RETIRED A STARS AND THEIR COMPANIONS. VI. A PAIR OF INTERACTING EXOPLANET PAIRS AROUND THE SUBGIANTS 24 SEXTANIS AND HD 200964

Journal Article · Sat Jan 15 00:00:00 EST 2011 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/141/1/16· OSTI ID:21583275

Johnson, John Asher ^[1]; Payne, Matthew; Ford, Eric B ^[2]; Howard, Andrew W; Marcy, Geoffrey W ^[3]; Clubb, Kelsey I ^[4]; Bowler, Brendan P ^[5]; Henry, Gregory W ^[6]; Fischer, Debra A; Brewer, John M; Schwab, Christian ^[7]; Reffert, Sabine ^[8]

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1. California Institute of Technology, Department of Astrophysics, MC 249-17, Pasadena, CA 91125 (United States)
2. Department of Astronomy, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611-2055 (United States)
3. Department of Astronomy, University of California, Mail Code 3411, Berkeley, CA 94720 (United States)
4. Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132 (United States)
5. Institute for Astronomy, University of Hawai'i, Honolulu, HI 96822 (United States)
6. Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Boulevard, Box 9501, Nashville, TN 37209 (United States)
7. Department of Astronomy, Yale University, New Haven, CT 06511 (United States)
8. ZAH-Landessternwarte, Koenigstuhl 12, D-69117 Heidelberg (Germany)

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 RV time 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 M{sub Jup} and 0.86 M{sub Jup}, assuming a stellar mass M{sub *}= 1.54 M{sub sun}. 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 M{sub Jup} and 0.90 M{sub Jup}, assuming M{sub *}= 1.44 M{sub sun}. 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.

• OSTI ID: 21583275
• Journal Information: Astronomical Journal (New York, N.Y. Online), Vol. 141, Issue 1; Other Information: DOI: 10.1088/0004-6256/141/1/16; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
BRIGHTNESS
GRAVITATIONAL INTERACTIONS
MASS
PERIODICITY
PLANETS
RADIAL VELOCITY
SATELLITES
STARS
BASIC INTERACTIONS
INTERACTIONS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
VARIATIONS
VELOCITY