Instabilities in the Envelopes and Winds of Very Massive Stars

Owocki, S. P.

doi:10.1007/978-3-319-09596-7_5

Cited by 45 publications

(26 citation statements)

References 62 publications

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“…Vink et al 2001;Smith & Owocki 2006;Vink et al 2011); less well understood continuum driven mass loss and envelope instabilities which may play an important role in luminous blue variables (e.g. Bestenlehner et al 2014;Owocki 2015;Petrov et al 2016); and mass loss where grain formation is important, as in red supergiants (RSGs; Voors et al 2000;Groenewegen et al 2009). Of these, line-driven mass loss is most studied and best understood.…”

Section: Pre-explosive Mass Loss and Opacitymentioning

confidence: 99%

“…Higher opacities favor a larger stellar radius and hence greater mass loss. The OPAL opacities used here (Rogers & Iglesias 1992;Iglesias & Rogers 1996) have a well-known "iron bump" at low temperature that can lead to artificial density inversions in the outer envelopes of RSGs (Owocki 2015). This tends to overinflate the star and thus boost its mass loss.…”

Section: Pre-explosive Mass Loss and Opacitymentioning

confidence: 99%

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Pulsational Pair-instability Supernovae

Woosley

2017

ApJ

716

796

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The final evolution of stars in the mass range 70 -140 M is explored. Depending upon their mass loss history and rotation rates, these stars will end their lives as pulsational pair-instability supernovae producing a great variety of observational transients with total durations ranging from weeks to millennia and luminosities from 10 41 to over 10 44 erg s −1 . No non-rotating model radiates more than 5 × 10 50 erg of light or has a kinetic energy exceeding 5 × 10 51 erg, but greater energies are possible, in principle, in magnetar-powered explosions which are explored. Many events resemble Type Ibn, Icn, and IIn supernovae, and some potential observational counterparts are mentioned. Some PPISN can exist in a dormant state for extended periods, producing explosions millennia after their first violent pulse. These dormant supernovae contain bright Wolf-Rayet stars, possibly embedded in bright x-ray and radio sources. The relevance of PPISN to supernova impostors like Eta Carinae, to super-luminous supernovae, and to sources of gravitational radiation is discussed. No black holes between 52 and 133 M are expected from stellar evolution in close binaries.

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Section: Pre-explosive Mass Loss and Opacitymentioning

confidence: 99%

Section: Pre-explosive Mass Loss and Opacitymentioning

confidence: 99%

Pulsational Pair-instability Supernovae

Woosley

2017

ApJ

716

796

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“…Radiative forces of high luminosity young massive stars are accelerating near-surface layers initiating fast winds and stellar mass loss. Simulations of the line-driven stellar winds require a careful study of the instabilities at different scales, clumping and porosity effects Abbott (1982), Owocki et al (1988), Kudritzki and Puls (2000), Puls et al (2008), Owocki (2014) to model the dependence of mass loss and wind terminal velocity on the metallicity and stellar rotation and to establish the maximal mass limit and pursue evolution of young massive stars.…”

Section: Hydrodynamical Models Of Massive Star Winds and Superbubblesmentioning

confidence: 99%

Nonthermal particles and photons in starburst regions and superbubbles

Bykov

2014

Astron Astrophys Rev

114

102

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Starforming factories in galaxies produce compact clusters and loose associations of young massive stars. Fast radiation-driven winds and supernovae input their huge kinetic power into the interstellar medium in the form of highly supersonic and superalfvenic outflows. Apart from gas heating, collisionless relaxation of fast plasma outflows results in fluctuating magnetic fields and energetic particles. The energetic particles comprise a long-lived component which may contain a sizeable fraction of the kinetic energy released by the winds and supernova ejecta and thus modify the magnetohydrodynamic flows in the systems. We present a concise review of observational data and models of nonthermal emission from starburst galaxies, superbubbles, and compact clusters of massive stars. Efficient mechanisms of particle acceleration and amplification of fluctuating magnetic fields with a wide dynamical range in starburst regions are discussed. Sources of cosmic rays, neutrinos and multi-wavelength nonthermal emission associated with starburst regions including potential galactic "PeVatrons" are reviewed in the global galactic ecology context.

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“…A tidal spin-up of the star may be sufficient to trigger some kind of rotational instability and it may not be necessary to invoke an additional internal instability. Owocki (2005) suggested that the rapid (near-critical) stellar rotation of η Car induces an equatorial gravity darkening. While the radiative flux itself scales in proportion to the effective surface gravity, the mass flux scales directly with effective gravity, i.e., it is, contrary to intuitive expectations, at minimum near the equator and at maximum near the poles (Owocki et al 1996).…”

Section: Possible Scenarios For the Observed Changes In η Carmentioning

confidence: 99%

Near-infrared evidence for a sudden temperature increase in Eta Carinae

Mehner¹,

Ishibashi²,

Whitelock³

et al. 2014

A&A

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Aims. Eta Car's ultra-violet, optical, and X-ray light curves and its spectrum suggest a physical change in its stellar wind over the last decade. It was proposed that the mass-loss rate decreased by a factor of about 2 in the last 15 years. We complement these recent results by investigating the past evolution and the current state of η Car in the near-infrared (IR). Results. The long-term brightening trends in η Car's JHKL light curves were discontinuous around the 1998 periastron passage. After 1998, the star shows excess emission above the extrapolated trend from earlier dates, foremost in J and H, and the blueward, cyclical progression in its near-IR colors is accelerated. The near-IR color evolution is strongly correlated with the periastron passages. After correcting for the secular trend we find that the color evolution matches an apparent increase in blackbody temperature of an optically thick near-IR emitting plasma component from about 3500 to 6000 K over the last 20 years. Conclusions. We suggest that the changing near-IR emission may be caused by variability in optically thick bremsstrahlung emission. Periastron passages play a key role in the observed excess near-IR emission after 1998 and the long-term color evolution. We thus propose as a hypothesis that angular momentum transfer (via tidal acceleration) during periastron passages leads to sudden changes in η Car's atmosphere resulting in a long-term decrease in the mass-loss rate.

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Instabilities in the Envelopes and Winds of Very Massive Stars

Cited by 45 publications

References 62 publications

Pulsational Pair-instability Supernovae

Pulsational Pair-instability Supernovae

Nonthermal particles and photons in starburst regions and superbubbles

Near-infrared evidence for a sudden temperature increase in Eta Carinae

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