PSR J1311-3430: A Heavyweight Neutron Star with a Flyweight Helium   Companion
  We have obtained initial spectroscopic observations and additional photometry of the newly discovered Pb=94min gamma-ray black-widow pulsar PSR J1311-3430. The Keck spectra show a He-dominated, nearly H-free photosphere and a large radial-velocity amplitude of 609.5+/-7.5km/s. Simultaneous seven-color GROND photometry further probes the heating of this companion, and shows the presence of a flaring infrared excess. We have modeled the quiescent light curve, constraining the orbital inclination and masses. Simple heated light-curve fits give M_NS=2.7Msun, but show systematic light-curve differences. Adding extra components allows a larger mass range to be fit, but all viable solutions have M_NS>2.1Msun. If confirmed, such a large M_NS substantially constrains the equation of state of matter at supernuclear densities. 
Roger W. Romani, Alexei V. Filippenko, Jeffery M. Silverman, S.   Bradley Cenko, Jochen Greiner, Arne Rau, Jonathan Elliott ...
astro-ph.HE