2FGL J1653.6-0159: A New Low in Evaporating Pulsar Binary Periods.

摘要

We have identified an optical binary with orbital period P(sub b) = 4488 s as the probable counterpart of the Fermi source 2FGL J1653.6?0159. Although pulsations have not yet been detected, the source properties are consistent with an evaporating millisecond pulsar binary; this Pb = 75 minutes is the record low for a spin-powered system. The heated side of the companion shows coherent radial-velocity variations, with amplitude K = 666.9 +/- 7.5 km per sec for a large mass function of f (M) = 1.60 +/- 0.05 solar mass. This heating suggests a pulsar luminosity approximately 3 x 10(exp 34) erg per sec. The colors and spectra show an additional blue component dominating at binary minimum. Its origin is, at present, unclear. This system is similar to PSR J1311?3430, with a low-mass H-depleted companion, a dense shrouding wind and, likely, a large pulsar mass. Key words: gamma rays: stars - pulsars