The HD 181433 Planetary System: Dynamics and a New Orbital Solution

Context. The comet C/2017 K2 PANSTARRS drew attention to its activity at the time of its discovery in May 2017 when it was about 16 au from the Sun. This Oort spike comet will approach its perihelion in December 2022, and the question about its dynamical past is an important issue to explore. Aims. In order to answer the question of whether C/2017 K2 is a dynamically old or new comet it is necessary to obtain its precise osculating orbit, its original orbit, and propagate its motion backwards in time to the previous perihelion. Knowledge of the previous perihelion distance is necessary to distinguish between these two groups of the Oort spike comets. We have studied the dynamical evolution of C/2017 K2 to the previous perihelion (backward calculations for about 3–4 Myr) as well as to the future (forward calculations for about 0.033 Myr) using the swarm of virtual comets (VCs) constructed from a nominal osculating orbit of this comet which we determined here using all positional measurements available at the moment. Outside the planetary system both Galactic and stellar perturbations were taken into account. Results. We derive that C/2017 K2 is a dynamically old Oort spike comet (1/aprev = (48.7 ± 7.9) × 10−6 au−1) with the previous perihelion distance below 10 au for 97% of VCs (nominal qprev = 3.77 au). According to the present data this comet will be perturbed into a more tightly bound orbit after passing the planetary zone (1/afut = (1140.4 ± 8.0) × 10−6 au−1, qfut = 1.79336 ± 0.00006 au) provided that non-gravitational effects will not change the orbit significantly. Conclusions. C/2017 K2 has already visited our planetary zone during its previous perihelion passage. Thus, it is almost certainly a dynamically old Oort spike comet. The future orbital solution of this comet is formally very precise, however, it is much less definitive since the presented analysis is based on pre-perihelion data taken at very large heliocentric distances (23.7–14.6 au from the Sun), and this comet can experience a significant non-gravitational perturbation during the upcoming perihelion passage in 2022.

Download Full-text

Asteroseismic inference on rotation, gyrochronology and planetary system dynamics of 16 Cygni

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stu2331 ◽

2014 ◽

Vol 446 (3) ◽

pp. 2959-2966 ◽

Cited By ~ 65

Author(s):

G. R. Davies ◽

W. J. Chaplin ◽

W. M. Farr ◽

R. A. García ◽

M. N. Lund ◽

...

Keyword(s):

System Dynamics ◽

Planetary System

Download Full-text

The HADES RV Programme with HARPS-N at TNG

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732535 ◽

2018 ◽

Vol 617 ◽

pp. A104 ◽

Cited By ~ 8

Author(s):

M. Pinamonti ◽

M. Damasso ◽

F. Marzari ◽

A. Sozzetti ◽

S. Desidera ◽

...

Keyword(s):

Planetary System ◽

Orbital Evolution ◽

Dynamical Analysis ◽

Outer Planet ◽

Orbital Configuration ◽

Orbital Instability ◽

Astrometric Data ◽

Long Term Trend ◽

Orbital Solution

We present 20 yr of radial velocity (RV) measurements of the M1 dwarf Gl15A, combining five years of intensive RV monitoring with the HARPS-N spectrograph with 15 yr of archival HIRES/Keck RV data. We have carried out an MCMC-based analysis of the RV time series, inclusive of Gaussian Process (GP) approach to the description of stellar activity induced RV variations. Our analysis confirms the Keplerian nature and refines the orbital solution for the 11.44-day period super Earth, Gl15A b, reducing its amplitude to 1.68−0.18+0.17 m s−1 (M sin i = 3.03−0.44+0.46 M⊕), and successfully models a long-term trend in the combined RV dataset in terms of a Keplerian orbit with a period around 7600 days and an amplitude of 2.5−1.0+1.3 m s−1, corresponding to a super-Neptune mass (M sin i = 36−18+25 M⊕) planetary companion. We also discuss the present orbital configuration of Gl15A planetary system in terms of the possible outcomes of Lidov–Kozai interactions with the wide-separation companion Gl15B in a suite of detailed numerical simulations. In order to improve the results of the dynamical analysis, we have derived a new orbital solution for the binary system, combining our RV measurements with astrometric data from the WDS catalogue. The eccentric Lidov–Kozai analysis shows the strong influence of Gl15B on the Gl15A planetary system, which can produce orbits compatible with the observed configuration for initial inclinations of the planetary system between 75° and 90°, and can also enhance the eccentricity of the outer planet well above the observed value, even resulting in orbital instability, for inclinations around 0° and 15°−30°. The Gl15A system is the multi-planet system closest to Earth, at 3.56 pc, and hosts the longest period RV sub-Jovian mass planet discovered so far. Its orbital architecture constitutes a very important laboratory for the investigation of formation and orbital evolution scenarios for planetary systems in binary stellar systems.

