Context.We present the discovery of two very-high-energy γ-ray sources in an ongoing systematic search for emission above 100 GeV from pulsar wind nebulae in survey data from the HESS telescope ...array. Aims.Imaging Atmospheric Cherenkov Telescopes are ideal tools for searching for extended emission from pulsar wind nebulae in the very-high-energy regime. HESS, with its large field of view of 5° and high sensitivity, gives new prospects for the search for these objects. Methods.An ongoing systematic search for very-high-energy emission from energetic pulsars over the region of the Galactic plane between $-60^\circ < l < 30^\circ$, $-2^\circ < b < 2^\circ$ is performed. For the resulting candidates, the standard HESS analysis was applied and a search for multi-wavelength counterparts was performed. Results. We present the discovery of two new candidate γ-ray pulsar wind nebulae, HESS J1718-385 and HESS J1809-193. Conclusions.HESS has proven to be a suitable instrument for pulsar wind nebula searches.
HERA-B: overview and engineering runs Lohse, Thomas
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/1998, Volume:
408, Issue:
1
Journal Article
Peer reviewed
HERA-B represents the pioneering hadronic B factory, using fixed target techniques at the HERA proton storage ring at DESY. Although the experiment has been primarily optimized for measuring CP ...violation in the decay B
0→J/ψK
S
0, it addresses a wide range of topics in heavy quark physics, complementing the physics accessible at e
+e
− colliders. The detector and target design, the physics capabilities, and the technical status of the HERA-B project are discussed. Recent results from engineering runs using a partially installed detector are presented.
The previously unidentified very high-energy (VHE) gamma -ray source HESS J1303-631 is re-examined including new data from the HESS Cherenkov telescope array in order to identify this object. ...Detailed morphological and spectral studies of VHE gamma -ray emission as well as of the XMM-Newton X-ray data are performed. Significant energy-dependent morphology of this source, as well as the identification of an associated X-ray PWN from XMM-Newton observations enable identification of the VHE source as an evolved PWN associated to the pulsar PSR J1301-6305. This identification is supported by the one zone leptonic model, which suggests that the energetics of the gamma -ray and X-ray radiation are such that they may have a similar origin in the pulsar nebula. This would explain the low level of synchrotron radiation and the difficulty in detecting counterparts at lower energies, the reason this source was originally classified as a "dark' VHE gamma -ray source.
Vela X is a region of extended radio emission in the western part of the Vela constellation: one of the nearest pulsar wind nebulae, and associated with the energetic Vela pulsar. A deeper ...observation of the entire Vela X nebula region, also including larger offsets from the cocoon, has been performed with HESS. This re-observation was carried out in order to probe the extent of the non-thermal emission from the Vela X region at TeV energies and to investigate its spectral properties. To increase the sensitivity to the faint gamma -ray emission from the very extended Vela X region, a multivariate analysis method combining three complementary reconstruction techniques of Cherenkov-shower images is applied for the selection of gamma -ray events. The Vela X region exhibits almost uniform gamma -ray spectra over its full extent: the differential energy spectrum can be described by a power-law function with a hard spectral index ... and an exponential cutoff at an energy of TeV.(ProQuest: ... denotes formulae/symbols omitted.)
In some galaxy clusters, powerful active galactic nuclei (AGN) have blown bubbles with cluster scale extent into the ambient medium. The main pressure support of these bubbles is not known to date, ...but cosmic rays are a viable possibility. Hydra A, the closest galaxy cluster hosting a cluster scale AGN outburst, located at a redshift of 0.0538, is investigated for being a gamma-ray emitter with the High Energy Stereoscopic System (H.E.S.S.) array and the Fermi Large Area Telescope (Fermi-LAT). Data obtained in 20.2 h of dedicated H.E.S.S. observations and 38 months of Fermi-LAT data, gathered by its usual all-sky scanning mode, have been analyzed to search for a gamma-ray signal. No signal has been found in either data set. Upper limits on the gamma-ray flux are derived and are compared to models. The non-detection of Hydra A in gamma-rays has important implications on the particle populations and physical conditions inside the bubbles in this system.
1RXS J101015.9-311909 is a galaxy located at a redshift of z = 0.14 hosting an active nucleus belonging to the class of bright BL Lac objects. The authors report on results from VHE observations ...performed between 2006 and 2010 with the H.E.S.S. instrument, an array of four imaging atmospheric Cherenkov telescopes. H.E.S.S. data have been analysed with enhanced analysis methods, making the detection of faint sources more significant. VHE emission at a position coincident with 1RXS J101015.9-311909 is detected with H.E.S.S. for the first time. In a total good-quality livetime of about 49 h, the authors measure 263 excess counts, corresponding to a significance of 7.1 standard deviations. The photon spectrum above 0.2 TeV can be described by a power-law with a photon index of ... . The integral flux above 0.2 TeV is about 0.8% of the flux of the Crab nebula and shows no significant variability over the time reported. (ProQuest: ... denotes formulae/symbols omitted.)
Multiwavelength (MWL) observations of the blazar PKS 2155-304 during two weeks in July 2006 and August 2006, the period when two exceptional flares at very high energies occurred, provide a detailed ...picture of the evolution of its emission. The data set offers a close view of the evolution of the source on different time scales and yields new insights into the properties of the emission process. The predictions of synchrotron self-Compton (SSC) scenarios are compared to the MWL data, with the aim of describing the dominant features in the data down to the hour time scale. SSC modelling is used to interpret the general trends of the varying spectral energy distribution. The X-ray and VHE gamma -ray emission are correlated during the observed high state of the source, but show no direct connection with longer wavelengths. The long-term flux evolution in the optical and radio bands is found to be correlated and shows that the source reaches a high state at long wavelengths after the occurrence of the VHE flares.
The 1ES 0414++009 is a distant high-frequency-peaked BL Lac object, and has long been considered a likely emitter of very-high-energy gamma -rays due to its high X-ray and radio flux. The authors ...report observations made between October 2005 and December 2009 with HESS, an array of four imaging atmospheric Cherenkov telescopes. Observations at high energies with the Fermi-LAT instrument in the first 20 months of its operation are also reported. Based on the observations with HESS, 1ES 0414++009 is detected for the first time in the VHE band. An excess of 224 events is measured, corresponding to a significance of 7.8 sigma . The photon spectrum of the source is well described by a power law, with photon index of ... . The integral flux above 200 GeV is ... . Observations with the Fermi-LAT in the first 20 months of operation show a flux between 200 MeV and 100 GeV of ... , and a spectrum well described by a power-law function with a photon index ... . (ProQuest: ... denotes formulae/symbols omitted.)
This study aims to investigate particle acceleration processes in the vicinity of the young massive stellar cluster Westerlund 1. Imaging of Cherenkov light from gamma -ray induced particle cascades ...in the Earth's atmosphere is used to search for VHE gamma rays from the region around Wd 1. Possible catalogued counterparts are searched for and discussed in terms of morphology and energetics of the HESS source. The detection of the degree-scale extended VHE gamma -ray source HESS J1646-458 is reported based on 45 h of HESS observations performed between 2004 and 2008. The VHE gamma -ray source is centred on the nominal position of Wd 1 and detected with a total statistical significance of similar to 20 sigma . Four objects coincident with HESS J1646-458 are discussed in the search of a counterpart, namely the magnetar CXOU J164710.2-455216, the X-ray binary 4U 1642-45, the pulsar PSR J1648-4611 and the massive stellar cluster Wd 1. In a single-source scenario, Wd 1 is favoured as site of VHE particle acceleration.
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