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Astron. Astrophys. 325, 159-166

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A search for companions to nearby southern M dwarfs
with near-infrared speckle interferometry*

Ch. Leinert1, T. Henry2,3, A. Glindemann1, and D.W. McCarthy, Jr.4

1Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
2Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA
3Hubble Fellow
4Steward Observatory, Tucson, Arizona 85721, USA

Received 30 September 1996 / Accepted 17 February 1997


We searched the 9 M-dwarf primaries nearer than 5 pc and south of declination FORMULA = -30FORMULA for companions with separations 1-10 AU and 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 FORMULA 9%, and the average number of companions per system is 0.32 FORMULA 0.10. This is lower by 2 FORMULA than the observed multiplicity fraction of 43 FORMULA 5%, and companions per system of 0.49 FORMULA 0.05 in the sample of nearby solar-type main sequence stars. It is also much lower than the extrapolated binary fraction among young stars in Taurus. We discuss the implications of this finding.

Key words: binaries: general - stars: low-mass - stars: luminosity function, mass function

*Based on observations collected at the European Southern Observatory, La Silla, Chile and at the Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy under contract with the National Science Foundation.
Tables are also available in electronic form at CDS via anonymous ftp to cdsarc.u-strasbg.fr ( or via http://cdsweb.u-starsbg.fr/ Abstract.html.

Send offprint requests to: Ch. Leinert

© European Southern Observatory (ESO) 1997