On the nature of small amplitude peaks in δ Scuti oscillation spectra
J. Daszynska-Daszkiewicz, W. A. Dziembowski, A. A. Pamyatnykh
Abstract
The standard assumption in interpretation of stellar oscillation spectra from photometry is that the excited mode have low angular degrees, typically
ℓ<3
. Considering the case of FG Vir, the
δ
Scuti star with the richest known oscillation spectrum, we show that this assumption is not justified for low amplitude peaks. The
ℓ<3
identifications have been found for 12 dominant peaks from pulsation amplitudes and phases. However, we show that for the rest of the peaks (55), whose amplitudes are typically below 1 mmag, much higher
ℓ
's are most likely.
We argue that improving amplitude resolution to the micromagnitude level, as expected from space observations, is not likely to be rewarded with a credible mode identifications because the spectra will be dominated by high-
ℓ
modes of unknown azimuthal order,
m
.