X-Ray Pulsar 1E 2259+586: A Merged White Dwarf with a 7 Second Rotation Period?

The enigmatic X-ray pulsar 1E 2259 + 586, located at the center of the supernova remnant G109.1 - 1.0, may be a recent merger of two white dwarfs, with a present rotation period of P = 6.98 s. The required mass is higher than 1.32 solar masses, making 1E 2259 + 586 the most massive white dwarf known. The surface gravity is well over one billion cm/sec sq, allowing the effective temperature to be as high as 2 million K, and opening up a possibility that the observed soft X-rays come from the white dwarf photosphere. The rate of rotational energy loss implied by the observed period increase is about 10 to the 36th ergs/s, a factor of a few more than the observed X-ray luminosity. If the interstellar extinction toward 1E 2259 + 586 is 4 mag, then the optical counterpart should be fainter than 26 mag. Observational and theoretical tests of this scenario are discussed.

Английский

Astrophysical Journal Letters. – 1990. – Vol. 365. – P. L9–L12.