Two Super-Earths in the 3:2 MMR around KOI-1599 Panichi, F; Migaszewski, C; Goździewski, K
Monthly notices of the Royal Astronomical Society,
06/2019, Letnik:
485, Številka:
4
Journal Article
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Abstract
We validate the planetary origin of the KOI-1599 transit time variations (TTVs) with statistical and dynamical tests. We re-analysed KEPLER Q1–Q17 light-curves of the star, and we ...independently derived the TTVs. They appear as strongly anticorrelated, suggestive of two mutually interacting planets. We found similar radii of the candidates, 1.9 ± 0.2R⊕ for the inner KOI-1599.02, and 1.9 ± 0.3R⊕ for the outer KOI-1599.01. The standard MCMC TTV analysis constrains the planet masses safely below the dynamical instability limit of ${\simeq } 3\, \mbox{M}_{{\mbox{Jup}}}$. The best-fitting MCMC model yields $(9.0\pm 0.3)\, \mbox{M}_{\oplus }$, and $(4.6\pm 0.3)\, \mbox{M}_{\oplus }$, for the inner and the outer planet, respectively. The planets are trapped in 3:2 mean motion resonance (MMR) with anti-aligned apsides (Δϖ = 180°) at low-eccentric (e ≃ 0.01) orbits. However, we found that the TTV mass determination depends on eccentricity priors with the dispersion in the (0.01,0.05) range. They permit a second family of TTV models with smaller masses of ${\simeq } 7\, \mbox{M}_{\oplus }$, and ${\simeq } 3.6\, \mbox{M}_{\oplus }$, respectively, exhibiting two modes of Δϖ = 0°, 180° librations. The 3:2 MMR is dynamically robust and persists for both modes. In order to resolve the mass duality, we re-analysed the TTV data with a quasi-analytic model of resonant TTV signals. This model favours the smaller masses. We also reproduced this model by simulating the migration capture of the system into the 3:2 MMR.
We investigate the dynamical stability of the Kepler-60 planetary system with three super-Earths. We determine their orbital elements and masses by transit timing variation (TTV) data spanning ...quarters Q1–Q16 of the Kepler mission. The system is dynamically active but the TTV data constrain masses to ∼4 M⊕ and orbits in safely wide stable zones. The observations prefer two types of solutions. The true three-body Laplace mean-motion resonance (MMR) exhibits the critical angle librating around ≃45° and aligned apsides of the inner and outer pair of planets. In the Laplace MMR formed through a chain of two-planet 5:4 and 4:3 MMRs, all critical angles librate with small amplitudes ∼30° and apsidal lines in planet's pairs are anti-aligned. The system is simultaneously locked in a three-body MMR with librations amplitude ≃10o. The true Laplace MMR can evolve towards a chain of two-body MMRs in the presence of planetary migration. Therefore, the three-body MMR formed in this way seems to be more likely state of the system. However, the true three-body MMR cannot be disregarded a priori and it remains a puzzling configuration that may challenge the planet formation theory.
From its discovery, the WASP-18 system with its massive transiting planet on a tight orbit was identified as a unique laboratory for studies on tidal planet-star interactions. In an analysis of ...Doppler data, which include five new measurements obtained with the HIRES/Keck-I instrument between 2012 and 2018, we show that the radial velocity signal of the photosphere following the planetary tidal potential can be distilled for the host star. Its amplitude is in agreement with both theoretical predictions of the equilibrium tide approximation and an ellipsoidal modulation observed in an orbital phase curve. Assuming a circular orbit, we refine system parameters using photometric time series from TESS. With a new ground-based photometric observation, we extend the span of transit timing observations to 28 yr in order to probe the rate of the orbital period shortening. Since we found no departure from a constant-period model, we conclude that the modified tidal quality parameter of the host star must be greater than 3.9×106 with 95% confidence. This result is in line with conclusions drawn from studies of the population of hot Jupiters, predicting that the efficiency of tidal dissipation is 1 or 2 orders of magnitude weaker. As the WASP-18 system is one of the prime candidates for detection of orbital decay, further timing observations are expected to push the boundaries of our knowledge on stellar interiors.
We report the discovery of a brown dwarf on an eccentric orbit and with a semimajor axis that places it in the brown dwarf desert region around the star HD 191760. The star has a spectral type of ...G3IV/V and a metallicity (Fe/H) of 0.29 dex. HD 191760 adds to the small number of metal-rich stars with brown dwarf companions. The brown dwarf (HD 191760b) is found to have an orbital period of 505.57 ± 0.40 d and semimajor axis of 1.35 ± 0.01 au, placing it firmly in the brown dwarf desert. The eccentricity of HD 191760b is found to be 0.63 ± 0.01, meaning it reaches as close as 0.5 au from the host star. Dynamical simulations indicate that no inner planets could reside at separations beyond ∼0.17 au due to the disastrous gravity imposed by HD 191760b. In addition to these first results, we also refine the orbits found for the exoplanets around the stars HD 48265, HD 143361 and HD 154672. All one-planet solutions are in agreement with those previously published by the Magellan Planet Search.
