  We present results from a Near Infrared multi-epoch spectroscopic campaign to
detect a young low-mass companion to a T Tauri star. AS 205A is a late-type
dwarf (~K5) of ~1 Msun that belongs to a triple system. Independent photometric
surveys discovered that AS 205A has two distinct periods (P1=6.78 and P2=24.78
days) detected in the light curve that persist over several years. Period P1
seems to be linked to the axial-rotation of the star and is caused by the
presence of cool surface spots. Period P2 is correlated with the modulation in
AS 205A brightness (V) and red color (V-R), consistent with a gravitating
object within the accretion disk. We here derive precise Near Infrared radial
velocities to investigate the origin of period P2 which is predicted to
correspond to a cool source in a Keplerian orbit with a semi-major axis of
~0.17 AU positioned close to the inner disk radius of 0.14 AU. The radial
velocity variations of AS 205A were found to have a period of P ~ 24.84 days
and a semi-amplitude of 1.529 kms-1. This result closely resembles the P2
period in past photometric observations (P ~ 24.78 days). The analysis of the
cross-correlation function bisector has shown no correlation with the radial
velocity modulations, strongly suggesting that the period is not controlled by
stellar rotation. Additional activity indicators should however be explored in
future surveys. Taking this into account we found that the presence of a
substellar companion is the explanation that best fits the results. We derived
an orbital solution for AS 205A and found evidence of a m2sini 19.25 MJup
object in an orbit with moderate eccentricity of e~0.34. If confirmed with
future observations, preferably using a multiwavelength survey approach, this
companion could provide interesting constraints on brown dwarf and planetary
formation models.
