Inflation Radius Research Articles

Inflated Eccentric Migration of Evolving Gas Giants I – Accelerated Formation and Destruction of Hot and Warm Jupiters

Hot and warm Jupiters (HJs and WJs, correspondingly) are gas giants orbiting their host stars at very short orbital periods (P HJ < 10 days; 10 < P WJ < 200 days). HJs and a significant fraction of WJs are thought to have migrated from initially farther-out birth locations. While such migration processes have been extensively studied, the thermal evolution of gas giants and its coupling with migration processes are usually overlooked. In particular, gas giants end their core accretion phase with large radii, then contract slowly to their final radii. Moreover, intensive heating can slow the contraction at various evolutionary stages. The initial large inflated radii lead to faster tidal migration, due to the strong dependence of tides on the radius. Here, we explore this accelerated migration channel, which we term inflated eccentric migration, using a semi-analytical, self-consistent model of the thermal–dynamical evolution of the migrating gas giants, later validated by our numerical model (see the companion paper, paper II). We demonstrate our model for specific examples and carry out a population synthesis study. Our results provide a general picture of the properties of the formed HJs and WJs via inflated migration, and their dependence on the initial parameters/distributions. We show that the tidal migration of gas giants could occur much more rapidly then previously thought, and could lead to the accelerated destruction and formation of HJs and an enhanced formation rate for WJs. Accounting for the coupled thermal–dynamical evolution is therefore critical to understanding the formation of HJs/WJs, and the evolution and final properties of the population, and it plays a key role in their migration processes.

Properties and evolutions of starspots on three detached eclipsing binaries in the LAMOST–Kepler survey

ABSTRACT Spotted detached eclipsing binaries (DEBs) offer insights into starspots on binaries. In this work, we study three spotted DEBs, KIC 8097825, KIC 6859813 and KIC 5527172, which have been observed using Kepler photometry and Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) spectroscopy. The physical parameters of binaries are determined by binary modelling. The size, lifetime and single/-double-dip ratio (SDR) of starspots are derived by starspot analysis. KIC 8097825 has large starspots. KIC 6859813 has a spot rotation period shorter than its orbital period but the system should be synchronized by inference from time-scale estimation. The difference may be the result of the surface differential rotation. KIC 5527172 has a long spot lifetime and an M-dwarf component with an inflation radius. The primaries of these binaries and the secondary of KIC 8097825 have spots. Adding spotted DEBs from the literature, we compare the starspots on binaries with those on the single stars. The spot sizes of starspots on 65 per cent of binaries are smaller than the median of those on single stars. The lifetimes of starspots on binaries are consistent with those on single stars when the rotation periods are larger than 3 d. SDRs for half of the binaries are consistent with those of single-star systems, while the other half are smaller. The relative lifetime positively correlates with the rms and SDR but negatively correlates with the rotation period. These relations are similar to those of spots on single-star systems. Binaries with luminosity ratios close to the unit tend to have more double dips.

Spline-based Path Planning and Reconfiguration for Rigid Multi-Robot Formations

This paper presents an approach for continuous path planning in rigid formations containing nonholonomic mobile robots using Beziér-splines. Unlike most existing approaches, the focus is on maintaining a rigid formation, as required in many scenarios such as object transport, handling or assembly. In these scenarios, a constant distance between the individual robots must be kept to avoid damaging the transported object. Also, limitations regarding the velocity and acceleration of each robot have to be taken into account, as every robot traverses in a slightly different path. Especially the distance from the center of the formation to an individual robot has a big impact on the path a mobile robot has to move on to comply with the formation constraints during an orientation change of the formation. Therefore, we use splines to control and optimize the curvature of the formation’s path and limit the velocity and acceleration. The usage of splines requires the calculation of specific support points that can be interpolated. To achieve this, we calculate the formation’s diameter, including the transported object and adjust the inflation radius of the global costmap. To guarantee a collision-free movement from the start to the target position, we use an existing path planner to generate an initial path. The employed Relaxed-A*-Algorithm provides fast computation and an almost optimal initial path, although this path is not continuous. From this path, we extract a number of support points based on the size of the formation. We then fit a fifth-degree Beziér-spline through these points to smooth the discontinuous path. The final result is a computationally efficient, smooth and jerk-limited path that induces minimal disturbances to the formation control. Also, this approach allows us to continuously transition from one formation to another, which can be used to pass narrow passages. To valid the path planning approach presented in this study we showcase simulative and experimental results.

