THE OCCURRENCE OF WIDE-ORBIT PLANETS IN BINARY STAR SYSTEMS

The occurrence of planets in binary star systems has been investigated via a variety of techniques that sample a wide range of semi-major axes, but with a preponderance of such results applicable to planets with semi-major axes less than a few astronomical units. We utilize a new method-the presence or absence of heavy elements in the atmospheres of white dwarf stars-to elucidate the frequency in main sequence binary star systems of planets with semi-major axes greater than a few astronomical units. We consider only binaries where a putative planetary system orbits one member (no circumbinary planets). For main sequence binaries where the primary star is of spectral type A or F, data in the published literature suggests that the existence of a secondary star with a semi-major axis less than about 1000 AU suppresses the formation and/or long-term stability of an extended planetary system around the primary. For these spectral types and initial semi-major axis >= 1000 AU, extended planetary systems appear to be as common around stars in binary systems as they are around single stars.