VACUUM DISCHARGE AS A POSSIBLE SOURCE OF GAMMA-RAY BURSTS

2000 ◽  
Vol 09 (02) ◽  
pp. 185-192
Author(s):  
G. MAO ◽  
S. CHIBA ◽  
W. GREINER ◽  
K. OYAMATSU
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Ambient Medium ◽  
Critical Density ◽  
Compact Object ◽  
Dense Matter ◽  
Initial Energy ◽  
Strong Interactions ◽  
Γ Ray ◽  
The Impact

We propose that spontaneous particle–anti-particle pair creations from the discharged vacuum caused by the strong interactions in dense matter are major sources of γ-ray bursts. Two neutron star collisions or black-hole-neutron star mergers at cosmological distance could produce a compact object with its density exceeding the critical density for pair creations. The emitted anti-particles annihilate with corresponding particles at the ambient medium. This releases a large amount of energy. We discuss the spontaneous [Formula: see text] pair creations within two neutron star collision and estimate the exploded energy from [Formula: see text] annihilation processes. The total energy could be around 1051–1053 erg depending on the impact parameter of colliding neutron stars. This value fits well into the range of the initial energy of the most energetic γ-ray bursts.

scholarly journals The dynamic ejecta of compact object mergers and eccentric collisions

2013 ◽  
Vol 371 (1992) ◽  
pp. 20120272 ◽  
Author(s):  
Stephan Rosswog
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
Ambient Medium ◽  
Compact Object ◽  
Solar Mass ◽  
Abundance Pattern ◽  
Compact Binary ◽  
Hydrodynamical Simulations ◽  
Rich Material ◽  
R Process

Compact object mergers eject neutron-rich matter in a number of ways: by the dynamical ejection mediated by gravitational torques, as neutrino-driven winds, and probably also a good fraction of the resulting accretion disc finally becomes unbound by a combination of viscous and nuclear processes. If compact binary mergers indeed produce gamma-ray bursts, there should also be an interaction region where an ultra-relativistic outflow interacts with the neutrino-driven wind and produces moderately relativistic ejecta. Each type of ejecta has different physical properties, and therefore plays a different role for nucleosynthesis and for the electromagnetic (EM) transients that go along with compact object encounters. Here, we focus on the dynamic ejecta and present results for over 30 hydrodynamical simulations of both gravitational wave-driven mergers and parabolic encounters as they may occur in globular clusters. We find that mergers eject approximately 1 per cent of a Solar mass of extremely neutron-rich material. The exact amount, as well as the ejection velocity, depends on the involved masses with asymmetric systems ejecting more material at higher velocities. This material undergoes a robust r-process and both ejecta amount and abundance pattern are consistent with neutron star mergers being a major source of the ‘heavy’ ( A >130) r-process isotopes. Parabolic collisions, especially those between neutron stars and black holes, eject substantially larger amounts of mass, and therefore cannot occur frequently without overproducing gala- ctic r-process matter. We also discuss the EM transients that are powered by radioactive decays within the ejecta (‘macronovae’), and the radio flares that emerge when the ejecta dissipate their large kinetic energies in the ambient medium.

scholarly journals Gamma-Ray Bursts and Binary Neutron Star Mergers

1996 ◽  
Vol 165 ◽  
pp. 489-502
Author(s):  
Tsvi Piran
Keyword(s):  
Neutron Star ◽  
Gravitational Radiation ◽  
Gamma Ray ◽  
Indirect Evidence ◽  
Gamma Ray Bursts ◽  
Binary Neutron Star ◽  
Merger Event ◽  
Γ Rays ◽  
Γ Ray ◽  
The One

Neutron star binaries, such as the one observed in the famous binary pulsar PSR 1913+16, end their life in a catastrophic merger event (denoted here NS2M). The merger releases ∼5 1053 ergs, mostly as neutrinos and gravitational radiation. A small fraction of this energy suffices to power γ-ray bursts (GRBs) at cosmological distances. Cosmological GRBs must pass, however, an optically thick fireball phase and the observed γ rays emerge only at the end of this phase. Hence, it is difficult to determine the nature of the source from present observations (the agreement between the rates of GRBs and NS2Ms providing only indirect evidence for this model). In the future a coinciding detection of a GRB and a gravitational-radiation signal could confirm this model.

