scholarly journals SPIN LIGHT OF NEUTRINO IN GRAVITATIONAL FIELDS

2005 ◽  
Vol 14 (02) ◽  
pp. 309-321 ◽  
Author(s):  
MAXIM DVORNIKOV ◽  
ALEXANDER GRIGORIEV ◽  
ALEXANDER STUDENIKIN
Keyword(s):  
Black Hole ◽  
Gamma Rays ◽  
Dense Matter ◽  
Total Power ◽  
Fourth Power ◽  
Gravitational Fields ◽  
Quasiclassical Theory ◽  
Relativistic Jet ◽  
First Time ◽  
Gamma Factor

We develop the quasiclassical theory of a massive neutrino spin evolution in the presence of gravitational fields, and the corresponding probability of the neutrino spin oscillations in gravitational fields is derived for the first time. On this basis we also predict a new mechanism for electromagnetic radiation by a neutrino moving in the vicinity of gravitating objects (the "spin light of neutrino," SLν, in gravitational fields). It is shown that the total power of this radiation is proportional to the neutrino gamma factor to the fourth power, and the emitted photon energy, for the case of an ultra relativistic neutrino, spans up to gamma-rays. We investigate the SLν caused by both gravitational and electromagnetic fields, also accounting for effects of arbitrary moving and polarized matter, in various astrophysical environments. In particular, we discuss the SLν emitted by a neutrino moving in the vicinity of a rotating neutron star, black hole surrounded by dense matter, as well as by a neutrino propagating in the relativistic jet from a quasar.

scholarly journals On the formation and stability of fermionic dark matter halos in a cosmological framework

2020 ◽  
Author(s):  
Carlos R Argüelles ◽  
Manuel I Díaz ◽  
Andreas Krut ◽  
Rafael Yunis
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Space Distribution ◽  
Coarse Grained ◽  
Dark Matter Halos ◽  
The Core ◽  
The Galaxy ◽  
Gravitating Systems ◽  
The Given ◽  
First Time

Abstract The formation and stability of collisionless self-gravitating systems is a long standing problem, which dates back to the work of D. Lynden-Bell on violent relaxation, and extends to the issue of virialization of dark matter (DM) halos. An important prediction of such a relaxation process is that spherical equilibrium states can be described by a Fermi-Dirac phase-space distribution, when the extremization of a coarse-grained entropy is reached. In the case of DM fermions, the most general solution develops a degenerate compact core surrounded by a diluted halo. As shown recently, the latter is able to explain the galaxy rotation curves while the DM core can mimic the central black hole. A yet open problem is whether this kind of astrophysical core-halo configurations can form at all, and if they remain stable within cosmological timescales. We assess these issues by performing a thermodynamic stability analysis in the microcanonical ensemble for solutions with given particle number at halo virialization in a cosmological framework. For the first time we demonstrate that the above core-halo DM profiles are stable (i.e. maxima of entropy) and extremely long lived. We find the existence of a critical point at the onset of instability of the core-halo solutions, where the fermion-core collapses towards a supermassive black hole. For particle masses in the keV range, the core-collapse can only occur for Mvir ≳ E9M⊙ starting at zvir ≈ 10 in the given cosmological framework. Our results prove that DM halos with a core-halo morphology are a very plausible outcome within nonlinear stages of structure formation.

scholarly journals Radio jets and gamma-ray emission in radio-silent narrow-line Seyfert 1 galaxies

2018 ◽  
Vol 614 ◽  
pp. L1 ◽  
Author(s):  
A. Lähteenmäki ◽  
E. Järvelä ◽  
V. Ramakrishnan ◽  
M. Tornikoski ◽  
J. Tammi ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Spiral Galaxies ◽  
Narrow Line ◽  
Radio Jets ◽  
Relativistic Jet ◽  
Gamma Ray Emission

We have detected six narrow-line Seyfert 1 (NLS1) galaxies at 37 GHz that were previously classified as radio silent and two that were classified as radio quiet. These detections reveal the presumption that NLS1 galaxies labelled radio quiet or radio silent and hosted by spiral galaxies are unable to launch jets to be incorrect. The detections are a plausible indicator of the presence of a powerful, most likely relativistic jet because this intensity of emission at 37 GHz cannot be explained by, for example, radiation from supernova remnants. Additionally, one of the detected NLS1 galaxies is a newly discovered source of gamma rays and three others are candidates for future detections.

