Glitches in the X-ray pulsar 1E 2259+586

Abstract

Starquakes are considered for fast-rotating magnetic white dwarfs. The X-ray pulsar 1E 2259+586 may be such a white dwarf. It is shown that in this case starquakes may be responsible for the decrease of the mean spin-down rate that was observed for 1E 2259+586 between 1987 and 1990. The required mass of the white dwarf that is identified with 1E 2259+586 is approximately 1.4-1.5 solar mass making this X-ray pulsar the most massive white dwarf known.