Misaligned spin and orbital axes cause the anomalous precession of DI Herculis
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Author(s)
Albrecht, Simon H.
Winn, Joshua Nathan
Reffert, Sabine
Snellen, Ignas A.G.
Date Issued
September 2009
Journal
Nature
Publisher
Nature Publishing Group
Citation
Albrecht, Simon et al. “Misaligned spin and orbital axes cause the anomalous precession of DI[thinsp]Herculis.” Nature 461.7262 (2009): 373-376. © 2009 Nature Publishing Group.
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Author's final manuscript
Abstract
The orbits of binary stars precess as a result of general relativistic effects, forces
arising from the asphericity of the stars, and forces from additional stars or planets in
the system. For most binaries, the theoretical and observed precession rates are in
agreement1. One system, however—DI Herculis—has resisted explanation for 30
years2–4. The observed precession rate is a factor of four slower than the theoretical
rate, a disagreement that once was interpreted as evidence for a failure of general
relativity5. Among the contemporary explanations are the existence of a circumbinary
planet6 and a large tilt of the stellar spin axes with respect to the orbit7,8. Here we
report that both stars of DI Herculis rotate with their spin axes nearly perpendicular
to the orbital axis (contrary to the usual assumption for close binary stars). The
rotationally induced stellar oblateness causes precession in the direction opposite to
that of relativistic precession, thereby reconciling the theoretical and observed rates.
MIT Department
Massachusetts Institute of Technology. Department of Physics
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.1038/nature08408