Download Full-text

Do the planets in the HD 34445 system really exist?

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1945 ◽

2019 ◽

Vol 488 (3) ◽

pp. 3818-3825

Author(s):

Nikolaos Georgakarakos ◽

Ian Dobbs-Dixon

Keyword(s):

Time Scales ◽

Parameter Space ◽

Numerical Experiments ◽

Planetary System ◽

Dynamical Evolution ◽

Orbital Elements ◽

Large Area ◽

Open Question ◽

Orbital Solution ◽

Different Time Scales

ABSTRACT In 2010 the first planet was discovered around star HD 34445. Recently, another five planets were announced orbiting the same star. It is a rather dense multiplanet system with some of its planets having separations of fractions of an au and minimum masses ranging from Neptune to sub-Jupiter ones. Given the number of planets and the various uncertainties in their masses and orbital elements, the HD 34445 planetary system is quite interesting as there is the potential for mean motion and secular resonances that could render the outcome of its dynamical evolution and fate an open question. In this paper we investigate the dynamical stability of the six-planet system in order to check the validity of the orbital solution acquired. This is achieved by a series of numerical experiments, where the dynamical evolution of the system is tested on different time-scales. We vary the orbital elements and masses of the system within the error ranges provided. We find that for a large area of the parameter space we can produce stable configurations and therefore conclude it is very likely that the HD 34445 planetary system is real. Some discussion about the potential habitability of the system is also done.

Download Full-text

Astrometric versus Spectroscopic Radial Velocities

International Astronomical Union Colloquium ◽

10.1017/s0252921100048326 ◽

1999 ◽

Vol 170 ◽

pp. 41-47 ◽

Cited By ~ 5

Author(s):

Dainis Dravins ◽

Dag Gullberg ◽

Lennart Lindegren ◽

Søren Madsen

Keyword(s):

System Dynamics ◽

Radial Velocity ◽

Main Sequence ◽

Planetary System ◽

Radial Velocities ◽

Gravitational Redshift ◽

The Sun ◽

Cool Stars ◽

Space Astrometry ◽

F Stars

AbstractThe apparent radial velocity of a star, as deduced from wavelength shifts, comprises not merely its true velocity, but also components arising from dynamics in the star’s atmosphere, gravitational redshift, and other effects. For the Sun, such phenomena can be segregated since the relative Sun-Earth motion is known from planetary system dynamics. This is now becoming possible also for other stars, whose true radial motions are determined through space astrometry. A study of the differences between accurate astrometric velocities (from Hipparcos), and precise spectroscopic values (from ELODIE) is in progress. Data for cool stars in the Hyades indicate a tendency of relative blueshifts among earlier main-sequence F-type stars, and in giants. This is theoretically expected: an increased convective blueshift due to the more vigorous convection in F-stars, and a decreased gravitational redshift in giants.

Download Full-text

Resonance in the K2-19 system is at odds with its high reported eccentricities

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1736 ◽

2020 ◽

Vol 496 (3) ◽

pp. 3101-3111

Author(s):

Antoine C Petit ◽

Erik A Petigura ◽

Melvyn B Davies ◽

Anders Johansen

Keyword(s):

Planet Formation ◽

Planetary System ◽

Recent Analysis ◽

Circular Orbits ◽

Tidal Dissipation ◽

Outer Planets ◽

Mean Motion ◽

Orbital Configuration ◽

Orbital Solution ◽

Rule Out

ABSTRACT K2-19 hosts a planetary system composed of two outer planets, b and c, with size of 7.0 ± 0.2 R⊕ and 4.1 ± 0.2 R⊕, and an inner planet, d, with a radius of 1.11 ± 0.05 R⊕. A recent analysis of Transit-Timing Variations (TTVs) suggested b and c are close to but not in 3:2 mean motion resonance (MMR) because the classical resonant angles circulate. Such an architecture challenges our understanding of planet formation. Indeed, planet migration through the protoplanetary disc should lead to a capture into the MMR. Here, we show that the planets are in fact, locked into the 3:2 resonance despite circulation of the conventional resonant angles and aligned periapses. However, we show that such an orbital configuration cannot be maintained for more than a few hundred million years due to the tidal dissipation experienced by planet d. The tidal dissipation remains efficient because of a secular forcing of the innermost planet eccentricity by planets b and c. While the observations strongly rule out an orbital solution where the three planets are on close to circular orbits, it remains possible that a fourth planet is affecting the TTVs such that the four planet system is consistent with the tidal constraints.

Download Full-text