Identification of the Optical Counterpart of Fermi Black Widow   Millisecond Pulsar PSR J1544+4937
  We report the optical identification of the companion to the {\it Fermi} black widow millisecond pulsar PSR J1544+4937. We find a highly variable source on Keck LRIS images at the nominal pulsar position, with 2 magnitude variations over orbital period in the B, g, R, and I bands. The nearly achromatic light curves are difficult to explain with a simply irradiated hemisphere model, and suggest that the optical emission is dominated by a nearly isothermal hot patch on the surface of the companion facing the pulsar. We roughly constrain the distance to PSR J1544+4937 to be between 2 and 5 kpc. A more reliable distance measurement is needed in order to constrain the composition of the companion. 
Sumin Tang, David L. Kaplan, Sterl Phinney, Thomas A. Prince, Rene P.   Breton, Eric Bellm, Lars Bildsten, Yi Cao, A.K.H. Ko...
astro-ph.HE astro-ph.SR