Sarkar, Mrinmoy ; Joshi, Santosh ; De Cat, Peter

in press to Bulletin de la Société Royale des Sciences de Liège, 93 (2024)

Abstract: In this paper, we report the detection of amplitude modulation in a δ Scuti star HD118660. We found that the p-mode frequency at 24.3837 d^{−1} varies periodically in amplitude with frequency 0.0558 ± 0.00147 d^{−1}. However, all other modes are stable in both amplitude and phase which is clear evidence of non-conservation of visible pulsation mode energy. We constructed a two-frequency model by superimposing two sinusoïds with frequencies ν_1 = 24.3837 d^{−1} and ν_2 = 24.4420 d^{−1} and corresponding phases φ_1 = 0.5211 rad and φ_2 = 0.9481 rad to mimic the observed variations of amplitude and phase with time. The plausible explanation of the amplitude modulation in HD 118660 is due to beating of two unresolved closed frequencies ν_1 and ν_2.

Keyword(s): Stars: individual: HD118660 ; Stars: amplitude modulation ; TESS: δ Scuti pulsator ; Chemically peculiar ; Stars: oscillations
Funding: BL/33/IN12 (BINA)