Cepheids in spectroscopic binary systems -- current status and recent discoveries

TL;DR

This paper reviews the latest discoveries and progress in studying Cepheids in binary systems, highlighting new binary detections, orbital parameters, and the implications for stellar evolution.

Contribution

It provides an updated catalog of spectroscopic binary Cepheids, including newly confirmed systems and systems with unique orbital characteristics, advancing understanding of Cepheid multiplicity.

Findings

Confirmed 60 SB2 systems with significant orbital motion

Discovered systems with very short orbital periods

Identified systems with unusual mass ratios and double Cepheids

Abstract

We present a summary of the current knowledge about Cepheids in binary systems. We focus on the most recent findings and discoveries, such as the highly increasing number of confirmed and candidate spectroscopic binary Cepheids and the progress in determining their physical parameters. This includes new and newly analyzed binary Cepheids in the Milky Way and Magellanic Clouds. We will provide an update on the project to increase the number of the most valuable Cepheids in double-lined binary (SB2) systems from six to more than 100. To date, we have confirmed 60 SB2 systems, including detecting a significant orbital motion for 37. We identified systems with orbital periods up to five times shorter than the shortest period reported before and systems with mass ratios significantly different from unity (suggesting past binary interactions, including merger events). Both features are essential to understanding how multiplicity affects the formation and destruction of Cepheid progenitors and how this influences global Cepheid properties. We will also present nine new systems composed of two Cepheids. Only one such double Cepheid system was known before.