MONOS: Multiplicity Of Northern O-type Spectroscopic systems. III. New orbits and Gaia TESS analysis for 10 SB2E systems

TL;DR

This paper presents new orbital solutions and analysis of ten O-type spectroscopic binaries using Gaia, TESS, and high-resolution spectroscopy, revealing new systems and refining known orbits to improve understanding of massive star evolution.

Contribution

It introduces new orbital solutions for ten O-type binaries, including the first known Oe+O system, using combined Gaia, TESS, and spectroscopic data, expanding the sample of well-characterized massive binaries.

Findings

Eight new orbits, two with new periods, are presented.

First known Oe+O spectroscopic binary identified.

System with overcontact O-type supergiants and evidence of past mass transfer.

Abstract

The MONOS project (Multiplicity Of Northern O-type Spectroscopic systems) aims to characterize O-type spectroscopic binaries in the northern hemisphere (dec > -20 deg) using high-resolution spectroscopy and multi-epoch photometry. This study uses Gaia DR3 epoch photometry and TESS light curves to detect periodic variability and refine orbital solutions. We analyze ten O-type binaries with quality Gaia and TESS data and available high-resolution spectra, complemented by Hipparcos or MUDEHaR photometry. Periods are derived using three techniques and combined with radial velocities to model each system with the phoebe code, yielding orbital and stellar parameters. We present eight previously unpublished orbits-two with new periods-and refine two others. In several cases, our periods match Gaia's, though we highlight issues such as half-period aliases. Among our key results, we report the first known Oe+O spectroscopic binary (BD +61 487) and a system of overcontact O-type supergiants in an eccentric orbit with evidence of past mass transfer (HD 169 727). The solutions are consistent with spectral classifications and theory, including short periods (< 3 days), high mass ratios, and semi-detached or overcontact configurations. These results expand the sample of O-type binaries with robust orbital characterization, especially in the short-period regime where tidal effects and mass transfer dominate. The combined use of Gaia, TESS, and spectroscopy proves effective and scalable, supporting future surveys and aiding our understanding of massive multiple-star evolution.