KIC 3868420: A High-amplitude δ Scuti– γ Dor Hybrid Star Crossing the Hertzsprung Gap
Year: 2026
Type: article
Abstract: We report a photometric and asteroseismic analysis of KIC 3868420, a newly identified high-amplitude δ Scuti– γ Doradus hybrid star located in the Hertzsprung gap—a short-lived and rarely observed post-main-sequence phase. Using 4 yr of Kepler long-cadence photometry, we detect 36 significant frequencies, including 11 independent modes spanning both low- and high-frequency regimes. Grid-based modeling with MESA and GYRE, including rotation, shows that five independent frequencies match a combination of radial p -modes and nonradial g -modes, supporting its hybrid nature. The best-fit models yield an evolved post-main-sequence star ( M ∼ 2.26–2.30 M ⊙ , R ∼ 4.41–4.43 R ⊙ , and τ ∼ 5.4 × 10 8 yr), although degeneracies from rotation and unknown inclination preclude a unique solution. KIC 3868420 thus represents a rare example of a high-amplitude hybrid pulsator in the Hertzsprung gap, demonstrating that high-amplitude pulsation can coexist with mixed p -/ g -mode behavior in a rapidly evolving star. This finding highlights the value of space-based photometry for identifying such rare objects.
Source: The Astrophysical Journal
Authors: Tao-Zhi Yang, Zhao-Yu Zuo
Institution: Xi'an Jiaotong University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Awards: G7082580814, G7574210810
OpenAlex ID: W7154379953