An Eccentric Massive Protobinary Assembled via a Core-merger Parabolic Encounter
Abstract
Most massive stars form in binary systems, which profoundly influence their subsequent evolution. However, how such systems form remains poorly understood, with several competing scenarios proposed, including disk fragmentation, core fragmentation and capture. Determining the orbital architectures of massive binaries, particularly during their earliest embedded phases, is therefore crucial for distinguishing among these formation pathways, but direct measurements of their three-dimensional motions have remained exceptionally challenging. Here we present high-resolution, multi-epoch sub-millimeter-to-centimeter ALMA and JVLA observations of the massive protobinary IRAS 07299−1651, complemented by JWST and VLT infrared imaging. We detect orbital proper motion of the binary components, enabling a full three-dimensional orbital reconstruction. Combining orbital fitting, multi-wavelength continuum modelling, hydrogen recombination line kinematics and jet observations, we find that the preferred orbital solutions are highly eccentric and close to parabolic, while both circumstellar disks are strongly misaligned with the orbital plane. These properties are naturally explained by a ``core-merger'' scenario in which the two protostars originated independently from initially unbound cores that recently underwent a near-parabolic encounter, producing an eccentric binary with a current separation of about 200 au. These findings suggest that the core-merger process may represent an important pathway for forming eccentric massive binaries.
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BibTeX
@misc{wang2026eccentric,
title = {{An Eccentric Massive Protobinary Assembled via a Core-merger Parabolic Encounter}},
author = {Yao Wang and Yichen Zhang and Rubén Fedriani and Kei E. I. Tanaka and Viviana Rosero and Kai Yang and Morten Andersen and Maria T. Beltrán and Mélisse Bonfand and Yu Cheng and James M. De Buizer and Yihuan Di and Guido Garay and Prasanta Gorai and Zhi-Yun Li and Yao-Lun Yang and Jonathan C. Tan},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.07390},
eprint = {2609.07390},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.07390},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - An Eccentric Massive Protobinary Assembled via a Core-merger Parabolic Encounter
AU - Yao Wang
AU - Yichen Zhang
AU - Rubén Fedriani
AU - Kei E. I. Tanaka
AU - Viviana Rosero
AU - Kai Yang
AU - Morten Andersen
AU - Maria T. Beltrán
AU - Mélisse Bonfand
AU - Yu Cheng
AU - James M. De Buizer
AU - Yihuan Di
AU - Guido Garay
AU - Prasanta Gorai
AU - Zhi-Yun Li
AU - Yao-Lun Yang
AU - Jonathan C. Tan
PY - 2026
DA - 2026/09/07
PB - arXiv
DO - 10.48550/arxiv.2609.07390
UR - https://arxiv.org/abs/2609.07390
AB - Most massive stars form in binary systems, which profoundly influence their subsequent evolution. However, how such systems form remains poorly understood, with several competing scenarios proposed, including disk fragmentation, core fragmentation and capture. Determining the orbital architectures of massive binaries, particularly during their earliest embedded phases, is therefore crucial for distinguishing among these formation pathways, but direct measurements of their three-dimensional motions have remained exceptionally challenging. Here we present high-resolution, multi-epoch sub-millimeter-to-centimeter ALMA and JVLA observations of the massive protobinary IRAS 07299−1651, complemented by JWST and VLT infrared imaging. We detect orbital proper motion of the binary components, enabling a full three-dimensional orbital reconstruction. Combining orbital fitting, multi-wavelength continuum modelling, hydrogen recombination line kinematics and jet observations, we find that the preferred orbital solutions are highly eccentric and close to parabolic, while both circumstellar disks are strongly misaligned with the orbital plane. These properties are naturally explained by a ``core-merger'' scenario in which the two protostars originated independently from initially unbound cores that recently underwent a near-parabolic encounter, producing an eccentric binary with a current separation of about 200 au. These findings suggest that the core-merger process may represent an important pathway for forming eccentric massive binaries.
ER -