scholarly journals Mass and Orbit Constraints of the Gamma-ray Binary LS 5039

2011 ◽  
Vol 7 (S282) ◽  
pp. 331-332
Author(s):  
T. Szalai ◽  
G. E. Sarty ◽  
L. L. Kiss ◽  
J. M. Matthews ◽  
J. Vinkó ◽  
...  
Keyword(s):  
Light Curve ◽  
Orbital Period ◽  
Gamma Ray ◽  
Broad Band ◽  
Compact Object ◽  
Physical Parameters ◽  
Photometric Variability ◽  
Γ Ray

AbstractWe present the results of space-based photometric and ground-based spectroscopic observing campaigns on the γ-ray binary LS 5039. The new orbital and physical parameters of the system are similar to former results, except we found a lower eccentricity. Our MOST-data show that any broad-band optical photometric variability at the orbital period is below the 2 mmag level. Light curve simulations support the lower value of eccentricity and imply that the mass of the compact object is higher than 1.8 M⊙.

scholarly journals The binary progenitors of short and long GRBs and their gravitational-wave emission

2018 ◽  
Vol 168 ◽  
pp. 01006
Author(s):  
J. A. Rueda ◽  
R. Ruffini ◽  
J. F. Rodriguez ◽  
M. Muccino ◽  
Y. Aimuratov ◽  
...  
Keyword(s):  
Neutron Star ◽  
Gravitational Wave ◽  
Gamma Ray ◽  
Critical Mass ◽  
Compact Object ◽  
Annual Number ◽  
Black Hole Binaries ◽  
Nuclear Equation Of State ◽  
Long Duration ◽  
Wave Emission

We have sub-classified short and long-duration gamma-ray bursts (GRBs) into seven families according to the binary nature of their progenitors. Short GRBs are produced in mergers of neutron-star binaries (NS-NS) or neutron star-black hole binaries (NS-BH). Long GRBs are produced via the induced gravitational collapse (IGC) scenario occurring in a tight binary system composed of a carbon-oxygen core (COcore) and a NS companion. The COcore explodes as type Ic supernova (SN) leading to a hypercritical accretion process onto the NS: if the accretion is sufficiently high the NS reaches the critical mass and collapses forming a BH, otherwise a massive NS is formed. Therefore long GRBs can lead either to NS-BH or to NS-NS binaries depending on the entity of the accretion. We discuss for the above compact-object binaries: 1) the role of the NS structure and the nuclear equation of state; 2) the occurrence rates obtained from X and gamma-rays observations; 3) the predicted annual number of detections by the Advanced LIGO interferometer of their gravitational-wave emission.

scholarly journals High-energy emission from galaxies: the star-formation/gamma-ray connection

2011 ◽  
Vol 7 (S284) ◽  
pp. 382-388
Author(s):  
Stefan Ohm ◽  
Jim Hinton
Keyword(s):  
Particle Acceleration ◽  
Star Formation ◽  
Gamma Ray ◽  
Broad Band ◽  
High Energy ◽  
High Mass ◽  
Spectral Energy ◽  
Mass Star ◽  
Γ Ray ◽  
The Impact

AbstractThe impact of non-thermal processes on the spectral energy distributions of galaxies can be dramatic, but such processes are often neglected in considerations of their structure and evolution. Particle acceleration associated with high mass star formation and AGN activity not only leads to very broad band (radio-γ-ray) emission, but may also produce very significant feedback effects on galaxies and their environment. The recent detections of starburst galaxies at GeV and TeV energies suggest that γ-ray instruments have now reached the critical level of sensitivity to probe the connection between particle acceleration and star-formation in galaxies. In this paper we will try to summarise this recent progress, put it into a multi-wavelength context and also discuss the prospects for more precise and sensitive γ-ray measurements with the upcoming CTA observatory.

scholarly journals SECONDARY EMISSION BEHIND THE RADIO OUTFLOWS IN GAMMA-RAY BINARIES

