Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Design and Characterization of a double-layered silicon charge detector for cosmic ray measurements in CALET

CALET (CALorimetric Electron Telescope) is a space instrument to explore a new frontier at higher energies for the cosmic-rays (electrons, gamma rays and heavy nuclei) and to search for dark matter.1 This mission is designed for a long exposure observation on the external JEM-EF facility aboard the International Space Station. It is optimized for the search of nearby sources of acceleration of cosmic ray electrons in the TeV energy range and gamma rays up to several TeV range. It can also extend the available data on cosmic ray composition and on secondary-to-primary ratios to higher energies allowing to discriminate among different propagation models and to derive the acceleration spectra at the source. An accurate measurement of the charge of the incoming particle is performed in CALET by a double-layered array of pixelated silicon sensors (Silicon Array or SIA), covering a seamless sensitive area of the order of 0.3 m2 and providing single-element identification up to Fe and above. The design of SIA instrument and its characterization are presented

The HEPD particle detector of the CSES satellite mission for investigating seismo-associated perturbations of the Van Allen belts

CSES (China Seismo-Electromagnetic Satellite) is a mission developed by CNSA (Chinese National Space Administration) and ASI (Italian Space Agency), to investigate the near-Earth electromagnetic, plasma and particle environment, for studying the seismo-associated disturbances in the ionosphere-magnetosphere transition zone. The anthropogenic and electromagnetic noise, as well as the natural non-seismic electromagnetic emissions is mainly due to tropospheric activity. In particular, the mission aims to confirming the existence of possible temporal correlations between the occurrence of earthquakes for medium and strong magnitude and the observation in space of electromagnetic perturbations, plasma variations and precipitation of bursts with high-energy charged particles from the inner Van Allen belt. In this framework, the high energy particle detector (HEPD) of the CSES mission has been developed by the Italian LIMADOU Collaboration. HEPD is an advanced detector based on a tower of scintillators and a silicon tracker that provides good energy and angular resolution and a wide angular acceptance, for electrons of 3–100 MeV, protons of 30–200 MeV and light nuclei up to the oxygen. CSES satellite has been launched on February 2nd, 2018 from the Jiuquan Satellite Launch Center (China). © 2018, Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature