This paper presents new observations of the planet-hosting, visual binary GJ 86 (HR 637) using the Hubble Space Telescope. Ultraviolet and optical imaging with WFC3 confirms the stellar companion is a degenerate star and indicates the binary semimajor axis is larger than previous estimates, with a > 28 AU. Optical STIS spectroscopy of the secondary reveals a helium-rich white dwarf with C2 absorption bands and Teff = 8180 K, thus making the binary system rather similar to Procyon. Based on the 10.8 pc distance, the companion has 0.59 Msun and descended from a main-sequence A star of 1.9 Msun with an original orbital separation a > 14 AU. If the giant planet is coplanar with the binary, the mass of GJ 86Ab is between 4.4 and 4.7 MJup. The similarity of GJ 86 and Procyon prompted a re-analysis of the white dwarf in the latter system, with the tentative conclusion that Procyon hosts a planetesimal population. The periastron distance in Procyon is 20% smaller than in alpha Cen AB, but the metal-enriched atmosphere of Procyon B indicates that the planet formation process minimally attained 25 km bodies, if not small planets as in alpha Cen.
@article{arxiv.1212.5601,
title = {Orbital and Evolutionary Constraints on the Planet Hosting Binary GJ 86 from the Hubble Space Telescope},
author = {J. Farihi and Howard E. Bond and P. Dufour and N. Haghighipour and G. H. Schaefer and J. B. Holberg and M. A. Barstow and M. R. Burleigh},
journal= {arXiv preprint arXiv:1212.5601},
year = {2013}
}