamma Ray ◽  
Massive Stars ◽  
Power Source ◽  
Gamma Ray Bursts ◽  
Gravitational Potential Energy ◽  
Stellar Collapse ◽  
The Universe

The collapse of a massive star releases a considerable amount of gravitational potential energy. This energy is believed to be the power source of some of the largest explosions in the universe: supernovae, hypernovae, gamma-ray bursts. In this proceedings, we review the mechanisms by which the potential energy from stellar collapse can be tapped to produce these strong explosions, emphasizing how our understanding of massive stars can help constrain these mechanisms.

scholarly journals The Life and Death of Massive Stars in the Starburst Galaxy I Zw 18

2015 ◽  
Vol 11 (A29B) ◽  
pp. 215-216
Author(s):  
Dorottya Szécsi ◽  
Norbert Langer
Keyword(s):  
Stellar Evolution ◽  
Gamma Ray ◽  
Massive Stars ◽  
Gamma Ray Bursts ◽  
Starburst Galaxy ◽  
Life And Death ◽  
Long Duration ◽  
Low Metallicity ◽  
The Universe ◽  
Evolution Proceeds

AbstractMassive stars at low metallicity are strong candidates for two of the most energetic explosions in the Universe: long duration gamma-ray bursts and superluminous supernovae. But what is the reason these explosions prefer low metallicity environments? To answer this question, we investigate how massive stellar evolution proceeds in low metallicity environments.

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 DDO68-V1: an extremely metal-poor LBV in a void galaxy

2018 ◽  
Vol 14 (S344) ◽  
pp. 392-395
Author(s):  
Yulia Perepelitsyna ◽  
Simon Pustilnik
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Stars ◽  
Rare Event ◽  
Local Universe ◽  
Hii Region ◽  
V Band ◽  
Star Evolution ◽  
Low Metallicity ◽  
Massive Star Evolution

AbstractThe lowest metallicity massive stars in the Local Universe with $Z\sim \left( {{Z}_{\odot }}/50-{{Z}_{\odot }}/30 \right)$ are the crucial objects to test the validity of assumptions in the modern models of very low-metallicity massive star evolution. These models, in turn, have major implications for our understanding of galaxy and massive star formation in the early epochs. DDO68-V1 in a void galaxy DDO68 is a unique extremely metal-poor massive star. Discovered by us in 2008 in the HII region Knot3 with $Z={{Z}_{\odot }}/35\,\left[ 12+\log \left( \text{O/H} \right)\sim 7.14 \right]$, DDO68-V1 was identified as an LBV star. We present here the LBV lightcurve in V band, combining own new data and the last archive and/or literature data on the light of Knot3 over the 30 years. We find that during the years 2008-2011 the LBV have experienced a very rare event of ‘giant eruption’ with V-band amplitude of 4.5 mag ($V\sim {{24.5}^{m}}-{{20}^{m}}$).

scholarly journals UNVEILING THE SECRETS OF METALLICITY AND MASSIVE STAR FORMATION USING DLAS ALONG GAMMA-RAY BURSTS

2015 ◽  
Vol 804 (1) ◽  
pp. 51 ◽  
Author(s):  
A. Cucchiara ◽  
M. Fumagalli ◽  
M. Rafelski ◽  
D. Kocevski ◽  
J. X. Prochaska ◽  
...  
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Massive Star Formation

scholarly journals The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars

2020 ◽  
Vol 493 (1) ◽  
pp. 518-535 ◽  
Author(s):  
Z Keszthelyi ◽  
G Meynet ◽  
M E Shultz ◽  
A David-Uraz ◽  
A ud-Doula ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Magnetic Fields ◽  
Massive Star ◽  
Massive Stars ◽  
Rotation Rates ◽  
Momentum Loss ◽  
Star Models ◽  
Surface Rotation ◽  
Angular Momentum Loss ◽  
Magnetic Braking

ABSTRACT The time evolution of angular momentum and surface rotation of massive stars are strongly influenced by fossil magnetic fields via magnetic braking. We present a new module containing a simple, comprehensive implementation of such a field at the surface of a massive star within the Modules for Experiments in Stellar Astrophysics (mesa) software instrument. We test two limiting scenarios for magnetic braking: distributing the angular momentum loss throughout the star in the first case, and restricting the angular momentum loss to a surface reservoir in the second case. We perform a systematic investigation of the rotational evolution using a grid of OB star models with surface magnetic fields (M⋆ = 5–60 M⊙, Ω/Ωcrit = 0.2–1.0, Bp = 1–20 kG). We then employ a representative grid of B-type star models (M⋆ = 5, 10, 15 M⊙, Ω/Ωcrit = 0.2, 0.5, 0.8, Bp = 1, 3, 10, 30 kG) to compare to the results of a recent self-consistent analysis of the sample of known magnetic B-type stars. We infer that magnetic massive stars arrive at the zero-age main sequence (ZAMS) with a range of rotation rates, rather than with one common value. In particular, some stars are required to have close-to-critical rotation at the ZAMS. However, magnetic braking yields surface rotation rates converging to a common low value, making it difficult to infer the initial rotation rates of evolved, slowly rotating stars.

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