Retired a stars and their companions. VI. A pair of interacting exoplanet pairs around the subgiants 24 Sextanis and HD 200964

John Asher Johnson, Matthew Payne, Andrew W. Howard, Kelsey I. Clubb, Eric B. Ford, Brendan P. Bowler, Gregory W. Henry, Debra A. Fischer, Geoffrey W. Marcy, John M. Brewer, Christian Schwab, Sabine Reffert, Thomas B. Lowe

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Abstract

We report radial velocity (RV) measurements of the G-type subgiants 24 Sextanis (= HD 90043) and HD 200964. Both are massive, evolved stars that exhibit periodic variations due to the presence of a pair of Jovian planets. Photometric monitoring with the T12 0.80 m APT at Fairborn Observatory demonstrates both stars to be constant in brightness to ≤0.002 mag, thus strengthening the planetary interpretation of the RV variations. Based on our dynamical analysis of the RVtime series, 24 Sex b, c have orbital periods of 452.8 days and 883.0 days, corresponding to semimajor axes 1.333 AU and 2.08 AU, and minimum masses 1.99 MJup and 0.86 MJup, assuming a stellar mass M* =1.54M. HD 200964 b, c have orbital periods of 613.8 days and 825.0 days, corresponding to semimajor axes 1.601 AU and 1.95 AU, and minimum masses 1.99 MJup and 0.90 M Jup, assuming M* = 1.44M⊙. We also carry out dynamical simulations to properly account for gravitational interactions between the planets. Most, if not all, of the dynamically stable solutions include crossing orbits, suggesting that each system is locked in a mean-motion resonance that prevents close encounters and provides long-term stability. The planets in the 24 Sex system likely have a period ratio near 2:1, while the HD 200964 system is even more tightly packed with a period ratio close to 4:3. However, we caution that further RV observations and more detailed dynamical modeling will be required to provide definitive and unique orbital solutions for both cases, and to determine whether the two systems are truly resonant.

Original languageEnglish (US)
JournalAstronomical Journal
Volume141
Issue number1
DOIs
StatePublished - Jan 1 2011

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extrasolar planets
radial velocity
planets
planet
stars
orbitals
stellar mass
massive stars
velocity measurement
encounters
periodic variations
observatories
brightness
observatory
orbits
monitoring
modeling
simulation
interactions

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Johnson, John Asher ; Payne, Matthew ; Howard, Andrew W. ; Clubb, Kelsey I. ; Ford, Eric B. ; Bowler, Brendan P. ; Henry, Gregory W. ; Fischer, Debra A. ; Marcy, Geoffrey W. ; Brewer, John M. ; Schwab, Christian ; Reffert, Sabine ; Lowe, Thomas B. / Retired a stars and their companions. VI. A pair of interacting exoplanet pairs around the subgiants 24 Sextanis and HD 200964. In: Astronomical Journal. 2011 ; Vol. 141, No. 1.
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abstract = "We report radial velocity (RV) measurements of the G-type subgiants 24 Sextanis (= HD 90043) and HD 200964. Both are massive, evolved stars that exhibit periodic variations due to the presence of a pair of Jovian planets. Photometric monitoring with the T12 0.80 m APT at Fairborn Observatory demonstrates both stars to be constant in brightness to ≤0.002 mag, thus strengthening the planetary interpretation of the RV variations. Based on our dynamical analysis of the RVtime series, 24 Sex b, c have orbital periods of 452.8 days and 883.0 days, corresponding to semimajor axes 1.333 AU and 2.08 AU, and minimum masses 1.99 MJup and 0.86 MJup, assuming a stellar mass M* =1.54M⊙. HD 200964 b, c have orbital periods of 613.8 days and 825.0 days, corresponding to semimajor axes 1.601 AU and 1.95 AU, and minimum masses 1.99 MJup and 0.90 M Jup, assuming M* = 1.44M⊙. We also carry out dynamical simulations to properly account for gravitational interactions between the planets. Most, if not all, of the dynamically stable solutions include crossing orbits, suggesting that each system is locked in a mean-motion resonance that prevents close encounters and provides long-term stability. The planets in the 24 Sex system likely have a period ratio near 2:1, while the HD 200964 system is even more tightly packed with a period ratio close to 4:3. However, we caution that further RV observations and more detailed dynamical modeling will be required to provide definitive and unique orbital solutions for both cases, and to determine whether the two systems are truly resonant.",
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Johnson, JA, Payne, M, Howard, AW, Clubb, KI, Ford, EB, Bowler, BP, Henry, GW, Fischer, DA, Marcy, GW, Brewer, JM, Schwab, C, Reffert, S & Lowe, TB 2011, 'Retired a stars and their companions. VI. A pair of interacting exoplanet pairs around the subgiants 24 Sextanis and HD 200964', Astronomical Journal, vol. 141, no. 1. https://doi.org/10.1088/0004-6256/141/1/16

Retired a stars and their companions. VI. A pair of interacting exoplanet pairs around the subgiants 24 Sextanis and HD 200964. / Johnson, John Asher; Payne, Matthew; Howard, Andrew W.; Clubb, Kelsey I.; Ford, Eric B.; Bowler, Brendan P.; Henry, Gregory W.; Fischer, Debra A.; Marcy, Geoffrey W.; Brewer, John M.; Schwab, Christian; Reffert, Sabine; Lowe, Thomas B.

In: Astronomical Journal, Vol. 141, No. 1, 01.01.2011.

Research output: Contribution to journalArticle

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T1 - Retired a stars and their companions. VI. A pair of interacting exoplanet pairs around the subgiants 24 Sextanis and HD 200964

AU - Johnson, John Asher

AU - Payne, Matthew

AU - Howard, Andrew W.

AU - Clubb, Kelsey I.

AU - Ford, Eric B.

AU - Bowler, Brendan P.

AU - Henry, Gregory W.

AU - Fischer, Debra A.

AU - Marcy, Geoffrey W.

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AU - Schwab, Christian

AU - Reffert, Sabine

AU - Lowe, Thomas B.

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AB - We report radial velocity (RV) measurements of the G-type subgiants 24 Sextanis (= HD 90043) and HD 200964. Both are massive, evolved stars that exhibit periodic variations due to the presence of a pair of Jovian planets. Photometric monitoring with the T12 0.80 m APT at Fairborn Observatory demonstrates both stars to be constant in brightness to ≤0.002 mag, thus strengthening the planetary interpretation of the RV variations. Based on our dynamical analysis of the RVtime series, 24 Sex b, c have orbital periods of 452.8 days and 883.0 days, corresponding to semimajor axes 1.333 AU and 2.08 AU, and minimum masses 1.99 MJup and 0.86 MJup, assuming a stellar mass M* =1.54M⊙. HD 200964 b, c have orbital periods of 613.8 days and 825.0 days, corresponding to semimajor axes 1.601 AU and 1.95 AU, and minimum masses 1.99 MJup and 0.90 M Jup, assuming M* = 1.44M⊙. We also carry out dynamical simulations to properly account for gravitational interactions between the planets. Most, if not all, of the dynamically stable solutions include crossing orbits, suggesting that each system is locked in a mean-motion resonance that prevents close encounters and provides long-term stability. The planets in the 24 Sex system likely have a period ratio near 2:1, while the HD 200964 system is even more tightly packed with a period ratio close to 4:3. However, we caution that further RV observations and more detailed dynamical modeling will be required to provide definitive and unique orbital solutions for both cases, and to determine whether the two systems are truly resonant.

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