scholarly journals A search for short-term variability in the very high energy γ-ray emission from the Crab nebula

2012 ◽  
Author(s):  
Anna O'Faoláin de Bhróithe ◽  
VERITAS Collaboration
Keyword(s):  
Crab Nebula ◽  
High Energy ◽  
Short Term ◽  
Very High Energy ◽  
Γ Ray ◽  
The Crab Nebula ◽  
Very High ◽  
Short Term Variability

scholarly journals Very high-energy γ-ray observations of the Crab nebula and other potential sources with the GRAAL experiment

2002 ◽  
Vol 17 (3) ◽  
pp. 293-318 ◽  
Author(s):  
F. Arqueros ◽  
J. Ballestrin ◽  
M. Berenguel ◽  
D.M. Borque ◽  
E.F. Camacho ◽  
...  
Keyword(s):  
Crab Nebula ◽  
High Energy ◽  
Potential Sources ◽  
Very High Energy ◽  
Γ Ray ◽  
The Crab Nebula ◽  
Very High

scholarly journals An intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced state

2020 ◽  
Vol 496 (3) ◽  
pp. 3912-3928
Author(s):  
MAGIC Collaboration: V A Acciari ◽  
S Ansoldi ◽  
L A Antonelli ◽  
A Arbet Engels ◽  
A Babić ◽  
...  
Keyword(s):  
Crab Nebula ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
Bl Lac ◽  
Very High Energy ◽  
Γ Ray ◽  
Using Data ◽  
The Crab Nebula

ABSTRACT Extreme high-frequency BL Lacs (EHBL) feature their synchrotron peak of the broad-band spectral energy distribution (SED) at νs ≥ 1017 Hz. The BL Lac object 1ES 2344+514 was included in the EHBL family because of its impressive shift of the synchrotron peak in 1996. During the following years, the source appeared to be in a low state without showing any extreme behaviours. In 2016 August, 1ES 2344+514 was detected with the ground-based γ-ray telescope FACT during a high γ-ray state, triggering multiwavelength (MWL) observations. We studied the MWL light curves of 1ES 2344+514 during the 2016 flaring state, using data from radio to very-high-energy (VHE) γ-rays taken with OVRO, KAIT, KVA, NOT, some telescopes of the GASP-WEBT collaboration at the Teide, Crimean, and St. Petersburg observatories, Swift-UVOT, Swift-XRT, Fermi-LAT, FACT, and MAGIC. With simultaneous observations of the flare, we built the broad-band SED and studied it in the framework of a leptonic and a hadronic model. The VHE γ-ray observations show a flux level of 55 per cent of the Crab Nebula flux above 300 GeV, similar to the historical maximum of 1995. The combination of MAGIC and Fermi-LAT spectra provides an unprecedented characterization of the inverse-Compton peak for this object during a flaring episode. The Γ index of the intrinsic spectrum in the VHE γ-ray band is 2.04 ± 0.12stat ± 0.15sys. We find the source in an extreme state with a shift of the position of the synchrotron peak to frequencies above or equal to 1018 Hz.

scholarly journals New Constraints on Hidden Photons using Very High Energy Gamma-Rays from the Crab Nebula

2008 ◽  
Author(s):  
Hannes-Sebastian Zechlin ◽  
Dieter Horns ◽  
Javier Redondo ◽  
Felix A. Aharonian ◽  
Werner Hofmann ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Crab Nebula ◽  
High Energy ◽  
High Energy Gamma ◽  
Very High Energy ◽  
Energy Gamma ◽  
The Crab Nebula ◽  
Very High

scholarly journals The Crab Pulsar and Nebula as Seen in Gamma-Rays

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 448
Author(s):  
Elena Amato ◽  
Barbara Olmi
Keyword(s):  
Gamma Ray ◽  
Crab Nebula ◽  
High Energy ◽  
Crab Pulsar ◽  
Gamma Ray Astronomy ◽  
Very High Energy ◽  
Energy Gamma ◽  
The Crab Nebula ◽  
The Impact ◽  
Very High

Slightly more than 30 years ago, Whipple detection of the Crab Nebula was the start of Very High Energy gamma-ray astronomy. Since then, gamma-ray observations of this source have continued to provide new surprises and challenges to theories, with the detection of fast variability, pulsed emission up to unexpectedly high energy, and the very recent detection of photons with energy exceeding 1 PeV. In this article, we review the impact of gamma-ray observations on our understanding of this extraordinary accelerator.

scholarly journals TeV γ-ray source MGRO J2019+37 : PWN or SNR?

