scholarly journals The Rossiter-McLaughlin effect reloaded: Probing the 3D spin-orbit geometry, differential stellar rotation, and the spatially-resolved stellar spectrum of star-planet systems

2016 ◽  
Vol 588 ◽  
pp. A127 ◽  
Author(s):  
H. M. Cegla ◽  
C. Lovis ◽  
V. Bourrier ◽  
B. Beeck ◽  
C. A. Watson ◽  
...  
Keyword(s):  
Spin Orbit ◽  
Stellar Rotation ◽  
Stellar Spectrum ◽  
Spatially Resolved ◽  
Orbit Geometry

scholarly journals Inverse tides in pulsating binary stars

2020 ◽  
Vol 501 (1) ◽  
pp. 483-490
Author(s):  
Jim Fuller
Keyword(s):  
Binary Stars ◽  
Close Binary ◽  
Close Binaries ◽  
Spin Orbit ◽  
Misalignment Angle ◽  
Stellar Rotation ◽  
Transfer Energy ◽  
Pulsating Stars ◽  
Mode Amplitude ◽  
Rotation Periods

ABSTRACT In close binary stars, the tidal excitation of pulsations typically dissipates energy, causing the system to evolve towards a circular orbit with aligned and synchronized stellar spins. However, for stars with self-excited pulsations, we demonstrate that tidal interaction with unstable pulsation modes can transfer energy in the opposite direction, forcing the spins of the stars away from synchronicity, and potentially pumping the eccentricity and spin–orbit misalignment angle. This ‘inverse’ tidal process only occurs when the tidally forced mode amplitude is comparable to the mode’s saturation amplitude, and it is thus most likely to occur in main-sequence gravity mode pulsators with orbital periods of a few days. We examine the long-term evolution of inverse tidal action, finding the stellar rotation rate can potentially be driven to a very large or very small value, while maintaining a large spin–orbit misalignment angle. Several recent asteroseismic analyses of pulsating stars in close binaries have revealed extremely slow core rotation periods, which we attribute to the action of inverse tides.

scholarly journals Hint of curvature in the orbital motion of the exoplanet 51 Eridani b using 3 yr of VLT/SPHERE monitoring

2019 ◽  
Vol 624 ◽  
pp. A118 ◽  
Author(s):  
A.-L. Maire ◽  
L. Rodet ◽  
F. Cantalloube ◽  
R. Galicher ◽  
W. Brandner ◽  
...  
Keyword(s):  
Orbital Motion ◽  
Rotation Axis ◽  
Spectral Energy Distribution ◽  
Giant Planet ◽  
Spectral Energy ◽  
Spin Orbit ◽  
Stellar Rotation ◽  
Semi Major Axis ◽  
Primary Star ◽  
Orbital Parameters

Context. The 51 Eridani system harbors a complex architecture with its primary star forming a hierarchical system with the binary GJ 3305AB at a projected separation of 2000 au, a giant planet orbiting the primary star at 13 au, and a low-mass debris disk around the primary star with possible cold and warm components inferred from the spectral energy distribution. Aims. We aim to better constrain the orbital parameters of the known giant planet. Methods. We monitored the system over three years from 2015 to 2018 with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument at the Very Large Telescope (VLT). Results. We measure an orbital motion for the planet of ~130 mas with a slightly decreasing separation (~10 mas) and find a hint of curvature. This potential curvature is further supported at 3σ significance when including literature Gemini Planet Imager (GPI) astrometry corrected for calibration systematics. Fits of the SPHERE and GPI data using three complementary approaches provide broadly similar results. The data suggest an orbital period of 32−9+17 yr (i.e., 12−2+4 au in semi-major axis), an inclination of 133−7+14 deg, an eccentricity of 0.45−0.15+0.10, and an argument of periastron passage of 87−30+34 deg [mod 180°]. The time at periastron passage and the longitude of node exhibit bimodal distributions because we do not yet detect whether the planet is accelerating or decelerating along its orbit. Given the inclinations of the orbit and of the stellar rotation axis (134–144°), we infer alignment or misalignment within 18° for the star–planet spin-orbit. Further astrometric monitoring in the next 3–4 yr is required to confirm at a higher significance the curvature in the motion of the planet, determine if the planet is accelerating or decelerating on its orbit, and further constrain its orbital parameters and the star–planet spin-orbit.

scholarly journals Spin-orbit alignment and magnetic activity in the young planetary system AU Mic

