Pulsations and Long-Term Light Variability of Three Candidates to Protoplanetary Nebulae

TL;DR

This study analyzes long-term photometric data of three candidate protoplanetary nebulae, revealing quasiperiodic pulsations and brightness trends, contributing to understanding their variability and evolutionary status.

Contribution

It provides detailed pulsation periods and variability patterns for three protoplanetary nebula candidates, highlighting their quasiperiodic behavior and potential binary nature.

Findings

IRAS 18095+2704 has a 109-day pulsation period.

IRAS 19386+0155 shows a 102-day main period modulated by a 98-day close frequency.

IRAS 19500-1709 exhibits irregular pulsations with 39 and 47-day periods.

Abstract

We present new photometric data and analysis of the long-duration UBV photoelectric observations for three candidates to protoplanetary objects - F-supergiants with IR-excesses located at large galactic latitudes, IRAS 18095+2704, IRAS 19386+0155, and IRAS 19500-1709. All three stars have revealed quasiperiodic low-amplitude variabilities caused by pulsations observed against the long-term trends of brightnesses. For IRAS 18095+2704=V887 Her we have found a pulsation period of 109 days and a linear trend of brightness under the constant colours if being averaged over the year timescale. The light curve of IRAS 19386+0155=V1648 Aql over 2000-2008 can be approximated by a wave with a main period of 102 days which is modulated by close frequency, with a period of 98 days, that results in brightness oscillations with a variable amplitude. V1648 Aql has also shown synchronous reddening together with a persistent rise of brightness in the V-band. IRAS 19500-1709=V5112 Sgr experiences irregular pulsations with the periods of 39 and 47 days. The long-term component of the variability of V5112 Sgr may be related to the binary character of this star.