Probing the amplitude modulation and pulsational energy re-distribution in the oscillation of HD 137949

Abstract

We present the result of over 50-h of Johnson-B photometric observation of HD 137949. These high-speed photometric data were acquired between June 12 and August 19 2013 using the 0.5-m telescope of the South African Astronomical Observatory (SAAO). The result of our frequency analysis when compared with that of similar B-light photometric data obtained in 1981 and 1987 using the same telescope reveals the existence of a long-term stability in its principal frequency of oscillation at ${\nu }_1=2.014781\pm 0.000003$ mHz; even with the excitation of two new secondary oscillations (${\nu }_2=2.016787\pm 0.000006$ mHz; ${\nu }_3=2.012628\pm 0.000009$ mHz). On the contrary, the signature of its principal amplitude of oscillation ($A$) was found to have changed drastically within a time-span of about three decades. However, the aggregate amplitude ($\sum A$) of all the detected oscillations was observed to have remained constant within the period under investigation. In addition, HD 137949 was observed to have undergone pulsational energy re-distribution within this time-span of about three decades; with a signature that is suggestive of non-conservation of its total energy (pulsational). We discuss the possible implications of the recently observed dynamics in the oscillation-signature of HD 137949.