Spin-orbit alignment in the very low mass binary regime

The L dwarf tight binary 2MASSW J0746425+200032AB

L. K. Harding, G. Hallinan, Q. M. Konopacky, K. M. Kratter, R. P. Boyle, R. F. Butler, A. Golden

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Studies of solar-type binaries have found coplanarity between the equatorial and orbital planes of systems with <40 AU separation. By comparison, the alignment of the equatorial and orbital axes in the substellar regime, and the associated implications for formation theory, are relatively poorly constrained. Here we present the discovery of the rotation period of 3.32 ± 0.15 h from 2MASS J0746+20A - the primary component of a tight (2.7 AU) ultracool dwarf binary system (L0+L1.5). The newly discovered period, together with the established period via radio observations of the other component, and the well constrained orbital parameters and rotational velocity measurements, allow us to infer alignment of the equatorial planes of both components with the orbital plane of the system to within 10 degrees. This result suggests that solar-type binary formation mechanisms may extend down into the brown dwarf mass range, and we consider a number of formation theories that may be applicable in this case. This is the first such observational result in the very low mass binary regime. In addition, the detected period of 3.32 ± 0.15 h implies that the reported radio period of 2.07 ± 0.002 h is associated with the secondary star, not the primary, as was previously claimed. This in turn refutes the claimed radius of 0.78 ± 0.1 R J for 2MASS J0746+20A, which we demonstrate to be 0.99 ± 0.03 RJ.

Original languageEnglish (US)
Article numberA113
JournalAstronomy and Astrophysics
Volume554
DOIs
StatePublished - 2013

Fingerprint

alignment
orbits
orbitals
radio
formation mechanism
coplanarity
radio observation
velocity measurement
stars
radii
comparison
parameter

Keywords

  • Binaries: close
  • Brown dwarfs
  • Stars: formation
  • Stars: low-mass

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Harding, L. K., Hallinan, G., Konopacky, Q. M., Kratter, K. M., Boyle, R. P., Butler, R. F., & Golden, A. (2013). Spin-orbit alignment in the very low mass binary regime: The L dwarf tight binary 2MASSW J0746425+200032AB. Astronomy and Astrophysics, 554, [A113]. https://doi.org/10.1051/0004-6361/201220865

Spin-orbit alignment in the very low mass binary regime : The L dwarf tight binary 2MASSW J0746425+200032AB. / Harding, L. K.; Hallinan, G.; Konopacky, Q. M.; Kratter, K. M.; Boyle, R. P.; Butler, R. F.; Golden, A.

In: Astronomy and Astrophysics, Vol. 554, A113, 2013.

Research output: Contribution to journalArticle

Harding, L. K. ; Hallinan, G. ; Konopacky, Q. M. ; Kratter, K. M. ; Boyle, R. P. ; Butler, R. F. ; Golden, A. / Spin-orbit alignment in the very low mass binary regime : The L dwarf tight binary 2MASSW J0746425+200032AB. In: Astronomy and Astrophysics. 2013 ; Vol. 554.
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