SST-GATE: A dual mirror telescope for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) will be the world's first open observatory for very high energy gamma-rays. Around a hundred telescopes of different sizes will be used to detect the Cherenkov light that results from gamma-ray induced air showers in the atmosphere. Amongst them, a large number of Small Size Telescopes (SST), with a diameter of about 4 m, will assure an unprecedented coverage of the high energy end of the electromagnetic spectrum (above ~1TeV to beyond 100 TeV) and will open up a new window on the non-thermal sky. Several concepts for the SST design are currently being investigated with the aim of combining a large field of view (~9 degrees) with a good resolution of the shower images, as well as minimizing costs. These include a Davies-Cotton configuration with a Geiger-mode avalanche photodiode (GAPD) based camera, as pioneered by FACT, and a novel and as yet untested design based on the Schwarzschild-Couder configuration, which uses a secondary mirror to reduce the plate-scale and to allow for a wide field of view with a light-weight camera, e.g. using GAPDs or multi-anode photomultipliers. One objective of the GATE (Gamma-ray Telescope Elements) programme is to build one of the first Schwarzschild-Couder prototypes and to evaluate its performance. The construction of the SST-GATE prototype on the campus of the Paris Observatory in Meudon is under way. We report on the current status of the project and provide details of the opto-mechanical design of the prototype, the development of its control software, and simulations of its expected performance.Comment: In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.223

The Gamma-ray Cherenkov Telescope, an end-to end Schwarzschild-Couder telescope prototype proposed for the Cherenkov Telescope Array

The GCT (Gamma-ray Cherenkov Telescope) is a dual-mirror prototype of Small-Sized-Telescopes proposed for the Cherenkov Telescope Array (CTA) and made by an Australian-Dutch-French-German-Indian-Japanese-UK-US consortium. The integration of this end-to-end telescope was achieved in 2015. On-site tests and measurements of the first Cherenkov images on the night sky began on November 2015. This contribution describes the telescope and plans for the pre-production and a large scale production within CTA

GYES, a multifibre spectrograph for the CFHT

We have chosen the name of GYES, one of the mythological giants with one hundred arms, offspring of Gaia and Uranus, for our instrument study of a multifibre spectrograph for the prime focus of the Canada-France-Hawaii Telescope. Such an instrument could provide an excellent ground-based complement for the Gaia mission and a northern complement to the HERMES project on the AAT. The CFHT is well known for providing a stable prime focus environment, with a large field of view, which has hosted several imaging instruments, but has never hosted a multifibre spectrograph. Building upon the experience gained at GEPI with FLAMES-Giraffe and X-Shooter, we are investigating the feasibility of a high multiplex spectrograph (about 500 fibres) over a field of view 1 degree in diameter. We are investigating an instrument with resolution in the range 15000 to 30000, which should provide accurate chemical abundances for stars down to 16th magnitude and radial velocities, accurate to 1 km/s for fainter stars. The study is led by GEPI-Observatoire de Paris with a contribution from Oxford for the study of the positioner. The financing for the study comes from INSU CSAA and Observatoire de Paris. The conceptual study will be delivered to CFHT for review by October 1st 2010.Comment: Contributed talk at the Gaia ELSA conference 2010, S\`evres 7-11 June 2010, to be published on the EAS Series, Editors: C. Turon, F. Arenou & F. Meynadie

Design concepts for the Cherenkov Telescope Array CTA: an advanced facility for ground-based high-energy gamma-ray astronomy

Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA

Sensitivity of the Cherenkov Telescope Array for probing cosmology and fundamental physics with gamma-ray propagation

The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for $\gamma$-ray astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of $\gamma$-ray cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nuclei (AGN) and of their relativistic jets. Observations of AGN with CTA will enable a measurement of $\gamma$-ray absorption on the extragalactic background light with a statistical uncertainty below 15% up to a redshift $z=2$ and to constrain or detect $\gamma$-ray halos up to intergalactic-magnetic-field strengths of at least 0.3pG. Extragalactic observations with CTA also show promising potential to probe physics beyond the Standard Model. The best limits on Lorentz invariance violation from $\gamma$-ray astronomy will be improved by a factor of at least two to three. CTA will also probe the parameter space in which axion-like particles could constitute a significant fraction, if not all, of dark matter. We conclude on the synergies between CTA and other upcoming facilities that will foster the growth of $\gamma$-ray cosmology

Southern African Large Telescope Spectroscopy of BL Lacs for the CTA project

In the last two decades, very-high-energy gamma-ray astronomy has reached maturity: over 200 sources have been detected, both Galactic and extragalactic, by ground-based experiments. At present, Active Galactic Nuclei (AGN) make up about 40% of the more than 200 sources detected at very high energies with ground-based telescopes, the majority of which are blazars, i.e. their jets are closely aligned with the line of sight to Earth and three quarters of which are classified as high-frequency peaked BL Lac objects. One challenge to studies of the cosmological evolution of BL Lacs is the difficulty of obtaining redshifts from their nearly featureless, continuum-dominated spectra. It is expected that a significant fraction of the AGN to be detected with the future Cherenkov Telescope Array (CTA) observatory will have no spectroscopic redshifts, compromising the reliability of BL Lac population studies, particularly of their cosmic evolution. We started an effort in 2019 to measure the redshifts of a large fraction of the AGN that are likely to be detected with CTA, using the Southern African Large Telescope (SALT). In this contribution, we present two results from an on-going SALT program focused on the determination of BL Lac object redshifts that will be relevant for the CTA observatory

