GEOS RR Lyr survey: FM Del is indeed a cepheid

TL;DR

This paper confirms that FM Del is a Cepheid variable star, resolving previous conflicting classifications by analyzing observational data.

Contribution

The study provides observational evidence confirming FM Del as a Cepheid, clarifying its classification amidst prior conflicting reports.

Findings

FM Del is a Cepheid of period 3.95452 days.

Previous RR Lyrae classification is incorrect.

Observations support the Cepheid classification.

Abstract

Though FM Del has been considered as a RR Lyr star by Preston et al. in 1959 (following discovery by Huth, 1957), Huth (1960) eventually changed his mind by showing that it is in fact a cepheid of W Vir type of period of 3.95452 days. Various authors since then have considered it as a cepheid indeed, with the exception of Wils et al. (2006) who list this star in their RR Lyr catalog with a period of 0.79688 days. On this basis, FM Del was added to Tarot RR Lyr program. We present here these observations which confirm the cepheid type.