Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse
We examine a century of radial velocity, visual magnitude, and astrometric observations of the nearest red supergiant, Betelgeuse, in order to reexamine the century-old assertion that Betelgeuse might be a spectroscopic binary. These data reveal Betelgeuse varying stochastically over years and decad...
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2024-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad93c8 |
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| author | Morgan MacLeod Sarah Blunt Robert J. De Rosa Andrea K. Dupree Thomas Granzer Graham M. Harper Caroline D. Huang Emily M. Leiner Abraham Loeb Eric L. Nielsen Klaus G. Strassmeier Jason J. Wang Michael Weber |
| author_facet | Morgan MacLeod Sarah Blunt Robert J. De Rosa Andrea K. Dupree Thomas Granzer Graham M. Harper Caroline D. Huang Emily M. Leiner Abraham Loeb Eric L. Nielsen Klaus G. Strassmeier Jason J. Wang Michael Weber |
| author_sort | Morgan MacLeod |
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| description | We examine a century of radial velocity, visual magnitude, and astrometric observations of the nearest red supergiant, Betelgeuse, in order to reexamine the century-old assertion that Betelgeuse might be a spectroscopic binary. These data reveal Betelgeuse varying stochastically over years and decades due to its boiling, convective envelope, periodically with a 5.78 yr long secondary period (LSP), and quasiperiodically from pulsations with periods of several hundred days. We show that the LSP is consistent between astrometric and radial velocity data sets, and argue that it indicates a low-mass companion to Betelgeuse, less than a solar mass, orbiting in a 2110 day period at a separation of just over twice Betelgeuse’s radius. The companion star would be nearly 20 times less massive and a million times fainter than Betelgeuse, with similar effective temperature, effectively hiding it in plain sight near one of the best-studied stars in the night sky. The astrometric data favor an edge-on binary with orbital plane aligned with Betelgeuse’s measured spin axis. Tidal spin–orbit interaction drains angular momentum from the orbit and spins up Betelgeuse, explaining the spin–orbit alignment and Betelgeuse’s anomalously rapid spin. In the future, the orbit will decay until the companion is swallowed by Betelgeuse in the next 10,000 yr. |
| format | Article |
| id | doaj-art-c6f0ac642f194adb9c4ee575ecfb30c2 |
| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-c6f0ac642f194adb9c4ee575ecfb30c22025-08-20T02:32:31ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-0197815010.3847/1538-4357/ad93c8Radial Velocity and Astrometric Evidence for a Close Companion to BetelgeuseMorgan MacLeod0https://orcid.org/0000-0002-1417-8024Sarah Blunt1https://orcid.org/0000-0002-3199-2888Robert J. De Rosa2https://orcid.org/0000-0002-4918-0247Andrea K. Dupree3https://orcid.org/0000-0002-8985-8489Thomas Granzer4https://orcid.org/0000-0002-5310-1521Graham M. Harper5https://orcid.org/0000-0002-7042-4541Caroline D. Huang6https://orcid.org/0000-0001-6169-8586Emily M. Leiner7https://orcid.org/0000-0002-3944-8406Abraham Loeb8https://orcid.org/0000-0003-4330-287XEric L. Nielsen9https://orcid.org/0000-0001-6975-9056Klaus G. Strassmeier10https://orcid.org/0000-0002-6192-6494Jason J. Wang11https://orcid.org/0000-0003-0774-6502Michael Weber12https://orcid.org/0000-0002-7032-2967Center for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USA; Institute for Theory and Computation , USADepartment of Astronomy & Astrophysics, University of California , Santa Cruz, CA 95060, USA; Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , Evanston, IL 60208, USAEuropean Southern Observatory , Alonso de Córdova 3107, Vitacura, Santiago, ChileCenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USALeibniz-Institut für Astrophysik Potsdam (AIP) , An der Sternwarte 16, 14482, Potsdam, GermanyCenter for Astrophysics and Space Astronomy (CASA), University of Colorado , Boulder, CO 80309-0389, USACenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USA; Department of Physics, Illinois Institute of Technology , Chicago, IL 60616, USADepartment of Physics, Illinois Institute of Technology , Chicago, IL 60616, USA; Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , 1800 Sherman Avenue, Evanston, IL 60201, USACenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USA; Institute for Theory and Computation , USADepartment of Astronomy, New Mexico State University , P.O. Box 30001, MSC 4500, Las Cruces, NM 88003, USALeibniz-Institut für Astrophysik Potsdam (AIP) , An der Sternwarte 16, 14482, Potsdam, GermanyCenter for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , Evanston, IL 60208, USA; Department of Physics and Astronomy, Northwestern University , Evanston, IL 60208, USA; Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USALeibniz-Institut für Astrophysik Potsdam (AIP) , An der Sternwarte 16, 14482, Potsdam, GermanyWe examine a century of radial velocity, visual magnitude, and astrometric observations of the nearest red supergiant, Betelgeuse, in order to reexamine the century-old assertion that Betelgeuse might be a spectroscopic binary. These data reveal Betelgeuse varying stochastically over years and decades due to its boiling, convective envelope, periodically with a 5.78 yr long secondary period (LSP), and quasiperiodically from pulsations with periods of several hundred days. We show that the LSP is consistent between astrometric and radial velocity data sets, and argue that it indicates a low-mass companion to Betelgeuse, less than a solar mass, orbiting in a 2110 day period at a separation of just over twice Betelgeuse’s radius. The companion star would be nearly 20 times less massive and a million times fainter than Betelgeuse, with similar effective temperature, effectively hiding it in plain sight near one of the best-studied stars in the night sky. The astrometric data favor an edge-on binary with orbital plane aligned with Betelgeuse’s measured spin axis. Tidal spin–orbit interaction drains angular momentum from the orbit and spins up Betelgeuse, explaining the spin–orbit alignment and Betelgeuse’s anomalously rapid spin. In the future, the orbit will decay until the companion is swallowed by Betelgeuse in the next 10,000 yr.https://doi.org/10.3847/1538-4357/ad93c8Red supergiant starsBinary starsTidal interactionAstrometric binary starsRadial velocity |
| spellingShingle | Morgan MacLeod Sarah Blunt Robert J. De Rosa Andrea K. Dupree Thomas Granzer Graham M. Harper Caroline D. Huang Emily M. Leiner Abraham Loeb Eric L. Nielsen Klaus G. Strassmeier Jason J. Wang Michael Weber Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse The Astrophysical Journal Red supergiant stars Binary stars Tidal interaction Astrometric binary stars Radial velocity |
| title | Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse |
| title_full | Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse |
| title_fullStr | Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse |
| title_full_unstemmed | Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse |
| title_short | Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse |
| title_sort | radial velocity and astrometric evidence for a close companion to betelgeuse |
| topic | Red supergiant stars Binary stars Tidal interaction Astrometric binary stars Radial velocity |
| url | https://doi.org/10.3847/1538-4357/ad93c8 |
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