Modeling of the multiwavelength emission of M87 with H.E.S.S. observations

M87 is the first extragalactic source detected in the TeV range that is not a blazar. The large scale jet of M87 is not aligned with the line of sight. Modification of standard emission models of TeV blazars appears necessary to account for the gamma-ray observations made by H.E.S.S. despite this misalignment. We present a new multi-blob synchrotron self-Compton model that deals explicitly with large viewing angles and moderate values of the Lorentz factor inferred from MHD simulations of jet formation.Comment: 4 pages, 4 figures; to appear in "SF2A 2007 proceedings", eds. J. Bouvier, A. Chalabaev and C. Charbonne

Multiwavelength modeling of TeV AGN observed by HESS

The High Energy Stereoscopic System (H.E.S.S.) experiment, a ground-based gamma-ray Cherenkov telescope array located in Namibia, has now detected many extragalactic objects, which redshifts range from z=0.00183 up to z=0.2, possibly more. With the increasing performances of Cherenkov telescopes, it now becomes possible to probe these objects at small timescales in gamma-ray, allowing the study of regions thought to be very close to the central supermassive black holes. Furthermore, H.E.S.S. has confirmed a gamma-ray emission from M87, which is thus the first extragalactic source seen at the TeV range that is not a blazar. Among blazars, TeV BL Lacs are the most challenging objects to test the jet emission models and to shed light on particle acceleration mechanisms. The study of blazars with H.E.S.S. also revealed various temporal behaviors among them. Some objects presents a highly variable X-ray flux with small variation of the gamma-ray, while others show the inverse behavior. The interpretation of such differences is puzzling. Observations at very high energies also bring indirect measurements of the infrared extragalactic background light (EBL). The interpretation of gamma-ray emission of radiogalaxies such as M87 in terms of misaligned blazars and the understanding of the properties of the EBL represent new challenges brought by H.E.S.S. observations of extragalactic sources.Comment: 3 pages, 5 figures; to appear in "The Nuclear Region, Host Galaxy and Environment of Active Galaxies", eds. E. Benitez, I. Cruz-Gonzalez and Y. Krongold, RevMexAA (Serie de Conferencias); added reference

Predictions of Very High Energy gamma-ray fluxes for three Active Galactic Nuclei

M87 is the first extragalactic source detected at the TeV that is not a blazar. To account for the recent observations of M87 made by the High Energy Stereoscopic System (H.E.S.S.) telescope array, we developed a new multi-blob synchrotron self-Compton model. In the framework of this model, we present here the predictions for the very high energy emission of three active galactic nuclei with extended optical or X-ray jets which could be misaligned blazars, namely Cen A, PKS 0521-36 and 3C 273.Comment: 4 pages, 3 figures; to appear in "SF2A 2007 proceedings", eds. J. Bouvier, A. Chalabaev and C. Charbonne

Utilisation de la grille EGI pour l'astrophysique de très hautes énergies avec H.E.S.S.

Utilisation de la grille EGI pour l'astrophysique de très hautes énergies avec H.E.S.S

AGN observations with a less than 100 GeV threshold using H.E.S.S. II

The recent addition of the 28 m Cherenkov telescope (CT5) to the H.E.S.S. array extended the experiment's sensitivity towards low energies. The lowest energy threshold is obtained using monoscopic observations with CT5, providing access to gamma-ray energies below 100 GeV. This is particularly beneficial for studies of Active Galactic Nuclei (AGN) with soft spectra and located at redshifts >= 0.5. Stereoscopic measurements with the full array (CT1-5) provide a better background rejection than CT5 Mono, at a cost of a higher threshold. We report on the analysis employing the CT5 data for AGN observations with a < 100 GeV threshold. In particular, the spectra of PKS 2155-304 and PG 1553+113 are presented.Comment: In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherland

High energy blazars spectroscopy with X-Shooter on the VLT

We present results of observations in the UV to near-IR range for eight blazars, three of which have been recently discovered at Very High Energies (VHE) and five appearing as interesting candidates for VHE {\gamma}-ray detection. We focus in this paper on the search for their redshifts, which are unknown or considered as uncertain.Comment: 4 pages, 8 figures, to appear in the proceedings of the 5th International Symposium on High-Energy Gamma-Ray Astronomy (Gamma2012), July 9-13, 2012, Heidelberg, German

