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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 usethese data, in conjunction with TESS observations, to analyse thehigh-frequency pulsation in detail. We find a triplet which is split by therotation frequency of the star ($\nu_{\rm rot}=0.3756$ d$^{-1}$; $P_{\rmrot}=2.66$ d) and present both distorted dipole and distorted quadrupole modemodels. We show that the pulsation frequency, $150.9898$ d$^{-1}$ ($P_{\rmpuls}=9.54$ min) is greater than the acoustic cutoff frequency. We utilise 27high-resolution ($R\simeq65\,000$), high signal-to-noise ($\sim120$) spectra toprovide new orbital parameters for this, the only known roAp star to be in ashort period binary ($P_{\rm orb}=93.266$ d). We find the system to be moreeccentric than previously thought, with $e=0.317$, and suggest the companion isa mid-F to early-K star. We find no significant trend in the average pulsationmode amplitude with time, as measured by TESS, implying that the companion doesnot have an affect on the pulsation in this roAp star. We suggest furtherphotometric observations of this star, and further studies to find more roApstars in close binaries to characterise how binarity may affect the detectionof roAp pulsations.

HD 42659: The only known roAp star in a spectroscopic binary observed with B photometry, TESS and SALT