2011ApJ...743L..26R

We have measured dramatic flux and spectral variations through the 0.193 day orbit of the optical counterpart of the unidentified γ-ray source 0FGL J2339.8-0530. This compact object companion is strongly heated, with T_eff varying from ∼6900 K (superior conjunction) to <3000 K at minimum. A combined fit to the light curve and radial velocity amplitudes imply M₁~ 0.075 M_☉, M₂~ 1.4M_☉, and inclination i ~ 57°. Thus, this is a likely "black widow" system with a {dot}E ~ 10^34–34.5erg/s pulsar driving companion mass loss. This wind, also suggested by the X-ray light curve, may prevent radio pulse detection. Our measurements constrain the pulsar's reflex motion, increasing the possibility of a pulse detection in the γ-ray signal.