scholarly journals The structure of weakly magnetized γ-ray burst jets

2020 ◽  
Vol 498 (3) ◽  
pp. 3320-3333 ◽  
Author(s):  
Ore Gottlieb ◽  
Omer Bromberg ◽  
Chandra B Singh ◽  
Ehud Nakar
Keyword(s):  
Power Law ◽  
Gamma Ray ◽  
Interface Layer ◽  
Companion Paper ◽  
Hydrodynamic Instabilities ◽  
Power Law Decay ◽  
Dense Media ◽  
Power Law Function ◽  
Weak Fields ◽  
Magnetic Nature

ABSTRACT The interaction of gamma-ray burst (GRB) jets with the dense media into which they are launched promote the growth of local hydrodynamic instabilities along the jet boundary. In a companion paper, we study the evolution of hydrodynamic (unmagnetized) jets, finding that mixing of jet–cocoon material gives rise to an interface layer, termed jet–cocoon interface (JCI), which contains a significant fraction of the system energy. We find that the angular structure of the jet + JCI, when they reach the homologous phase, can be approximated by a flat core (the jet) + a power-law function (the JCI) with indices that depend on the degree of mixing. In this paper, we examine the effect of subdominant toroidal magnetic fields on the jet evolution and morphology. We find that weak fields can stabilize the jet against local instabilities. The suppression of the mixing diminishes the JCI and thus reshapes the jet’s post-breakout structure. Nevertheless, the overall shape of the outflow can still be approximated by a flat core + a power-law function, although the JCI power-law decay is steeper. The effect of weak fields is more prominent in long GRB jets, where the mixing in hydrodynamic jets is stronger. In short GRB jets, there is small mixing in both weakly magnetized and unmagnetized jets. This result influences the expected jet emission which is governed by the jet’s morphology. Therefore, prompt and afterglow observations in long GRBs may be used as probes for the magnetic nature at the base of the jets.

scholarly journals Using Swift observations of prompt and afterglow emission to classify GRBs

2007 ◽  
Vol 365 (1854) ◽  
pp. 1179-1188 ◽  
Author(s):  
Paul T O'Brien ◽  
Richard Willingale
Keyword(s):  
Light Curve ◽  
Power Law ◽  
Gamma Ray ◽  
Good Description ◽  
X Ray ◽  
Temporal Properties ◽  
Power Law Decay ◽  
Decay Index ◽  
Prompt Emission ◽  
Burst Alert Telescope

We present an analysis of early Burst Alert Telescope and X-ray Telescope data for 107 gamma-ray bursts (GRBs) observed by the Swift satellite. We use these data to examine the behaviour of the X-ray light curve and propose a classification scheme for GRBs based on this behaviour. As found for previous smaller samples, the earliest X-ray light curve can be well described by an exponential, which relaxes into a power-law, often with flares superimposed. The later emission is well fit using a similar functional form and we find that these two functions provide a good description of the entire X-ray light curve. For the prompt emission, the transition time between the exponential and the power-law gives a well-defined time-scale, T p , for the burst duration. We use T p , the spectral index of the prompt emission, β p , and the prompt power-law decay index, α p , to define four classes of burst: short, slow, fast and soft. Bursts with slowly declining emission have spectral and temporal properties similar to the short bursts despite having longer durations. Some of these GRBs may therefore arise from similar progenitors including several types of binary system. Short bursts tend to decline more gradually than longer duration bursts and hence emit a significant fraction of their total energy at times greater than T p . This may be due to differences in the environment or the progenitor for long, fast bursts.

scholarly journals The structure of hydrodynamic γ-ray burst jets

2020 ◽  
Vol 500 (3) ◽  
pp. 3511-3526
Author(s):  
Ore Gottlieb ◽  
Ehud Nakar ◽  
Omer Bromberg
Keyword(s):  
Power Law ◽  
Gamma Ray ◽  
Strong Mixing ◽  
Comparable Amount ◽  
Dense Media ◽  
Jet Characteristics ◽  
Jet Structure ◽  
Power Law Distributions ◽  
Emission Light ◽  
Prompt Emission

