  Low-mass and brown dwarfs have recently been found as wide companions to many
nearby stars, formerly believed to be single. Wide binaries are usually found
as common proper motion pairs. Sometimes, more than two objects share the same
large proper motion, identifying them as nearby systems. We have found a third,
low-mass component to a known wide binary at a distance of about 21pc,
consisting of a red and a white dwarf (LHS4039 and LHS4040; about 150AU
separation). The new companion, APMPMJ2354-3316C separated by about 2200AU, was
classified as M8.5 dwarf. In recent spectroscopic observations it shows a very
strong $H_{\alpha}$ emission line and blue continuum. Comparing this event to
flares in late-type M dwarfs, we find some similarity with LHS2397a, a nearby
M8 dwarf which is so far the only known example of a low-mass star with a tight
brown dwarf companion (separation of less than 4AU). The level of the activity
as measured by $L_{H_{\alpha}}/L_{bol}$ is comparable to that of the M9.5 dwarf
2MASSWJ0149+29 both during the flare and in quiescence.
