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We present here results from large zenith-angle observations with the CAT atmospheric Cherenkov imaging telescope, based on data taken on the Crab Nebula and on the blazar Mk501 from 1996 onwards. From Monte Carlo simulations, the threshold…

Astrophysics · Physics 2019-08-14 G. Mohanty

During 1997, the BL Lac Object Mkn 501 was the brightest known object in the TeV gamma-ray sky. The emission was characterized by dramatic variations in intensity with a mean flux exceeding by a factor of three the steady gamma-ray flux of…

Astrophysics · Physics 2007-05-23 F. Aharonian

The Crab nebula is a prominent pulsar wind nebula (PWN) detected in multiband observations ranging from radio to very high-energy (VHE) $\gamma$-rays. Recently, $\gamma$-rays with energies above $1 \mathrm{PeV}$ had been detected by the…

High Energy Astrophysical Phenomena · Physics 2022-01-05 Lu Wen , Ke-Yao Wu , Huan Yu , Jun Fang

The Cherenkov Telescope Array (CTA) will be the next generation gamma-ray observatory, which will consist of three kinds of telescopes of different sizes. Among those, the Large Size Telescope (LST) will be the most sensitive in the low…

Instrumentation and Methods for Astrophysics · Physics 2021-08-23 Y. Ohtani , A. Berti , D. Depaoli , F. Di Pierro , D. Green , L. Heckmann , M. Hütten , T. Inada , R. López-Coto , E. Medina , A. Moralejo , D. Morcuende , G. Pirola , M. Strzys , Y. Suda , I. Vovk

Surface radio antenna-based measurements of cosmic-ray air showers present significant computational challenges in accurately reconstructing physics observables, in particular, the depth of shower maximum, X$_{max}$. State-of-the-art…

High Energy Astrophysical Phenomena · Physics 2025-07-11 Paras Koundal

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…

High Energy Astrophysical Phenomena · Physics 2021-11-16 Elena Amato , Barbara Olmi

As of 2023, the low-frequency part of the Square Kilometre Array will go online in Australia. It will constitute the largest and most powerful low-frequency radio-astronomical observatory to date, and will facilitate a rich science…

In this paper, we present the results of an observational search for gas phase urea [(NH$_2$)$_2$CO] observed towards the Sgr B2(N-LMH) region. We show data covering urea transitions from $\sim$100 GHz to 250 GHz from five different…

In 2008 the blazar Markarian 421 entered a very active phase and was one of the brightest sources in the sky at TeV energies, showing frequent flaring episodes. Using the data of ARGO-YBJ, a full coverage air shower detector located at…

High Energy Astrophysical Phenomena · Physics 2015-05-18 G. Aielli et al.

Data taken with the HEGRA system of imaging atmospheric Cherenkov telescopes during the 1997 flares of Mkn 501 are reanalyzed using an algorithm providing improved energy resolution. A resolution of 10% to 12% is obtained by accounting for…

Astrophysics · Physics 2015-12-09 HEGRA Collaboration , F. Aharonian

Aims. The Crab nebula displayed a large gamma-ray flare on September 18, 2010. To more closely understand the origin of this phenomenon, we analyze the INTEGRAL (20-500 keV) and FERMI (0.1-300 GeV) data collected almost simultaneously…

High Energy Astrophysical Phenomena · Physics 2015-05-20 M. Balbo , R. Walter , C. Ferrigno , P. Bordas

The recently commissioned Compact Array Broadband Backend (CABB) on the Australia Telescope Compact Array (ATCA) provides 2 GHz bandwidth in each frequency and polarisation, significantly increasing the sensitivity of the Array. This…

Astrophysics of Galaxies · Physics 2010-08-27 Elizabeth K. Mahony , Elaine M. Sadler , Scott M. Croom , Ronald D. Ekers , Ilana J. Feain , Tara Murphy

In this proceeding, we summarize the key science goals and reference design for a next-generation Very Large Array (ngVLA) that is envisaged to operate in the 2030s. The ngVLA is an interferometric array with more than 10 times the…

Instrumentation and Methods for Astrophysics · Physics 2018-08-22 Eric J. Murphy

We present results from our analysis of Chandra X-ray Observatory, W. M. Keck Observatory, and Karl G. Jansky Very Large Array (VLA) images of the Crab Nebula that were contemporaneous with the gamma-ray flare of 2011 April. Despite hints…

We searched for a fast moving H$\alpha$ shell around the Crab nebula. Such a shell could account for this supernova remnant's missing mass, and carry enough kinetic energy to make SN 1054 a normal Type II event. Deep H$\alpha$ images were…

Solar and Stellar Astrophysics · Physics 2009-11-13 A. Tziamtzis , M. Schirmer , P. Lundqvist , J. Sollerman

The resolution power of current Imaging Atmospheric Cherenkov Telescopes is presently restricted to scales of a few arcminutes. In the very high-energy (VHE; E > 100 GeV) gamma-ray regime, the measurement of source sizes that are comparable…

High Energy Astrophysical Phenomena · Physics 2019-08-14 M. Holler , D. Berge , J. Hahn , D. Khangulyan , R. D. Parsons

The Very High Energy Radiation Telescope Array (VERITAS) is a system of four imaging Cherenkov telescopes currently under construction at Kitt Peak, Arizona, USA. The first telescope has been in operation at the Mt. Hopkins basecamp since…

Astrophysics · Physics 2019-08-14 G. Maier

The TeV gamma ray sky is observable by recording footprints of extensive air showers with an array of particle detectors. In the northern hemisphere there are currently two projects employing this technique: The HAWC gamma ray observatory…

Instrumentation and Methods for Astrophysics · Physics 2017-09-19 Harm Schoorlemmer , Rubén López-Coto , Jim Hinton

The "knee" of cosmic ray spectra may reflect the maximum energy accelerated by galactic cosmic ray sources or the limit of the galaxy's ability to bind cosmic rays. Measurements of individual energy spectra are a crucial tool to understand…

High Energy Astrophysical Phenomena · Physics 2026-03-02 Hu Liu , Fanping Li , J. Zhao , L. Y. Wang , Zhe Li , S. Z. Chen

The energy reconstruction of extensive air showers measured with the LOFAR Radboud Air Shower Array (LORA) is presented in detail. LORA is a particle detector array located in the center of the LOFAR radio telescope in the Netherlands. The…

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