scholarly journals Linking the central engine to the jet properties in radio loud AGN

2014 ◽  
Vol 10 (S313) ◽  
pp. 329-330
Author(s):  
A. Olguín-Iglesias ◽  
J. León-Tavares ◽  
V. Chavushyan ◽  
E. Valtaoja ◽  
C. Añorve ◽  
...  
Keyword(s):  
Black Hole ◽  
Host Galaxy ◽  
Base Line ◽  
Black Hole Mass ◽  
Host Galaxies ◽  
Optical Telescope ◽  
Central Engine ◽  
Early Results ◽  
Relativistic Jet ◽  
Line Array

AbstractWe explore the connection between the black hole mass and its relativistic jet for a sample of radio-loud AGN (z < 1), in which the relativistic jet parameters are well estimated by means of long term monitoring with the 14m Metsähovi millimeter wave telescope and the Very Long Base-line Array (VLBA). NIR host galaxy images taken with the NOTCam on the Nordic Optical Telescope (NOT) and retrieved from the 2MASS all-sky survey allowed us to perform a detailed surface brightness decomposition of the host galaxies in our sample and to estimate reliable black hole masses via their bulge luminosities. We present early results on the correlations between black hole mass and the relativistic jet parameters. Our preliminary results suggest that the more massive the black hole is, the faster and the more luminous jet it produces.

scholarly journals Stellar Core Collapse and Exotic Matter

2011 ◽  
Vol 7 (S279) ◽  
pp. 367-368
Author(s):  
Ken'ichiro Nakazato ◽  
Kohsuke Sumiyoshi
Keyword(s):  
Black Hole ◽  
Degrees Of Freedom ◽  
Gamma Ray ◽  
Dense Matter ◽  
Gamma Ray Bursts ◽  
Core Collapse ◽  
Hole Formation ◽  
Stellar Core ◽  
Black Hole Formation ◽  
Hydrodynamical Simulations

AbstractSome supernovae and gamma-ray bursts are thought to accompany a black hole formation. In the process of a black hole formation, a central core becomes hot and dense enough for hyperons and quarks to appear. In this study, we perform neutrino-radiation hydrodynamical simulations of a stellar core collapse and black hole formation taking into account such exotic components. In our computation, general relativity is fully considered under spherical symmetry. As a result, we find that the additional degrees of freedom soften the equation of state of matter and promote the black hole formation. Furthermore, their effects are detectable as a neutrino signal. We believe that the properties of hot and dense matter at extreme conditions are essential for the studies on the astrophysical black hole formation. This study will be hopefully a first step toward a physics of the central engine of gamma-ray bursts.

Back Where We Started

2017 ◽  
Author(s):  
John A. Adam
Keyword(s):  
Integral Equation ◽  
Black Hole ◽  
Angular Momentum ◽  
Gravitational Lensing ◽  
Airy Functions ◽  
Ray Optics ◽  
Gravitational Fields ◽  
The Subject ◽  
Luneberg Lens

This chapter returns to the subject of rainbows, offering some reflections based on the author's review of the book The Rainbow Bridge: Rainbows in Art, Myth, and Science by Raymond L. Lee, Jr. and Alistair B. Frase. In particular, it discusses various topics related to the rainbow, including historical descriptions of the rainbow, some common misperceptions about rainbows, theories of the rainbow, angular momentum, rainbow ray, and Airy functions. The chapter also considers ray optics, with emphasis on Luneberg inversion and gravitational lensing, Abel's integral equation, and the Luneberg lens. Finally, it explains the rainbow's connection with classical scattering and gravitational lensing, focusing on weak gravitational fields and the black hole lens.

