The AstraLux large M dwarf survey

TL;DR

The AstraLux large M dwarf survey uses Lucky Imaging to study binarity among late-type stars, aiming to refine binary statistics and improve mass-luminosity relations for M dwarfs.

Contribution

This survey provides new high-resolution imaging data on over 1000 M dwarfs, enhancing understanding of their binary properties and stellar parameters.

Findings

Refined binarity fraction dependence on spectral type.

Calibration data for mass-luminosity relation at the red end.

High-resolution imaging of faint M dwarfs.

Abstract

AstraLux is the Lucky Imaging camera for the Calar Alto 2.2-m telescope and the 3.5-m NTT at La Silla. It allows nearly diffraction limited imaging in the SDSS i' and z' bands of objects as faint as i'=15.5mag with minimum technical effort. One of the ongoing AstraLux observing programs is a binarity survey among late-type stars with spectral types K7 to M8, covering more than 1000 targets on the northern and southern hemisphere. The survey is designed to refine binarity statistics and especially the dependency of binarity fraction on spectral type. The choice of the SDSS i' and z' filters allows to obtain spectral type and mass estimates for resolved binaries. With an observing efficiency of typically 6 targets per hour we expect to complete the survey in mid-2009. Selected targets will be followed up astrometrically and photometrically, contributing to the calibration of the mass-luminosity relation at the red end of the main sequence and at visible wavelengths.