scholarly journals Gamma-ray flux depressions of the Crab Nebula in the high-energy range

2020 ◽  
Vol 496 (4) ◽  
pp. 5227-5232
Author(s):  
M S Pshirkov ◽  
B A Nizamov ◽  
A M Bykov ◽  
Yu A Uvarov
Keyword(s):  
Energy Range ◽  
Gamma Ray ◽  
Crab Nebula ◽  
High Energy ◽  
Synchrotron Emission ◽  
Pulsar Wind Nebulae ◽  
Average Value ◽  
Order Of Magnitude ◽  
Pulsar Wind ◽  
The Crab Nebula

ABSTRACT The giant gamma-ray flares of the Crab Nebula discovered by AGILE and Fermi observatories came as a surprise and have challenged the existing models of pulsar wind nebulae. We have carried out an analysis of 10.5 yr of Fermi-LAT observations (August 2008 to February 2019) and investigated variability of the Crab Nebula in the 100–300 MeV range. Besides the flares, we found several month long depressions of the gamma-ray flux and identified several cases of sharp flux drops, where during 1 week the flux decreased by an order of magnitude with respect to its average value. No statistically significant variations of the nebula flux in the E > 10 GeV range were found in the data. We discuss possible implications of the observed gamma-ray flux depressions on the model of synchrotron emission of the Crab Nebula.

scholarly journals Time-Domain Astronomy with Swift, Fermi and Lobster

2011 ◽  
Vol 7 (S285) ◽  
pp. 41-46 ◽  
Author(s):  
Neil Gehrels ◽  
Scott D. Barthelmy ◽  
John K. Cannizzo
Keyword(s):  
Gamma Ray ◽  
Crab Nebula ◽  
High Energy ◽  
Tidal Disruption ◽  
X Ray ◽  
Order Of Magnitude ◽  
New Type ◽  
The Crab Nebula ◽  
High Energy Emission ◽  
Higher Sensitivity

AbstractThe dynamic transient gamma-ray sky is revealing many interesting results, largely due to findings by Fermi and Swift. The list includes new twists on gamma-ray bursts (GRBs), a GeV flare from a symbiotic star, GeV flares from the Crab Nebula, high-energy emission from novae and supernovae, and, within the last year, a new type of object discovered by Swift—a jetted tidal disruption event. In this review we present highlights of these exciting discoveries. A new mission concept called Lobster is also described; it would monitor the X-ray sky at order-of-magnitude higher sensitivity than current missions can.

scholarly journals Impact of H.E.S.S. Lidar profiles on Crab Nebula data

2019 ◽  
Vol 197 ◽  
pp. 01001 ◽  
Author(s):  
Justine Devin ◽  
Johan Bregeon ◽  
Georges Vasileiadis ◽  
Yves Gallant
Keyword(s):  
Energy Range ◽  
Photon Energy ◽  
Gamma Ray ◽  
Crab Nebula ◽  
Systematic Errors ◽  
High Energy ◽  
Atmospheric Composition ◽  
Direct Impact ◽  
Energy Gamma ◽  
The Crab Nebula

The H.E.S.S. experiment in Namibia is a high-energy gamma-ray telescope sensitive in the energy range from 30 GeV to a several tens of TeV, that uses the atmospheric Cherenkov technique to detect showers developed within the atmosphere. The elastic lidar, installed on the H.E.S.S. site, allows to reduce the systematic errors related to the atmospheric composition uncertainties thanks to the estimation of the extinction profile for the Cherenkov light (300-650 nm). The latter has a direct impact on the reconstructed parameters, such as the photon energy and the source flux. In this paper we report on physics results obtained on the Crab Nebula spectrum using the lidar profiles obtained at the H.E.S.S. site.

scholarly journals Multi-D magnetohydrodynamic modelling of pulsar wind nebulae: recent progress and open questions