3. Extrasolar tests of gravity

2017 ◽  
pp. 35-45
Author(s):  
Timothy Clifton
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Field ◽  
Solar System ◽  
Neutron Stars ◽  
Event Horizon ◽  
Gravitational Fields ◽  
Binary Pulsars ◽  
Tests Of Gravity ◽  
Triple Star

By studying objects outside our Solar System, we can observe star systems with far greater gravitational fields. ‘Extrasolar tests of gravity’ considers stars of different sizes that have undergone gravitational collapse, including white dwarfs, neutron stars, and black holes. A black hole consists of a region of space-time enclosed by a surface called an event horizon. The gravitational field of a black hole is so strong that anything that finds its way inside the event horizon can never escape. Other star systems considered are binary pulsars and triple star systems. With the invention of even more powerful telescopes, there will be more tantalizing possibilities for testing gravity in the future.

scholarly journals The primordial black hole formation criterion re-examined: Parametrisation, timing and the choice of window function

2019 ◽  
Vol 29 (02) ◽  
pp. 2030002 ◽  
Author(s):  
Sam Young
Keyword(s):  
Black Hole ◽  
Density Perturbation ◽  
Density Contrast ◽  
Smoothing Function ◽  
Primordial Black Hole ◽  
Curvature Perturbation ◽  
Order Of Magnitude ◽  
Horizon Limit ◽  
First Time ◽  
Peak Value

In this paper, the criterion used to determine whether a density perturbation will collapse to form a primordial black hole (PBH) is re-examined in respect of its use to determine the abundance of PBHs. There is particular focus on which parameter to use, the time at which the abundance should be calculated, and the use of different smoothing functions. It is concluded that, with the tools currently available, the smoothed density contrast should be used rather than the peak value, and should be calculated from the time-independent component of the density contrast in the super-horizon limit (long before perturbations enter the horizon) rather than at horizon crossing. For the first time, the effect of the choice of smoothing function upon the formation criterion is calculated, and, for a given abundance of PBHs, it is found that the uncertainty in the amplitude of the power spectrum due to this is [Formula: see text], an order of magnitude smaller than that suggested by previous calculations. The relation between the formation criterion stated in terms of the density contrast and the curvature perturbation [Formula: see text] is also discussed.

scholarly journals Very High-Energy Emission from the Direct Vicinity of Rapidly Rotating Black Holes

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 122 ◽  
Author(s):  
Kouichi Hirotani
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Black Hole ◽  
Electric Field ◽  
Gamma Rays ◽  
Accretion Rate ◽  
High Energy ◽  
Relativistic Electrons ◽  
Field Lines ◽  
The Magnetic Field

When a black hole accretes plasmas at very low accretion rate, an advection-dominated accretion flow (ADAF) is formed. In an ADAF, relativistic electrons emit soft gamma-rays via Bremsstrahlung. Some MeV photons collide with each other to materialize as electron-positron pairs in the magnetosphere. Such pairs efficiently screen the electric field along the magnetic field lines, when the accretion rate is typically greater than 0.03–0.3% of the Eddington rate. However, when the accretion rate becomes smaller than this value, the number density of the created pairs becomes less than the rotationally induced Goldreich–Julian density. In such a charge-starved magnetosphere, an electric field arises along the magnetic field lines to accelerate charged leptons into ultra-relativistic energies, leading to an efficient TeV emission via an inverse-Compton (IC) process, spending a portion of the extracted hole’s rotational energy. In this review, we summarize the stationary lepton accelerator models in black hole magnetospheres. We apply the model to super-massive black holes and demonstrate that nearby low-luminosity active galactic nuclei are capable of emitting detectable gamma-rays between 0.1 and 30 TeV with the Cherenkov Telescope Array.

scholarly journals Gamma-Ray Bursts Polarization

2016 ◽  
Vol 12 (S324) ◽  
pp. 54-61
Author(s):  
Diego Götz ◽  
Stefano Covino
Keyword(s):  
Black Hole ◽  
Kinetic Energy ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Central Source ◽  
Poynting Flux ◽  
Relativistic Jet ◽  
Theoretical Status ◽  
Prompt Emission ◽  
Open Point

AbstractWe review the current observational and theoretical status of the polarization measurements of Gamma-ray Bursts at all wavelengths. Gamma-Ray Bursts are thought to be produced by an ultra-relativistic jet, possibly powered by a black hole. One of the most important open point is the composition of the jet: the energy may be carried out from the central source either as kinetic energy (of baryons and/or pairs), or in electromagnetic form (Poynting flux). The polarization properties are expected to help disentangling main energy carrier. The prompt emission and afterglow polarization are also a powerful diagnostic of the jet geometry.

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