Amplitude Modulation in a Delta Scuti star HD118660

TL;DR

This study reports amplitude modulation in the delta Scuti star HD118660, attributed to beating between two unresolved close frequencies, with stable other modes indicating non-conservation of pulsation energy.

Contribution

It provides the first detailed analysis of amplitude modulation in HD118660 and models the phenomenon as beating of two close unresolved frequencies.

Findings

Amplitude modulation observed in one p-mode at 24.3837 c/d.

Other modes remain stable in amplitude and phase.

Beating of two close frequencies explains the observed modulation.

Abstract

In this paper, we report the detection of amplitude modulation in a delta Scuti star HD118660. We found that the p-mode frequency at 24.3837 c/d varies periodically in amplitude with frequency 0.0558 c/d. 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 sinusoids with frequencies n1 = 24.3837 c/d and n2 = 24.4420 c/d and corresponding phases f1 = 0:5211 rad and f2 = 0:9481 rad to mimic the observed variations of amplitude and phase with time. The plausible explanation of the amplitude modulation in HD118660 is due to beating of two unresolved closed frequencies n1 and n2.