THE LICK-CARNEGIE EXOPLANET SURVEY: A URANUS-MASS FOURTH PLANET FOR GJ 876 IN AN EXTRASOLAR LAPLACE CONFIGURATION

By E. Rivera, Gregory Laughlin, R. P. Butler, S. Vogt, N. Haghighipour, S. Meschiari. 2010

200 citations recorded by the source corpus.

Continued radial velocity (RV) monitoring of the nearby M4V red dwarf star GJ 876 with Keck/High Resolution Echelle Spectrograph has revealed the presence of a Uranus-mass fourth planetary companion in the system. The new planet has a mean period of Pe = 126.6 days (over the 12.6-year baseline of the RV observations), and a minimum mass of mesin ie = 12.9 ± 1.7 M⊕. The detection of the new planet has been enabled by significant improvements to our RV data set for GJ 876. The data have been augmented by 36 new high-precision measurements taken over the past five years. In addition, the precision of all of the Doppler measurements have been significantly improved by the incorporation of a high signal-to-noise template spectrum for GJ 876 into the analysis pipeline. Implementation of the new template spectrum improves the internal rms errors for the velocity measurements taken during 1998–2005 from 4.1 m s−1 to 2.5 m s−1. Self-consistent, N-body fits to the RV data set show that the four-planet system has an invariable plane with an inclination relative to the plane of the sky of i = 59.°5. The fit is not significantly improved by the introduction of a mutual inclination between the planets “b” and “c,” but the new data do confirm a non-zero eccentricity, ed = 0.207 ± 0.055 for the innermost planet, “d.” In our best-fit coplanar model, the mass of the new component is me = 14.6 ± 1.7 M⊕. Our best-fitting model places the new planet in a three-body resonance with the previously known giant planets (which have mean periods of Pc = 30.4 and Pb = 61.1 days). The critical argument, φLaplace = λc − 3λb + 2λe, for the Laplace resonance librates with an amplitude of ΔφLaplace = 40° ± 13° about φLaplace = 0°. Numerical integration indicates that the four-planet system is stable for at least a billion years (at least for the coplanar cases). This resonant configuration of three giant planets orbiting an M dwarf primary differs from the well-known Laplace configuration of the three inner Galilean satellites of Jupiter, which are executing very small librations about φLaplace = 180° and which never experience triple conjunctions. The GJ 876 system, by contrast, comes close to a triple conjunction between the outer three planets once per every orbit of the outer planet, “e.”

View Paper: https://www.semanticscholar.org/paper/6d894e48e88c2eb17048ac98cd81670a06beed67

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

1. M. Perryman
2. A. Morbidelli
3. J. Winn
4. D. Nesvorný
5. S. Raymond
6. D. Charbonneau
7. E. Petigura
8. K. Batygin

Citations in the corpus

• TRANSIT TIMING OBSERVATIONS FROM KEPLER. IV. CONFIRMATION OF FOUR MULTIPLE-PLANET SYSTEMS BY SIMPLE PHYSICAL MODELS (2012, background): “…for that sort of architecture has been building on several different fronts: radial velocity detections (HD 40307: Mayor et al. 2009; GJ 876: Rivera et al. 2010; HD 20794: Pepe et al. 2011), and a dramatic 4-planet system discovered by direct imaging (HR 8799: Fabrycky & Murray-Clay 2010b;…”
• DISSIPATIVE DIVERGENCE OF RESONANT ORBITS (2012, background): “…of confirmed extrasolar planets, examples of multi-resonant systems include the GL876 system - where the Laplace resonance is directly observed (Rivera et al. 2010), the HD40307 (Mayor et al. 2009) system - which contains three planets that reside suspiciously close to a 4:2:1 period…”
• Limits on Planetary Companions from Doppler Surveys of Nearby Stars (2016, background): “…because detectable planet–planet interactions require planets to be near or in meanmotion resonances, which have only been detected for a handful of Doppler systems (e.g., Rivera et al. 2010; Tan et al. 2013), and those systems can be discovered using their Keplerian approximations (Equation (1)).”
• The Occurrence and Architecture of Exoplanetary Systems (2014, background): “The dataset is rich enough to have attracted many investigators (Rivera & Lissauer 2001, Bean & Seifahrt 2009, Correia et al. 2010, Rivera et al. 2010, Baluev 2011) who all concluded that the mutual inclination between the two giants is <∼ 5◦, although their results differ in detail.”
• Debris disks as signposts of terrestrial planet formation (2011, background): “Second, there exist individual systems that show no obvious signs of instability, for example with planets in resonance (e.g., GJ 876; Rivera et al. 2010) or with many relatively closelypacked giant planets (e.g., 55 Cancri; Fischer et al. 2008).”
• Breaking the chains: hot super-Earth systems from migration and disruption of compact resonant chains (2017, background): “Indeed, several chains of three or more resonant planets have been identified, such as Kepler-223 (Mills et al. 2016), Kepler-80 (MacDonald et al. 2016), GJ 876 (Rivera et al. 2010) and TRAPPIST-1 (Gillon et al. 2017).”
• ORBITAL MOTION OF HR 8799 b, c, d USING HUBBLE SPACE TELESCOPE DATA FROM 1998: CONSTRAINTS ON INCLINATION, ECCENTRICITY, AND STABILITY (2011, background): “These include discoveries using radial velocities (Fischer et al. 2008; Rivera et al. 2010), transits (Holman et al. 2010; Lissauer et al. 2011a,b), microlensing (Gaudi et al. 2008), and pulsar timing (Wolszczan 1994).”
• The minimum-mass extrasolar nebula: in situ formation of close-in super-Earths (2012, background): “Even for Gliese 876 b and c — a pair of giant planets trapped deeply in a 2:1 resonance — the amount by which these planets migrated differentially could have been as small as ∼7% (Lee & Peale 2002; see also Rivera et al. 2010).”
• THE HARPS-TERRA PROJECT. I. DESCRIPTION OF THE ALGORITHMS, PERFORMANCE, AND NEW MEASUREMENTS ON A FEW REMARKABLE STARS OBSERVED BY HARPS (2012, background): “Perhaps for this reason and because it is relatively faint, the star has not been as intensively monitored as other earlier type nearby M dwarfs such as GJ 581(Forveille et al. 2011b) or GJ 876 (Rivera et al. 2010).”
• THE MUSCLES TREASURY SURVEY. I. MOTIVATION AND OVERVIEW (2016, background): “GJ 876 has a rich planetary system with four planets ranging from a super-Earth (GJ 876d, Mplan ≈ 6.6 M⊕) in a short-period orbit (aplan = 0.02 AU; Rivera et al. 2010) to two Jovian-mass planets in the HZ (GJ 876b, Mplan ≈ 2.27 MJup, aplan = 0.21 AU; GJ 876c, Mplan ≈ 0.72 MJup, aplan = 0.13 AU;…”
• THE ULTRAVIOLET RADIATION ENVIRONMENT AROUND M DWARF EXOPLANET HOST STARS (2012, background): “It is estimated to have an age of 8 ± 1 Gyr (Selsis et al. 2007) and a somewhat subsolar metallicity, [Fe/H] = −0.10 – −0.02 (Johnson & Apps 2009; Rojas-Ayala et al. 2010).”
• LATE ORBITAL INSTABILITIES IN THE OUTER PLANETS INDUCED BY INTERACTION WITH A SELF-GRAVITATING PLANETESIMAL DISK (2011, background): “Many observed planetary systems contain planets in MMRs (Marois et al. 2008; Rivera et al. 2010) with one another, while others appear to have undergone a global dynamical instability (Ford et al. 2001; Matsumura et al. 2010).”