The Components of Cepheid Systems: The FN Vel System

TL;DR

This paper demonstrates a method to determine Cepheid masses using ultraviolet spectra, Gaia data, and orbital inclination, with FN Vel as a case study, to improve evolutionary models of intermediate mass stars.

Contribution

It introduces a new approach combining UV spectra, Gaia data, and orbital inclination to accurately measure Cepheid masses.

Findings

Mass of the companion derived from UV spectra.

Constraints on Cepheid mass for specific orbital inclinations.

Demonstration of method using FN Vel system.

Abstract

Cepheid masses continue to be important tests of evolutionary tracks for intermediate mass stars as well as important predictors of their future fate. For systems where the secondary is a B star, {\it Hubble Space Telescope} ultraviolet spectra have been obtained. From these spectra a temperature can be derived, and from this a mass of the companion M$_2$. Once {\it Gaia} DR4 is available, proper motions can be used to determine the inclination of the orbit. Combining mass of the companion, M$_2$, the mass function from the ground-based orbit of the Cepheid and the inclination produces the mass of the Cepheid, M$_1$. The Cepheid system FN Vel is used here to demonstrate this approach and what limits can be put on the Cepheid mass for inclination between 50 and 130$^o$.