Amplitude Variations in Pulsating Red Supergiants

TL;DR

This study analyzes long-term amplitude variations in pulsating red supergiants using observational data and spectral analysis, revealing diverse period behaviors and amplitude changes over decades.

Contribution

It provides the first detailed analysis of amplitude variations and period behaviors in a sample of 44 red supergiants using Fourier and wavelet techniques.

Findings

26 stars show amplitude variations up to a factor of 8.

Longer periods are analogous to long secondary periods in red giants.

Median amplitude variation timescale is 18 periods.

Abstract

We have used long-term AAVSO visual observations and Fourier and wavelet analysis to identify periods and study long-term amplitude variations in 44 red supergiants. Of these, 12 stars had data which were too sparse and/or had low amplitude and/or were without conspicuous peaks in the Fourier spectrum; 6 stars had only long (2500-4000 days) periods without significant amplitude variation. The other 26 stars had one or two periods, either "short" (hundreds of days) or "long" (thousands of days), whose amplitudes varied by up to a factor of 8, but more typically 2-4. The median timescale of the amplitude variation was 18 periods. We interpret the shorter periods as due to pulsation, and the longer periods as analogous to the "long secondary periods" found in pulsating red giants.