scholarly journals Rotationally driven VHE emission from the Vela pulsar

2019 ◽  
Vol 627 ◽  
pp. A22 ◽  
Author(s):  
Z. Osmanov ◽  
F. M. Rieger
Keyword(s):  
Particle Acceleration ◽  
Gamma Ray ◽  
Spectral Characteristics ◽  
High Energy ◽  
Radiation Mechanisms ◽  
Inverse Compton ◽  
Photon Index ◽  
Very High Energy ◽  
Vela Pulsar ◽  
Very High

Context. The recent detection of pulsed γ-ray emission from the Vela pulsar in the ∼10 to 100 GeV range by H.E.S.S. promises important potential to probe into the very high energy (VHE) radiation mechanisms of pulsars. Aims. A combined analysis of H.E.S.S. and Fermi-LAT data suggests that the leading wing of the P2 peak shows a new, hard gamma-ray component (with photon index as hard as Γ ∼ 3.5), setting in above 50 GeV and extending beyond 100 GeV. We study these findings in the context of rotationally driven (centrifugal) particle acceleration. Methods. We analyze achievable particle energies in the magnetosphere of the Vela pulsar and calculate the resultant emission properties. Results. Inverse Compton up-scattering of thermal photons from the surface of the star is shown to lead a pulsed VHE contribution reaching into the TeV regime with spectral characteristics compatible with current findings. If confirmed by further observations this could be the second case where rotationally driven processes turn out to be important to understand the VHE emission in young pulsars.

scholarly journals Revealing x-ray and gamma ray temporal and spectral similarities in the GRB 190829A afterglow

Science ◽  
2021 ◽  
Vol 372 (6546) ◽  
pp. 1081-1085
Author(s):  
◽  
H. Abdalla ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
E. O. Angüner ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
High Energy ◽  
X Ray ◽  
Photon Index ◽  
Very High Energy ◽  
Stereoscopic System ◽  
Very High ◽  
Intrinsic Energy

Gamma-ray bursts (GRBs), which are bright flashes of gamma rays from extragalactic sources followed by fading afterglow emission, are associated with stellar core collapse events. We report the detection of very-high-energy (VHE) gamma rays from the afterglow of GRB 190829A, between 4 and 56 hours after the trigger, using the High Energy Stereoscopic System (H.E.S.S.). The low luminosity and redshift of GRB 190829A reduce both internal and external absorption, allowing determination of its intrinsic energy spectrum. Between energies of 0.18 and 3.3 tera–electron volts, this spectrum is described by a power law with photon index of 2.07 ± 0.09, similar to the x-ray spectrum. The x-ray and VHE gamma-ray light curves also show similar decay profiles. These similar characteristics in the x-ray and gamma-ray bands challenge GRB afterglow emission scenarios.

scholarly journals On the reprocessing of gamma-rays produced by jets

2010 ◽  
Vol 6 (S275) ◽  
pp. 98-99
Author(s):  
M. Orellana ◽  
L. J. Pellizza ◽  
G. E. Romero
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
High Energy ◽  
High Mass ◽  
Cooling Channels ◽  
Inverse Compton ◽  
Very High Energy ◽  
Study Case ◽  
Very High ◽  
Photon Annihilation

AbstractSystems of two very different sizescales are known to produce very high-energy (VHE) radiation in their jets: AGNs and microquasars. The produced VHE photons (Eγ ~ 1 TeV) can be absorbed by the intense environmental soft photon fields, coming from the companion star (in high mass binaries) or from the accreting material (disk+corona in AGNs), as these are the dominant sources at energies around ~(mec2)2/Eγ. Energetic pairs are created by the photon-photon annihilation, and, depending on how efficient are the competing cooling channels, the absorption can lead to a reprocessing by Inverse Compton pair-cascade development. A self-consistent modeling of these systems as gamma-ray sources should then include, along with the emission and absorption processes, a thorough treatment of the pair cascades. We discuss here on this issue, focusing on our (preliminary) results of numerical simulations devoted to a study case similar to the high-mass microquasar candidate LS 5039.

scholarly journals A STRONG RADIO BRIGHTENING AT THE JET BASE OF M 87 DURING THE ELEVATED VERY HIGH ENERGY GAMMA-RAY STATE IN 2012

2014 ◽  
Vol 788 (2) ◽  
pp. 165 ◽  
Author(s):  
K. Hada ◽  
M. Giroletti ◽  
M. Kino ◽  
G. Giovannini ◽  
F. D'Ammando ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
High Energy Gamma ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

scholarly journals Future science issues for Galactic very-high-energy gamma-ray astronomy

2008 ◽  
Author(s):  
Diego F. Torres ◽  
Felix A. Aharonian ◽  
Werner Hofmann ◽  
Frank Rieger
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Gamma Ray Astronomy ◽  
High Energy Gamma ◽  
Future Science ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

BINARY PULSAR SYSTEM PSR B1259-63/LS2883 AS A GAMMA-RAY EMITTER

2014 ◽  
Vol 28 ◽  
pp. 1460169 ◽  
Author(s):  
DMITRY KHANGULYAN ◽  
SERGEY V. BOGOVALOV ◽  
FELIX A. AHARONIAN
Keyword(s):  
Energy Band ◽  
Gamma Ray ◽  
High Energy ◽  
Energy Losses ◽  
Binary Pulsar ◽  
Emission Component ◽  
Emission Enhancement ◽  
Very High Energy ◽  
Hydrodynamical Simulations ◽  
Very High

Observations of the binary pulsar PSR B1259-63/LS2883 in the high energy and very high energy domains have revealed a few quite unusual features. One of the most puzzling phenomena is the bright GeV flare detected with Fermi/LAT in 2011 January, approximately one month after periastron passage. Since the maximum luminosity in the high energy band during the flare nearly achieved the level of the pulsar spin-down energy losses, it is likely that the particles, responsible for this emission component, had a strongly anisotropic distribution, which resulted in the emission enhancement. One of the most prolific scenarios for such an emission enhancement is the Doppler boosting, which is realized in sources with relativistic motions. Interestingly, a number of hydrodynamical simulations have predicted a formation of highly relativistic outflows in binary pulsar systems, therefore scenarios, involving relativistic boosting, are very natural for these systems. However a more detailed analysis of such a possibility, presented in this study, reveals certain limitations which put strict constraints on the maximum luminosity achievable in this scenario. These constraints render the "Doppler boosting" scenario to be less feasible, especially for the synchrotron models.

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