The origin of the obliquity in planetary systems studied with infrared interferometry

2020 ◽  
Author(s):  
Stefan Kraus
Keyword(s):  
Formation Process ◽  
Planet Formation ◽  
Rotation Axis ◽  
Scattered Light ◽  
Dynamical Evolution ◽  
Asymmetric Structure ◽  
Stellar Rotation ◽  
3 Dimensional ◽  
Beam Combination ◽  
Infrared Interferometry

<p>Observations of the Rossiter-McLaughlin effect have revealed that the orbits of many exoplanets are misaligned with respect to the stellar rotation axis. Various scenarios have been proposed that associate the orbit obliquity either with multi-body interactions or dynamical processes in the disc during the planet formation process. In this talk, I will present how infrared interferometry allows us to study the origin of the planet obliquity:</p> <p>In the first part of the talk I will present observations that reveal the recently-posted disc tearing effect, where the gravitational torque of companions on misaligned orbits can tear the disc apart into distinct rings that precess independently around the central objects. We imaged the triple system GW Orionis using VLTI, CHARA, ALMA, SPHERE, and GPI and discover three rings in thermal light and an asymmetric structure with radial shadows in scattered light. The inner-most ring is eccentric (e=0.3; 43 au radius) and strongly misaligned both with respect to the orbital planes and with respect to the outer disc. Modelling the scattered light signatures and the shape of the shadows cast by the misaligned ring allows us derive the shape and 3-dimensional orientation of the disc surface, revealing that the disc is strongly warped and breaks at a radius of about 50 au. Based on the measured triple star orbits and disc properties, we conducted smoothed particle hydrodynamic simulations which show that the system is susceptible to the disc tearing effect. The ring offers suitable conditions for planet formation, providing a mechanism for forming wide-separation planets on highly oblique orbits. Our results imply that there may exist a significant, yet undiscovered population of long-period planets on highly oblique orbits that has formed around misaligned multiple systems.</p> <p>In the second part I will show how infrared interferometry can be used to search for this predicted population of wide-separation planets on oblique orbits, probing a highly complementary regime to the parameter space accessible with the Rossiter-McLaughlin effect. I will present the first study where the spin-orbit alignment has been measured for a directly-imaged exoplanet, namely on Beta Pictoris b. We used VLTI/GRAVITY spectro-interferometry with an astrometric accuracy of 1 microarcsecond to measure the photocenter displacement associated with the stellar rotation. Taking inclination constraints from astroseismology into account, we constrain the 3-dimensional orientation of the stellar spin axis and find that Beta Pic b orbits its host star on a prograde orbit with a small obliquity angle. </p> <p>I will conclude by offering a near-term perspective on how infrared interferometry with the proposed BIFROST beam-combination instrument could advance our understanding of the planet formation process and of the early dynamical evolution of exoplanetary systems.</p>

Planet formation process as a phase transition

1979 ◽  
Vol 20 (4) ◽  
pp. 371-384 ◽  
Author(s):  
Paolo Farinella ◽  
Paolo Paolicchi ◽  
Federico Ferrini
Keyword(s):  
Phase Transition ◽  
Formation Process ◽  
Planet Formation

Exploring the dust ring in the circum-binary disc around GG Tau A

2021 ◽  
Author(s):  
Claudia Toci ◽  
Simone Ceppi ◽  
Nicolas Cuello ◽  
Giuseppe Lodato ◽  
Cristiano Longarini ◽  
...  
Keyword(s):  
Binary Systems ◽  
Planet Formation ◽  
Initial Conditions ◽  
Scattered Light ◽  
Complex Structure ◽  
Semimajor Axis ◽  
Continuum Emission ◽  
Orbital Parameter ◽  
Semi Major Axis ◽  
Multiple Systems

<p>Binaries and multiple systems are common among young stars (Reipurth et al. 2014). These stars are often surrounded by discs of gas and dust, formed due to the conservation of angular momentum of the collapsing cloud, thought to be the site of planet formation.<br />In the case of binary systems, three discs can form: an outer disc surrounding all the stars (called circumbinary disc), and two inner discs around the stars. As circumbinary planets have recently been discovered by Kepler (see e.g., Martin 2018, Bonavita & Desidera 2020), it is crucial to understand the dynamics and evolution of circumbinary discs to better understand the initial conditions of planet formation in multiple systems.<br />The GG Tau A system is an example of a young multiple T Tauri star. The binary is surrounded by a bright disc, observed in the continuum emission at different wavelengths (see e.g., Guilloteau et al. 1999; Dutrey et al. 2014; Phuong et al. 2020b) and in scattered light (e.g., Duchene et al. 2014, Keppler et al. 2020). The disc extends in the dust from 180 to 280 au from the center of mass, and in the gas up to 850 au. The inner (<180 au) part is depleted in gas and dust. Scattered light images show a complex structure in the inner part of the disc, with arcs and filamentary structures connecting the outer ring with the arcs and three shadows.<br />Two different configurations are possible fitting the proper motion data for the system: a co-planar case with a low eccentricity binary with a semi-major axis of 34 au, explored by Cazzoletti et al. 2017 and Keppler et al. 2020, and a misaligned case (i=30) with an eccentric binary (e=0.45) and a wider semimajor axis of 60 au (Aly et al.2018). At the state of the art, all these analyses focused on the gas dynamics only.<br />We will show the results of new 3D SPH simulations of dust and gas performed with the code PHANTOM, devised to test the two possible scenarios. We will describe the dynamics of the system in the two cases, comparing our models with observational results in order to better constraint the orbital parameter of the GG Tau A system. Our predictions will guide future observing campaigns and shed light on the complex evolution of discs in triple stellar systems.</p> <p> </p>

