ON THE MASS OF THE BLACK-HOLE IN GS-2000+25

We present J- and K'-band (1.95-2.35 mu m) photometry of the quiescent X-ray nova GS 2000+25, obtained in an attempt to constrain the mass o f the compact object (M(X)). Combined with the mass function of 4.97 M (.), the infrared light curves imply M(X) less than or equal to 11 M(. ) (90% confidence level), regardless of the evolutionary state of the secondary, for a mass ratio q of 4 < q < 30. For a secondary mass in t he range M(2) = 0.4-0.9 M(.) (as expected for a K dwarf companion), an d assuming a negligible contribution from the disk at these wavelength s, we find M(X) = 8.5 +/- 1.5 M(.) and an inclination of 65 degrees +/ - 9 degrees. The observed infrared color is consistent with that expec ted of a K dwarf secondary. If the accretion disk continuum is given b y f(lambda) proportional to lambda(-1.8), as observed in other quiesce nt X-ray novae, we constrain the accretion disk contribution to the K' flux (independently of optical estimates) to less than or equal to 12 %.