2013 ◽  
Vol 9 (S296) ◽  
pp. 300-304
Author(s):  
Lab Saha ◽  
Pijushpani Bhattacharjee
Keyword(s):  
Crab Nebula ◽  
High Energy ◽  
Emission Region ◽  
Pulsar Wind Nebulae ◽  
Upper Limit ◽  
Multi Wavelength ◽  
Very High Energy ◽  
Hadronic Energy ◽  
Γ Ray ◽  
Very High

AbstractMilagro has recently reported an extended TeV γ-ray source MGRO J2019+37 in the Cygnus region. It is the second brightest TeV source after Crab nebula in their source catalogue. No confirmed counterparts of this source are known although possible associations with several known sources have been suggested. We study leptonic as well as hadronic models of TeV emission within the context of Pulsar Wind Nebulae (PWN) and Supernova Remnant (SNR) type sources, using constraints from multi-wavelength data from observations made on sources around MGRO J2019+37. These include radio upper limit given by GMRT, GeV observations by Fermi-LAT, EGRET and AGILE and very high energy data taken from Milagro. We find that, within the PWN scenario, while both leptonic as well as hadronic models can explain the TeV flux from this source, the GMRT upper limit imposes a stringent upper limit on the size of the emission region in the case of leptonic model. In the SNR scenario, on the other hand, a purely leptonic origin of TeV flux is inconsistent with the GMRT upper limit. At the same time, a dominantly hadronic origin of the TeV flux is consistent with all observations, and the required hadronic energy budget is comparable to that of typical supernovae explosions.

scholarly journals HESS J1741−302: a hidden accelerator in the Galactic plane

2018 ◽  
Vol 612 ◽  
pp. A13 ◽  
Author(s):  
◽  
H. Abdalla ◽  
A. Abramowski ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
...  
Keyword(s):  
Galactic Plane ◽  
Crab Nebula ◽  
Angular Size ◽  
High Energy ◽  
Spread Function ◽  
Very High Energy ◽  
Pulsar Wind ◽  
The Crab Nebula ◽  
Best Fit ◽  
Very High

The H.E.S.S. Collaboration has discovered a new very high energy (VHE, E > 0.1 TeV) γ-ray source, HESS J1741−302, located in the Galactic plane. Despite several attempts to constrain its nature, no plausible counterpart has been found so far at X-ray and MeV/GeV γ-ray energies, and the source remains unidentified. An analysis of 145-h of observations of HESS J1741−302 at VHEs has revealed a steady and relatively weak TeV source (~1% of the Crab Nebula flux), with a spectral index of Γ = 2.3 ± 0.2stat ± 0.2sys, extending to energies up to 10 TeV without any clear signature of a cut-off. In a hadronic scenario, such a spectrum implies an object with particle acceleration up to energies of several hundred TeV. Contrary to most H.E.S.S. unidentified sources, the angular size of HESS J1741−302 is compatible with the H.E.S.S. point spread function at VHEs, with an extension constrained to be below 0.068° at a 99% confidence level. The γ-ray emission detected by H.E.S.S. can be explained both within a hadronic scenario, due to collisions of protons with energies of hundreds of TeV with dense molecular clouds, and in a leptonic scenario, as a relic pulsar wind nebula, possibly powered by the middle-aged (20 kyr) pulsar PSR B1737−30. A binary scenario, related to the compact radio source 1LC 358.266+0.038 found to be spatially coincident with the best fit position of HESS J1741−302, is also envisaged.

Sign in / Sign up

Export Citation Format

Share Document