Context.We re-analyze the precision radial velocity (RV) data of HD 208487 by the Anglo-Australian Planet Search Team, HD 190360, HD 188015, HD 114729 by the California and Carnegie Planet Search ...Team, and HD 147513 by the Geneva Planet Search Team. All these stars are supposed to host Jovian companions in long-period orbits. Aims.We test a hypothesis that the residuals of the 1-planet model of the RV or an irregular scatter of the measurements around the synthetic RV curve may be explained by the existence of additional planets in short-period orbits. Methods. We performed a global search for the best fits in the orbital parameters space with genetic algorithms and simplex method. This makes it possible to verify and extend the results with an application of commonly used FFT-based periodogram analysis for identifying the leading periods. Results. Our analysis confirms the presence of a periodic component in the RV of HD 190360 that may correspond to a hot-Neptune planet. We found four new cases in which the 2-planet model yields significantly better fits to the RV data than the best 1-planet solutions. If the periodic variability of the residuals of single-planet fits indeed has a planetary origin, then hot-Neptune planets may exist in these extrasolar systems. We estimate their orbital periods as in the range of 7–20 d and minimal masses of about 20 masses of the Earth.
We consider the hierarchical three-body problem, with a binary and a planet-mass object. We investigate the effect of general relativity (GR) corrections to the Newtonian interactions. We focus on ...the Lidov-Kozai resonance, and the secular dynamics are analyzed over wide ranges of the semi-major axes and masses. We found regions in the parameter space where the GR corrections may be important for the long-term dynamics. We try to constrain the inclinations of putative Jovian planets in the recently announced binary systems of HD 4113 and HD 156846.
We present a method for the analysis of radial velocity (RV) measurements, in the context of searching for planets around chromospherically active stars. We assume that the observed RV signal is ...induced by the reflex motion of the star as well as by distortions of spectral line profiles, measured by the Bisector Velocity Span (BVS). The RVs are fitted with a Keplerian planetary model complemented by a correction term that is linearly dependent on the BVS. The BVS represents the stellar activity contribution to the observed RV. The coefficient of this linear dependence is an additional free parameter of the model. This approach differs from methods in the literature, which make usage of the BVS measurements before or after fitting the planetary model. We test the method on a simulated data set of a 1-planet configuration. The results are compared with the outcomes of algorithms found in the literature.
The detailed study of the exoplanetary systems HD189733 and HD209458 has given rise to a wealth of exciting information on the physics of exoplanetary atmospheres. To further our understanding of the ...make-up and processes within these atmospheres we require a larger sample of bright transiting planets. We have began a project to detect more bright transiting planets in the southern hemisphere by utilising precision radial-velocity measurements. We have observed a constrained sample of bright, inactive and metal-rich stars using the HARPS instrument and here we present the current status of this project, along with our first discoveries which include a brown dwarf/extreme-Jovian exoplanet found in the brown dwarf desert region around the star HD191760 and improved orbits for three other exoplanetary systems HD48265, HD143361 and HD154672. Finally, we briefly discuss the future of this project and the current prospects we have for discovering more bright transiting planets.
We reanalyze the precision radial velocity (RV) observations of HD 160691 (k Ara) by the Anglo-Australian Planet Search Team. The star is supposed to host two Jovian companions (HD 160691b, HD ...160691c) in long-period orbits (6630 days and 62500 days, respectively) and a hot Neptune (HD 160691d) in 69 day orbit. We perform a global search for the best fits in the orbital parameter space with a hybrid code employing the genetic algorithm and simplex method. The stability of Keplerian fits is verified with the N-body model of the RV signal that takes into account the dynamical constraints (so called GAMP method). Our analysis reveals a signature of the fourth, as yet unconfirmed, Jupiter-like planet HD 160691e in 6307 day orbit. Overall, the global architecture of four-planet configuration recalls the solar system. All companions of k Ara move in quasi-circular orbits. The orbits of two inner Jovian planets are close to the 2: 1 mean motion resonance. The alternative three-planet system involves two Jovian planets in eccentric orbits (e 6 0.3), close to the 4: 1 MMR, but it yields a significantly worse fit to the data. We also verify a hypothesis of the 1: 1 MMR in the subsystem of two inner Jovian planets in the four-planet model.
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