THE SPECTRUM AND VARIABILITY OF RADIO-EMISSION FROM AE AQUARII

We report the first detections of the magnetic cataclysmic variable AE Aquarii at millimeter wavelengths. AE Aqr was detected at a wavelength lambda = 3.4 mm on five independent observing runs by the interferometer on the Plateau de Bure, France. It was also detected by the Caltech Submillimeter Observatory on Mauna Kea at a wavelength lambda = 1.25 mm. Both of these observations were accompanied by contemporaneous microwave observations at the Very Large Array. We use these data to show that (1) the time-averaged spectrum is generally well fitted by a power law S(nu) is-proportional-to nu(alpha), where alpha almost-equal-to 0.35-0.60, and (2) the power law extends to millimeter wavelengths-i.e., the spectral turnover is at a frequency higher than 240 GHz. We suggest that the spectrum is consistent with that expected from a superposition of flarelike events where the frequency distribution of initial flux density is a power law f(S0) is-proportional-to S-0(-epsilon) with index epsilon almost-equal-to 1.8. Within the context of this model, the high turnover frequency of the radio spectrum implies magnetic field strengths in excess of 250 G in the source. The observed properties of AE Aqr are compared to those of a related class of objects, the low-mass X-ray binaries.