scholarly journals Evaluation of thermal- nuclear effects from pair-creation in the final fate very-massive stars

2021 ◽  
Vol 14 (1) ◽  
pp. 237-250
Author(s):  
L. Garba ◽  
E. A. Chidi ◽  
F.S. Koki
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Pair Creation ◽  
Lower Mass ◽  
Core Mass ◽  
Electron Positron ◽  
Solar Metallicity ◽  
Low Metallicity ◽  
Nuclear Effects ◽  
Electron Positron Pair

Thermonuclear conditions found in explosive massive-stars requirethe use of not only efficient, accurate but thermodynamically consistent stellar equation of state (EOS) routines.The use of tables to describe EoS involved in stellar models is very much needed in understanding the final fate of massive stars. Many massive-low metallicity stars end their life as pair creation supernova (PCSN) through the creation of electron-positron pairs.We used thermodynamically consistent EoS tables to numerically evaluate the thermonuclear effects of the electron electron-positron pair creation in rotating 150 and 200 Massive starsat SMC and rotating and non-rotating 500 M⊙at LMC.As expected, the effect of rotationofreducing the oxygen core masshad increasedthe thermal energy within the threshold of the pair-creation instability.Similarly, lower mass loss stars with SMC model produced higher thermal energies,which can cmpletely explode the stars as PCSNe without remnant.On the other hand, the non-rotating 500 M⊙ might have only reached the instability region due to its lower metallicity (compared to solar metallicity) that iscapable of suppressing the mass loss such that the thermonuclear energy maintains certain amount of elements into the pair creation region. At the final explosion of the stars, the helium core mass educed the thermal energies in trying to avoid the pair-creation region. Many implications of these results for the evolution and explosion of massive stars are discussed.

scholarly journals Is GW190521 the merger of black holes from the first stellar generations?

2020 ◽  
Author(s):  
Eoin J Farrell ◽  
Jose H Groh ◽  
Raphael Hirschi ◽  
Laura Murphy ◽  
Etienne Kaiser ◽  
...  
Keyword(s):  
Black Holes ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Massive Stars ◽  
Compact Star ◽  
Binary Interaction ◽  
Core Mass ◽  
Convective Mixing ◽  
Low Metallicity ◽  
Instability Regime

Abstract GW190521 challenges our understanding of the late-stage evolution of massive stars and the effects of the pair-instability in particular. We discuss the possibility that stars at low or zero metallicity could retain most of their hydrogen envelope until the pre-supernova stage, avoid the pulsational pair-instability regime and produce a black hole with a mass in the mass gap by fallback. We present a series of new stellar evolution models at zero and low metallicity computed with the Geneva and MESA stellar evolution codes and compare to existing grids of models. Models with a metallicity in the range 0 – 0.0004 have three properties which favour higher BH masses. These are (i) lower mass-loss rates during the post-MS phase, (ii) a more compact star disfavouring binary interaction and (iii) possible H-He shell interactions which lower the CO core mass. We conclude that it is possible that GW190521 may be the merger of black holes produced directly by massive stars from the first stellar generations. Our models indicate BH masses up to 70-75 M⊙. Uncertainties related to convective mixing, mass loss, H-He shell interactions and pair-instability pulsations may increase this limit to ∼85M⊙.

Vacuum polarization and particle creation in the presence of a potential step

2016 ◽  
Vol 31 (02n03) ◽  
pp. 1641031 ◽  
Author(s):  
S. P. Gavrilov ◽  
D. M. Gitman
Keyword(s):  
Electric Potential ◽  
Canonical Quantization ◽  
Particle Creation ◽  
Pair Creation ◽  
Dirac Field ◽  
Potential Step ◽  
Electron Positron ◽  
Physical Impact ◽  
Particle Interpretation ◽  
Electron Positron Pair

We consider QED with strong external backgrounds that are concentrated in restricted space areas. The latter backgrounds represent a kind of spatial x-electric potential steps for charged particles. They can create particles from the vacuum, the Klein paradox being closely related to this process. We describe a canonical quantization of the Dirac field with x-electric potential step in terms of adequate in- and out-creation and annihilation operators that allow one to have consistent particle interpretation of the physical system under consideration and develop a nonperturbative (in the external field) technics to calculate scattering, reflection, and electron-positron pair creation. We resume the physical impact of this development.

scholarly journals Mass loss and evolution of massive stars in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 480-482 ◽  
Author(s):  
Claus Leitherer ◽  
Norbert Langer
Keyword(s):  
Mass Loss ◽  
Iterative Procedure ◽  
Metal Content ◽  
Loss Rate ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Magellanic Clouds ◽  
Evolutionary Models ◽  
Low Metallicity ◽  
Self Consistency

The structure and evolution of massive stars is significantly influenced by effects of chemical composition in a low-metallicity environment (as compared to the solar neighbourhood, SN), such as the Magellanic Clouds. A fundamental ingredient in evolutionary models is the stellar mass-loss rate M. Lower metal content decreases the mass-loss rates derived theoretically, which in turn affects the stellar evolution models. On the other hand, different evolutionary models predict different stellar parameters (especially L), which again influence M so that an iterative procedure is required to achieve self-consistency.

scholarly journals Modes of Energy Loss from Isolated Magnetized Neutron Star

1987 ◽  
Vol 125 ◽  
pp. 450-450
Author(s):  
S. Shibata
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Gamma Ray ◽  
Rotational Energy ◽  
Pair Creation ◽  
Dipole Radiation ◽  
Pair Plasma ◽  
Electron Positron ◽  
Closed Current ◽  
Electron Positron Pair

Pulsar may be regarded as a discharge tube by electron-positron pair creation. On this viewpoint we carry out two numerical calculations. The obtained magnetic field is consistent with the flow. We find that pulsars emit their rotational energy through three modes simultaneously. The three modes are (1)relativistic acceleration and following gamma-ray emission in the closed current circuit in the magnetosphere, (2)wind of the electron-positron pair plasma, and (3)dipole radiation.

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