  We present a multi-instrument analysis of the rapidly oscillating Ap (roAp)
star HD 42659. We have obtained $B$ photometric data for this star and use
these data, in conjunction with TESS observations, to analyse the
high-frequency pulsation in detail. We find a triplet which is split by the
rotation frequency of the star ($\nu_{\rm rot}=0.3756$ d$^{-1}$; $P_{\rm
rot}=2.66$ d) and present both distorted dipole and distorted quadrupole mode
models. We show that the pulsation frequency, $150.9898$ d$^{-1}$ ($P_{\rm
puls}=9.54$ min) is greater than the acoustic cutoff frequency. We utilise 27
high-resolution ($R\simeq65\,000$), high signal-to-noise ($\sim120$) spectra to
provide new orbital parameters for this, the only known roAp star to be in a
short period binary ($P_{\rm orb}=93.266$ d). We find the system to be more
eccentric than previously thought, with $e=0.317$, and suggest the companion is
a mid-F to early-K star. We find no significant trend in the average pulsation
mode amplitude with time, as measured by TESS, implying that the companion does
not have an affect on the pulsation in this roAp star. We suggest further
photometric observations of this star, and further studies to find more roAp
stars in close binaries to characterise how binarity may affect the detection
of roAp pulsations.