2016 ◽  
Vol 82 (6) ◽  
Author(s):  
B. Olmi ◽  
L. Del Zanna ◽  
E. Amato ◽  
N. Bucciantini ◽  
A. Mignone
Keyword(s):  
Gamma Ray ◽  
Crab Nebula ◽  
Three Dimensional ◽  
Pulsar Wind Nebulae ◽  
Dissipation Process ◽  
Tearing Instability ◽  
Open Questions ◽  
Pulsar Wind ◽  
The Crab Nebula

In the last decade, the relativistic magnetohydrodynamic (MHD) modelling of pulsar wind nebulae, and of the Crab nebula in particular, has been highly successful, with many of the observed dynamical and emission properties reproduced down to the finest detail. Here, we critically discuss the results of some of the most recent studies: namely the investigation of the origin of the radio emitting particles and the quest for the acceleration sites of particles of different energies along the termination shock, by using wisp motions as a diagnostic tool; the study of the magnetic dissipation process in high magnetization nebulae by means of new long-term three-dimensional simulations of the pulsar wind nebula evolution; the investigation of the relativistic tearing instability in thinning current sheets, leading to fast reconnection events that might be at the origin of the Crab nebula gamma-ray flares.

scholarly journals ALMA and NOEMA constraints on synchrotron nebular emission from embryonic superluminous supernova remnants and radio–gamma-ray connection

2021 ◽  
Author(s):  
Kohta Murase ◽  
Conor M B Omand ◽  
Deanne L Coppejans ◽  
Hiroshi Nagai ◽  
Geoffrey C Bower ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Gamma Ray ◽  
Thermal Emission ◽  
Crab Nebula ◽  
Pulsar Wind Nebulae ◽  
Pulsar Wind ◽  
The Crab Nebula ◽  
Gamma Ray Telescopes ◽  
Very High ◽  
Fast Rotating

Abstract Fast-rotating pulsars and magnetars have been suggested as the central engines of super-luminous supernovae (SLSNe) and fast radio bursts, and this scenario naturally predicts non-thermal synchrotron emission from their nascent pulsar wind nebulae (PWNe). We report results of high-frequency radio observations with ALMA and NOEMA for three SLSNe (SN 2015bn, SN 2016ard, and SN 2017egm), and present a detailed theoretical model to calculate non-thermal emission from PWNe with an age of ∼1 − 3 yr. We find that the ALMA data disfavors a PWN model motivated by the Crab nebula for SN 2015bn and SN 2017egm, and argue that this tension can be resolved if the nebular magnetization is very high or very low. Such models can be tested by future MeV-GeV gamma-ray telescopes such as AMEGO.

scholarly journals Ultra-high-energy Gamma-Ray Radiation from the Crab Pulsar Wind Nebula

2022 ◽  
Vol 924 (2) ◽  
pp. 42
Author(s):  
Lin Nie ◽  
Yang Liu ◽  
Zejun Jiang ◽  
Xiongfei Geng
Keyword(s):  
Gamma Ray ◽  
Crab Nebula ◽  
High Energy ◽  
Model Parameters ◽  
Wave Band ◽  
Crab Pulsar ◽  
High Energy Gamma ◽  
Energy Gamma ◽  
Pulsar Wind ◽  
The Crab Nebula

Abstract It has been long debated whether the high-energy gamma-ray radiation from the Crab Nebula stems from leptonic or hadronic processes. In this work, we investigate the multiband nonthermal radiation from the Crab pulsar wind nebula with the leptonic and leptonic–hadronic hybrid models, respectively. Then we use the Markov Chain Monte Carlo sampling technology and method of sampling trace to study the stability and reasonability of the model parameters according to the recently observed results and obtain the best-fitting values of parameters. Finally, we calculate different radiative components generated by the electrons and protons in the Crab Nebula. The modeling results indicate that the pure leptonic origin model with the one-zone only can partly agree with some segments of the data from various experiments (including the PeV gamma-ray emission reported by the LHAASO and the other radiation ranging from the radio to very-high-energy gamma-ray wave band), and the contribution of hadronic interaction is hardly constrained. However, we find that the hadronic process may also contribute, especially in the energy range exceeding the PeV. In addition, it can be inferred that the higher energy signals from the Crab Nebula could be observed in the future.

