  The state of supranuclear matter in compact star remains puzzling, and it is
argued that pulsars could be strangeon stars. What if binary strangeon stars
merge? This kind of merger could result in the formation of a hyper-massive
strangeon star, accompanied by bursts of gravitational waves and
electromagnetic radiation (and even strangeon kilonova explained in the paper).
The tidal polarizability of binary strangeon stars is different from that of
binary neutron stars, because a strangeon star is self-bound on surface by
fundamental strong force while a neutron star by the gravity, and their
equations of state are different. Our calculation shows that the tidal
polarizability of merging binary strangeon stars is favored by GW170817. Three
kinds of kilonovae (i.e., of neutron, quark and strangeon) are discussed, and
the light curve of the kilonova AT 2017gfo following GW170817 could be
explained by considering the decaying strangeon nuggets and remnant star
spin-down. Additionally, the energy ejected to the fireball around the nascent
remnant strangeon star, being manifested as a Gamma-ray burst (GRB), is
calculated. It is found that, after a promote burst, an X-ray plateau could
follow in a timescale of $10^{2-3}$ s. Certainly, the results could be tested
also by further observational synergies between gravitational wave detectors
(e.g., aLIGO) and X-ray telescopes (e.g., Chinese HXMT and eXTP), and
especially if the detected gravitational wave form is checked by peculiar
equation of state provided by the numerical relativistical simulation.
