The γ Dor variable HD 164615: Results from a multisite photometric campaign

We present in this paper the results from a multisite photometric campaign devoted to the γ Dor variable HD 164615. During the campaign data were collected in the Johnson and Strömgren photometric systems. A first search for sinusoidal periodicities yielded a three-term solution with frequencies f1 = 1.2328, f2 = 1.0899 and f3 = 2.3501 d-1, and a long-term trend f4 = 0.1301 d-1. The star may therefore be multiperiodic with each frequency related to a pulsation mode. However, a further examination of the curve provided evidence that the amplitude at the instant of maximum brightness is modulated. Alternatively, HD 164615 may be a monoperiodic variable with frequency f1 = 1.2321 d-1, showing amplitude modulation with frequency f4 = 0.1301 d-1. The presence in the power spectra of the coupling terms f2 = f1 - f4 and f3 = f1 + f4 - 1 supports the latter interpretation. In the monoperiodic case the previously given interpretation based on a spot carried through the visible disc by rotation still holds, provided that the spot is bright and evolves on a time-scale of a few days. However, similarities with other γ Dor stars provide indirect indication in favour of the existence of a non-radial pulsation interpretation. © 1997 RAS.