ABSTRACT After being launched, gamma-ray burst (GRB) jets propagate through dense media prior to their breakout. The jet-medium interaction results in the formation of a complex structured outflow, often referred to as a ‘structured jet’. The underlying physics of the jet-medium interaction that sets the post-breakout jet morphology has never been explored systematically. Here, we use a suite of 3D simulations to follow the evolution of hydrodynamic long and short gamma-ray bursts (lGRBs and sGRBs) jets after breakout to study the post-breakout structure induced by the interaction. Our simulations feature Rayleigh–Taylor fingers that grow from the cocoon into the jet, mix cocoon with jet material and destabilize the jet. The mixing gives rise to a previously unidentified region sheathing the jet from the cocoon, which we denote the jet–cocoon interface (JCI). lGRBs undergo strong mixing, resulting in most of the jet energy to drift into the JCI, while in sGRBs weaker mixing is possible, leading to a comparable amount of energy in the two components. Remarkably, the jet structure (jet-core plus JCI) can be characterized by simple universal angular power-law distributions, with power-law indices that depend solely on the mixing level. This result supports the commonly used power-law angular distribution, and disfavours Gaussian jets. At larger angles, where the cocoon dominates, the structure is more complex. The mixing shapes the prompt emission light curve and implies that typical lGRB afterglows are different from those of sGRBs. Our predictions can be used to infer jet characteristics from prompt and afterglow observations.

Decay phases of Swift X-ray afterglows and the forward-shock model

2007 ◽  
Vol 365 (1854) ◽  
pp. 1197-1205 ◽  
Author(s):  
A Panaitescu
Keyword(s):  
Light Curve ◽  
Power Law ◽  
Gamma Ray ◽  
Large Angle ◽  
Light Curves ◽  
X Ray ◽  
Power Law Decay ◽  
Decay Index ◽  
Shock Region ◽  
Forward Shock

The X-ray flux of the gamma-ray burst (GRB) afterglows monitored by the Swift satellite from January 2005 to July 2006 displays one to four phases of flux power-law decay. In chronological order, they are: the GRB tail, the ‘hump’, the standard decay and the post-jet-break decay. More than half of the GRB tails can be identified with the large-angle emission produced during the burst (but arriving later at observer). The remaining, slower GRB tails imply that the gamma-ray mechanism continues to radiate after the burst, as also suggested by the frequent occurrence of X-ray flares during the burst tail. The several GRB tails exhibiting a slow unbroken power-law decay until 100 ks must be attributed to the forward shock. In fact, the decay of most GRB tails is also consistent with that of the forward-shock emission from a narrow jet. The X-ray light-curve hump may be due to an increase of the kinetic energy per solid angle of the forward-shock region visible to the observer, caused by either the transfer of energy from ejecta to the forward shock or the emergence of the emission from an outflow seen from a location outside the jet opening. The decay following the X-ray light-curve hump is consistent with the emission from an adiabatic blast wave but, contrary to expectations, the light-curve decay index and spectral slope during this phase are not correlated. The X-ray light curves of two dozens X-ray afterglows that followed for more than a week do not exhibit a jet break, in contrast with the behaviour of pre-Swift optical afterglows, which displayed jet breaks at 0.5–2 days. Nevertheless, the X-ray light curves of several Swift afterglows show a second steepening break at 0.4–3 days that is consistent with the break expected for a jet when its edge becomes visible to the observer.

scholarly journals When an oscillating center in an open system undergoes power law decay

2018 ◽  
Vol 57 (3) ◽  
pp. 750-768 ◽  
Author(s):  
Sandip Saha ◽  
Gautam Gangopadhyay
Keyword(s):  
Power Law ◽  
Open System ◽  
Power Law Decay

scholarly journals Detection of the Geminga pulsar with MAGIC hints at a power-law tail emission beyond 15 GeV

2020 ◽  
Vol 643 ◽  
pp. L14
Author(s):  
◽  
V. A. Acciari ◽  
S. Ansoldi ◽  
L. A. Antonelli ◽  
A. Arbet Engels ◽  
...  
Keyword(s):  
Energy Range ◽  
Power Law ◽  
Gamma Ray ◽  
Low Energy ◽  
Significance Level ◽  
Inverse Compton Scattering ◽  
Curvature Radiation ◽  
Sensitivity Range ◽  
Inverse Compton ◽  
First Time

