Variability in Proto-Planetary Nebulae: IV. Light Curve Analyses of Four Oxygen-Rich, F Spectral-Type Objects

TL;DR

This study analyzes 14-19 years of light curves for four oxygen-rich proto-planetary nebulae, revealing multiple pulsation periods, temperature variations, and relationships between period and temperature, enhancing understanding of their variability.

Contribution

It provides the first detailed long-term period analysis of four O-rich F-type PPNs, identifying dominant and secondary pulsation periods and their relation to temperature.

Findings

Identified dominant periods ranging from 41 to 113 days.

Detected multiple pulsation periods close to the dominant ones.

Observed temperature variations of 400 to 770 K due to pulsations.

Abstract

We present new light curves covering 14 to 19 years of observations of four bright proto-planetary nebulae (PPNs), all O-rich and of F spectral type. They each display cyclical light curves with significant variations in amplitude. All four were previously known to vary in light. Our data were combined with published data and searched for periodicity. The results are as follows: IRAS 19475+3119 (HD 331319; 41.0 days), 17436+5003 (HD 161796; 45.2 days), 19386+0155 (101.8 days), and 18095+2704 (113.3 days). The two longer periods are in agreement with previous studies while the two shorter periods each reveal for the first time reveal a dominant period over these long observing intervals. Multiple periods were also found for each object. The secondary periods were all close to the dominant periods, with P2/P1 ranging from 0.86 to 1.06. The variations in color reveal maximum variations in T(eff) of 400 to 770 K. These variations are due to pulsations in these post-AGB objects. Maximum seasonal light variations are all less than 0.23 mag (V), consistent for their temperatures and periods with the results of Hrivnak et al. (2010) for 12 C-rich PPNs. For all of these PPNs, there is an inverse relationship between period and temperature; however, there is a suggestion that the period-temperature relationship may be somewhat steeper for the O-rich than for the C-rich PPNs.