Submillimeter Array Observations of Disks in the SR 24 Multiple Star   System
  We present high-resolution aperture synthesis images from the Submillimeter Array of the 225 GHz (1.3 mm) continuum and CO J=2-1 line emission from the disks around components of the hierarchical triple system SR 24, located in the Ophiuchus star-forming region. The most widely separated component, SR 24 S (with a projected semimajor axis of 832 AU), has a circumstellar disk with properties typical of those around single T Tauri stars. The binary SR 24 N (with a projected semimajor axis of 32 AU) is undetected in the continuum, but has strong, resolved CO emission which likely originates in a circumbinary disk with a central gap. The data constrain the total disk mass in the SR 24 N system to be < 10^-3 M_sun and indicate that the depletion of CO onto dust grains is not more than 100 times larger than the mean value in the interstellar medium. The SR 24 N disk is unusual in that it is only detected in line emission. It is possible that other low mass disks around binaries and single stars may have been missed in single-dish continuum surveys. 
Sean M. Andrews, Jonathan P. Williams (University of Hawaii Institute   for Astronomy)