# Fundamental Parameters of Cepheids: Masses and Multiplicity

## TL;DR

This paper reviews recent advances in determining Cepheid masses through binary systems and discusses how these findings inform star formation theories, multiplicity, and binary characteristics.

## Contribution

It summarizes recent mass measurements of Cepheids using combined ground and space-based data, highlighting implications for stellar evolution and star formation models.

## Key findings

- Cepheid masses have been refined using multi-instrument observations.
- Multiplicity studies reveal diverse binary properties among massive stars.
- Results constrain star formation scenarios and binary evolution models.

## Abstract

Masses determined from classical Cepheids in binary systems are a primary test of both pulsation and evolutionary calculations. The first step is to determine the orbit from ground-based radial velocities. Complementary satellite data from Hubble, FUSE, IUE, and Chandra provide full information about the system. A summary of recent results on masses is given. Cepheids have also provided copious information about the multiplicity of massive stars, as well as the distribution of mass ratios and separations. This provides some important constraints for star formation scenarios including differences between high and low mass results and differences between close and wide binaries.