Cool dwarfs in wide multiple systems. Paper 4: a common-proper-motion pair of two identical mid-M dwarfs separated by about 10000 AU

TL;DR

This paper characterizes a wide binary system of two mid-M dwarfs with a separation of about 9500 AU, contributing to the understanding of ultrafragile, low-mass stellar systems.

Contribution

It provides detailed astrometric and photometric analysis confirming the system's nature and its classification as an ultrafragile, wide-separation binary.

Findings

The pair consists of two M4+/-1 dwarfs.

The separation is approximately 9500 AU.

The system is classified as ultrafragile due to its low mass and wide separation.

Abstract

LSPM J0651+1843 and LSPM J0651+1845 are two high-proper-motion stars recently claimed to form a binary system, FMR 83, by Rica (2012). Here we characterize the system in detail, using astrometric and photometric data, and find that the pair consists of two M4+/-1 dwarfs separated by 9500^(+6200)_(-3800) AU. With these results, FMR 83 becomes one of the very few 'ultrafragile' systems (i.e., systems with very low total masses and very wide physical separations), many of which have been identified in this series of papers.