2014ApJ...793L..20R

We have identified an optical binary with orbital period P_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 P_b= 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/s for a large mass function of f(M) = 1.60±0.05 M_☉. This heating suggests a pulsar luminosity ∼3x10³⁴ erg/s. 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.