scholarly journals High-eccentricity migration of planetesimals around polluted white dwarfs

2020 ◽  
Vol 498 (3) ◽  
pp. 4005-4020
Author(s):  
Christopher E O’Connor ◽  
Dong Lai
Keyword(s):  
White Dwarfs ◽  
Physical Parameters ◽  
High Eccentricity ◽  
Tidal Friction ◽  
Pressure Drag ◽  
Ram Pressure ◽  
Tidal Heating ◽  
Analytical Expressions ◽  
Internal Viscosity ◽  
Orbital Migration

ABSTRACT Several white dwarfs (WDs) with atmospheric metal pollution have been found to host small planetary bodies (planetesimals) orbiting near the tidal disruption radius. We study the physical properties and dynamical origin of these bodies under the hypothesis that they underwent high-eccentricity migration from initial distances of several astronomical units. We examine two plausible mechanisms for orbital migration and circularization: tidal friction and ram-pressure drag in a compact disc. For each mechanism, we derive general analytical expressions for the evolution of the orbit that can be rescaled for various situations. We identify the physical parameters that determine whether a planetesimal’s orbit can circularize within the appropriate time-scale and constrain these parameters based on the properties of the observed systems. For tidal migration to work, an internal viscosity similar to that of molten rock is required, and this may be naturally produced by tidal heating. For disc migration to operate, a minimal column density of the disc is implied; the inferred total disc mass is consistent with estimates of the total mass of metals accreted by polluted WDs.

scholarly journals Measurements of Physical Parameters of White Dwarfs: A Test of the Mass–Radius Relation

2017 ◽  
Vol 848 (1) ◽  
pp. 11 ◽  
Author(s):  
A. Bédard ◽  
P. Bergeron ◽  
G. Fontaine
Keyword(s):  
White Dwarfs ◽  
Physical Parameters

scholarly journals Tidal dynamics of transiting exoplanets

2010 ◽  
Vol 6 (S276) ◽  
pp. 252-257
Author(s):  
Daniel C. Fabrycky
Keyword(s):  
A Priori ◽  
Misalignment Angle ◽  
Tidal Dynamics ◽  
High Eccentricity ◽  
Tidal Friction ◽  
Hot Jupiters ◽  
Pile Up ◽  
Stellar Temperature ◽  
Host Stars ◽  
Alternative Theories

AbstractTransits give us the mass, radius, and orbital properties of the planet, all of which inform dynamical theories. Two properties of the hot Jupiters suggest they had a dramatic origin via tidal damping from high eccentricity. First, the tidally circularized planets (in the 1-4 day pile-up) lie along a relation or boundary in the mass-period plane. This observation may implicate a tidal damping process regulated by planetary radius inflation and Roche lobe overflow, early in the planets' lives. Second, the host stars of many planets have spins misaligned from the planets' orbits. This observation was not expected a priori from the conventional disk migration theory, and it was a boon for the alternative theories of planet-planet scattering and Kozai cycles, accompanied by tidal friction, which predicted it. Now we are faced with a curious observation that the misalignment angle depends on the stellar temperature. It may mean that the tide raised on the stars realigns them, the final result being the tidal consumption of hot Jupiters.

scholarly journals The influence of a thermal plasma on synchrotron radiation

1988 ◽  
Vol 6 (3) ◽  
pp. 421-436 ◽  
Author(s):  
A. Crusius
Keyword(s):  
Synchrotron Radiation ◽  
Energy Loss ◽  
Total Energy ◽  
Thermal Plasma ◽  
Large Scale ◽  
Lorentz Factor ◽  
Physical Parameters ◽  
Relativistic Electrons ◽  
Physical Conditions ◽  
Analytical Expressions

The synchrotron emission from relativistic electrons in a thermal plasma with large-scale random magnetic fields is considered. In this case, the spectral synchrotron power of a single electron can be given in closed form allowing exact analytical expressions for the synchrotron emissivity, absorption coefficient, intensity and total energy loss of particles to be derived. The influence of various physical parameters such as gas density, magnetic field strength, particle's Lorentz factor on the resulting emissivities, intensities and energy loss is discussed in detail. Below the Razin– Tsytovich frequency vR = 20 Hz (ne/l cm−3) (B/l Gauss)−1, the spectral appearance of synchrotron radiation both in the optically thin and thick case is quite different than the vacuum behaviour. Since in the quasar broad line regions, vR is of the order 1011 Hz the suppression of synchrotron radiation may explain why most quasars are radio quiet. Likewise, the necessary physical conditions for the occurrence of synchrotron masering in the optically thick case are given. We obtain optical depth |τ|>1 for compact nonthermal sources. The total energy loss of a single particle is shown to be exponentially reduced at Lorentz factors less than γR = 2·1. 10−3 (ne/1 cm−3)½ (B/1 Gauss)−1.

