The Formation of Very Close Binary Stars

Abstract

The majority of very close binaries (orbital periods P < 5 days) are in triples. Previous studies surmised that the tertiary hardened the inner binary via Kozai-Lidov cycles coupled with tidal friction. Alternatively, the trend could be due to a common origin, e.g., more massive molecular cores and protostellar disks are more likely to fragment twice into a triple and harden the inner binary to very short periods via disk migration. Disk migration occurs during the embedded Class I protostellar phase while secular evolution with a tertiary occurs on much longer timescales. To determine the dominant migration mechanism, I accurately measure the very close binary fractions of both late-type and early-type primaries in star-forming environments. After combining five surveys, the late-type Class II/III T Tauri very close binary fraction is F_VCB = 2.1_{-0.5}^{+1.0}%, which is consistent with the measurement for late-type field main-sequence stars (1.7% +/- 0.1%). More than 85% of very close late-type binaries hardened via disk migration during the Class I protostellar phase. I next measure the OGLE-III eclipsing binary (EB) fractions of young massive stars in the LMC. The very close EB fractions of massive young stellar objects (YSOs; F_VCEB = 8.3_{-3.2}^{+4.9}%), OB stars near massive YSOs (4.7% +/- 0.8%), and OB stars in small, young H II regions (6.4% +/- 1.5%) are consistent with each other and the measurement for OB stars in slightly older clusters (4.7% +/- 0.3%). More than 90% of very close massive binaries hardened via disk migration during the embedded protostellar phase.

Rotating models of very massive close binary stars at solar metallicity: Evolution and remnant masses
J. Petrović, M. I. Jurkovic Malagurski, A. Mitrašinović +3
Astronomy & Astrophysics22 Oct 2026Peer-reviewedPublisher termsSolar & stellar physicsCrossref
Proto-Planetary Nebulae Are Not the Precursors of Planetary Nebulae With Close Binary Central Stars
Todd C. Hillwig, Bruce J. Hrivnak, David Jones
arXiv15 Sep 2026PreprintarXiv licenceFull textGalaxies Solar & stellar physicsarXiv
GW231123 Formation from Population III Stars: Isolated Binary Evolution
Ataru Tanikawa, Shuai 帅 Liu 刘, Weiwei Wu +2
The Astrophysical Journal15 May 2026Peer-reviewedCC BY19 citedHigh-energy astrophysicsOpenAlex
Formation and Detectability of PSR J0653+0443-like Extremely Eccentric Binary Neutron Stars in the Milky Way
Zhiwei Chen, Jihui Zhang, Youjun Lu
arXiv22 Oct 2026PreprintarXiv licenceFull textHigh-energy astrophysics Solar & stellar physicsarXiv
When the stars don't align: Investigating inconsistencies in binary black hole formation across population synthesis codes
Alexandra G. Guerrero, Michael Zevin, Duncan B. Maclean +4
arXiv21 Sep 2026PreprintarXiv licenceFull textGalaxies High-energy astrophysicsarXiv

Cite

BibTeX RIS

BibTeX

@misc{moe2026formation,
  title = {{The Formation of Very Close Binary Stars}},
  author = {Maxwell Moe},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.00426},
  eprint = {2609.00426},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.00426},
}

RIS

TY  - UNPB
TI  - The Formation of Very Close Binary Stars
AU  - Maxwell Moe
PY  - 2026
DA  - 2026/09/01
PB  - arXiv
DO  - 10.48550/arxiv.2609.00426
UR  - https://arxiv.org/abs/2609.00426
AB  - The majority of very close binaries (orbital periods P < 5 days) are in triples. Previous studies surmised that the tertiary hardened the inner binary via Kozai-Lidov cycles coupled with tidal friction. Alternatively, the trend could be due to a common origin, e.g., more massive molecular cores and protostellar disks are more likely to fragment twice into a triple and harden the inner binary to very short periods via disk migration. Disk migration occurs during the embedded Class I protostellar phase while secular evolution with a tertiary occurs on much longer timescales. To determine the dominant migration mechanism, I accurately measure the very close binary fractions of both late-type and early-type primaries in star-forming environments. After combining five surveys, the late-type Class II/III T Tauri very close binary fraction is F_VCB = 2.1_{-0.5}^{+1.0}%, which is consistent with the measurement for late-type field main-sequence stars (1.7% +/- 0.1%). More than 85% of very close late-type binaries hardened via disk migration during the Class I protostellar phase. I next measure the OGLE-III eclipsing binary (EB) fractions of young massive stars in the LMC. The very close EB fractions of massive young stellar objects (YSOs; F_VCEB = 8.3_{-3.2}^{+4.9}%), OB stars near massive YSOs (4.7% +/- 0.8%), and OB stars in small, young H II regions (6.4% +/- 1.5%) are consistent with each other and the measurement for OB stars in slightly older clusters (4.7% +/- 0.3%). More than 90% of very close massive binaries hardened via disk migration during the embedded protostellar phase.
ER  -

Abstract

Related

Cite