Masses of Isolated Spiral KIG Galaxies
  We have updated the classification of late-type galaxies presented in the
Catalog of Isolated Galaxies (KIG) using the advanced digital sky surveys. Our
search for companions around 959 KIG galaxies revealed 141 neighbors associated
with 111 KIG galaxies within the mutual projection separation of less than 330
kpc and the radial velocity difference not exceeding 500 km s$^{-1}$. Typical
luminosity of the companions turned out to be weaker than the luminosity of the
main galaxies by more than an order of magnitude. Considering these small
companions as test particles that move around the KIG galaxies along the
Keplerian orbits with eccentricity of $e\simeq0.7$, we estimated the total
(orbital) masses of spiral KIG galaxies. Their average orbital mass-to-$K$-band
luminosity ratio, $(20.9\pm3.1) M_{\odot}/L_{\odot}$, is in a good agreement
with the corresponding value for the nearby Milky Way, M31 and M81-type massive
spirals. Isolated disk-shaped galaxies have an on the average 2-3 times smaller
total-mass-to-stellar-mass ratio than those of isolated bulge-shaped galaxies.
