The recent discoveries of high-energy cosmic neutrinos and gravitational waves from
astrophysical objects have led to a new era of multimessenger astrophysics. In particular,
electromagnetic follow-up observations triggered by these cosmic signals have proved to be
highly successful and have brought about new opportunities in time-domain astronomy. We
review high-energy particle production in various classes of astrophysical transient
phenomena related to black holes and neutron stars, and discuss how high-energy …