Monte Carlo simulation and data analysis of sky observation mode with the Cherenkov Telescope Array

The success of the current generation of Imaging Atmospheric Cherenkov Telescopes (IACTs) has affirmed the importance of gamma-ray astronomy for modern astrophysics. This field focuses on the upper end of the electromagnetic spectrum, with energies in the range of ~ 50 GeV to hundreds of TeV. Gamma rays, due to their neutral charge, are not disturbed by deflection from magnetic fields in their journey across the Universe, and can be traced back through their incoming direction. Thus, they can address to identify the acceleration processes of high-energy particles close to their acceleration sites, and also answer to some of the most fundamental physics issues, like the Lorentz invariance or the mystery of Dark Matter. Currently in the construction stage, the Cherenkov Telescope Array (CTA) is the next generation ground-based observatory for gamma-ray astronomy at very-high energies and it will exceed its predecessors in every aspect, e.g. energy range, sensitivity, field of view or angular resolution. The galactic and extragalactic surveys are two of the main proposed legacy projects of CTA, providing an unbiased view of the Universe at energies above tens of GeV. Surveys provide an immense service to the researchers community in the context of an open observatory, since they constitute versatile datasets that enable the detection of unexpected sources and provide testing ground for new theoretical ideas. Considering Cherenkov telescopes' limited field of view (FoV), the time needed for those science projects is large. The limited duty cycle of about 1000 hours per year of imaging Cherenkov facilities is a strong motivation to try to reduce the observation time needed for the surveys. The huge number of telescopes of CTA with respect to existing instruments, will allow taking full advantage of new pointing modes in which telescopes point slightly offset from one another, like the divergent mode. This pointing mode leads to an increase in the field of view of the sub-array of telescopes with competitive performance compared to normal pointing of the same sub-array. This type of observation should also improve CTA capacity to detect transient events, such as Gamma Ray Bursts (GRBs), thanks to the Large Size Telescope (LST) fast repointing capability and low energy threshold, and the ability to cover more complex patterns of the sky, like mapping a Gravitational Wave (GW) probability sky map or GRB large error boxes. A divergent pointing mode was included in the CTA science requirements document but, apart from a few publications, up to now it has never been the center of an in-depth study. This thesis is devoted to the improvement of the analysis in divergent mode and to study the performance of this modality for different array configurations and number of telescopes, in order to investigate if the performance are competitive compared to normal pointing

Measurement of χ c1 and χ c2 production with s√ = 7 TeV pp collisions at ATLAS

The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at s√ = 7 TeV with the ATLAS detector at the LHC using 4.5 fb−1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ −) where photons are reconstructed from γ → e + e − conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured

Measurement of the inclusive jet cross-section in proton-proton collisions at √s=7 TeV using 4.5 fb−1 of data with the ATLAS detector

The inclusive jet cross-section is measured in proton-proton collisions at a centre-of-mass energy of 7 TeV using a data set corresponding to an integrated luminosity of 4.5 fb−1 collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-kt algorithm with radius parameter values of 0.4 and 0.6. The double-differential cross-sections are presented as a function of the jet transverse momentum and the jet rapidity, covering jet transverse momenta from 100 GeV to 2 TeV. Next-to-leading-order QCD calculations corrected for non-perturbative effects and electroweak effects, as well as Monte Carlo simulations with next-to-leading-order matrix elements interfaced to parton showering, are compared to the measured cross-sections. A quantitative comparison of the measured cross-sections to the QCD calculations using several sets of parton distribution functions is performed

Observation of the Gamma-Ray Binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS Telescopes

The results of gamma-ray observations of the binary system HESS J0632 + 057 collected during 450 hr over 15 yr, between 2004 and 2019, are presented. Data taken with the atmospheric Cherenkov telescopes H.E.S.S., MAGIC, and VERITAS at energies above 350 GeV were used together with observations at X-ray energies obtained with Swift-XRT, Chandra, XMM-Newton, NuSTAR, and Suzaku. Some of these observations were accompanied by measurements of the Hα emission line. A significant detection of the modulation of the very high-energy gamma-ray fluxes with a period of 316.7 4.4 days is reported, consistent with the period of 317.3 0.7 days obtained with a refined analysis of X-ray data. The analysis of data from four orbital cycles with dense observational coverage reveals short-timescale variability, with flux-decay timescales of less than 20 days at very high energies. Flux variations observed over a timescale of several years indicate orbit-to-orbit variability. The analysis confirms the previously reported correlation of X-ray and gamma-ray emission from the system at very high significance, but cannot find any correlation of optical Hα parameters with fluxes at X-ray or gamma-ray energies in simultaneous observations. The key finding is that the emission of HESS J0632 + 057 in the X-ray and gamma-ray energy bands is highly variable on different timescales. The ratio of gamma-ray to X-ray flux shows the equality or even dominance of the gamma-ray energy range. This wealth of new data is interpreted taking into account the insufficient knowledge of the ephemeris of the system, and discussed in the context of results reported on other gamma-ray binary systems

