scholarly journals Does Nature use neutral beams for interstellar plasma heating around compact objects?

2020 ◽  
Vol 495 (1) ◽  
pp. L51-L55
Author(s):  
E Churazov ◽  
I Khabibullin ◽  
R Sunyaev
Keyword(s):  
Plasma Heating ◽  
Compact Objects ◽  
Shock Acceleration ◽  
Injection Technique ◽  
Neutral Atoms ◽  
Lateral Direction ◽  
Interstellar Plasma ◽  
Astrophysical Objects ◽  
Gas Cooling ◽  
Distinct Features

ABSTRACT A neutral beam injection technique is employed in all major TOKAMAK facilities for heating of magnetically confined plasma. The question then arises, whether a similar mechanism might work in astrophysical objects? For instance, a hyper-Eddington Galactic binary SS433 possesses baryonic jets, moving at a quarter of the speed of light, and observations revealed signs of gas cooling and recombination on sub-pc scales and equally strong signs of powerful energy deposition on much larger scales ∼100 pc. Here, we consider a model where neutral atoms transport this energy. A sub-relativistic beam of neutral atoms penetrates the interstellar medium; these atoms gradually get ionized and deposit their energy over a region, whose longitudinal dimension is set by the ‘ionization length’. The channel, where the energy is deposited, expands sideways and drives a shock in the lateral direction. Once the density in the channel drops, the heating rate by the beam drops accordingly, and the region of the energy release moves along the direction of the beam. We discuss distinct features associated with this scenario and speculate that such configuration might also boost shock acceleration of the ‘pick-up’ protons that arise due to ionization of neutral atoms both upstream and downstream of the shock.

The DITE tokamak experiment

1981 ◽  
Vol 300 (1456) ◽  
pp. 535-545 ◽  
Keyword(s):  
Boundary Layer ◽  
Plasma Heating ◽  
Neutral Beam ◽  
Spent Fuel ◽  
Neutral Atoms ◽  
Fusion Reactions ◽  
Energetic Neutral Atoms ◽  
Hot Plasma

The expectation of power from fusion reactions currently involves magnetic containment of hot plasma in the tokamak toroidal configuration, and plasma heating by injection of energetic neutral atoms. Isolation of the plasma from the walls, to maintain the required purity, and exhaust of the spent fuel both involve the use of a divertor. This removes plasma from the boundary layer into a separate chamber. We report tests of these concepts in the Divertor Injection Tokamak Experiment (DITE) at Culham Laboratory. We also present the first measurements in a tokamak of the neutral-beam driven current. This demonstrates the principle of a continuously operating tokamak, with possible advantages for a reactor.

Avinash–Shukla mass limit for the maximum dust mass supported against gravity by electric fields

2010 ◽  
Vol 76 (3-4) ◽  
pp. 493-500 ◽  
Author(s):  
K. AVINASH
Keyword(s):  
Electric Fields ◽  
Stable Equilibrium ◽  
Compact Objects ◽  
Correlation Effects ◽  
Mass Limit ◽  
Interstellar Clouds ◽  
New Class ◽  
The Core ◽  
Dust Mass ◽  
Astrophysical Objects

AbstractThe existence of a new class of astrophysical objects, where gravity is balanced by the shielded electric fields associated with the electric charge on the dust, is shown. Further, a mass limit MA for the maximum dust mass that can be supported against gravitational collapse by these fields is obtained. If the total mass of the dust in the interstellar cloud MD > MA, the dust collapses, while if MD < MA, stable equilibrium may be achieved. Heuristic arguments are given to show that the physics of the mass limit is similar to the Chandrasekar's mass limit for compact objects and the similarity of these dust configurations with neutron and white dwarfs is pointed out. The effect of grain size distribution on the mass limit and strong correlation effects in the core of such objects is discussed. Possible location of these dust configurations inside interstellar clouds is pointed out.

