HZ Her/Her X-1 is one of the most popular low-mass X-ray binary star systems, which consists of a neutron star (Her X-1) and a post-main-sequence star (HZ Her). Her X-1 is one of the first two founding members of the accretion-powered X-ray pulsars class. Due to its large luminosity and low interstellar absorption Her X-1 remains one of the most studied pulsars. The system is characterized by a great wealth of phenomena including 1.24 s regular X-ray pulsations, 1.7-day orbital period eclipses, a superorbital X-ray intensity cycle of 35 days, and a large number of highly variable X-ray...