Investigating hot-Jupiter inflated radii with hierarchical Bayesian modelling

Context.As of today, hundreds of hot Jupiters have been found, yet the inflated radii of a large fraction of them remain unexplained. A number of mechanisms have been proposed to explain these anomalous radii, however most of these can only work under certain conditions and may not be sufficient to explain the most extreme cases. It is still unclear whether a single mechanism can sufficiently explain the entire distribution of radii, or whether a combination of these mechanisms is needed.Aims.We seek to understand the relationship of radius with stellar irradiation and mass and to find the range of masses over which hot Jupiters are inflated. We also aim to find the intrinsic physical scatter in their radii, caused by unobservable parameters, and to constrain the fraction of hot Jupiters that exhibit inflation.Methods.By constructing a hierarchical Bayesian model, we inferred the probabilistic relation between planet radius, mass, and incident flux for a sample of 286 gas giants. We separately incorporated the observational uncertainties of the data and the intrinsic physical scatter in the population. This allowed us to treat the intrinsic physical scatter in radii, due to latent parameters such as the heavy element fraction, as a parameter to be inferred.Results.We find that the planetary mass plays a key role in the inflation extent and that planets in the range ~0.37−0.98 MJshow the most inflated radii. At higher masses, the radius response to incident flux begins to decrease. Below a threshold of 0.37 ± 0.03 MJwe find that giant exoplanets as a population are unable to maintain inflated radii ≿1.4 RJbut instead exhibit smaller sizes as the incident flux is increased beyond 106W m−2. We also find that below 1 MJ, there is a cut-off point at high incident flux beyond which we find no more inflated planets, and that this cut-off point decreases as the mass decreases. At incident fluxes higher than ~1.6 × 106W m−2and in a mass range 0.37−0.98 MJ, we find no evidence for a population of non-inflated hot Jupiters. Our study sheds a fresh light on one of the key questions in the field and demonstrates the importance of population-level analysis to grasp the underlying properties of exoplanets.

Analysis on nonlinear turning motion of multi-spherical soft robots

A modular multi-spherical soft robot, which consists of five deformable spherical cells, two friction feet, the electromagnetic valves and the control systems, is constructed. According to the deflating action and the inflating action of the spherical cells, the size and the shape of each spherical cell can be changed. With two friction feet sticking with the ground in turn, the soft robot can move forwards, make a turning motion and avoid the obstacle. This paper creates a nonlinear relation between the pressure P and the inflation radius \(\left( r \right) \) at different original radii \(\left( {r_0 } \right) \) and obtains the inflation or deflation velocity \(v_r \). Six inflating and deflating steps to finish the turning motion are presented. Based on the geometric relationship between the inflation radius (r) and the original radius \((r_0 )\) of each cell, the nonlinear turning process is described to control the center positions (x, y, z) of the spherical cell. Last, a simulation and an experiment of five spherical cells are shown to emulate the turning process. Experiment results show that the robot has a maximum turning capability of \(20{^{\circ }}\) in one period.

