Andreas Zech

Discovery of VHE emission from PKS 0447 439 with H.E.S.S. and MWL studies

Very-high energy (VHE) emission has been detected from PKS 0447-439 with the H.E.S.S. Cherenkov telescope array. This blazar is one of the brightest hard-spectrum extragalactic objects in the Fermi bright source list. Its detection with H.E.S.S. triggered Target of Opportunity observations with the Swift and RXTE telescopes, which show rapid flaring in the X-ray band. The spectrum and light curve measured by H.E.S.S. are presented. Along with the Fermi LAT data it is possible to put an upper limit on the redshift of the source. Implications of the flux evolution are discussed briefly.

The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342

The detection of several radio-loud narrow-line Seyfert 1 (NLS1) galaxies by the Fermi Gamma-Ray Space Telescope hints at the existence of a rare, new class of γ-ray emitting active galactic nuclei with low black hole masses. Like flat spectrum radio quasars (FSRQs), their γ-ray emission is thought to be produced via the external Compton mechanism whereby relativistic jet electrons upscatter a photon field external to the jet, e.g. from the accretion disc, broad line region (BLR), and dusty torus, to higher energies. Here we study the origin of the γ-ray emission in the lowest-redshift candidate among the currently known γ-ray emitting NLS1s, 1H 0323+342, and take a new approach. We observationally constrain the external photon field using quasi-simultaneous near-infrared, optical, and X-ray spectroscopy. Applying a one-zone leptonic jet model, we simulate the range of jet parameters for which this photon field, when Compton scattered to higher energies, can explain the γ-ray emission. We find that the site of the γ-ray emission lies well within the BLR and that the seed photons mainly originate from the accretion disc. The jet power that we determine, 1.0 × 1045u2009ergu2009s−1, is approximately half the accretion disc luminosity. We show that this object is not simply a low-mass FSRQ, its jet is intrinsically less powerful than predicted by scaling a typical FSRQ jet by black hole mass and accretion rate. That γ-ray-emitting NLS1s appear to host underpowered jets may go some way to explaining why so few have been detected to date.

SST-GATE: an innovative telescope for very high energy astronomy

The Cherenkov Telescope Array (CTA) is an international collaboration that aims to create the worlds largest (ever) Very High Energy gamma-ray telescope array, consisting of more than 100 telescopes covering an area of several square kilometers to observe the electromagnetic showers generated by incoming cosmic gamma-rays with very high energies (from a few tens of GeV up to over 100 TeV). Observing such sources requires - amongst many other things - a large FoV (Field of View). In the framework of CTA, SST-GATE (Small Size Telescope - GAmma-ray Telescope Elements) aims to investigate and to build one of the two first CTA prototypes based on the Schwarzschild-Couder (SC) optical design that delivers a FoV close to 10 degrees in diameter. To achieve the required performance per unit cost, many improvements in mirror manufacturing and in other technologies are required. We present in this paper the current status of our project. After a brief introduction of the very high energy context, we present the opto-mechanical design, discuss the technological tradeoffs and explain the electronics philosophy that will ensure the telescopes cost is minimised without limiting its capabilities. We then describe the software nedeed to operate the telescope and conclude by presenting the expected telescope performance and some management considerations.

Extragalactic source population studies at very high energies in the Cherenkov Telescope Array era

The Cherenkov Telescope Array (CTA) is the next generation ground-based

SST-GATE telescope: An innovative dual-mirror prototype for the Cherenkov Telescope Array

gamma

Final characterisation and design of the Gamma-ray Cherenkov Telescope (GCT) for the Cherenkov telescope array

-ray observatory. It will provide an order of magnitude better sensitivity and an extended energy coverage, 20 GeV - 300 TeV, relative to current Imaging Atmospheric Cherenkov Telescopes (IACTs). IACTs, despite featuring an excellent sensitivity, are characterized by a limited field of view that makes the blind search of new sources very time inefficient. Fortunately, the

Gammapy: high level data analysis for extragalactic science cases with the Cherenkov Telescope Array

textit{Fermi}

The Giant Radio Array for Neutrino Detection (GRAND) : Present and Perspectives

-LAT collaboration recently released a new catalog of 1,556 sources detected in the 10 GeV - 2 TeV range by the Large Area Telescope (LAT) in the first 7 years of its operation (the 3FHL catalog). This catalog is currently the most appropriate description of the sky that will be energetically accessible to CTA. Here, we discuss a detailed analysis of the extragalactic source population (mostly blazars) that will be studied in the near future by CTA. This analysis is based on simulations built from the expected array configurations and information reported in the 3FHL catalog. These results show the improvements that CTA will provide on the extragalactic TeV source population studies, which will be carried out by Key Science Projects as well as dedicated proposals.

Modeling the Broad-Band Emission from the Gamma-Ray Emitting Narrow-Line Seyfert-1 Galaxies 1H 0323+342 and B2 0954+25A

The Observatoire de Paris is involved in the Cherenkov Telescope Array (CTA) project by designing and constructing on the site of Meudon a Small Size Telescope prototype, named SST-GATE, in collaboration with the CHEC team (Compact High Energy Camera) which is providing the camera. The telescope structure is based on the Schwarzschild- Couder optical design which has never been adopted before in the design of a ground-based telescope. This concept allows a larger field of view and cheaper and smaller telescope and camera design with improved performance compared to the Davies-Cotton design traditionally used in very high energy gamma-ray telescopes. The SST-GATE telescope has been designed with the prime objectives of being light, versatile and simple to assemble with a minimal maintenance cost. This papers aims at reviewing the SST-GATE telescope structure from mechanics to optics along with the control command architecture; several innovative developments implemented within the design are discussed. Updates of the project status and perspectives are made.

The Cherenkov Telescope Array Observatory: top level use cases

The Gamma-ray Cherenkov Telescope (GCT) is one of the telescopes proposed for the Small Sized Telescope (SST) section of CTA. Based on a dual-mirror Schwarzschild-Couder design, which allows for more compact telescopes and cameras than the usual single-mirror designs, it will be equipped with a Compact High-Energy Camera (CHEC) based on silicon photomultipliers (SiPM). In 2015, the GCT prototype was the first dual-mirror telescope constructed in the prospect of CTA to record Cherenkov light on the night sky. Further tests and observations have been performed since then. This report describes the current status of the GCT, the results of tests performed to demonstrate its compliance with CTA requirements, and the optimisation of the design for mass production. The GCT collaboration, including teams from Australia, France, Germany, Japan, the Netherlands and the United Kingdom, plans to install the first telescopes on site in Chile for 2019-2020 as part of the CTA pre-production phase.