scholarly journals Assessing uncertainties in the predicted very high energy flux of globular clusters in the Cherenkov Telescope Array era

2020 ◽  
Vol 500 (4) ◽  
pp. 4827-4836
Author(s):  
Hambeleleni Ndiyavala-Davids ◽  
Christo Venter ◽  
Andreas Kopp ◽  
Michael Backes
Keyword(s):  
Globular Clusters ◽  
High Energy ◽  
Model Parameters ◽  
Telescope Array ◽  
Cluster Emission ◽  
Cherenkov Telescope ◽  
Upper Limits ◽  
Very High Energy ◽  
Emission Models ◽  
Very High

ABSTRACT Terzan 5 is the only Galactic globular cluster that has plausibly been detected in the very high energy range. Stacking upper limits by High-Energy Stereoscopic System on the integral γ-ray flux of a population of other globular clusters are very constraining for leptonic cluster emission models. We demonstrate that uncertainty in model parameters leads to a large spread in the predicted flux, and there are indeed regions in parameter space for which the stringent stacking upper limits are satisfied. We conduct two more case studies: we study the uncertainties in differential TeV flux for M15, showing that our model can satisfy the stringent MAGIC upper limits for this cluster, for typical cluster parameters. We also calculate the differential flux at TeV energies for ω Cen, from which five pulsars have recently been detected at radio energies. It is thus important to increase measurement accuracy on key model parameters in order to improve predictions of cluster fluxes so as to better guide the observational strategy of the Cherenkov Telescope Array.

scholarly journals A search for very high-energy flares from the microquasars GRS 1915+105, Circinus X-1, and V4641 Sgr using contemporaneous H.E.S.S. and RXTE observations

2018 ◽  
Vol 612 ◽  
pp. A10 ◽  
Author(s):  
◽  
H. Abdalla ◽  
A. Abramowski ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
...  
Keyword(s):  
Theoretical Models ◽  
High Energy ◽  
Photon Flux ◽  
Telescope Array ◽  
X Ray ◽  
Cherenkov Telescope ◽  
Intrinsic Absorption ◽  
Upper Limits ◽  
Very High Energy ◽  
Very High

Context. Microquasars are potential γ-ray emitters. Indications of transient episodes of γ-ray emission were recently reported in at least two systems: Cyg X-1 and Cyg X-3. The identification of additional γ-ray-emitting microquasars is required to better understand how γ-ray emission can be produced in these systems.Aim. Theoretical models have predicted very high-energy (VHE) γ-ray emission from microquasars during periods of transient outburst. Observations reported herein were undertaken with the objective of observing a broadband flaring event in the γ-ray and X-ray bands.Methods. Contemporaneous observations of three microquasars, GRS 1915+105, Circinus X-1, and V4641 Sgr, were obtained using the High Energy Spectroscopic System (H.E.S.S.) telescope array and the Rossi X-ray Timing Explorer (RXTE) satellite. X-ray analyses for each microquasar were performed and VHE γ-ray upper limits from contemporaneous H.E.S.S. observations were derived.Results. No significant γ-ray signal has been detected in any of the three systems. The integral γ-ray photon flux at the observational epochs is constrained to be I(>560 GeV) < 7.3 × 10−13 cm−2 s−1, I(>560 GeV ) < 1.2 × 10−12 cm−2 s−1, and I(>240 GeV) < 4.5 × 10−12 cm−2 s−1 for GRS 1915+105, Circinus X-1, and V4641 Sgr, respectively.Conclusions. The γ-ray upper limits obtained using H.E.S.S. are examined in the context of previous Cherenkov telescope observations of microquasars. The effect of intrinsic absorption is modelled for each target and found to have negligible impact on the flux of escaping γ-rays. When combined with the X-ray behaviour observed using RXTE, the derived results indicate that if detectable VHE γ-ray emission from microquasars is commonplace, then it is likely to be highly transient.

scholarly journals Searching for very-high-energy electromagnetic counterparts to gravitational-wave events with the Cherenkov Telescope Array

2021 ◽  
Author(s):  
Barbara Patricelli ◽  
Alessandro Carosi ◽  
Lara Nava ◽  
Monica Seglar-Arroyo ◽  
Fabian Schüssler ◽  
...  
Keyword(s):  
Gravitational Wave ◽  
High Energy ◽  
Telescope Array ◽  
Cherenkov Telescope ◽  
Very High Energy ◽  
Very High

scholarly journals Performance optimization of the air shower simulation program for the Cherenkov Telescope Array

2019 ◽  
Vol 214 ◽  
pp. 05041 ◽  
Author(s):  
Luisa Arrabito ◽  
Konrad Bernlöhr ◽  
Johan Bregeon ◽  
Gernot Maier ◽  
Philippe Langlois ◽  
...  
Keyword(s):  
Performance Optimization ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
High Energy ◽  
Telescope Array ◽  
Cherenkov Telescope ◽  
Cpu Time ◽  
Very High Energy ◽  
Under Construction ◽  
Very High

