An Interferometric and Spectroscopic Analysis of the Multiple Star System HD 193322

TL;DR

This study combines spectroscopic and interferometric observations to analyze the complex multiple star system HD 193322, revealing detailed orbital parameters and stellar masses of its massive components.

Contribution

It presents the first combined spectroscopic and interferometric analysis of HD 193322, improving orbital solutions and mass estimates of its massive stars.

Findings

Determined orbital periods of 312 days and 35 years for the close and wide binaries.

Measured stellar masses of approximately 21 and 23 solar masses for the primary stars.

Identified differences in rotational velocities among the massive stars.

Abstract

The star HD 193322 is a remarkable multiple system of massive stars that lies at the heart of the cluster Collinder 419. Here we report on new spectroscopic observations and radial velocities of the narrow-lined component Ab1 that we use to determine its orbital motion around a close companion Ab2 ($P = 312$ d) and around a distant third star Aa ($P = 35$ y).We have also obtained long baseline interferometry of the target in the $K^\prime$-band with the CHARA Array that we use in two ways. First, we combine published speckle interferometric measurements with CHARA separated fringe packet measurements to improve the visual orbit for the wide Aa,Ab binary. Second, we use measurements of the fringe packet from Aa to calibrate the visibility of the fringes of the Ab1,Ab2 binary, and we analyze these fringe visibilities to determine the visual orbit of the close system. The two most massive stars, Aa and Ab1, have masses of approximately 21 and $23 M_\odot$, respectively, and their spectral line broadening indicates that they represent extremes of fast and slow projected rotational velocity, respectively.