We report the detection of pulsed gamma-ray emission from the Geminga pulsar (PSR J0633+1746) between 15 GeV and 75 GeV. This is the first time a middle-aged pulsar has been detected up to these energies. Observations were carried out with the MAGIC telescopes between 2017 and 2019 using the low-energy threshold Sum-Trigger-II system. After quality selection cuts, ∼80 h of observational data were used for this analysis. To compare with the emission at lower energies below the sensitivity range of MAGIC, 11 years of Fermi-LAT data above 100 MeV were also analysed. From the two pulses per rotation seen by Fermi-LAT, only the second one, P2, is detected in the MAGIC energy range, with a significance of 6.3σ. The spectrum measured by MAGIC is well-represented by a simple power law of spectral index Γ = 5.62 ± 0.54, which smoothly extends the Fermi-LAT spectrum. A joint fit to MAGIC and Fermi-LAT data rules out the existence of a sub-exponential cut-off in the combined energy range at the 3.6σ significance level. The power-law tail emission detected by MAGIC is interpreted as the transition from curvature radiation to Inverse Compton Scattering of particles accelerated in the northern outer gap.

scholarly journals Analysis of the buildup of spatiotemporal correlations and their bounds outside of the light cone

2018 ◽  
Vol 5 (5) ◽  
Author(s):  
Nils O. Abeling ◽  
Lorenzo Cevolani ◽  
Stefan Kehrein
Keyword(s):  
Correlation Function ◽  
Power Law ◽  
Light Cone ◽  
Relativistic Quantum ◽  
Initial State ◽  
Quantum Theories ◽  
Luttinger Model ◽  
Power Law Decay ◽  
Exactly Solvable ◽  
Exponentially Small

In non-relativistic quantum theories the Lieb-Robinson bound defines an effective light cone with exponentially small tails outside of it. In this work we use it to derive a bound for the correlation function of two local disjoint observables at different times if the initial state has a power-law decay. We show that the exponent of the power-law of the bound is identical to the initial (equilibrium) decay. We explicitly verify this result by studying the full dynamics of the susceptibilities and correlations in the exactly solvable Luttinger model after a sudden quench from the non-interacting to the interacting model.

scholarly journals A formula for hidden regular variation behavior for symmetric stable distributions

Extremes ◽  
2020 ◽  
Vol 23 (4) ◽  
pp. 667-691
Author(s):  
Malin Palö Forsström ◽  
Jeffrey E. Steif
Keyword(s):  
Power Law ◽  
Spectral Measure ◽  
Regular Variation ◽  
Stable Distributions ◽  
Decay Rates ◽  
Random Vectors ◽  
Power Law Decay ◽  
Exact Power ◽  
Hidden Regular Variation ◽  
Stable Random Vectors

Abstract We develop a formula for the power-law decay of various sets for symmetric stable random vectors in terms of how many vectors from the support of the corresponding spectral measure are needed to enter the set. One sees different decay rates in “different directions”, illustrating the phenomenon of hidden regular variation. We give several examples and obtain quite varied behavior, including sets which do not have exact power-law decay.

scholarly journals On The Critical Phenomena in The Dynamics of Asteroids

1999 ◽  
Vol 172 ◽  
pp. 383-386
Author(s):  
Ivan I. Shevchenko
Keyword(s):  
Phase Space ◽  
Critical Phenomena ◽  
Power Law ◽  
Anomalous Transport ◽  
Selection Effects ◽  
Recurrence Times ◽  
Statistical Selection ◽  
Power Law Decay ◽  
Statistical Effects

AbstractTwo statistical effects in the long-term chaotic asteroidal dynamics are considered, namely the power-law character of the dependence of recurrence times on local Lyapunov times and the power-law decay in the tails of the recurrence distributions. The dependences in both cases are shaped by effects of anomalous transport, due to the presence of the chaos border in phase space, and by statistical selection effects.

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