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

Research output: Contribution to journalArticleResearchpeer-review

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.

LanguageEnglish
Article number16
Pages1-10
Number of pages10
JournalAstronomical Journal
Volume141
Issue number1
DOIs
Publication statusPublished - Jan 2011
Externally publishedYes

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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

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Johnson, J. A., Payne, M., Howard, A. W., Clubb, K. I., Ford, E. B., Bowler, B. P., ... Lowe, T. B. (2011). Retired a stars and their companions. VI. A pair of interacting exoplanet pairs around the subgiants 24 Sextanis and HD 200964. Astronomical Journal, 141(1), 1-10. [16]. https://doi.org/10.1088/0004-6256/141/1/16
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. pp. 1-10.
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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.",
author = "Johnson, {John Asher} and Matthew Payne and Howard, {Andrew W.} and Clubb, {Kelsey I.} and Ford, {Eric B.} and Bowler, {Brendan P.} and Henry, {Gregory W.} and Fischer, {Debra A.} and Marcy, {Geoffrey W.} and Brewer, {John M.} and Christian Schwab and Sabine Reffert and Lowe, {Thomas B.}",
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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, 16, pp. 1-10. 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, 16, 01.2011, p. 1-10.

Research output: Contribution to journalArticleResearchpeer-review

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