A self-consistent orbital architecture for GG Tau A. I. Simultaneous orbital fitting of the hierarchical triple
Abstract
GG Tau A is a young triple system with the close pair, Ab1--Ab2, and Aa, surrounded by a massive circumtriple disk with a large inner cavity difficult to explain in a binary framework. We aim to determine the orbital architecture and individual stellar masses of GG Tau A and assess how the available astrometric and disk-based constraints restrict the range of admissible solutions. We performed a joint fit using Oracle, developed specifically for hierarchical stellar systems. All astrometric measurements were placed in a common reference frame, since the historical wide-orbit astrometry is given relative to the unresolved photocenter of the Ab subsystem. The fit included one new wide-orbit astrometric epoch and a prior on the total stellar mass derived from disk kinematics. We then applied, in post-processing, an additional geometrical constraint based on the observed center of the circumtriple disk. The fit yields orbital solutions compatible with the available astrometric and disk-based constraints and provides estimates of the individual stellar masses. The additional wide-orbit epoch only marginally reduces the range of admissible solutions. By contrast, the disk-center constraint leaves the favored orbital architectures largely unchanged but significantly tightens the stellar-mass partition. This yields posterior masses of 0.521+0.069−0.051, 0.106+0.017−0.013, and 0.79+0.10−0.10 M⊙ for Ab1, Ab2, and Aa, respectively. The reported values are posterior medians with 16th--84th percentile intervals. A joint treatment of the two orbital levels is required to recover a physically meaningful architecture and constrain the individual stellar masses. The resulting solutions provide a basis for future dynamical modeling of the circumtriple disk and for testing whether the observed cavity can further constrain the system architecture.
Versions
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BibTeX
@misc{lacquement2026selfconsistent,
title = {{A self-consistent orbital architecture for GG Tau A. I. Simultaneous orbital fitting of the hierarchical triple}},
author = {A. Lacquement and H. Beust and G. Duchêne and C. Lawlor and C. Ginski and E. Di Folco and A. Dutrey},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.17322},
eprint = {2609.17322},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.17322},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A self-consistent orbital architecture for GG Tau A. I. Simultaneous orbital fitting of the hierarchical triple
AU - A. Lacquement
AU - H. Beust
AU - G. Duchêne
AU - C. Lawlor
AU - C. Ginski
AU - E. Di Folco
AU - A. Dutrey
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.17322
UR - https://arxiv.org/abs/2609.17322
AB - GG Tau A is a young triple system with the close pair, Ab_1--Ab_2, and Aa, surrounded by a massive circumtriple disk with a large inner cavity difficult to explain in a binary framework. We aim to determine the orbital architecture and individual stellar masses of GG Tau A and assess how the available astrometric and disk-based constraints restrict the range of admissible solutions. We performed a joint fit using Oracle, developed specifically for hierarchical stellar systems. All astrometric measurements were placed in a common reference frame, since the historical wide-orbit astrometry is given relative to the unresolved photocenter of the Ab subsystem. The fit included one new wide-orbit astrometric epoch and a prior on the total stellar mass derived from disk kinematics. We then applied, in post-processing, an additional geometrical constraint based on the observed center of the circumtriple disk. The fit yields orbital solutions compatible with the available astrometric and disk-based constraints and provides estimates of the individual stellar masses. The additional wide-orbit epoch only marginally reduces the range of admissible solutions. By contrast, the disk-center constraint leaves the favored orbital architectures largely unchanged but significantly tightens the stellar-mass partition. This yields posterior masses of 0.521^+0.069_−0.051, 0.106^+0.017_−0.013, and 0.79^+0.10_−0.10 M_⊙ for Ab_1, Ab_2, and Aa, respectively. The reported values are posterior medians with 16th--84th percentile intervals. A joint treatment of the two orbital levels is required to recover a physically meaningful architecture and constrain the individual stellar masses. The resulting solutions provide a basis for future dynamical modeling of the circumtriple disk and for testing whether the observed cavity can further constrain the system architecture.
ER -