KIC 2857323: A Double-mode High-amplitude δ Scuti Star with Amplitude Decline of the First Overtone Mode

Niu

Res. Astron. Astrophys.

et al. 2023

In this work, the pulsation analysis is performed on 83 high-amplitude $\delta$ Scuti stars, which have been observed by the Transiting Exoplanet Survey Satellite (TESS). The results show that 49 of these HADS show single-mode pulsation, 27 of them show radial double-modes pulsation (in which 22 of them pulsate with the fundamental and first overtone modes and 5 of them pulsate with the first and second overtone modes), and 7 of them show radial triple-modes pulsation (3 of which are newly confirmed triple-mode HADS). The histogram of the fundamental periods and the ratios between the fundamental and first overtone periods show bimodal structures, which might be caused by the stellar evolution in this specific phase. Most of the radial triple-mode HADS have a fundamental amplitude of 41-54 mmag, and 50\% of them have similar amplitudes of the fundamental and first overtone pulsation modes. All these hints require further confirmation not only in observations with more HADS samples, but also in theoretical models with suitable treatments of stellar evolution and pulsation.

Section: Introductionmentioning

confidence: 96%

Pulsation Analysis of High-Amplitude δ Scuti Stars with TESS

Niu

Res. Astron. Astrophys.

et al. 2023

“…However, it is very difficult to identify them, since the asymptotic theory is invalid due to the low radial order. Conversely, identification of the modes in HADS stars is clear and straightforward, because HADS stars typically pulsate in the radial fundamental mode and/or low-overtone radial modes (McNamara 2000), such as for VX Hydrae (Xue et al 2018), GSC 4552-1498 (Sun et al 2021), KIC 2987323 (Yang et al 2022), and TIC 448892817 (Lv et al 2022). The pulsation of δ Scuti stars contains both radial and nonradial p modes, signifying the potential to investigate the stellar envelope.…”

Section: Introductionmentioning

confidence: 99%

Two High-amplitude δ Scuti–γ Doradus Hybrids Constrained by the Radial Fundamental p and Equally Spaced g Modes

Chen,

Zhang,

et al. 2024

ApJ

Based on 2 minutes cadence TESS data, we investigate pulsations of TIC 65138566 and TIC 139729335 and discover them to be two new high-amplitude δ Scuti stars with equally spaced g modes. We recognize the radial fundamental mode f 1 = 18.3334 c d−1 and the first overtone f 3 = 23.6429 c d−1 for TIC 65138566, and identify the highest peak f 1 = 19.0955 c d−1 as the radial fundamental mode for TIC 139729335. For g modes, both stars display a regular period spacing of 2413 s. Through detailed seismological analysis, we deduce that these period-spacing patterns correspond to modes with ℓ = 1. Moreover, our analysis reveals that with increases in masses and metallicities, the star should display a higher degree of evolution to match a specific period spacing Π0. Conversely, the star should have a lower extent of evolution to match the radial fundamental mode. These two contradictory behaviors allow us to precisely obtain stellar physical parameters. TIC 65138566 and TIC 139729335 are determined to be two main-sequence stars that have almost the same range of masses and metallicities, with M = 1.36 ± 0.06 M ⊙ and Z = 0.005 ± 0.002. The hydrogen abundance in the core of TIC 65138566 is estimated to be about 0.28, while TIC 139729335 has a slightly higher value of around 0.31. Finally, we suggest that the high-amplitude δ Scuti–γ Doradus star TIC 308396022 is a main-sequence star with M = 1.54 ± 0.08 M ⊙, Z = 0.007 ± 0.001, and X c = 0.18 ± 0.02.

“…It has been observed that most δ Sct stars have amplitude modulations accompanied by period variations, representing different evolutionary stages . Thus, the identification of modes of δ Sct stars is an important research focus in asteroseismology (Balona & Evers 1999;Lv et al 2022;Yang et al 2022). Mode identification is performed by analyzing the light curves (LCs) of δ Sct stars (Breger et al 1993).…”

Section: Introductionmentioning

confidence: 99%

Multimode δ Sct stars from the Zwicky Transient Facility Survey

Jia,

Chen,

Wang

et al. 2024

ApJS

We obtain the largest catalog of multimode δ Sct stars in the northern sky to date using the Zwicky Transient Facility (ZTF) Data Release 20. The catalog includes 2254 objects, of which 2181 are new to our study. Among these multimode δ Sct stars, 2142 objects are double-mode δ Sct, while 109 objects are triple-mode δ Sct and three are quadruple-mode δ Sct. By analyzing the light curves in the r and g bands of the ZTF, we determine the basic parameters of multimode δ Sct stars, including the periods and amplitudes. Periods are checked by comparison with the Optical Gravitational Lensing Experiment catalog of double-mode δ Sct stars. On the Petersen diagram, multimode δ Sct stars form six sequences. We find that in Galactic coordinates, the periods of 1O/F double-mode δ Sct stars at high latitudes are shorter than those of 1O/F double-mode δ Sct stars in the disk, due to metallicity variations. In the future, our catalog can be used to establish the period–luminosity relation and the period–metallicity relation of double-mode δ Sct stars, and to study the Galactic structure.