Discovery of Multiple Periodicity and Nonlinearity in the Pulsations of the Roap-Star HD19918

Details Discovery of Multiple Periodicity and Nonlinearity in the Pulsations of the Roap-Star HD19918 Discovery of Multiple Periodicity and Nonlinearity in the Pulsations of the Roap-Star HD19918

Oct 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995mnras.276.1435m&link_type=abstract

Monthly Notices of the Royal Astronomical Society, Vol. 276, NO. 4/OCT15, P.1435, 1995

Astronomy and Astrophysics

Astronomy

1

Stars: Chemically Peculiar - Stars: Individual: Hd 19918 - Stars: Oscillations

Scientific paper

We present new high-speed photometric observations of the rapidly oscillating Ap star HD 19918 obtained at SAAO on 31 nights in 1991, 1992 and 1994. These observations reveal that HD 19918 pulsates with at least two modes which are either consecutive overtones of a single l, or modes of alternating even and odd l. The principal frequency of oscillation is shown to be V1 = 1510.208±0.004 μHz, but the second frequency, V2, is ambiguous by 1 cycle d-1. Removal of V1 and V2 indicates the presence of further signal content although no secure frequency determinations are possible with the data at hand. A multi-site campaign will be required to identify V2 unambiguously and to solve the frequency spectrum fully. The first harmonic of the principal oscillation frequency is also present in the data, bringing to eight the number of rapidly oscillating Ap stars that have non-linear light variations. We also present differential mean light Johnson UBVRI observations of HD 19918 and two comparison stars acquired on 23 nights in 1991 for the purpose of determining HD 19918's rotation period. A frequency analysis of these observations does not reveal any significant oscillations.

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