Milimetre-band variability of the radio-quiet nucleus of NGC 7469

We report short-cadence monitoring of a radio-quiet (RQ) Active Galactic Nuclei (AGN), NGC 7469, at 95 GHz (3 mm) over a period of 70 d with the CARMA telescope. The AGN varies significantly (±3σ from the mean) by a factor of 2 within 4-5 d. The intrinsic 95 GHz variability amplitude in excess of the measurement noise (10 per cent) and relative to the mean flux is comparable to that in the X-rays, and much higher than at 8.4 GHz. The mm-band variability and its similarity to the X-ray variability adds to the evidence that the mm and X-ray emission have the same physical origin, and are associated with the accretion disc corona.