  We present the serendipitous detection of the two main OH maser lines at 1667
and 1665 MHz associated with IRAS 10597+5926 at z = 0.19612 in the untargeted
Apertif Wide-area Extragalactic Survey (AWES), and the subsequent measurement
of the OH 1612 MHz satellite line in the same source. With a total OH
luminosity of log(L/L_Sun) = 3.90 +/- 0.03, IRAS 10597+5926 is the fourth
brightest OH megamaser (OHM) known. We measure a lower limit for the 1667/1612
ratio of R_1612 > 45.9 which is the highest limiting ratio measured for the
1612 MHz OH satellite line to date. OH satellite line measurements provide a
potentially valuable constraint by which to compare detailed models of OH maser
pumping mechanisms. Optical imaging shows the galaxy is likely a late-stage
merger. Based on published infrared and far ultraviolet fluxes, we find that
the galaxy is an ultra luminous infrared galaxy (ULIRG) with log(L_TIR/L_Sun) =
12.24, undergoing a star burst with an estimated star formation rate of 179 +/-
40 M_Sun/yr. These host galaxy properties are consistent with the physical
conditions responsible for very bright OHM emission. Finally, we provide an
update on the predicted number of OH masers that may be found in AWES, and
estimate the total number of OH masers that will be detected in each of the
individual main and satellite OH 18 cm lines.
