Optical spectroscopy of X-Mega targets in the Carina nebula - VII On the multiplicity of Tr 16-112, HD 93343 and HD 93250

TL;DR

This study uses spectroscopic monitoring to analyze the multiplicity and orbital characteristics of three massive O-type stars in the Carina nebula, revealing a new binary system and discussing the multiplicity status of others.

Contribution

First spectroscopic orbital solution for Tr 16-112 and first detection of SB2 signature in HD 93343, advancing understanding of massive star multiplicity in Carina.

Findings

Tr 16-112 is a dissymmetrical binary with an eccentric orbit.

HD 93343 is confirmed as an SB2 binary system.

HD 93250 shows no signs of multiplicity.

Abstract

We present the results of a spectroscopic monitoring campaign devoted to three O-type stars in the Carina nebula. We derive the full SB2 orbital solution of the binary system Tr 16-112, an exceptional dissymmetrical system consisting of an O5.5-6V((f$^+$?p)) primary and a B2V-III secondary. We also report on low-amplitude brightness variations in Tr 16-112 that are likely due to the ellipsoidal shape of the O5.5-6 primary revolving in an eccentric orbit around the system's centre of mass. We detect for the first time a clear SB2 binary signature in the spectrum of HD 93343 (O8 + O8), although our data are not sufficient to establish an orbital solution. This system also displays low amplitude photometric modulations. On the other hand, no indication of multiplicity is found in the optical spectra of HD 93250. Finally, we discuss the general properties of multiple massive stars in the Carina OB1 association.