The gravitational wave and short gamma-ray burst GW170817/SHB170817A

This event, so far unique, beautifully confirmed the standard views on the gravitational waves produced by a merger of two neutron stars, but its electro-magnetic multi-wavelenth observations disagreed with the numerous initial versions of the "standard fireball model(s)" of gamma ray bursts. Contrariwise, they pro-vided strong evidence in favour of the "cannonball" model. Most uncontroversially, a cannonball was observed at radio wavelengths, with an overwhelming statistical significance (> 17 sigma), and travelling in the plane of the sky, as expected, at an average apparent superluminal velocity Vapp 4 c.