On the multiplicity of the zero-age main-sequence O star Herschel 36

TL;DR

This study analyzes high-resolution spectra of Herschel 36, revealing it as a multiple system with a close binary and a distant companion, providing detailed orbital parameters and highlighting the system's complex multiplicity.

Contribution

First detailed spectroscopic analysis of Herschel 36 revealing its triple system nature and orbital characteristics of its components.

Findings

Identified a close binary with a 1.5415-day period.

Detected a third luminous component with ~498-day RV variation.

Confirmed Herschel 36 as a multiple star system.

Abstract

We present the analysis of high-resolution optical spectroscopic observations of the zero-age main-sequence O star Herschel 36 spanning six years. This star is definitely a multiple system, with at least three components detected in its spectrum. Based on our radial-velocity (RV) study, we propose a picture of a close massive binary and a more distant companion, most probably in wide orbit about each other. The orbital solution for the binary, whose components we identify as O9 V and B0.5 V, is characterized by a period of 1.5415 +/- 0.0006 days. With a spectral type O7.5 V, the third body is the most luminous component of the system and also presents RV variations with a period close to 498 days. Some possible hypotheses to explain the variability are briefly addressed and further observations are suggested.