G. Anglada-Escud ́e et al, https://arxiv.org/pdf/1406.0818.pdf with a small football team of co-authors.
I noticed the paper while searching for something else on Arxiv ; the title hooked me, but on second reading I'm realising it's old (2014) work.
Kapteyn's Star is one of the closest stars to the Solar system (well known) ; it's a red dwarf with a parallax of 0.25 arcsec (4 parsecs). It is considered a halo star - a star passing through the Milky Way's disc, but generally residing in the galaxy's halo). Proper motion just under 9 mas/year. Discovered about 1897 in compilation of the Cape photographic Durchmusterung. It has a low spectroscopic rotational speed (v.sin(i) <~3km/s) and low metallicity. It is considered a pretty ancient star, and possibly derived from the Omega Centaurus galaxy's halo into the Milky Way's halo, stripped off during the collision.
Located in Pictor, southern hemisphere. It moves, relatively quickly.
Between 1999 and 2013, using several devices, a sequence of spectra were taken and yield a periodic drift with two period peaks of 121 and 48.6 days.
With a low-mass primary, and relatively large planets (4.8 and 7.0 Msin(i)_earth) the orbits seem stable on the 10 Gyr timescale (appropriate for a merger star).
This work has been challenged several times, but seems to survive it reasonably well.