MAGIC and H.E.S.S. detect VHE gamma rays from the blazar OT081 for the first time: a deep multiwavelength study

https://pos.sissa.it/395/815/pdfPublished versio

Musicothérapie et pluridisciplinarité, de l'indication à la place

International audiencePluridisciplinary groups using music therapy are frequent however there are few scholarly works referring to this type of therapy in a CMPP (Centre Medico Psycho Pedagogique). This article presents three examples of co-therapy associating psychology, psycho-motor therapy and speech therapy with music therapy. This pluridisciplinary approach focuses on the question of therapeutic indication and the role of patients and therapists within the session. In order to explore these elements, this article first proposes a comparison of clinical situations that emerged during the construction of a sound-based communication group. Second, we explore the questions that arose during a psychomotor-music therapy group, and third, the analysis in the aftermath of a group led by a speech therapist and a music therapist. Through our clinical observations, we look at how music therapy exists in an institution such as a CMPP and explore the questions of sound and language in each of the pluridisciplinary groups.La musicothérapie donne souvent lieu à des groupes thérapeutiques mais la littérature recense peu de références en lien avec un travail pluridisciplinaire en CMPP. Ainsi, nous vous présenterons trois exemples de co-thérapies associant la psychologie, la psychomotricité et l'orthophonie à la musicothérapie. A travers ce travail multidisciplinaire nous explorerons la question de l'indication à celle de la place. Pour cela, cet article propose d'abord « l'avant » d'un groupe de communication sonore en présentant les bilans psychologique et psychomusical, puis les questions sous-tendues lors d'un groupe musicothérapie-psychomotricité qui aborde le « pendant » de la séance et enfin, l'analyse à posteriori du groupe associant l'orthophonie et musicothérapie c'est-à-dire « l'après ». Le fonctionnement institutionnel et la co-thérapie sont abordés à travers nos observations cliniques, avec pour résultat une mise en perspective de la place de la musicothérapie au CMPP et du traitement de la question du sonore et du langage dans chacun de ces groupes

Performance study update of observations in divergent mode for the Cherenkov Telescope Array

Due to the limited field of view (FoV) of Cherenkov telescopes, the time needed to achieve target sensitivity for surveys of the extragalactic and Galactic sky is large. To optimize the time spent to perform such surveys, a so-called “divergent mode” of the Cherenkov Telescope Array Observatory (CTAO) was proposed as an alternative observation strategy to the traditional parallel pointing. In the divergent mode, each telescope points to a position in the sky that is slightly offset, in the outward direction, from the original center of the field of view. This bring the advantage of increasing the total instantaneous arrays’ FoV. From an enlarged field of view also benefits the search for very-high-energy transient sources, making it possible to cover large sky regions in follow-up observations, or to quickly cover the probability sky map in case of Gamma Ray Bursts (GRB), Gravitational Waves (GW), and other transient events. In this contribution, we present the proposed implementation of the divergent pointing mode and its first preliminary performance estimation for the southern CTAO array

First follow-up of transient events with the CTA Large Size Telescope prototype

International audienceThe recent detection of a very high energy (VHE) emission from Gamma-Ray Bursts (GRBs) above 100 GeV performed by the MAGIC and H.E.S.S. collaborations, has represented a significant, long-awaited result for the VHE astrophysics community. Although these results’ scientific impact has not yet been fully exploited, the possibility to detect VHE gamma-ray signals from GRBs has always been considered crucial for clarifying the poorly known physics of these objects. Furthermore, the discovery of high-energy neutrinos and gravitational waves associated with astrophysical sources have definitively opened the era of multi-messenger astrophysics, providing unique insights into the physics of extreme cosmic accelerators. In the near future, the Cherenkov Telescope Array (CTA) will play a major role in these observations. Within this framework, the Large Size Telescopes (LSTs) will be the instruments best suited to significantly impact on short time-scale transients follow-up thanks to their fast slewing and large effective area. The observations of the early emission phase of a wide range of transient events with good sensitivity below 100 GeV will allow us to open new opportunities for time-domain astrophysics in anenergy range not affected by selective absorption processes typical of other wavelengths. In this contribution, we will report about the observational program and first transients follow-up observations performed by the LST-1 telescope currently in its commissioning phase on La Palma, Canary Islands, the CTA northern hemisphere site

Intensity interferometry with the MAGIC telescopes

Due to their large mirror size, fast response to single photons, sensitivity and telescope baselines in the order of 100 m, Imaging Atmospheric Cherenkov Telescopes are ideally suited to perform intensity interferometry observations. In 2019 a test readout setup was installed in the two 17-m diameter MAGIC telescopes to allow performing interferometry measurements with them. The first on-sky measurements were able to detect correlated intensity fluctuations consistent with the stellar diameters of three different stars: Adhara (n CMa), Benetnasch ([ UMa) and Mirzam (V CMa). After the upgrade of the setup in 2021, MAGIC is now equipped with a high-duty-cycle intensity interferometer, already in operation. A technical description of the interferometer and first performance results obtained by measuring several known stellar diameter are presented