Fm. Zerbi et al., THE GAMMA-DOR VARIABLE HD-164615 - RESULTS FROM A MULTISITE PHOTOMETRIC CAMPAIGN, Monthly Notices of the Royal Astronomical Society, 292(1), 1997, pp. 43-51
We present in this paper the results from a multisite photometric camp
aign devoted to the gamma Dor variable HD 164615. During the campaign
data were collected in the Johnson and Stromgren photometric systems.
A first search for sinusoidal periodicities yielded a three-term solut
ion with frequencies f(1) = 1.2328, f(2) = 1.0899 and f(3) = 2.3501 d(
-1), and a long-term trend f(4) = 0.1301 d(-1). The star may therefore
be multiperiodic with each frequency related to a pulsation mode. How
ever, a further examination of the curve provided evidence that the am
plitude at the instant of maximum brightness is modulated. Alternative
ly, HD 164615 may be a monoperiodic variable with frequency f(1) = 1.2
321 d(-1), showing amplitude modulation with frequency f(4) = 0.1301 d
(-1). The presence in the power spectra of the coupling terms f(2) = f
(1) - f(4) and f(3) = f(1) + f(4) - 1 supports the latter interpretati
on. In the monoperiodic case the previously given interpretation based
on a spot carried through the visible disc by rotation still holds, p
rovided that the spot is bright and evolves on a time-scale of a few d
ays. However, similarities with other gamma Dor stars provide indirect
indication in favour of the existence of a non-radial pulsation inter
pretation.