scholarly journals Magnetic Braking and the Oblique Rotator Model

1970 ◽  
Vol 4 ◽  
pp. 269-273
Author(s):  
L. Mestel ◽  
C. S. Selley
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Stellar Wind ◽  
Rotation Axis ◽  
Dynamical Evolution ◽  
Magnetic Star ◽  
Rotator Model ◽  
Oblique Rotator ◽  
Magnetic Braking

This work investigates the dynamical evolution of a rotating magnetic star which drives a stellar wind. The basic magnetic field of the star is supposed symmetric about an axis, which is inclined at an angle X to the rotation axis k (Figure 1). We adopt the familiar equations of an inviscid perfectly conducting gas. In a steady state, the velocity as seen in a frame rotating with the star is taken as

scholarly journals Magnetic braking of supermassive stars through winds

2019 ◽  
Vol 623 ◽  
pp. L7 ◽  
Author(s):  
L. Haemmerlé ◽  
G. Meynet
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Formation Process ◽  
Magnetic Coupling ◽  
Rotation Velocity ◽  
Stellar Surface ◽  
Stellar Winds ◽  
Stellar Rotation ◽  
Magnetic Braking ◽  
The Magnetic Field

Context. Supermassive stars (SMSs) are candidates for being progenitors of supermassive quasars at high redshifts. However, their formation process requires strong mechanisms that would be able to extract the angular momentum of the gas that the SMSs accrete. Aims. We investigate under which conditions the magnetic coupling between an accreting SMS and its winds can remove enough angular momentum for accretion to proceed from a Keplerian disc. Methods. We numerically computed the rotational properties of accreting SMSs that rotate at the ΩΓ-limit and estimated the magnetic field that is required to maintain the rotation velocity at this limit using prescriptions from magnetohydrodynamical simulations of stellar winds. Results. We find that a magnetic field of 10 kG at the stellar surface is required to satisfy the constraints on stellar rotation from the ΩΓ-limit. Conclusions. Magnetic coupling between the envelope of SMSs and their winds could allow for SMS formation by accretion from a Keplerian disc, provided the magnetic field is at the upper end of present-day observed stellar fields. Such fields are consistent with primordial origins.

scholarly journals Planets in Binaries: Formation and Dynamical Evolution

Galaxies ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 84 ◽  
Author(s):  
Francesco Marzari ◽  
Philippe Thebault
Keyword(s):  
Binary Systems ◽  
Planet Formation ◽  
Dynamical Evolution ◽  
Type Systems ◽  
Hyperbolic Orbit ◽  
Companion Star ◽  
Mean Motion Resonances ◽  
Disk Formation ◽  
P Type ◽  
Two Populations

Binary systems are very common among field stars, yet the vast majority of known exoplanets have been detected around single stars. While this relatively small number of planets in binaries is probably partly due to strong observational biases, there is, however, statistical evidence that planets are indeed less frequent in binaries with separations smaller than 100 au, strongly suggesting that the presence of a close-in companion star has an adverse effect on planet formation. It is indeed possible for the gravitational pull of the second star to affect all the different stages of planet formation, from proto-planetary disk formation to dust accumulation into planetesimals, to the accretion of these planetesimals into large planetary embryos and, eventually, the final growth of these embryos into planets. For the crucial planetesimal-accretion phase, the complex coupling between dynamical perturbations from the binary and friction due to gas in the proto-planetary disk suggests that planetesimal accretion might be hampered due to increased, accretion-hostile impact velocities. Likewise, the interplay between the binary’s secular perturbations and mean motion resonances lead to unstable regions, where not only planet formation is inhibited, but where a massive body would be ejected from the system on a hyperbolic orbit. The amplitude of these two main effects is different for S- and P-type planets, so that a comparison between the two populations might outline the influence of the companion star on the planet formation process. Unfortunately, at present the two populations (circumstellar or circumbinary) are not known equally well and different biases and uncertainties prevent a quantitative comparison. We also highlight the long-term dynamical evolution of both S and P-type systems and focus on how these different evolutions influence the final architecture of planetary systems in binaries.

scholarly journals Oblique Pulsator Model for the Blazhko Effect of RR Lyrae Stars

