SIMBAD references

We present high-speed optical photometric observations, spanning ∼2 yr, of the recently discovered white dwarf pulsar AR Scorpii. The amplitudes of the orbital, spin, and beat modulations appear to be remarkably stable and repeatable over the time span of our observations. It has been suggested that the polarized and non-polarized emission from AR Scorpii is powered by the spin-down of the white dwarf. However, we find that our new data are inconsistent with the published spin-down ephemeris. Whilst our data are consistent with a constant spin period, further observations over an extended time-base are required in order to ascertain the true spin-evolution of the white dwarf. This may have implications for the various models put forward to explain the energetics and evolution of AR Scorpii.