Based on high precision time-series data from Kepler Space Telescope, researchers from Optical Group of Xinjiang Astronomical Observatory reported a double-modulation effect in a double-mode high-amplitude delta Scuti (HADS) star. This work has been published in The Astrophysical Journal(ApJ, 2019,879, 59).

HADS stars are typical late-A or early-F pulsators, located in the intersection of the main sequence and the classical instability. Their oscillation periods are between 1 and 6 h, and the peak-to-peak amplitudes are usually larger than 0.3 mag. Their pulsation modes are relatively simple, generally showing mono- or double radial modes.

The researchers presented an in-depth frequency analysis for short cadence data of HADS star KIC 10284901 delivered from Kepler Space Telescope, based on the fact that the first two are the main frequencies: F0 = 18.994054(1) cycle/day，F1 = 24.335804(4) cycle/day, the other two independent frequency fm1 = 0.4407 cycle/day and fm2 = 0.8125 cycle/day are detected for the first time. In addition, a double- modulation of fm1 and fm2 to F0 and F1 modes (quintuplet structures centered on F0 and F1) are detected, as shown in the figure. This is the first detection of a double- modulation effect in a double-mode HADS star. They discussed the origin of this modulation, and pointed out the most possible cause of the modulation effect in the light curve is similar to that in Blazhko RR Lyare stars.

Figure：Amplitude spectra of modulation frequencies fm1 and fm2 to main frequencies F0 and F1. The central dashed lines indicate the locations of the main frequencies of KIC 10284901. The space of the quintuplet structure spectra lines are indicated with fm1 and fm2.