GJ 900 - a new hierarchical system with low-mass components

E. Malogolovets, Yu. Balega, D. Rastegaev, K.-H. Hofmann, G. Weigelt

Speckle interferometric observations made with the 6 m telescope of the
Special Astrophysical Observatory of the Russian Academy of Sciences in
2000 revealed the triple nature of the nearby (d=19.3 pc) low-mass young
(age about 200 Myr) star GJ 900. The configuration of the triple system
allowed it to be dynamically unstable. Differential photometry performed
from 2000 through 2004 yielded I- and K-band absolute magnitudes and
spectral types for the components to be
I_A=6.66+-0.08, I_B=9.15+-0.11, I_C=10.08+-0.26,
K_A=4.84+-0.08, K_B=6.76+-0.20, K_C=7.39+-0.31,
Sp_A: K5-K7, Sp_B: M3-M4, Sp_C: M5-M6.
The "mass-luminosity" relation is used to estimate the individual masses of
the components: 0.64, 0.21, 0.13 Msun. From the observations of the
components relative motion in the period
2000-2006, we conclude that GJ 900 is a hierarchical triple star with the
possible orbital periods P_(A-BC) about 80 yrs and P_(BC) about 20 yrs.
An analysis is of the 2MASS images of the region around GJ 900 leads us to
suggest that the system can include other very-low-mass components.