No Arabic abstract
The HERMES-TP/SP (High Energy Rapid Modular Ensemble of Satellites -- Technologic and Scientific Pathfinder) is an in-orbit demonstration of the so-called distributed astronomy concept. Conceived as a mini-constellation of six 3U nano-satellites hosting a new miniaturized detector, HERMES-TP/SP aims at the detection and accurate localisation of bright high-energy transients such as Gamma-Ray Bursts. The large energy band, the excellent temporal resolution and the wide field of view that characterize the detectors of the constellation represent the key features for the next generation high-energy all-sky monitor with good localisation capabilities that will play a pivotal role in the future of Multi-messenger Astronomy. In this work, we will describe in detail the temporal techniques that allow the localisation of bright transient events taking advantage of their almost simultaneous observation by spatially spaced detectors. Moreover, we will quantitatively discuss the all-sky monitor capabilities of the HERMES Pathfinder as well as its achievable accuracies on the localisation of the detected Gamma-Ray Bursts.
COMPTEL was the Compton telescope on NASAs Compton Gamma Ray Observatory CGRO launched in April 1991 and which was re-entered in June 2000. COMPTEL covered the energy range 0.75 to 30 MeV, and performed a full-sky survey which is still unique in this range, with no followup mission yet approved. This remains a major uncharted region, and the heritage data from COMPTEL are still our main source of information. Data analysis has continued at MPE however, since the data were never fully analysed during the mission or in the period following, and improvements in analysis techniques and computer power make this possible.
Neutrinos may offer a unique opportunity to explore the far Universe at high energy. The ANTARES collaboration aims at building a large undersea neutrino detector able to observe astrophysical sources (AGNs, X-ray binary systems, ...) and to study particle physics topics (neutrino oscillation, ...). After a description of the research opportunities of such a detector, a status report of the experiment will be made.
The short review of theoretical aspects of ultra high energy (UHE) neutrinos. The accelerator sources, such as Supernovae remnants, Gamma Ray Bursts, AGN etc are discussed. The top-down sources include Topological Defects (TDs), Superheavy Dark Matter (SHDM) and Mirror Matter. The diffuse fluxes are considered accordingly as that of cosmogenic and top-down neutrinos. Much attention is given to the cascade upper limit to the diffuse neutrino fluxes in the light of Fermi-LAT data on diffuse high energy gamma radiation. This is most general and rigorous upper limit, valid for both cosmogenic and top-down models. At present upper limits from many detectors are close to the cascade upper limit, and 5 yr IceCube upper limit will be well below it.
We report on the high-precision timing of 42 radio millisecond pulsars (MSPs) observed by the European Pulsar Timing Array (EPTA). This EPTA Data Release 1.0 extends up to mid-2014 and baselines range from 7-18 years. It forms the basis for the stochastic gravitational-wave background, anisotropic background, and continuous-wave limits recently presented by the EPTA elsewhere. The Bayesian timing analysis performed with TempoNest yields the detection of several new parameters: seven parallaxes, nine proper motions and, in the case of six binary pulsars, an apparent change of the semi-major axis. We find the NE2001 Galactic electron density model to be a better match to our parallax distances (after correction from the Lutz-Kelker bias) than the M2 and M3 models by Schnitzeler (2012). However, we measure an average uncertainty of 80% (fractional) for NE2001, three times larger than what is typically assumed in the literature. We revisit the transverse velocity distribution for a set of 19 isolated and 57 binary MSPs and find no statistical difference between these two populations. We detect Shapiro delay in the timing residuals of PSRs J1600$-$3053 and J1918$-$0642, implying pulsar and companion masses $m_p=1.22_{-0.35}^{+0.5} text{M}_{odot}$, $m_c = 0.21_{-0.04}^{+0.06} text{M}_{odot }$ and $m_p=1.25_{-0.4}^{+0.6} text{M}_{odot}$, $m_c = 0.23_{-0.05}^{+0.07} text{M}_{odot }$, respectively. Finally, we use the measurement of the orbital period derivative to set a stringent constraint on the distance to PSRs J1012$+$5307 and J1909$-$3744, and set limits on the longitude of ascending node through the search of the annual-orbital parallax for PSRs J1600$-$3053 and J1909$-$3744.
We present an analysis technique that uses the timing information of Cherenkov images from extensive air showers (EAS). Our emphasis is on distant, or large core distance gamma-ray induced showers at multi-TeV energies. Specifically, combining pixel timing information with an improved direction reconstruction algorithm, leads to improvements in angular and core resolution as large as ~40% and ~30%, respectively, when compared with the same algorithm without the use of timing. Above 10 TeV, this results in an angular resolution approaching 0.05 degrees, together with a core resolution better than ~15 m. The off-axis post-cut gamma-ray acceptance is energy dependent and its full width at half maximum ranges from 4 degrees to 8 degrees. For shower directions that are up to ~6 degrees off-axis, the angular resolution achieved by using timing information is comparable, around 100 TeV, to the on-axis angular resolution. The telescope specifications and layout we describe here are geared towards energies above 10 TeV. However, the methods can in principle be applied to other energies, given suitable telescope parameters. The 5-telescope cell investigated in this study could initially pave the way for a larger array of sparsely spaced telescopes in an effort to push the collection area to >10 km2. These results highlight the potential of a `sparse array approach in effectively opening up the energy range above 10 TeV.