High-Amplitude δ Scuti stars (HADS) are intermediate-mass pulsating variables. Traditionally, their pulsations are thought to be dominated by radial modes, which makes them powerful probes of stellar structure and evolution. However, recent high-precision space photometry has shown that some HADS display more complex pulsation behaviors and amplitude variations.

Using high-precision short-cadence data from Transiting Exoplanet Survey Satellite, Dr. LV Chenglong of the Xinjiang Astronomical Observatory of the Chinese Academy of Sciences discovered three new HADS: TIC 408074920, TIC 189714989, and TIC 34137913. The team investigated their pulsation properties using Fourier analysis, sliding-window amplitude variations, spectral energy distribution (SED) fitting, and asteroseismic modeling. The findings have been published in The Astrophysical Journal.

The study found that all three stars show dominant radial pulsations with rich harmonic structures. TIC 189714989 exhibits symmetric side peaks around the main frequency, suggesting possible amplitude and/or phase modulation similar to the Blazhko effect in RR Lyrae stars, and also shows an additional non-radial mode. TIC 408074920 displays an amplitude decrease of approximately 4 millimagnitudes over about 20 days, indicating possible short-term amplitude variability.

Combining Gaia DR3-based SED fitting with stellar evolution and pulsation modeling, all three stars are found to lie within the classical instability strip, with masses ranging from 1.5 to 1.8 solar masses. However, discrepancies between SED and asteroseismically derived estimates of radius and luminosity suggest that higher-precision spectroscopic constraints are still needed.

These results indicate that HADS pulsation behavior is more complex than traditionally assumed, highlighting the rich nonlinear processes revealed by space-based photometry. Future missions such as PLATO will further improve our understanding of mode excitation and amplitude modulation in intermediate-mass stars.