A photometric search for rapid oscillations in the cool Ap star βCrB near magnetic maximum

We have obtained photoelectric photometry on eight nights, all within one day of the magnetic maximum of βCrB based on Kurtz' ephemeris, in order to attempt to clarify whether this cool magnetic oblique rotator is or is not a rapidly oscillating Ap (roAp) star. If an roAp star, oscillations should reach a maximum photometric amplitude at magnetic maximum, which mandates that photometry be obtained very close to the maximum. We fail to detect coherent oscillations down to a level of 0.34 millimagnitude (mmag) using narrow-band filters close in wavelength to Johnson B. This implies that βCrB may not be an roAp star, in spite of possessing characteristics very similar to other known roAp stars. (author)