2020 ◽  
Vol 641 ◽  
pp. L1 ◽  
Author(s):  
E. Martioli ◽  
G. Hébrard ◽  
C. Moutou ◽  
J.-F. Donati ◽  
É. Artigau ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Template Matching ◽  
Near Infrared ◽  
Rotation Axis ◽  
Magnetic Activity ◽  
Radial Velocities ◽  
Model Parameters ◽  
Correlation Technique ◽  
Spin Orbit ◽  
Stellar Rotation

We present high-resolution near-infrared spectropolarimetric observations using the SPIRou instrument at Canada-France-Hawaii Telescope (CFHT) during a transit of the recently detected young planet AU Mic b, with supporting spectroscopic data from iSHELL at NASA InfraRed Telescope Facility. We detect Zeeman signatures in the Stokes V profiles and measure a mean longitudinal magnetic field of ¯Bℓ = 46.3 ± 0.7 G. Rotationally modulated magnetic spots likely cause long-term variations of the field with a slope of dBℓ/dt = −108.7 ± 7.7 G d−1. We apply the cross-correlation technique to measure line profiles and obtain radial velocities through CCF template matching. We find an empirical linear relationship between radial velocity and Bℓ, which allows us to estimate the radial-velocity induced by stellar activity through rotational modulation of spots for the five hours of continuous monitoring of AU Mic with SPIRou. We model the corrected radial velocities for the classical Rossiter-McLaughlin effect, using MCMC to sample the posterior distribution of the model parameters. This analysis shows that the orbit of AU Mic b is prograde and aligned with the stellar rotation axis with a sky-projected spin-orbit obliquity of λ = 0°−15°+18°. The aligned orbit of AU Mic b indicates that it formed in the protoplanetary disk that evolved into the current debris disk around AU Mic.

scholarly journals Forced Nonradial Oscillations in Early-Type Rotating Stars

2000 ◽  
Vol 176 ◽  
pp. 376-376
Author(s):  
M. G. Witte ◽  
G. J. Savonije
Keyword(s):  
Gravitational Force ◽  
Rotation Speed ◽  
Internal Damping ◽  
Rotating Stars ◽  
Stellar Rotation ◽  
Stellar Spectrum ◽  
Coriolis Forces ◽  
Nonradial Oscillation ◽  
External Driving ◽  
Nonradial Oscillations

A method of calculating nonradial oscillations in rotating stars is presented. Using this method, we are able to calculate the spectrum of g-, f- and p-mode eigenfunctions of a star for different stellar rotation speeds, and also the spectrum of rotational r modes. Stability of the modes as a function of stellar rotation speed can be investigated. By regarding the response of a star which undergoes periodic deformations due to the gravitational force of an orbiting companion as a forced nonradial oscillation, the problem of determining the eigenfrequencies of the star becomes one of finding resonances with the forcing potential. Expanding the potential of the orbiting (point mass) companion in terms of the usual spherical functions, the response of the star to each tidal term , with l and m fixed, can be calculated separately. By varying the forcing frequency σ we are then able to calculate the stellar spectrum. To calculate the response of the star we numerically solve the fully non-adiabatic, but linearised hydrodynamical equations for the star, in which the Coriolis forces due to stellar rotation are fully taken into account. To this end we utilise an implicit 2D finite difference scheme which solves the equations on an (r, ϑ) grid. A calculated solution describes the steady state in which the power σT due to the external driving force is in equilibrium with the internal damping. For results and more references see Witte & Savonije (1999).

scholarly journals Activity Tracers

1993 ◽  
Vol 137 ◽  
pp. 605-619
Author(s):  
Klaus G. Strassmeier
Keyword(s):  
Solar Activity ◽  
Magnetic Fields ◽  
Binary Stars ◽  
Main Sequence ◽  
Stellar Atmospheres ◽  
Late Type ◽  
Stellar Rotation ◽  
Strong Magnetic Fields ◽  
Rapid Rotation ◽  
Spatially Resolved

AbstractThe vast variety of solar-like phenomena on other late-type stars, so-called activity tracers, provide an important tool for studying the structure of active stellar atmospheres and their connection to the stellar interior via strong magnetic fields. These “chromospherically active” stars include single and binary stars as well as pre- and post-main sequence objects and have rapid rotation and deep convective layers in common. They serve as astrophysical laboratories to study the vast phenomenology of activity tracers: starspots, plages, flares, prominences, which might be seen as enhanced analogs of solar activity and could be spatially resolved due to rotationally modulated indicators. In this paper we review the current observational material and discuss its impact on our knowledge of “active” atmospheres, especially in the context of stellar rotation.

