Dynamical Formation of Close Binaries during the Pre-main-sequence Phase
Solar-type binaries with short orbital periods (P-close equivalent to 1-10. days; a less than or similar to 0.1. au) cannot form directly via fragmentation of molecular clouds or protostellar disks, yet their component masses are highly correlated, suggesting interaction during the pre-main-sequence...
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ndltd-arizona.edu-oai-arizona.openrepository.com-10150-6271002018-03-25T03:00:28Z Dynamical Formation of Close Binaries during the Pre-main-sequence Phase Moe, Maxwell Kratter, Kaitlin M. Univ Arizona, Steward Observ binaries: close stars: formation stars: kinematics and dynamics stars: pre-main sequence Solar-type binaries with short orbital periods (P-close equivalent to 1-10. days; a less than or similar to 0.1. au) cannot form directly via fragmentation of molecular clouds or protostellar disks, yet their component masses are highly correlated, suggesting interaction during the pre-main-sequence (pre-MS) phase. Moreover, the close binary fraction of pre-MS stars is consistent with that of their MS counterparts in the field (F-close = 2.1%). Thus, we can infer that some migration mechanism operates during the early pre-MS phase (tau less than or similar to 5 Myr) that reshapes the primordial separation distribution. We test the feasibility of this hypothesis by carrying out a population synthesis calculation which accounts for two formation channels: Kozai-Lidov (KL) oscillations and dynamical instability in triple systems. Our models incorporate (1) more realistic initial conditions compared to previous studies, (2) octupole-level effects in the secular evolution, (3) tidal energy dissipation via weak-friction equilibrium tides at small eccentricities and via non-radial dynamical oscillations at large eccentricities, and (4) the larger tidal radius of a pre-MS primary. Given a 15% triple-star fraction, we simulate a close binary fraction from KL oscillations alone of F-close approximate to 0.4% after tau = 5. Myr, which increases to F-close 0.8% by tau = 5. Gyr. Dynamical ejections and disruptions of unstable coplanar triples in the disk produce solitary binaries with slightly longer periods P approximate to 10-100. days. The remaining approximate to 60% of close binaries with outer tertiaries, particularly those in compact coplanar configurations with log P-out (days) approximate to 2-5 (a(out) < 50 au), can be explained only with substantial extra energy dissipation due to interactions with primordial gas. 2018-02-09 Article Dynamical Formation of Close Binaries during the Pre-main-sequence Phase 2018, 854 (1):44 The Astrophysical Journal 1538-4357 10.3847/1538-4357/aaa6d2 http://hdl.handle.net/10150/627100 http://arizona.openrepository.com/arizona/handle/10150/627100 The Astrophysical Journal en http://stacks.iop.org/0004-637X/854/i=1/a=44?key=crossref.109f7e85bf9ab3998e19ae2b54c7b236 © 2018. The American Astronomical Society. All rights reserved. IOP PUBLISHING LTD |
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language |
en |
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topic |
binaries: close stars: formation stars: kinematics and dynamics stars: pre-main sequence |
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binaries: close stars: formation stars: kinematics and dynamics stars: pre-main sequence Moe, Maxwell Kratter, Kaitlin M. Dynamical Formation of Close Binaries during the Pre-main-sequence Phase |
description |
Solar-type binaries with short orbital periods (P-close equivalent to 1-10. days; a less than or similar to 0.1. au) cannot form directly via fragmentation of molecular clouds or protostellar disks, yet their component masses are highly correlated, suggesting interaction during the pre-main-sequence (pre-MS) phase. Moreover, the close binary fraction of pre-MS stars is consistent with that of their MS counterparts in the field (F-close = 2.1%). Thus, we can infer that some migration mechanism operates during the early pre-MS phase (tau less than or similar to 5 Myr) that reshapes the primordial separation distribution. We test the feasibility of this hypothesis by carrying out a population synthesis calculation which accounts for two formation channels: Kozai-Lidov (KL) oscillations and dynamical instability in triple systems. Our models incorporate (1) more realistic initial conditions compared to previous studies, (2) octupole-level effects in the secular evolution, (3) tidal energy dissipation via weak-friction equilibrium tides at small eccentricities and via non-radial dynamical oscillations at large eccentricities, and (4) the larger tidal radius of a pre-MS primary. Given a 15% triple-star fraction, we simulate a close binary fraction from KL oscillations alone of F-close approximate to 0.4% after tau = 5. Myr, which increases to F-close 0.8% by tau = 5. Gyr. Dynamical ejections and disruptions of unstable coplanar triples in the disk produce solitary binaries with slightly longer periods P approximate to 10-100. days. The remaining approximate to 60% of close binaries with outer tertiaries, particularly those in compact coplanar configurations with log P-out (days) approximate to 2-5 (a(out) < 50 au), can be explained only with substantial extra energy dissipation due to interactions with primordial gas. |
author2 |
Univ Arizona, Steward Observ |
author_facet |
Univ Arizona, Steward Observ Moe, Maxwell Kratter, Kaitlin M. |
author |
Moe, Maxwell Kratter, Kaitlin M. |
author_sort |
Moe, Maxwell |
title |
Dynamical Formation of Close Binaries during the Pre-main-sequence Phase |
title_short |
Dynamical Formation of Close Binaries during the Pre-main-sequence Phase |
title_full |
Dynamical Formation of Close Binaries during the Pre-main-sequence Phase |
title_fullStr |
Dynamical Formation of Close Binaries during the Pre-main-sequence Phase |
title_full_unstemmed |
Dynamical Formation of Close Binaries during the Pre-main-sequence Phase |
title_sort |
dynamical formation of close binaries during the pre-main-sequence phase |
publisher |
IOP PUBLISHING LTD |
publishDate |
2018 |
url |
http://hdl.handle.net/10150/627100 http://arizona.openrepository.com/arizona/handle/10150/627100 |
work_keys_str_mv |
AT moemaxwell dynamicalformationofclosebinariesduringthepremainsequencephase AT kratterkaitlinm dynamicalformationofclosebinariesduringthepremainsequencephase |
_version_ |
1718617218539847680 |