Xmax reconstruction from amplitude information with AERA

The standard method to estimate the mass of a cosmic ray is the measurement of the atmospheric depth of the shower maximum (Xmax). This depth is strongly correlated with the mass of the primary because it depends on the interaction cross section of the primary with the constituents of the atmosphere. Measuring the electric field, emitted by the secondary particles of an extensive air shower (EAS), with the Auger Engineering Radio Array (AERA) in the 30-80 MHz band allows the determination of the depth of shower maximum on the basis of the good understanding of the radio emission mechanisms. The duty cycle of radio detectors is close to 100%, making possible the statistical determination of the cosmic-ray mass composition through the study of a large number of cosmic rays above 1017 eV. In this contribution, Xmax reconstruction methods based on the study of the radio signal with AERA are detailed

H.E.S.S. observations of very-high-energy emission from 1RXS J023832.6-311658

International audienceObservations of the HBL blazar 1RXS J023832.6-311658 were made in 2013, 2015 and 2016 with the High Energy Stereoscopic System (H.E.S.S.). An excess of very high energy (VHE: > 100 GeV) gamma rays is clearly observed. The spectral energy distribution including the VHE spectrum will be presented. This object has a hard spectrum at TeV energies, and has a redshift z=0.23. These characteristics could be suitable for extragalactic magnetic fields for which the perspectives with H.E.S.S. will be discussed

ps2chitt!ps^2chitt! – A Python package for the modelling of atmoSpheric Showers and CHerenkov Imaging Terrestrial Telescopes

International audienceThe simulation of atmospheric showers through Monte-Carlo processes as well as their projection into Imaging Atmospheric Cherenkov Telescopes (IACT) is long and very computing intensive. As these simulations are the most advanced ones from a physics point of view, they are not suited for simple tests.Here we present a Python package developed in order to model atmospheric showers using different profiles and to image them with an array of IACT. This allows for first order studies of the influence of the primary photon energy and angular direction on the stereoscopic images. Its simplicity also makes it convenient for public dissemination and outreach as well as for teaching purposes.This package has been developed to make the most out of the simplicity of Python but has also been optimised for fast calculations. It is developed in the framework of the ASTERICS H2020 project and as such is available as an open-source software

Main features of cosmic ray induced air showers measured by the CODALEMA experiment

International audienceThe radio signals produced by extensive air showers initiated in the atmosphere by high energy cosmic rays are routinely observed and registered by the various instruments of the CODALEMA experiment located at the Nançay radio observatory and notably by the large array of self-triggering stations equipped with wide band and dual polarization antennas. Precise comparisons between observed radio signals and simulations performed with the SELFAS code allow most of the main features of the primary cosmic ray to be determined: arrival direction, energy and $X_{max}$ estimates from which a the composition in the energy range covered by CODALEMA may be derived. After a presentation of the analysis methods, its sensitivity will be discussed and the results obtained over a significant set of experimental events will be detailed

Astrophysical interpretation of Pierre Auger Observatory measurements of the UHECR energy spectrum and mass composition

We present a combined fit of a simple astrophysical model of UHECR sources to both the energy spectrum and mass composition data measured by the Pierre Auger Observatory. The fit has been performed for energies above 5 EeV, i.e. the region of the all-particle spectrum above the so-called "ankle"' feature. The astrophysical model we adopted consists of identical sources uniformly distributed in a comoving volume, where nuclei are accelerated with a rigidity-dependent mechanism. The fit results suggest sources characterized by relatively low maximum injection energies and hard spectral indices. The impact of various systematic uncertainties on the above result is discussed.0SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Recent results from CODALEMA and the Nançay radio facilities related to cosmic-ray measurements

Since 2003, the NanÇay Radio Observatory hosts the CODALEMA experiment, dedicated to radio detection of cosmic ray induced extensive air showers. CODALEMA also features the R&D EXTASIS project, aiming at detecting the lowfrequency signal ([2-6] MHz) produced at the sudden disappearance of the air shower particles hitting the ground. The 3 current antenna arrays present different antenna density and extent, and can be operated in a joint mode to record simultaneously the radio signal coming from air showers. Therefore, the NanÇay facilities may offer a complete description of the air shower induced electric field at small, medium and large scale, and over an unique and very wide frequency band (from ~ 2 to 200 MHz)

Studying cosmological γ\gamma-ray propagation with the Cherenkov Telescope ArrayumCT

The measurement of $\gamma$-rays originating from active galactic nuclei offers the unique opportunity to study the propagation of very-high-energy photons over cosmological distances. Most prominently, $\gamma$-rays interact with the extragalactic background light (EBL) to produce $e^+e^-$ pairs, imprinting an attenuation signature on $\gamma$-ray spectra. The $e^+e^-$ pairs can also induce electromagnetic cascades whose detectability in $\gamma$-rays depends on the intergalactic magnetic field (IGMF). Furthermore, physics beyond the Standard Model such as Lorentz invariance violation (LIV) or oscillations between photons and weakly interacting sub-eV particles (WISPs) could affect the propagation of $\gamma$-rays. The future Cherenkov Telescope Array (CTA), with its unprecedented $\gamma$-ray source sensitivity, as well as enhanced energy and spatial resolution at very high energies, is perfectly suited to study cosmological effects on $\gamma$-ray propagation. Here, we present first results of a study designed to realistically assess the capabilities of CTA to probe the EBL, IGMF, LIV, and WISPs