Identification of the companion stars of Type Ia supernovae
  The nature of the binary systems giving rise to Type Ia supernovae (SNeIa) remains an unsolved problem. In this {\it Letter} we calculate, from the statistics of initial conditions (masses and binary separations), the mass, luminosity, and velocity distributions of the possible binary companions (main-sequence star, subgiant, red giant) following the explosion of the white dwarf which gives rise to the SNeIa. Those companions could be detected from either their proper or their radial motions, by means of high-precision astrometric and radial-velocity measurements in young, nearby supernova remnants. Peculiar velocities typically ranging from 100 to 450 km s$^{-1}$ should be expected, which places proper-motion measurements within reach of HST instruments and makes radial-velocity ones feasible with 2.5-4m class telescopes from the ground. Detections would solve the long-standing problem of which kind of binaries do produce SNeIa and clear up the way to accurate physical modeling of the explosions. 
R. Canal (U. Barcelona), J. Mendez (U. Barcelona & ING), and P.   Ruiz-Lapuente (U. Barcelona & MPA)