A SEARCH FOR COMPANIONS TO NEARBY SOUTHERN M-DWARFS WITH NEAR-INFRARED SPECKLE INTERFEROMETRY

We searched the 9 M-dwarf primaries nearer than 5 pc and south of decl ination delta = -30 degrees for companions with separations 1-10 AU an d found none. Taken together with the 25 northern primaries studied by Henry and McCarthy (1990) the fraction of binaries and triples within the now complete sample of all M dwarfs within 5 pc is 9/34 = 26 +/- 9%, and the average number of companions per system is 0.32 +/- 0.10. This is lower by 2 sigma than the observed multiplicity fraction of 43 +/- 5%, and companions per system of 0.49 +/- 0.05 in the sample of n earby solar-type main sequence stars. It is also much lower than the e xtrapolated binary fraction among young stars in Taurus. We discuss th e implications of this finding.