2010 ◽  
Vol 19 (06) ◽  
pp. 741-747 ◽  
Author(s):  
VALENTÍ BOSCH-RAMON
Keyword(s):  
Radio Emission ◽  
Binary Systems ◽  
Gamma Ray ◽  
Orbital Motion ◽  
Compact Object ◽  
Radio Spectrum ◽  
Secondary Emission ◽  
Primary Star ◽  
Structure Extension ◽  
The Impact

Several binary systems consisting of a massive star and a compact object have been detected above 100 GeV in the Galaxy. In most of these sources, gamma-rays show a modulation associated to the orbital motion, which means that the emitter should not be too far from the bright primary star. This implies that gamma-ray absorption will be non-negligible, and large amounts of secondary electron–positron pairs will be created in the stellar surroundings. In this work, we show that the radio emission from these pairs should be accounted for when interpreting the radio spectrum, variability, and morphology found in gamma-ray binaries. Relevant features of the secondary radio emission are the relatively hard spectrum, the orbital motion of the radio peak center and the radio structure extension following a spiral-like trajectory. The impact of the stellar wind free–free absorption should not be neglected.

scholarly journals Probing the Nuclear Equation of State from the Existence of a ∼2.6 M⊙ Neutron Star: The GW190814 Puzzle

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 183
Author(s):  
Alkiviadis Kanakis-Pegios ◽  
Polychronis S. Koliogiannis ◽  
Charalampos C. Moustakidis
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Equation Of State ◽  
Speed Of Sound ◽  
Compact Object ◽  
Dense Matter ◽  
High Mass ◽  
Nuclear Equation Of State ◽  
Dense Nuclear Matter ◽  
Low Mass

On 14 August 2019, the LIGO/Virgo collaboration observed a compact object with mass ∼2.59−0.09+0.08M⊙, as a component of a system where the main companion was a black hole with mass ∼23M⊙. A scientific debate initiated concerning the identification of the low mass component, as it falls into the neutron star–black hole mass gap. The understanding of the nature of GW190814 event will offer rich information concerning open issues, the speed of sound and the possible phase transition into other degrees of freedom. In the present work, we made an effort to probe the nuclear equation of state along with the GW190814 event. Firstly, we examine possible constraints on the nuclear equation of state inferred from the consideration that the low mass companion is a slow or rapidly rotating neutron star. In this case, the role of the upper bounds on the speed of sound is revealed, in connection with the dense nuclear matter properties. Secondly, we systematically study the tidal deformability of a possible high mass candidate existing as an individual star or as a component one in a binary neutron star system. As the tidal deformability and radius are quantities very sensitive on the neutron star equation of state, they are excellent counters on dense matter properties. We conjecture that similar isolated neutron stars or systems may exist in the universe and their possible future observation will shed light on the maximum neutron star mass problem.

scholarly journals Structured, relativistic jets driven by radiation

2020 ◽  
Vol 499 (3) ◽  
pp. 3158-3177 ◽  
Author(s):  
Eric R Coughlin ◽  
Mitchell C Begelman
Keyword(s):  
Fast Moving ◽  
Gamma Ray ◽  
Ambient Medium ◽  
Dynamical Evolution ◽  
Compact Object ◽  
Lorentz Factor ◽  
Radiation Hydrodynamics ◽  
Relativistic Jets ◽  
Radiative Processes ◽  
Jet Structure

ABSTRACT Relativistic jets, or highly collimated and fast-moving outflows, are endemic to many astrophysical phenomena. The jets produced by gamma-ray bursts (GRBs) and tidal disruption events (TDEs) are accompanied by the accretion of material on to a black hole or neutron star, with the accretion rate exceeding the Eddington limit of the compact object by orders of magnitude. In such systems, radiation dominates the energy–momentum budget of the outflow, and the dynamical evolution of the jet is governed by the equations of radiation hydrodynamics. Here, we show that there are analytical solutions to the equations of radiation hydrodynamics in the viscous (i.e. diffusive) regime that describe structured, relativistic jets, which consist of a fast-moving, highly relativistic core surrounded by a slower moving, less relativistic sheath. In these solutions, the slower moving, outer sheath contains most of the mass, and the jet structure is mediated by local anisotropies in the radiation field. We show that, depending on the pressure and density profile of the ambient medium, the angular profile of the jet Lorentz factor is Gaussian or falls off even more steeply with angle. These solutions have implications for the nature of jet production and evolution in hyperaccreting systems, and demonstrate that such jets – and the corresponding jet structure – can be sustained entirely by radiative processes. We discuss the implications of these findings in the context of jetted TDEs and short and long GRBs.

