  We present the results of recent multicolor photometric and high-resolution
spectroscopic observations of the bright Be star Pi Aquarii. Observational data
collected from the literature were used to study the star's variations over the
last four decades. The star is identified with the IR sources F22227+0107 in
the IRAS Faint Point Source catalog and MSX5_G066.0066-44.7392 in the MSX
catalog. The variations in near-IR brightness of Pi Aqr are found to be among
the largest reported for Be stars. Since 1996, the star has shown only weak
signs of circumstellar emission, which has allowed us to refine the fundamental
stellar parameters: A_V=0.15 mag., T_eff=24000K, log g=3.9, and M_V=-2.95 mag.
A weak emission component of the H-alpha line has been detected during the
recent quasi-normal star phase. From analysis of the H-alpha line profiles, we
find anti-phased radial velocity variations of the emission component and the
photospheric absorption, with a period of 84.1 days and semi-amplitudes of
101.4 and 16.7 km/s, respectively. This result suggests that Pi Aqr may be a
binary system consisting of stars with masses of M_1 sin^{3}i = 12.4 M_sun, M_2
sin^{3}i = 2.0 M_sun. We also estimate the orbital inclination angle to be
between 50 and 75 degrees. We suggest that the photometric, spectroscopic, and
polarimetric variations observed during the second half of the 20th century may
be due to variable mass transfer between the binary components.