HATS-31B THROUGH HATS-35B: FIVE TRANSITING HOT JUPITERS DISCOVERED BY THE HATSOUTH SURVEY*

ABSTRACT We report the discovery of five new transiting hot-Jupiter planets discovered by the HATSouth survey, HATS-31b through HATS-35b. These planets orbit moderately bright stars with V magnitudes within the range of – mag while the planets span a range of masses of – and have somewhat inflated radii between and . These planets can be classified as typical hot Jupiters, with HATS-31b and HATS-35b being moderately inflated gas giant planets with radii of and , respectively, that can be used to constrain inflation mechanisms. All five systems present a higher Bayesian evidence for a fixed-circular-orbit model than for an eccentric orbit. The orbital periods range from day for HATS-35b) to day for HATS-31b. Additionally, HATS-35b orbits a relatively young F star with an age of Gyr. We discuss the analysis to derive the properties of these systems and compare them in the context of the sample of well-characterized transiting hot Jupiters known to date.

Study on nonlinear obstacle avoidance on modular soft robots

A modular soft robot, which consists of three deformable spherical cells, the electromagnetic valves and the control systems, is constructed. According to the deflating action and the inflating action of the spherical cells, the size and the shape of each spherical cell can be changed. Thus, the soft robot can move through a narrow or low complicated passage. In this paper, the nonlinear relationship between the pressure (P) and the inflation radius (R) of each cell with different original diameters (r) is described to control the change of the spherical cell. In order to move through a narrow or low obstacle, based on the different distances $$S_{i}$$ between spherical cell i and the obstacle, four kinds of different moving orders are obtained. For each kind of moving order, the nonlinear dynamic moving process is analyzed with the deflating and inflating modes of each cell. The theoretical analysis of nonlinear obstacle avoidance is proposed, and the moving conditions are presented in details. Last, a simulation and an experiment of three spherical cells are shown to emulate the obstacle avoidance process of the soft robot.

Nonlinear dynamic modeling on multi-spherical modular soft robots

A soft robot, which consists of multi-deformable spherical cells, is constructed. According to the deflating action and the inflating action of the spherical cells, the size and the shape of each spherical cell can be changed. Thus, the soft robot can move in a narrow complicated passage. In the paper, a modular soft robot is built. The nonlinear relationship between the inflation radius ( $$R)$$ of each cell and the inflation time ( $$t)$$ is described to control the action of the spherical cell. The nonlinear dynamic moving process is analyzed with the deflating and inflating modes of each cell. The theoretical analysis of the forward locomotion is counted. Then, two special positions are described, and the moving conditions are presented in details. Last, a simulation and an experiment of three spherical cells are shown to emulate the moving process of the soft robot. It shows that the modular soft robot consisting of multi-deformable spherical modules can move forward with the nonlinear dynamic inflating and deflating process.

Discovery of WASP-65b and WASP-75b: Two hot Jupiters without highly inflated radii

We report the discovery of two transiting hot Jupiters, WASP-65b (M_pl = 1.55 +/- 0.16 M_J; R_pl = 1.11 +/- 0.06 R_J), and WASP-75b (M_pl = 1.07 +/- 0.05 M_J; R_pl = 1.27 +/- 0.05 R_J). They orbit their host star every 2.311, and 2.484 days, respectively. The planet host WASP-65 is a G6 star (T_eff = 5600 K, [Fe/H] = -0.07 +/- 0.07, age > 8 Gyr); WASP-75 is an F9 star (T_eff = 6100 K, [Fe/H] = 0.07 +/- 0.09, age of 3 Gyr). WASP-65b is one of the densest known exoplanets in the mass range 0.1 and 2.0 M_J (rho_pl = 1.13 +/- 0.08 rho_J), a mass range where a large fraction of planets are found to be inflated with respect to theoretical planet models. WASP-65b is one of only a handful of planets with masses of around 1.5 M_J, a mass regime surprisingly underrepresented among the currently known hot Jupiters. The radius of Jupiter-mass WASP-75b is slightly inflated (< 10%) as compared to theoretical planet models with no core, and has a density similar to that of Saturn (rho_pl = 0.52 +/- 0.06 rho_J).