Unos L-alanil-L-glutamina tijekom kratkotrajne visokointenzivne vježbe u uvjetima blagoga hidracijskoga stresa

The effect of acute L-alanyl-L-glutamine (AG) ingestion on selected hormonal and electrolyte measures was examined during repetitive, short duration, high intensity exercise with mild hypohydration. Subjects (20.3±1.1 yrs; 180.3±10.4 cm; 83.1±14.0 kg; 11.6±3.6% body fat) reported to the Human Performance Laboratory on four occasions. During each trial subjects were hypohydrated to -2.5% of their baseline body mass. During one trial (DHY) subjects rested in a recumbent position for 45 minutes before commencing the exercise session. During the other three trials subjects were rehydrated to 1.5% of their baseline body mass, before exercise, by drinking water only (W), or with two different doses of AG – a low dose (LDAG: 0.05 g�kg-1) and a high dose (HDAG: 0.2 g�kg-1). The exercise protocol consisted of ten 10-second sprints on a cycle ergometer with a 1-min rest between each sprint. Blood draws were collected once the subject achieved the desired level of hypohydration, immediately pre-exercise, immediately post-exercise, and 24 hrs postexercise. Blood samples were analyzed for glutamine, potassium, sodium, aldosterone, arginine vasopressin, C-reactive protein, interleukin-6, malondialdehyde, testosterone, cortisol, ACTH, and growth hormone. The area under the curve (AUC) analysis demonstrated significantly greater sodium concentrations for DHY compared to all other trials. The AUC analysis for aldosterone showed significantly lower concentrations at LDAG compared to DHY. No other differences between trials were observed in any other hormonal or biochemical responses. AG ingestion during a short duration, anaerobic exercise and mild hypohydration stress had a limited effect on selected hormonal and biochemical measures.Učinci akutnoga, trenutačnoga uzimanja L-alanil-L-glutamina (AG) na odabrane hormonske i elektrolitne pokazatelje ispitani su tijekom ponavljajuće kratkotrajne visokointenzivne aktivnosti u uvjetima blage hipohidracije ispitanika. Ispitanici (20,3±1,1 godina; 180,3±10,4 cm; 83,1±14,0 kg; 11,6±3,6% tjelesne masti) bili su testirani u Human Performance Laboratory u četiri navrata. Tijekom svakoga pojedinačnoga mjerenja ispitanici su bili hipohidrirani do -2,5% svoje početne, osnovne tjelesne mase. Tijekom prvoga testiranja (DHY) ispitanici su se odmarali ležeći 45 minuta prije no što su počeli provoditi protokol vježbanja. Tijekom sljedeća tri mjerenja ispitanici su rehidrirani do 1,5% njihove početne tjelesne mase prije vježbanja, i to: pijenjem samo vode (W) te unosom dviju različitih doza AG - male doze (LDAG: 0,05 g∙kg-1) i velike doze (HDAG: 0,2 g∙kg-1). Protokol vježbanja sastojao se od po deset sprintova na bicikl-ergometru u trajanju od 10 sekunda s jednominutnim odmorom između svakoga sprinta. Uzorci krvi vađeni su odmah nakon što je ispitanik dosegao željenu razinu hipohidracije, neposredno prije početka vježbanja, neposredno nakon završetka vježbanja i 24 sata nakon vježbanja. U uzorcima krvi analizirana je koncentracija glutamina, kalija, natrija, aldosterona, arginin vazopresina, C-reaktivnoga proteina, interleukina-6, malondialdehida, testosterona, kortizola, ACTH-a i hormona rasta. Analiza površine ispod krivulje pokazala je statistički značajno veću razinu koncentracije natrija u ispitanika u prvom testu (DHY) u odnosu na sva ostala mjerenja. Analiza površine ispod krivulje za aldosteron je pokazala značajno nižu koncentraciju u testu LDAG u odnosu na test DHY. Nisu zapažene značajne razlike između pojedinih mjerenja ni u jednoj drugoj hormonskoj i biokemijskoj reakciji na protokol vježbanja. Uzimanje AG tijekom kratkotrajne anaerobne aktivnosti i u stanju blagoga hipohidracijskoga stresa pokazalo je ograničene učinke na odabrane hormonske i biokemijske pokazatelje

Sensitivity of the Cherenkov Telescope Array for probing cosmology and fundamental physics with gamma-ray propagation

The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for γ astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of γ cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nuclei (AGN) and of their relativistic jets. Observations of AGN with CTA will enable a measurement of γ absorption on the extragalactic background light with a statistical uncertainty below 15% up to a redshift z=2 and to constrain or detect γ halos up to intergalactic-magnetic-field strengths of at least 0.3 pG . Extragalactic observations with CTA also show promising potential to probe physics beyond the Standard Model. The best limits on Lorentz invariance violation from γ astronomy will be improved by a factor of at least two to three. CTA will also probe the parameter space in which axion-like particles could constitute a significant fraction, if not all, of dark matter. We conclude on the synergies between CTA and other upcoming facilities that will foster the growth of γ cosmology.</p

30 m Stable towers for optimum astronomical observations at dome c/concordia

International audienceThis paper gives an overview of conceptual studies that have been realized since 2007 on 30 m towers for Dome C taking into account local available infrastructures and conditions. Some 30 m tower's concepts are presented and finite element simulations are carried to determine their dynamic behaviour including wind-induced vibrations, and to optimize their desig