scholarly journals Introducing the HD+B model for pulsar wind nebulae: a hybrid hydrodynamics/radiative approach

2020 ◽  
Vol 494 (3) ◽  
pp. 4357-4370
Author(s):  
B Olmi ◽  
D F Torres
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Theoretical Modelling ◽  
X Rays ◽  
Pulsar Wind Nebulae ◽  
New Approach ◽  
Energy Gamma ◽  
Radiative Model ◽  
Pulsar Wind

ABSTRACT Identification and characterization of a rapidly increasing number of pulsar wind nebulae is, and will continue to be, a challenge of high-energy gamma-ray astrophysics. Given that such systems constitute -by far- the most numerous expected population in the TeV regime, such characterization is important not only to learn about the sources per se from an individual and population perspective, but also to be able to connect them with observations at other frequencies, especially in radio and X-rays. Also, we need to remove the emission from nebulae in highly confused regions of the sky for revealing other underlying emitters. In this paper, we present a new approach for theoretical modelling of pulsar wind nebulae: a hybrid hydrodynamic-radiative model able to reproduce morphological features and spectra of the sources, with relatively limited numerical cost.

scholarly journals A corrugated termination shock in pulsar wind nebulae?

2016 ◽  
Vol 82 (4) ◽  
Author(s):  
Martin Lemoine
Keyword(s):  
Magnetic Field ◽  
Crab Nebula ◽  
Radiation Reaction ◽  
Termination Shock ◽  
Pulsar Wind Nebulae ◽  
Order Unity ◽  
Poynting Flux ◽  
Electron Positron ◽  
Pulsar Wind ◽  
The Crab Nebula

Successful phenomenological models of pulsar wind nebulae assume efficient dissipation of the Poynting flux of the magnetized electron–positron wind as well as efficient acceleration of the pairs in the vicinity of the termination shock, but how this is realized is not yet well understood. This paper suggests that the corrugation of the termination shock, at the onset of nonlinearity, may lead towards the desired phenomenology. Nonlinear corrugation of the termination shock would convert a fraction of order unity of the incoming ordered magnetic field into downstream turbulence, slowing down the flow to sub-relativistic velocities. The dissipation of turbulence would further preheat the pair population on short length scales, close to equipartition with the magnetic field, thereby reducing the initial high magnetization to values of order unity. Furthermore, it is speculated that the turbulence generated by the corrugation pattern may sustain a relativistic Fermi process, accelerating particles close to the radiation reaction limit, as observed in the Crab nebula. The required corrugation could be induced by the fast magnetosonic modes of downstream nebular turbulence; but it could also be produced by upstream turbulence, either carried by the wind or seeded in the precursor by the accelerated particles themselves.

scholarly journals Gamma-ray line features from the Crab Nebula in the energy range 50-2000 keV

1983 ◽  
Vol 205 (2) ◽  
pp. 285-295 ◽  
Author(s):  
C. A. Ayre ◽  
P. N. Bhat ◽  
Y. Q. Ma ◽  
R. M. Myers ◽  
M. G. Thompson
Keyword(s):  
Energy Range ◽  
Gamma Ray ◽  
Crab Nebula ◽  
Line Features ◽  
The Crab Nebula

scholarly journals Peculiar Differences in Radio and X-ray Synchrotron Radiation from Pulsar Wind Nebulae

2004 ◽  
Vol 218 ◽  
pp. 221-224
Author(s):  
John R. Dickel ◽  
Shiya Wang
Keyword(s):  
Synchrotron Radiation ◽  
Radio Emission ◽  
Supernova Remnants ◽  
Crab Nebula ◽  
Pulsar Wind Nebulae ◽  
X Ray ◽  
Pulsar Wind ◽  
The Crab Nebula

Several Crab-type supernova remnants appear to have very bright non-thermal X-ray cores just around the pulsar or expected pulsar. This X-ray brightness is often not matched by a corresponding increase in radio emission. The best example of this phenomenon is in N157B in the LMC. G21.5−0.9 and possibly 3C 58 also show it while the Crab Nebula and 0540−69.3 do not. Some method to enhance the higher energy particles must be present in these objects.

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