scholarly journals Orbital misalignment of the super-Earth π Men c with the spin of its star

2021 ◽  
Vol 502 (2) ◽  
pp. 2893-2911 ◽  
Author(s):  
Vedad Kunovac Hodžić ◽  
Amaury H M J Triaud ◽  
Heather M Cegla ◽  
William J Chaplin ◽  
Guy R Davies
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Radial Velocity ◽  
Gaussian Processes ◽  
Giant Planet ◽  
Spin Axis ◽  
Physical Parameters ◽  
Eccentric Orbit ◽  
High Eccentricity ◽  
Migration History

ABSTRACT Planet–planet scattering events can leave an observable trace of a planet’s migration history in the form of orbital misalignment with respect to the stellar spin axis, which is measurable from spectroscopic time-series taken during transit. We present high-resolution spectroscopic transits observed with ESPRESSO of the close-in super-Earth π Men c. The system also contains an outer giant planet on a wide, eccentric orbit, recently found to be inclined with respect to the inner planetary orbit. These characteristics are reminiscent of past dynamical interactions. We successfully retrieve the planet-occulted light during transit, and find evidence that the orbit of π Men c is moderately misaligned with the stellar spin axis with λ = − 24${_{.}^{\circ}}$0 ± 4${_{.}^{\circ}}$1 ($\psi = {26{_{.}^{\circ}} 9}^{+5{_{.}^{\circ}}8 }_{-4{_{.}^{\circ}}7 }$). This is consistent with the super-Earth π Men c having followed a high-eccentricity migration followed by tidal circularization, and hints that super-Earths can form at large distances from their star. We also detect clear signatures of solar-like oscillations within our ESPRESSO radial velocity time series, where we reach a radial velocity precision of ∼20 cm s−1. We model the oscillations using Gaussian processes (GPs) and retrieve a frequency of maximum oscillation, $\nu _\mathrm{max}{} = 2771^{+65}_{-60}\, \mu \mathrm{Hz}$. These oscillations make it challenging to detect the Rossiter–McLaughlin effect using traditional methods. We are, however, successful using the reloaded Rossiter–McLaughlin approach. Finally, in the appendix, we also present physical parameters and ephemerides for π Men c from a GP transit analysis of the full Transiting Exoplanet Survey Satellite Cycle 1 data.

scholarly journals The origin of retrograde hot Jupiters

2010 ◽  
Vol 6 (S276) ◽  
pp. 263-266
Author(s):  
Smadar Naoz ◽  
Will M. Farr ◽  
Yoram Lithwick ◽  
Frederic A. Rasio
Keyword(s):  
Angular Momentum ◽  
Equatorial Plane ◽  
Rotation Axis ◽  
Order Effects ◽  
High Eccentricity ◽  
Tidal Friction ◽  
Hot Jupiters ◽  
Secular Dynamics ◽  
Accurate Treatment ◽  
Very High

AbstractMany hot Jupiters are observed to be misaligned with respect to the rotation axis of the star (as measured through the Rossiter–McLaughlin effect) and some (about ~ 25%) even appear to be in retrograde orbits. We show that the presence of an additional, moderately inclined and eccentric massive planet in the system can naturally explain close, inclined, eccentric, and even retrograde orbits. We have derived a complete and accurate treatment of the secular dynamics including both the key octupole-order effects and tidal friction. The flow of angular momentum from the inner orbit to the orbit of the perturber can lead to both high eccentricities and inclinations, and even flip the inner orbit. In our treatment the component of the inner orbit's angular momentum perpendicular to the stellar equatorial plane can change sign; a brief excursion to very high eccentricity during the chaotic evolution of the inner orbit can then lead to rapid “tidal capture,” forming a retrograde hot Jupiter. Previous treatments of the secular dynamics focusing on stellar-mass perturbers would not allow for such an outcome, since in that limit the component of the inner orbit's angular momentum perpendicular to the stellar equatorial plane is strictly conserved. Thus, the inclination of the planet's orbit could not change from prograde to retrograde.

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