Sarkar, Mrinmoy ; Joshi, Santosh ; Dupret, Marc-Antoine ; Buldgen, Gaël ; Dileep, Athul ; De Cat, Peter ; Ghosh, Surath C. ; Gupta, Archana

submitted to Monthly Notices of the Royal Astronomical Society (2026)

Abstract: In this paper, we present an asteroseismic analysis of two mild Am δ Scuti (δ Sct) pulsators, HD 13038 and HD 13079, utilising both the space and ground-based photometry. From multi-sector TESS observations with different cadences, 37 pulsation frequencies for HD 13038 and 69 for HD 13079 were extracted with SNR > 5. Notably, light curves of HD 13079 are affected by ∼ 12.3% of the flux from its neighbourhood star HD 13079B situated at an angular separation of 6.48 ± 2.70 arcsec. For HD 13038, the large frequency separation is 6.08 d^{-1} exhibiting two vertical ridges of radial modes consistent with the frequency ratios and pulsation constants (Q-value). However, the seismic age indicates the left-ridge frequencies are more acceptable as radial modes with orders n = 5, 7. We found that one radial ridge is visible for HD 13079 at a large separation of 5.15 d^{-1} with orders n = 1, 2, 3, 4, 6. For both stars, excited radial overtones are higher than the predicted values for these T_{eff} range. The stellar parameters were calculated using a mass-metallicity grid followed by seismic-chi² minimisation technique constraining identified radial modes. In the frequency spectrum of HD 13038, the spotted rotation frequency at f_{rot} ≈ 0.94 d^{-1} provides an inclination angle ≈ 90 degrees. The frequency spectrum of combined TESS light curve for HD 13079, reveals f_{rot} ≈ 0.86 d^{-1} is in close agreement to the observed mean quintuplet splitting frequency ≈ 0.77 d^{-1}, provides an inclination angle of 42 ± 4◦. The present study is a crucial step in comprehending the processes that underlie the excitation of high-order radial modes in Am stars.

Keyword(s): Asteroseismology ; Am Star ; δ Sct pulsations ; Individual: HD 13038 ; Individual: HD 13079 ; Stellar Rotation ; Quintuplets