scholarly journals Imprints of r-process heating on fall-back accretion: distinguishing black hole–neutron star from double neutron star mergers

2019 ◽  
Vol 485 (3) ◽  
pp. 4404-4412 ◽  
Author(s):  
D Desai ◽  
B D Metzger ◽  
F Foucart
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Star ◽  
Gamma Ray ◽  
Late Time ◽  
X Ray ◽  
Power Law Decay ◽  
Process Heating ◽  
R Process ◽  
The Impact

ABSTRACT Mergers of compact binaries containing two neutron stars (NS–NS), or a neutron star and a stellar mass black hole (NS–BH), are likely progenitors of short-duration gamma-ray bursts (SGRBs). A fraction ${\gtrsim } 20{{\ \rm per\ cent}}$ of SGRBs is followed by temporally extended (≳minute-long), variable X-ray emission, attributed to ongoing activity of the central engine. One source of late-time engine activity is fall-back accretion of bound tidal ejecta; however, observed extended emission light curves do not track the naively anticipated, uninterrupted t−5/3 power-law decay, instead showing a lull or gap in emission typically lasting tens of seconds after the burst. Here, we re-examine the impact of heating due to rapid neutron capture (r-process) nucleosynthesis on the rate of the fall-back accretion, using ejecta properties extracted from numerical relativity simulations of NS–BH mergers. Heating by the r-process has its greatest impact on marginally bound matter, hence its relevance to late-time fall-back. Depending on the electron fraction of the ejecta and the mass of the remnant black hole, r-process heating can imprint a range of fall-back behaviour, ranging from temporal gaps of up to tens of seconds to complete late-time cut-off in the accretion rate. This behaviour is robust to realistic variations in the nuclear heating experienced by different parts of the ejecta. Central black holes with masses ${\lesssim } 3\, \mathrm{M}_{\odot }$ typically experience absolute cut-offs in the fall-back rate, while more massive ${\gtrsim } 6\!-\!8\, \mathrm{M}_{\odot }$ black holes instead show temporal gaps. We thus propose that SGRBs showing extended X-ray emission arise from NS–BH, rather than NS–NS, mergers. Our model implies an NS–BH merger detection rate by LIGO that, in steady state, is comparable to or greater than that of NS–NS mergers.

scholarly journals GRB 130603B: No Compelling Evidence for Neutron Star Merger

2015 ◽  
Vol 2015 ◽  
pp. 1-5
Author(s):  
Shlomo Dado ◽  
Arnon Dar
Keyword(s):  
Neutron Star ◽  
Near Infrared ◽  
Gamma Ray ◽  
Hubble Space Telescope ◽  
Compact Star ◽  
Compact Object ◽  
Late Time ◽  
Quark Star ◽  
X Ray ◽  
Relativistic Jet

The near infrared (NIR) flare/rebrightening in the afterglow of the short hard gamma ray burst (SHB) 130603B measured with the Hubble Space Telescope (HST) and an alleged late-time X-ray excess were interpreted as possible evidence of a neutron star merger origin of SHBs. However, the X-ray afterglow that was measured with the Swift XRT and Newton XMM has the canonical behaviour of a synchrotron afterglow produced by a highly relativistic jet. The H-band flux observed with HST 9.41 days after burst is that expected from the measured late-time X-ray afterglow. The late-time flare/rebrightening of the NIR-optical afterglow of SHB 130603B could have been produced also by jet collision with an interstellar density bump. Moreover, SHB plus a kilonova can be produced also by the collapse of a compact star (neutron star, strange star, or quark star) to a more compact object due to cooling, loss of angular momentum, or mass accretion.

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