Hubble Space Telescope Observations of the Very Low Mass Companion to Gliese 105A

Abstract

Hubble Space Telescope images of the astrometric binary Gl 105A confirm the previous ground-based detection of a faint, very red companion (Gl 105C) located 3."39 from Gl 105A at P.A. 290 deg. The instrumental magnitudes of Gl 105C are V555 = 16.86 and I814 = 13.54. The observed position of Gl 105C differs significantly from the positions expected from current astrometric solutions. No other companions brighter than I814 = 20.3 are seen between 1" and 13."5 from Gl 105A. Using the M dwarf model atmospheres of Allard and Hauschildt, we obtain for Gl 105C a standard color of V - I = 4.6, which suggests a spectral type of M7 V.