scholarly journals The spatially resolved gas and dust connection in neutral inflows and outflows in nearby AGN

2021 ◽  
Vol 503 (4) ◽  
pp. 4748-4766
Author(s):  
David S N Rupke ◽  
Adam D Thomas ◽  
Michael A Dopita
Keyword(s):  
Major Axis ◽  
Wide Field ◽  
Stellar Rotation ◽  
Nearby Star ◽  
Star Forming ◽  
Spatially Resolved ◽  
Neutral Gas ◽  
Integral Field Spectroscopy ◽  
Colour Excess ◽  
External Galaxies

ABSTRACT Dusty, neutral outflows and inflows are a common feature of nearby star-forming galaxies. We characterize these flows in eight galaxies – mostly active galactic nuclei (AGN) – selected for their widespread Na i D signatures from the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7). This survey employs deep, wide field-of-view (FOV) integral field spectroscopy at moderate spectral resolution (R = 7000 at Na i D). We significantly expand the sample of sightlines in external galaxies in which the spatially resolved relationship has been studied between cool, neutral gas properties – N(Na i), Weq(Na i D) – and dust – E(B − V) from both stars and gas. Our sample shows strong, significant correlations of total Weq with E(B − V)⋆ and g − i colour within individual galaxies; correlations with E(B − V)gas are present but weaker. Regressions yield slope variations from galaxy to galaxy and intrinsic scatter ∼1 Å. The sample occupies regions in the space of N(Na i) and $W_\mathrm{eq}^\mathrm{abs}$ versus E(B − V)gas that are consistent with extrapolations from other studies to higher colour excess [E(B − V)gas ∼ 1]. For perhaps the first time in external galaxies, we detect inverse P Cygni profiles in the Na i D line, presumably due to inflowing gas. Via Doppler-shifted Na i D absorption and emission lines, we find ubiquitous flows that differ from stellar rotation by $\gtrsim$100 km s−1 or have $|v_{\mathrm{ abs}} - v_{\mathrm{ em}}|\gtrsim 100$ km s−1. Inflows and outflows extend towards the edge of the detected stellar disc/FOV, together subtend 10–40 per cent of the projected disc, and have similar mean N(Na i) and Weq(Na i D). Outflows are consistent with minor axis or jet-driven flows, while inflows tend towards the projected major axis. The inflows may result from non-axisymmetric potentials, tidal motions, or halo infall.

scholarly journals KELT-9 b’s Asymmetric TESS Transit Caused by Rapid Stellar Rotation and Spin–Orbit Misalignment

2020 ◽  
Vol 160 (1) ◽  
pp. 4 ◽  
Author(s):  
John P. Ahlers ◽  
Marshall C. Johnson ◽  
Keivan G. Stassun ◽  
Knicole D. Colón ◽  
Jason W. Barnes ◽  
...  
Keyword(s):  
Spin Orbit ◽  
Stellar Rotation

scholarly journals Spin-orbit alignment of exoplanet systems: how can Asteroseismology help us?

2015 ◽  
Vol 11 (A29A) ◽  
pp. 71-76
Author(s):  
Tiago L. Campante
Keyword(s):  
Signal To Noise Ratio ◽  
Spin Orbit ◽  
Hot Jupiters ◽  
Long Period ◽  
Oscillation Modes ◽  
And Migration ◽  
Stellar Properties ◽  
Orbit Geometry ◽  
Exoplanet Systems ◽  
Host Stars

AbstractMeasuring the obliquities of exoplanet-host stars provides invaluable diagnostic information for theories of planetary formation and migration. Most of these results have so far been obtained by measuring the Rossiter--McLaughlin effect, clearly favoring systems that harbor hot Jupiters. While it would be extremely helpful to extend these measurements to long-period and multiple-planet systems, it is also true that the latter systems tend to involve smaller planets, making it ever so difficult to apply such techniques. Asteroseismology provides a powerful method of determining the inclination of the stellar spin axis from an analysis of the rotationally-induced splittings of the oscillation modes. This provides an estimate of the obliquity independently of other methods. The applicability of the asteroseismic method is determined by the stellar properties and not by the signal-to-noise ratio of the transit data. Here we present a recap of the spin-orbit geometry, explain how the asteroseismic method works, and review previous applications of the method to exoplanet-host stars.

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