Trend Analysis of Long Period Variables

Abstract

We have performed a trend analysis of 383 long period variables (LPVs) using 90 years of AAVSO data. We studied the period and amplitude, as well as the mean magnitude and asymmetry (time from minimum to the following maximum as a fraction of the period). We conclude that the period is a much more stable parameter than the others, with only 9% of the sample stars showing long-term trends in period. Longer-period stars are more likely to show period fluctuations than shorter-period stars. The light curve asymmetry is the parameter most likely to show a trend; half of the sample stars show some trend in their asymmetry. A significant fraction of the stars seem to be getting fainter in their mean visual magnitude, while only a handful appear to be brightening. We point out a few stars that show very large changes in their light curve parameters.