Evidence for event horizons: Long-lived modes in ultracompact objects

2015 ◽  
Vol 24 (09) ◽  
pp. 1542023 ◽  
Author(s):  
Caio F. B. Macedo ◽  
Luís C. B. Crispino ◽  
Vitor Cardoso ◽  
Hirotada Okawa ◽  
Paolo Pani
Keyword(s):  
Strong Field ◽  
Null Geodesic ◽  
Compact Objects ◽  
Nonlinear Instability ◽  
Event Horizons ◽  
First Order ◽  
Astrophysical Objects ◽  
Theories Of Gravity ◽  
First Order Perturbation ◽  
Light Ring

Gravitational compact astrophysical objects are excellent laboratories to test the strong field regime of theories of gravity. Among these compact objects, lies the ultracompact class: stellar structures that possess a light ring (circular null geodesic). Such ultracompact stars were presented in literature in the earlier solutions of general relativity, and some are claimed to be good candidates to the supermassive objects present at the center of galaxies. In this paper, we present evidences for the claim that compact objects with a light ring should be black holes, based on the existence of long-lived modes obtained through a first-order perturbation theory. These first-order long-lived modes can source nonlinear terms which could turn the star unstable. We show, in particular, a comparison between modes computed through an exact direct integration and through the WKB approximation. Moreover, we present the time evolution of wavepackets for different field configurations. We conjecture some possible outcomes of the nonlinear instability. The discussion presented in this work complements our previous paper [Phys. Rev. D90 (2014) 044069].

scholarly journals Strange stars in energy–momentum-conserved f(R,T) gravity

2020 ◽  
Vol 29 (10) ◽  
pp. 2050075
Author(s):  
G. A. Carvalho ◽  
S. I. Dos Santos ◽  
P. H. R. S. Moraes ◽  
M. Malheiro
Keyword(s):  
Energy Momentum Tensor ◽  
Equations Of State ◽  
Linear Equations ◽  
Momentum Tensor ◽  
Compact Objects ◽  
Strange Stars ◽  
Cosmological Scenario ◽  
Astrophysical Objects ◽  
Tensor Formula ◽  
Tov Equation

For the accurate understanding of compact astrophysical objects, the Tolmann–Oppenheimer–Volkoff (TOV) equation has proved to be of great use. Nowadays, it has been derived in many alternative gravity theories, yielding the prediction of different macroscopic features for such compact objects. In this work, we apply the TOV equation of the energy–momentum–conserved version of the [Formula: see text] gravity theory to strange quark stars. The [Formula: see text] theory, with [Formula: see text] being a generic function of the Ricci scalar [Formula: see text] and trace of the energy–momentum tensor [Formula: see text] to replace [Formula: see text] in the Einstein–Hilbert gravitational action, has shown to provide a very interesting alternative to the cosmological constant [Formula: see text] in a cosmological scenario, particularly in the energy–momentum conserved case (a general [Formula: see text] function does not conserve the energy–momentum tensor). Here, we impose the condition [Formula: see text] to the astrophysical case, particularly the hydrostatic equilibrium of strange stars. We solve the TOV equation by taking into account linear equations of state to describe matter inside strange stars, such as [Formula: see text] and [Formula: see text], known as the MIT bag model, with [Formula: see text] the pressure and [Formula: see text] the energy density of the star, [Formula: see text] constant and [Formula: see text] the bag constant.

scholarly journals The first 5 years of gravitational-wave astrophysics

Science ◽  
2021 ◽  
Vol 372 (6546) ◽  
pp. eabc7397
Author(s):  
Salvatore Vitale
Keyword(s):  
General Relativity ◽  
Gravitational Wave ◽  
Electromagnetic Waves ◽  
Gamma Ray ◽  
Direct Consequence ◽  
Compact Objects ◽  
Tests Of General Relativity ◽  
Astrophysical Objects ◽  
Progenitor Stars ◽  
The Universe

Gravitational waves are ripples in spacetime generated by the acceleration of astrophysical objects; a direct consequence of general relativity, they were first directly observed in 2015. Here, I review the first 5 years of gravitational-wave detections. More than 50 gravitational-wave events have been found, emitted by pairs of merging compact objects such as neutron stars and black holes. These signals yield insights into the formation of compact objects and their progenitor stars, enable stringent tests of general relativity, and constrain the behavior of matter at densities higher than that of an atomic nucleus. Mergers that emit both gravitational and electromagnetic waves probe the formation of short gamma-ray bursts and the nucleosynthesis of heavy elements, and they measure the local expansion rate of the Universe.

scholarly journals Detection of Nonthermal Optical Flashes with 10−3-10−1 s Duration from Some LMXBs

1995 ◽  
Vol 151 ◽  
pp. 330-333
Author(s):  
G.M. Beskin ◽  
S.I. Neizvestny ◽  
S.N. Mitronova ◽  
V.L. Plokhotnichenko ◽  
M. Yu. Popova ◽  
...  
Keyword(s):  
Binary Systems ◽  
High Energy ◽  
Compact Objects ◽  
Registration System ◽  
X Ray ◽  
Multichannel Analysis ◽  
Astrophysical Objects ◽  
Very High Energy ◽  
Nonthermal Radio Emission ◽  
Optical Flashes

