Ground-based gamma-ray astronomy with Cherenkov telescopes

Hinton, J. A.

doi:10.1088/1367-2630/11/5/055005

Cited by 73 publications

(30 citation statements)

References 61 publications

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“…The event was classified into a SIZE bin if SIZE detected by a fixed telescope was in the chosen range -condition (3) of SIZE, which is described in the text above. Similar values were obtained for conditions (1) and (2). The presented ratio decreases from 1.8 to 0.6 when the trigger threshold increases from 2 p.e.…”

Section: Ratio Of the Hardly Reducible Background To The Signal From supporting

confidence: 84%

The background from single electromagnetic subcascades for a stereo system of air Cherenkov telescopes

Sobczyńska¹

2009

J. Phys. G: Nucl. Part. Phys.

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Abstract.The MAGIC experiment, a very large Imaging Air Cherenkov Telescope (IACT) with sensitivity to low energy (E < 100 GeV) VHE gamma rays, has been operated since 2004. It has been found that the γ/hadron separation in IACTs becomes much more difficult below 100 GeV [1]. A system of two large telescopes may eventually be triggered by hadronic events containing Cherenkov light from only one electromagnetic subcascade or two γ subcascades, which are products of the single π 0 decay. This is a possible reason for the deterioration of the experiment's sensitivity below 100 GeV. In this paper a system of two MAGIC telescopes working in stereoscopic mode is studied using Monte Carlo simulations. The detected images have similar shapes to that of primary γ-rays and they have small sizes (mainly below 400 photoelectrons (p.e.)) which correspond to an energy of primary γ-rays below 100 GeV. The background from single or two electromagnetic subcascdes is concentrated at energies below 200 GeV. Finally the number of background events is compared to the number of VHE γ-ray excess events from the Crab Nebula. The investigated background survives simple cuts for sizes below 250 p.e. and thus the experiment's sensitivity deteriorates at lower energies.PACS numbers: 95.55. Ka; 95.55.Vj; 95.75.Mn; 95.85.Pw; 95.85.Ry

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Section: Ratio Of the Hardly Reducible Background To The Signal From supporting

confidence: 84%

The background from single electromagnetic subcascades for a stereo system of air Cherenkov telescopes

Sobczyńska¹

2009

J. Phys. G: Nucl. Part. Phys.

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“…The objective of gamma hadron separation is the statistical separation of gamma-ray induced air shower events among the (more or less) constant and isotropic abundance of (charged) cosmic ray events 4 . Since the observable differences between photonic and hadronic air showers are rather subtle, it is traditionally a difficult task to distinguish them with any air Cherenkov detector, but particularly with non-imaging detectors.…”

Section: Gamma Hadron Separationmentioning

confidence: 99%

Event reconstruction techniques for the wide-angle air Cherenkov detector HiSCORE

Hampf

Tluczykont

Horns

2013

Nuclear Instruments and Methods in Physics Research Section A:

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Wide-angle, non-imaging air Cherenkov detectors provide a way to observe cosmic gamma-rays which is complementary to observations by imaging Cherenkov telescopes. Their particular strength lies in the multi-TeV to ultra high energy range (E γ > 30 TeV), where large effective areas, yet small light sensitive areas per detector station are needed. To exploit this potential to full extent, a large station spacing is required to achieve a large effective area at a reasonable effort.In such a detector, the low number of signals per event, the absence of imaging information, and the poor signal to noise ratio of Cherenkov light to night sky brightness pose considerable challenges for the event reconstruction, especially the gamma hadron separation. The event reconstruction presented in this paper has been developed for the wide-angle detector HiSCORE, but the concepts may be applied more generically. It is tested on simulated data in the 10 TeV to 5 PeV energy range using the air shower simulation CORSIKA and the HiSCORE detector simulation sim score. For the tests, a regular grid of 22 × 22 detector stations with a spacing of 150 m is assumed, covering an area of 10 km 2 . The angular resolution of individual events is found to be about 0.3• near the energy threshold, improving to below 0.1 • at higher energies. The relative energy resolution is 20% at the threshold and improves to 10% at higher energies. Several parameters for gamma hadron separation are described. With a combination of these parameters, 80% to 90% of the hadronic background can be suppressed, while about 60% of the gamma-ray events are retained. The point source sensitivity to gamma-ray sources is estimated, using conservative assumptions, to be about 8 × 10 −13 erg s −1 cm −2 at 100 TeV gamma-ray energy for a 10 km 2 array. With more optimistic assumptions, and a 100 km 2 array, a sensitivity of about 1 × 10 −13 erg s −1 cm −2 can be achieved (at 100 TeV). Even in the former case the detector is sensitive enough to measure the continuation of currently known gamma-ray spectra into the ultra high energy domain. Due to its large field of view of 0.6 sr it also offers a great potential for the discovery of new gamma-ray sources at the so far largely unexplored energies of 100 TeV and above.

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“…Contrary to optical telescopes, IACTs observe dim (∼100 photons / m 2 / TeV) short (∼ ns) flashes produced by extended air showers developing in the atmosphere (see reviews by, e.g., Hinton 2009;Lorenz and Wagner 2012). The light, mostly emitted in the UV and optical wave bands, is produced via Cherenkov radiation from the charged particles of the atmospheric shower, which travel faster than the light in the air.…”

Section: Introductionmentioning

confidence: 99%

The major upgrade of the MAGIC telescopes, Part I: The hardware improvements and the commissioning of the system

Aleksić

Ansoldi

Antonelli

et al. 2016

Astroparticle Physics

221

123

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Figure 1: The two 17 m diameter MAGIC telescope system operating at the Roque de los Muchachos observatory in La Palma. The telescope in front is MAGIC-II. AbstractThe MAGIC telescopes are two Imaging Atmospheric Cherenkov Telescopes (IACTs) located on the Canary island of La Palma. The telescopes are designed to measure Cherenkov light from air showers initiated by gamma rays in the energy regime from around 50 GeV to more than 50 TeV. The two telescopes were built in 2004 and 2009, respectively, with different cameras, triggers and readout systems. In the years 2011-2012 the MAGIC collaboration undertook a major upgrade to make the stereoscopic system uniform, improving its overall performance and easing its maintenance. In particular, the camera, the receivers and the trigger of the first telescope were replaced and the readout of the two telescopes was upgraded. This paper (Part I) describes the details of the upgrade as well as the basic performance parameters of MAGIC such as raw data treatment, linearity in the electronic chain and sources of noise. In Part II, we describe the physics performance of the upgraded system.

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Ground-based gamma-ray astronomy with Cherenkov telescopes

Cited by 73 publications

References 61 publications

The background from single electromagnetic subcascades for a stereo system of air Cherenkov telescopes

The background from single electromagnetic subcascades for a stereo system of air Cherenkov telescopes

Event reconstruction techniques for the wide-angle air Cherenkov detector HiSCORE

The major upgrade of the MAGIC telescopes, Part I: The hardware improvements and the commissioning of the system

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