Orbital Monitoring of the AstraLux Large M-dwarf Multiplicity Sample

TL;DR

This study presents ongoing astrometric monitoring of over 200 young M-dwarf binaries from the AstraLux survey to refine their orbital parameters and improve age estimation of young stellar populations.

Contribution

It provides new astrometric data for a large sample of M-dwarf binaries, identifying targets suitable for orbit determination and age calibration of young moving groups.

Findings

Approximately 30 targets have potential for orbit determination within a few years to decades.

One target, GJ 4326, is likely older than previously thought based on astrometric and isochronal data.

The data will help calibrate theoretical isochrones and refine age estimates of young stellar groups.

Abstract

Orbital monitoring of M-type binaries is essential for constraining their fundamental properties. This is particularly useful in young systems, where the extended pre-main sequence evolution can allow for precise isochronal dating. Here, we present the continued astrometric monitoring of the more than 200 binaries of the AstraLux Large Multiplicity Survey, building both on our previous work, archival data, and new astrometric data spanning the range of 2010-2012. The sample is very young overall -- all included stars have known X-ray emission, and a significant fraction (18%) of them have recently also been identified as members of young moving groups in the Solar neighborhood. We identify ~30 targets that both have indications of being young and for which an orbit either has been closed or appears possible to close in a reasonable timeframe (a few years to a few decades). One of these cases, GJ 4326, is however identified as probably being substantially older than has been implied from its apparent moving group membership, based on astrometric and isochronal arguments. With further astrometric monitoring, these targets will provide a set of empirical isochrones, against which theoretical isochrones can be calibrated, and which can be used to evaluate the precise ages of nearby young moving groups.