In order to study very rapid optical variability of astrophysical objects on time scales between 10−7 s and 102 s (Shvartsman 1977), at SAO the MANIA (Multichannel Analysis of Nanosecond Intensity Alterations) experiment is being used. A special photometric registration system and software has been developed (Beskin et al. 1982’ Plokhotnichenko 1983, Zhuravkov et al. 1994).One of the applications of these tools is the detection of radiation from accreted or ejected plasma near compact objects. A choice between two models of accretion onto compact objects in binary systems - hydrodynamic flow or magnetc flaring (Shakura & Sunyaev 1973, Pustil’nik & Shvartsman 1974) has not yet been made. Recent optical and X-ray observations of X-ray binaries provide information on their (fast) variability, their nonthermal radio emission, generation of very high energy particles, and nonthermal processes in rapid optical flares (Bartolini et al. 1994, Beskin et al. 1994). However, the data are not fully described by classical hydrodynamical models.

scholarly journals Multi-scale simulations of particle acceleration in astrophysical systems

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Alexandre Marcowith ◽  
Gilles Ferrand ◽  
Mickael Grech ◽  
Zakaria Meliani ◽  
Illya Plotnikov ◽  
...  
Keyword(s):  
Particle Acceleration ◽  
Energetic Particle ◽  
Large Scale ◽  
Numerical Study ◽  
Cosmic Ray ◽  
Compact Objects ◽  
Shock Acceleration ◽  
Fermi Acceleration ◽  
The Subject ◽  
Astrophysical Flows

AbstractThis review aims at providing an up-to-date status and a general introduction to the subject of the numerical study of energetic particle acceleration and transport in turbulent astrophysical flows. The subject is also complemented by a short overview of recent progresses obtained in the domain of laser plasma experiments. We review the main physical processes at the heart of the production of a non-thermal distribution in both Newtonian and relativistic astrophysical flows, namely the first and second order Fermi acceleration processes. We also discuss shock drift and surfing acceleration, two processes important in the context of particle injection in shock acceleration. We analyze with some details the particle-in-cell (PIC) approach used to describe particle kinetics. We review the main results obtained with PIC simulations in the recent years concerning particle acceleration at shocks and in reconnection events. The review discusses the solution of Fokker–Planck problems with application to the study of particle acceleration at shocks but also in hot coronal plasmas surrounding compact objects. We continue by considering large scale physics. We describe recent developments in magnetohydrodynamic (MHD) simulations. We give a special emphasis on the way energetic particle dynamics can be coupled to MHD solutions either using a multi-fluid calculation or directly coupling kinetic and fluid calculations. This aspect is mandatory to investigate the acceleration of particles in the deep relativistic regimes to explain the highest cosmic ray energies.

Studies of the Portal Venous System by Injection Technique

1951 ◽  
Vol 17 (2) ◽  
pp. 209-223 ◽  
Author(s):  
R.O. Holmes ◽  
W.V. Lovitt
Keyword(s):  
Venous System ◽  
Injection Technique ◽  
Portal Venous System

Plasma Components which Interfere with Ristocetin-induced Platelet Aggregation

1975 ◽  
Vol 33 (03) ◽  
pp. 540-546 ◽  
Author(s):  
Robert F Baugh ◽  
James E Brown ◽  
Cecil Hougie
Keyword(s):  
Platelet Aggregation ◽  
Human Plasma ◽  
Plasma Proteins ◽  
Binding Protein ◽  
Plasma Heating ◽  
Protein S ◽  
Fold Increase ◽  
Normal Human Plasma ◽  
Preliminary Examination ◽  
Normal Human

SummaryNormal human plasma contains a component or components which interfere with ristocetin-induced platelet aggregation. Preliminary examination suggests a protein (or proteins) which binds ristocetin and competes more effectively for ristocetin than do the proteins involved in ristocetin-induced platelet aggregation. The presence of this protein in normal human plasma also prevents ristocetin-induced precipitation of plasma proteins at levels of ristocetin necessary to produce platelet aggregation (0.5–2.0 mg/ml). Serum contains an apparent two-fold increase of this component when compared with plasma. Heating serum at 56° for one hour results in an additional 2 to 4 fold increase. The presence of a ristocetin-binding protein in normal human plasma requires that this protein be saturated with ristocetin before ristocetin-induced platelet aggregation will occur. Variations in the ristocetin-binding protein(s) will cause apparent discrepancies in ristocetin-induced platelet aggregation in normal human plasmas.

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