The Cherenkov Telescope Array (CTA), currently under construction, is the next-generation instrument in the field of very high energy gamma-ray astronomy. The first data are expected by the end of 2018, while the scientific operations will start in 2022 for a duration of about 30 years. In order to characterize the instrument response to the Cherenkov light emitted when cosmic ray showers develop in the atmosphere, detailed Monte Carlo simulations will be regularly performed in parallel to CTA operation. The estimated CPU time associated to these simulations is very high, of the order of 200 millions HS06 hours per year. Reducing the CPU time devoted to simulations would allow either to reduce infrastructure cost or to better cover the large phase space. In this paper, we focus on the main computing step (70% of the whole CPU time) implemented in the CORSIKA program, and specifically on the mod-ule responsible for the propagation of Cherenkov photons in the atmosphere. We present our preliminary studies about different options of code optimization, with a particular focus on vectorization facilities (SIMD instructions). Our proposals take care, as automatically as possible, of the hardware portability constraints introduced by the grid computing environment that hosts these simulations. Performance evaluation in terms of running-time and accuracy is provided.

scholarly journals Supernova remnants in the very–high–energy gamma-ray domain: the role of the Cherenkov telescope array

2017 ◽  
Vol 471 (1) ◽  
pp. 201-209 ◽  
Author(s):  
P. Cristofari ◽  
S. Gabici ◽  
T. B. Humensky ◽  
M. Santander ◽  
R. Terrier ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Gamma Ray ◽  
High Energy ◽  
Telescope Array ◽  
Cherenkov Telescope ◽  
High Energy Gamma ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

scholarly journals Supernova remnants in the very–high–energy sky: prospects for the Cherenkov Telescope Array

2017 ◽  
Author(s):  
Pierre Cristofari ◽  
Roberta Zanin ◽  
Stefano Gabici ◽  
Brian Humensky ◽  
Regis Terrier ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
High Energy ◽  
Telescope Array ◽  
Cherenkov Telescope ◽  
Very High Energy ◽  
Very High

Deflectometric measurement of large mirrors

2014 ◽  
Vol 3 (3) ◽  
Author(s):  
Evelyn Olesch ◽  
Gerd Häusler ◽  
André Wörnlein ◽  
Friedrich Stinzing ◽  
Christopher van Eldik
Keyword(s):  
Gamma Rays ◽  
High Energy ◽  
Spherical Mirror ◽  
Large Space ◽  
Telescope Array ◽  
Spread Function ◽  
Very High Energy ◽  
Energy Gamma ◽  
Concentric Geometry ◽  
Very High

AbstractWe discuss the inspection of large-sized, spherical mirror tiles by ‘Phase Measuring Deflectometry’ (PMD). About 10 000 of such mirror tiles, each satisfying strict requirements regarding the spatial extent of the point-spread-function (PSF), are planned to be installed on the Cherenkov Telescope Array (CTA), a future ground-based instrument to observe the sky in very high energy gamma-rays. Owing to their large radii of curvature of up to 60 m, a direct PSF measurement of these mirrors with concentric geometry requires large space. We present a PMD sensor with a footprint of only 5×2×1.2 m

RESULTS FROM GALACTIC OBSERVATIONS WITH MAGIC

2010 ◽  
Vol 19 (06) ◽  
pp. 1023-1029
Author(s):  
◽  
JAVIER RICO
Keyword(s):  
Gamma Rays ◽  
Energy Band ◽  
Binary Systems ◽  
High Energy ◽  
Cherenkov Telescope ◽  
La Palma ◽  
Very High Energy ◽  
Energy Gamma ◽  
High Energy Emission ◽  
Very High

MAGIC is a single-dish Cherenkov telescope located on La Palma (Spain), hence with an optimal view on the Northern sky. Sensitive to the 30 GeV–30 TeV energy band, it is nowadays the only ground-based instrument being able to measure high-energy gamma-rays below 100 GeV. With the operation in coincidence with MACIC-II, starting in Fall 2009, the sensitivity will be improved by a factor ~ 2. We review the results obtained by MAGIC on the very-high energy emission from pulsars, binary systems and microquasars.

scholarly journals e±-rich GRB Fireball and Infrared Flashes

2003 ◽  
Vol 214 ◽  
pp. 331-332
Author(s):  
Zhuo Li ◽  
Z. G. Dai ◽  
T. Lu
Keyword(s):  
Gamma Ray ◽  
Lorentz Factor ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Rapid Response ◽  
Model Parameters ◽  
Wide Range ◽  
Very High Energy ◽  
Very High

Gamma-ray bursts (GRBs) are believed to originate from ultra-relativistic fireballs, with initial Lorentz factor η ∼ 102 − 103. However very high energy photons may still suffer from γγ interaction. We show here that in a wide range of model parameters, the resulting pairs may dominate electrons associated with the fireball baryons. This may provide an explanation for the rarity of prompt optical detections. A rapid response to the GRB trigger at the IR band would detect such a strong flash.

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