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 MSX 5 \ _ 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 } =24000 K , \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 ^ { -1 } , 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 _ { \odot } , M _ { 2 } sin ^ { 3 } i = 2.0 ~ { } M _ { \odot } .
We also estimate the orbital inclination angle to be between 50 and 75° .
We suggest that the photometric , spectroscopic , and polarimetric variations observed during the second half of the 20 ^ { th } century may be due to variable mass transfer between the binary components .