# The Angular Separation of the Components of the Cepheid AW Per

## TL;DR

This paper measures the angular separation of the Cepheid AW Per's binary components using HST data, paving the way for direct mass and distance determination through combined spectroscopic and visual orbit analysis.

## Contribution

It introduces a method to determine the angular separation of a Cepheid binary from HST data, enabling future mass and distance measurements.

## Key findings

- Angular separation of AW Per measured from HST data
- Potential to determine system inclination and masses with additional observations
- Method demonstrates feasibility of visual orbit analysis for Cepheids

## Abstract

The 6.4 day classical Cepheid AW Per is a spectroscopic binary with a period of 40 years. Analyzing the centroids of HST/STIS spectra obtained in November 2001, we have determined the angular separation of the binary system. Although we currently have spatially resolved data for a single epoch in the orbit, the success of our approach opens the possibility of determining the inclination, sini, for the system if the measurements are repeated at additional epochs. Since the system is potentially a double lined spectroscopic binary, the combination of spectroscopic orbits for both components and the visual orbit would give the distance to the system and the masses of its components, thereby providing a direct measurement of a Cepheid mass.