From Sco X-1 to magnetars . Past, present, and future of X-ray studies of neutron stars

A review is made on the 50 years of X-ray study of neutron stars (NSs), with emphasis on results from the series of Japanese satellites, Hakucho, Tenma, Ginga, ASCA, Suzaku, and MAXI, launched in 1979, 1983, 1987, 1993, 2005, and 2009, respectively. This review covers such topics as; NS diagnostics using X-ray bursts, verification of the concept of standard accretion disks, measurements of magnetic fields of accreting pulsars using electron cyclotron resonances, broad-band studies of magnetars, and study of luminosity-dependent spectral state transitions in low-mass X-ray binaries. Finally, our future with ASTRO-H is briefly described.