1995 ◽  
Vol 155 ◽  
pp. 42-43
Author(s):  
Hiromoto Shibahashi ◽  
Masao Takata
Keyword(s):  
Rotation Axis ◽  
Oscillation Mode ◽  
Stellar Rotation ◽  
Rr Lyrae Stars ◽  
Aspect Angle ◽  
Rr Lyrae ◽  
Quadrupole Component ◽  
Blazhko Effect ◽  
Apparent Variation ◽  
Lyrae Stars

AbstractBy assuming that the RR Lyrae stars have fairly strong dipole magnetic fields with the symmetry axis oblique to the rotation axis of the star, we show that the oscillation mode which would be a pure radial oscillation in absence of the magnetic field has a quadrupole component, which is axisymmetric with respect to the magnetic axis. The aspect angle of the quadrupole component changes due to the stellar rotation, and this apparent variation is interpreted as the Blazhko effect in RR Lyrae stars.

scholarly journals The Dynamical Evolution of Young Clusters and Associations

1986 ◽  
Vol 7 ◽  
pp. 481-488 ◽  
Author(s):  
Robert D. Mathieu
Keyword(s):  
Star Formation ◽  
Formation Process ◽  
Initial Conditions ◽  
Dynamical Evolution ◽  
Short Review ◽  
Stellar Systems ◽  
Galactic Field ◽  
Dynamical State ◽  
Orbital Mixing ◽  
Formation Efficiency

A young cluster or association bears the imprint of the conditions at its birth for perhaps ten million years, after which the initial conditions are lost to either dilution in the galactic field or erasure by orbital mixing and stellar encounters. In its youngest years, however, the dynamical state of the system can provide valuable information concerning the structure and energetics of the parent gas, the star-formation efficiency and the star-formation process itself. This short review discusses recent theoretical and observational progress in the study of the very youngest of stellar systems.

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 Misaligned spin-orbit in the XO-3 planetary system?

2008 ◽  
Vol 4 (S253) ◽  
pp. 508-511
Author(s):  
G. Hébrard ◽  
F. Bouchy ◽  
F. Pont ◽  
B. Loeillet ◽  
M. Rabus ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Planetary System ◽  
Rotation Axis ◽  
Gravitational Interaction ◽  
Stellar Rotation ◽  
Velocity Anomaly ◽  
Large Program ◽  
Formation And Evolution ◽  
Unusual Shape ◽  
Orbital Axis

AbstractThe SOPHIE Consortium started a large program of exoplanets search and characterization in the Northern hemisphere with the new spectrograph SOPHIE at the 1.93-m telescope of Haute-Provence Observatory, France. The objectives of this program are to characterize the zoo of exoplanets and to bring strong constraints on their processes of formation and evolution using the radial velocity technique. We present here new SOPHIE measurements of the transiting planet host star XO-3. This allowed us to observe the Rossiter-McLaughlin effect and to refine the parameters of the planet. The unusual shape of the radial velocity anomaly during the transit provides a hint for a nearly transverse Rossiter-McLaughlin effect. The sky-projected angle between the planetary orbital axis and the stellar rotation axis should be λ = 70° ± 15° to be compatible with our observations. This suggests that some close-in planets might result from gravitational interaction between planets and/or stars rather than migration. This result requires confirmation by additional observations.

scholarly journals Carbon-grain sublimation: a new top-down component to protostellar chemistry

2020 ◽  
Author(s):  
Merel van 't Hoff ◽  
Edwin Bergin ◽  
Jes Jorgensen ◽  
Geoffrey Blake
Keyword(s):  
Gas Phase ◽  
Formation Process ◽  
Organic Molecules ◽  
Planet Formation ◽  
Protoplanetary Disks ◽  
Excitation Temperature ◽  
Top Down ◽  
Carbon Chemistry ◽  
Episodic Nature ◽  
Protosolar Nebula

<p>One of the main goals in the fields of exoplanets and planet formation is to determine the composition of terrestrial, potentially habitable, planets and to link this to the composition of protoplanetary disks. A longstanding puzzle in this regard is the Earth's severe carbon deficit; Earth is 2-4 orders of magnitude depleted in carbon compared to interstellar grains and comets. The solution to this conundrum is that carbon must have been returned to the gas phase in the inner protosolar nebula, such that it could not get accreted onto the forming bodies. A process that could be responsible is the sublimation of carbon grains at the so-called soot line (~300 K) early in the planet-formation process. I will argue that the most likely signatures of this process are an excess of hydrocarbons and nitriles inside the soot line around protostars, and a higher excitation temperature for these molecules compared to oxygen-bearing complex organics that desorb around the water snowline (~100 K). Moreover, I will show that such characteristics have indeed been reported in the literature, for example, in Orion KL, although not uniformly, potentially due to differences in observational settings or related to the episodic nature of protostellar accretion. If this process is active, this would mean that there is an heretofore unrecognized component to the carbon chemistry during the protostellar phase that is acting from the top down - starting from the destruction of larger species - instead of from the bottom up from atoms. In the presence of such a top-down component, the origin of organic molecules needs to be re-explored. </p>

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