Infrared and millimeter observations of the galactic superluminal source GRS 1915+105

Millimeter observations of the galactic source of relativistic ejections GRS 1915+105 (Mirabel & Rodríguez 1994) are consistent with this source being at a kinematic distance D = 12.5 ± 1.5 kpc from the Sun, behind the core of a molecular cloud at 9.4 ± 0.2 kpc. At this distance, GRS 1915+105, frequently radiating ∼ 3 × 10³⁸ erg s^-1 in the X-rays, becomes the most luminous X-ray source in the Galaxy. The total hydrogen column density N(H) = 4.7 ± 0.2 × 10²² cm^-2 along the line of sight corresponds to a visual absorption A_v = 26.5 ± 1 magnitudes. The infrared counterpart of GRS 1915+105 exhibits in the 1.2 μm - 2.2 μm band variations of ∼ 1 magnitude in a few hours and of ∼ 2 magnitudes over longer intervals of time. In the infrared, GRS 1915+105 is strikingly similar to SS 433, and unlike any other known stellar source in the Galaxy. The infrared resemblance in absolute magnitude, color, and time variability, between these two sources of relativistic ejections suggests that GRS 1915+105, as SS 433, consists of a collapsed object (neutron star or black hole) with a thick accretion disk in a high-mass-luminous binary system.