ITAL]Hubble Space Telescope[/ITAL] Observations of the Very Low Mass Companion to Gliese 105A

Abstract

Hubble Space Telescope images of the astrometric binary GI 105A confirm the previous ground-based detection of a faint, very red companion (GI 105C) located 3.39 sec from GI 105A at P.A. 290 deg. The instrumental magnitudes of GI 105C are (visual magnitude) V(sub 555) = 16.86 and I(sub 814) = 13.54. The observed position of GI 105C differs significantly from the positions expected from current astrometric solutions. No other companions brighter than I(sub 814) = 20.3 are seen between 1 sec and 13.5 sec from GI 105A. Using the M dwarf model atmospheres of Allard and Hauschildt, we obtain for GI 105C a standard color of V - I = 4.6, which suggests a spectral type of M7 V.