The Valuable Long-period Cluster Cepheid KQ Scorpii and other Calibration Candidates

TL;DR

This paper highlights the importance of the long-period Cepheid KQ Scorpii as a key distance indicator, analyzing its cluster membership and proposing a collaborative database for cluster Cepheids to improve calibration.

Contribution

It provides detailed analysis of KQ Scorpii's cluster membership using Gaia DR3 data and suggests establishing a shared database for cluster Cepheid candidates.

Findings

KQ Scorpii is confirmed as a cluster Cepheid at 2.15 kpc.

Identification of additional cluster Cepheid candidates.

Proposal for a collaborative cluster Cepheid database.

Abstract

The classical Cepheid KQ Sco is a valuable anchor for the distance scale because of its long pulsation period ($28^{\rm d}.7$) and evidence implying membership in the open cluster UBC 1558. Analyses tied to Gaia DR3 astrometry, photometry, spectroscopy, radial velocities, and 2MASS-VVV photometry indicate a common distance of $2.15\pm0.15$ kpc (\citealt{lin21} DR3 corrections applied). Additional cluster Cepheid candidates requiring follow-up are identified, and it's suggested that a team of international researchers could maintain a cluster Cepheid database to guide the broader community to cases where consensus exists.