A Trio of Giant Planets Orbiting Evolved Star HD 184010

Abstract

We report the discovery of a triple-giant-planet system around an evolved star HD 184010 (HR 7421, HIP 96016). This discovery is based on observations from Okayama Planet Search Program, a precise radial velocity survey, undertaken at Okayama Astrophysical Observatory between 2004 April and 2021 June. The star is K0 type and located at beginning of the red-giant branch. It has a mass of $1.35_{-0.21}^{+0.19}{M}_{\odot }$, a radius of $4.86_{-0.49}^{+0.55}{R}_{\odot }$, and a surface gravity $\log g$ of $3.18_{-0.07}^{+0.08}$. The planetary system is composed of three giant planets in a compact configuration: The planets have minimum masses of $M_{\mathrm{b}}\sin i=0.31_{-0.04}^{+0.03}{M}_{\mathrm{J}}$, $M_{\mathrm{c}}\sin i=0.30_{-0.05}^{+0.04}{M}_{\mathrm{J}}$, and $M_{\mathrm{d}}\sin i=0.45_{-0.06}^{+0.04}{M}_{\mathrm{J}}$, and orbital periods of $P_{\mathrm{b}}=286.6_{-0.7}^{+2.4}\mathrm{d}$, $P_{\mathrm{c}}=484.3_{-3.5}^{+5.5}\mathrm{d}$, and $P_{\mathrm{d}}=836.4_{-8.4}^{+8.4}\mathrm{d}$, respectively, which are derived from a triple Keplerian orbital fit to three sets of radial velocity data. The ratio of orbital periods are close to $P_{\mathrm{d}}:P_{\mathrm{c}}:P_{\mathrm{b}}\sim 21:12:7$, which means the period ratios between neighboring planets are both lower than $2:1$. The dynamical stability analysis reveals that the planets should have near-circular orbits. The system could remain stable over 1 Gyr, initialized from co-planar orbits, low eccentricities ($e=0.05$), and planet masses equal to the minimum mass derived from the best-fit circular orbit fitting. Besides, the planets are not likely in mean motion resonance. HD 184010 system is unique: it is the first system discovered to have a highly evolved star ($\log g<3.5$ cgs) and more than two giant planets all with intermediate orbital periods ($10^2\mathrm{d}<\mathrm{P}<10^3\mathrm{d}$).

20 pages, 5 figures, Published in PASJ

References in corpus (24)

• Array Programming with NumPy
• The Gaia mission
• Modules for Experiments in Stellar Astrophysics (MESA)
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• Dynamical Outcomes of Planet-Planet Scattering
• Formation of Hot Planets by a combination of planet scattering, tidal circularization, and Kozai mechanism
• Origins of Eccentric Extrasolar Planets: Testing the Planet-Planet Scattering Model
• Assessing statistical significance of periodogram peaks
• Asteroseismology and Gaia: Testing Scaling Relations Using 2200 Kepler Stars with TGAS Parallaxes
• Formation of a disc gap induced by a planet: Effect of the deviation from Keplerian disc rotation
• Four New Exoplanets and Hints of Additional Substellar Companions to Exoplanet Host Stars
• The impact of red noise in radial velocity planet searches: Only three planets orbiting GJ581?
• Bisectors of the cross-correlation function applied to stellar spectra. Discriminating stellar activity, oscillations and planets
• Newly-Discovered Planets Orbiting HD~5319, HD~11506, HD~75784 and HD~10442 from the N2K Consortium
• Astrophysical Insights into Radial Velocity Jitter from an Analysis of 600 Planet-search Stars
• The Orbit and Mass of the Third Planet in the Kepler-56 System
• The 3-dimensional architecture of the Upsilon Andromedae planetary system
• Outer-planet scattering can gently tilt an inner planetary system
• Spectroscopic study of red giants in the Kepler field with asteroseismologically established evolutionary status and stellar parameters
• A Third Planet Orbiting HIP 14810
• Three planets around HD 27894. A close-in pair with a 2:1 period ratio and an eccentric Jovian planet at 5.4 AU
• Two Jovian planets around the giant star HD202696. A growing population of packed massive planetary pairs around massive stars?
• Regular Radial Velocity Variations in Nine G- and K-type Giant Stars: Eight Planets and One Planet Candidate