The M-dwarfs in Multiples (MinMs) survey - I. Stellar multiplicity among low-mass stars within 15 pc

TL;DR

This large-scale survey investigates stellar multiplicity among low-mass stars within 15 parsecs, revealing a high companion star fraction and a distribution favoring closer separations, with implications for star formation and planetary systems.

Contribution

It provides the first comprehensive, volume-limited binary statistics for low-mass stars within 15 pc, combining AO and wide-field data to analyze separation and mass ratio distributions.

Findings

Companion star fraction of 23.5% from 3 to 10,000 au.

Higher frequency of companions at smaller separations.

Flat mass ratio distribution across q = 0.2 to 1.0.

Abstract

We present a large-scale, volume-limited companion survey of 245 late-K to mid-M (K7-M6) dwarfs within 15 pc. Infrared adaptive optics (AO) data were analysed from the Very Large Telescope, Subaru Telescope, Canada-France-Hawaii Telescope, and MMT Observatory to detect close companions to the sample from $\sim$1 au to 100 au, while digitised wide-field archival plates were searched for wide companions from $\sim$100 au to 10,000 au. With sensitivity to the bottom of the main sequence over a separation range of 3 au to 10,000 au, multiple AO and wide-field epochs allow us to confirm candidates with common proper motions, minimize background contamination, and enable a measurement of comprehensive binary statistics. We detected 65 co-moving stellar companions and find a companion star fraction of $23.5 \pm 3.2$ per cent over the 3 au to 10,000 au separation range. The companion separation distribution is observed to rise to a higher frequency at smaller separations, peaking at closer separations than measured for more massive primaries. The mass ratio distribution across the $q = 0.2 - 1.0$ range is flat, similar to that of multiple systems with solar-type primaries. The characterisation of binary and multiple star frequency for low-mass field stars can provide crucial comparisons with star forming environments and hold implications for the frequency and evolutionary histories of their associated disks and planets.