Spectroscopy of High Energy BL Lac Objects with X-shooter on the VLT

Context. The study of BL Lac objects (BLL) detected in gamma-rays gives insights on the acceleration mechanisms in play in such systems and is also a valuable tool to constrain the density of the extragalactic background light. As their spectra are dominated by the non-thermal emission of the jet and the spectral features are weak and narrow in the optical domain, measuring their redshift is challenging. However such a measure is fundamental as it allows a firm determination of the distance and luminosity of the source, and therefore a consistent model of its emission. Aims. Measurement of the redshift of BLL detected in gamma-rays and determination of global properties of their host galaxies. Methods. We observed a sample of eight BLL (KUV 00311-1938, PKS 0447-439, PKS 0301-243, BZB J0238-3116, BZB J0543-5532, BZB J0505+0415, BZB J0816-1311 and RBS 334) with the X-shooter spectrograph installed at the ESO Very Large Telescope in order to take advantage of its unprecedented wavelength coverage and of its resolution about 5 times higher than generally used in such studies. We extracted UVB to NIR spectra that we then corrected for telluric absorption and calibrated in flux. We systematically searched for spectral features. When possible, we determined the contribution of the host galaxy to the overall emission. Results. Of the eight BLL, we measured the redshift of five of them and determined lower limits for two through the detection of intervening systems. All seven of these objects have redshifts greater than 0.2. In two cases, we refuted redshift values reported in other publications. Through careful modelling, we determined the magnitude of the host galaxies. In two cases, the detection of emission lines allowed to provide hints on the overall properties of the gas in the host galaxies.Comment: 19 pages, 10 figures, 7 tables, in press on A&

CTACG - CTA Computing Grid

International audienceCTACG - CTA Computing Gri

nectarchain\texttt{nectarchain}, the scientific software for the Cherenkov Telescope Array -- NectarCAM

The NectarCAM is a camera that will be mounted on the Medium-Sized Telescopes of the Cherenkov Telescope Array (CTA) observatory. Along with the hardware integration of the camera, the scientific software, $\texttt{nectarchain}$, is being developed. The software is responsible for transforming the raw data from the camera into analysis-ready calibrated data. In this contribution, we present the structure of the software, which consists of two modules: the calibration pipeline and the data quality check pipeline. The calibration pipeline reduces the data, performs flat fielding, and determines the gain for the analysis. The data quality monitoring pipeline is used to select the data that meets the necessary standards for analysis. Additionally, we discuss the format of the downstream data and the integration of the $\texttt{nectarchain}$ modules in the general software framework of CTA. We also present the necessary tests for validating each part of the code. We conclude by mentioning the prospects for the future of the software.Comment: Presented at the 38th International Cosmic Ray Conference (ICRC 2023), 2023 (arXiv:submit/5126940

On the elasto-viscoplastic behavior of the Ti5553 alloy

The elastoviscoplastic behavior of the Ti5553 alloy is characterized and compared to the classical Ti–6Al–4V alloy. The true stress–strain curves are determined based on tensile tests performed under different strain rates at room temperature and at 1501C, from which the elastic constants and the parameters of a Norton–Hoff viscoplastic model are identified. The strength of the Ti5553 alloy is 20–40% higher than the strength of the Ti–6Al–4V alloy. The Ti5553 alloy constitutes thus a promising candidate for advanced structural applications. In view of modeling structural applications of forming operations, the elastic and plastic initial anisotropy of the two alloys is investigated by combining compression on cylinders with elliptical sections, uniaxial tensile tests in different material directions, plane strain and shear tests. The initial anisotropy of the different alloys is very weak which justifies the modeling of the mechanical behavior with an isotropic yield surface. The identified elastoviscoplastic model is validated by comparing experimental results with FE predictions both on cylindrical notched specimens subjected to tensile tests and onflat specimens subjected to plane strain conditions