Gamma-ray astronomy with ARGO-YBJ

ARGO-YBJ is a full coverage air shower array located at the YangBaJing Cosmic Ray Laboratory (Tibet, P.R. China, 4300 m a.s.l., 606 g/cm2) recording data with a duty cycle ≥85% and an energy threshold of a few hundred GeV. In this paper the latest results in Gamma-Ray Astronomy are summarized

Fermi establishes classical novae as a distinct class of gamma-ray sources

A classical nova results from runaway thermonuclear explosions on the surface of a white dwarf that accretes matter from a low-mass main-sequence stellar companion. In 2012 and 2013, three novae were detected in γ rays and stood in contrast to the first γ-ray-detected nova V407 Cygni 2010, which belongs to a rare class of symbiotic binary systems. Despite likely differences in the compositions and masses of their white dwarf progenitors, the three classical novae are similarly characterized as soft-spectrum transient γ-ray sources detected over 2- to 3-week durations. The γ-ray detections point to unexpected high-energy particle acceleration processes linked to the mass ejection from thermonuclear explosions in an unanticipated class of Galactic γ-ray sources

Gamma-ray astronomy and cosmic-ray physics with ARGO-YBJ

The ARGO-YBJ detector, located 4300 m a.s.l. on the Tibet plateau, is a ground-based, full- coverage array of Resistive Plate Chambers (RPCs) covering a surface of 78×74 m2, surrounded by a guard ring of RPCs enclosing a total surface of about 11000 m2. ARGO-YBJ was designed to detect extensive air showers generated by cosmic rays and gamma rays with primary energy greater than few hundred GeV, in order to study the region of the cosmic-ray spectrum out of the reach of both satellite-based experiments and traditional ground-based arrays. The experiment has been running with its complete layout since November 2007, collecting over 2:5×1011 events. The main results obtained by ARGO-YBJ will be presented here, and specifically: the monitoring of astronomical gamma-ray sources, such as the Crab nebula and the MRK 421 AGN, the moon shadow, the medium-scale anisotropy map, the proton-proton inelastic cross section at center-of- mass energy between 70 and 500 GeV where no accelerator data are available