19 research outputs found
Trapping of giant-planet cores - I. Vortex aided trapping at the outer dead zone edge
In this paper the migration of a 10 Earth-mass planetary core is investigated
at the outer boundary of the dead zone of a protoplanetary disc by means of 2D
hydrodynamic simulations done with the graphics processor unit version of the
FARGO code. In the dead zone, the effective viscosity is greatly reduced due to
the disc self-shielding against stellar UV radiation, X-rays from the stellar
magnetosphere and interstellar cosmic rays. As a consequence, mass accumulation
occurs near the outer dead zone edge, which is assumed to trap planetary cores
enhancing the efficiency of the core-accretion scenario to form giant planets.
Contrary to the perfect trapping of planetary cores in 1D models, our 2D
numerical simulations show that the trapping effect is greatly dependent on the
width of the region where viscosity reduction is taking place. Planet trapping
happens exclusively if the viscosity reduction is sharp enough to allow the
development of large-scale vortices due to the Rossby wave instability. The
trapping is only temporarily, and its duration is inversely proportional to the
width of the viscosity transition. However, if the Rossby wave instability is
not excited, a ring-like axisymmetric density jump forms, which cannot trap the
10 Earth-mass planetary cores. We revealed that the stellar torque exerted on
the planet plays an important role in the migration history as the barycentre
of the system significantly shifts away from the star due to highly
non-axisymmetric density distribution of the disc. Our results still support
the idea of planet formation at density/pressure maximum, since the migration
of cores is considerably slowed down enabling them further growth and runaway
gas accretion in the vicinity of an overdense region.Comment: 23 pages, 31 figures, accepted for publication in MNRA
Scattered light images of spiral arms in marginally gravitationally unstable discs with an embedded planet
Scattered light images of transition discs in the near-infrared often show
non-axisymmetric structures in the form of wide-open spiral arms in addition to
their characteristic low-opacity inner gap region. We study self-gravitating
discs and investigate the influence of gravitational instability on the shape
and contrast of spiral arms induced by planet-disc interactions.
Two-dimensional non-isothermal hydrodynamical simulations including viscous
heating and a cooling prescription are combined with three-dimensional dust
continuum radiative transfer models for direct comparison to observations. We
find that the resulting contrast between the spirals and the surrounding disc
in scattered light is by far higher for pressure scale height variations, i.e.
thermal perturbations, than for pure surface density variations. Self-gravity
effects suppress any vortex modes and tend to reduce the opening angle of
planet-induced spirals, making them more tightly wound. If the disc is only
marginally gravitationally stable with a Toomre parameter around unity, an
embedded massive planet (planet-to-star mass ratio of ) can trigger
gravitational instability in the outer disc. The spirals created by this
instability and the density waves launched by the planet can overlap resulting
in large-scale, more open spiral arms in the outer disc. The contrast of these
spirals is well above the detection limit of current telescopes.Comment: Accepted for publication in MNRAS; 13 pages, 8 figure
Planet-vortex interaction:How a vortex can shepherd a planetary embryo
Context: Anticyclonic vortices are considered as a favourable places for
trapping dust and forming planetary embryos. On the other hand, they are
massive blobs that can interact gravitationally with the planets in the disc.
Aims: We aim to study how a vortex interacts gravitationally with a planet
which migrates toward it or a planet which is created inside the vortex.
Methods: We performed hydrodynamical simulations of a viscous locally
isothermal disc using GFARGO and FARGO-ADSG. We set a stationary Gaussian
pressure bump in the disc in a way that RWI is triggered. After a large vortex
is established, we implanted a low mass planet in the outer disc or inside the
vortex and allowed it to migrate. We also examined the effect of vortex
strength on the planet migration and checked the validity of the final result
in the presence of self-gravity. Results: We noticed regardless of the planet's
initial position, the planet is finally locked to the vortex or its migration
is stopped in a farther orbital distance in case of a stronger vortex. For the
model with the weaker vortex, we studied the effect of different parameters
such as background viscosity, background surface density, mass of the planet
and different planet positions. In these models, while the trapping time and
locking angle of the planet vary for different parameters, the main result,
which is the planet-vortex locking, remains valid. We discovered that even a
planet with a mass less than 5 * 10^{-7} M_{\star} comes out from the vortex
and is locked to it at the same orbital distance. For a stronger vortex, both
in non-self-gravitated and self-gravitating models, the planet migration is
stopped far away from the radial position of the vortex. This effect can make
the vortices a suitable place for continual planet formation under the
condition that they save their shape during the planetary growth.Comment: 13 pages, 21 figures,Accepted to be published in A&
A Multi-Wavelength Analysis of Dust and Gas in the SR 24S Transition Disk
We present new Atacama Large Millimeter/sub-millimeter Array (ALMA) 1.3 mm
continuum observations of the SR 24S transition disk with an angular resolution
(12 au radius). We perform a multi-wavelength investigation by
combining new data with previous ALMA data at 0.45 mm. The visibilities and
images of the continuum emission at the two wavelengths are well characterized
by a ring-like emission. Visibility modeling finds that the ring-like emission
is narrower at longer wavelengths, in good agreement with models of dust
trapping in pressure bumps, although there are complex residuals that suggest
potentially asymmetric structures. The 0.45 mm emission has a shallower profile
inside the central cavity than the 1.3 mm emission. In addition, we find that
the CO and CO (J=2-1) emission peaks at the center of the
continuum cavity. We do not detect either continuum or gas emission from the
northern companion to this system (SR 24N), which is itself a binary system.
The upper limit for the dust disk mass of SR 24N is , which gives a disk mass ratio in dust between the two
components of . The current ALMA observations may imply that either
planets have already formed in the SR 24N disk or that dust growth to mm-sizes
is inhibited there and that only warm gas, as seen by ro-vibrational CO
emission inside the truncation radii of the binary, is present.Comment: Accepted for publication in Ap
TOI-1130: A photodynamical analysis of a hot Jupiter in resonance with an inner low-mass planet
The TOI-1130 is a known planetary system around a K-dwarf consisting of a gas giant planet, TOI-1130 c on an 8.4-day orbit that is accompanied by an inner Neptune-sized planet, TOI-1130 b, with an orbital period of 4.1 days. We collected precise radial velocity (RV) measurements of TOI-1130 with the HARPS and PFS spectrographs as part of our ongoing RV follow-up program. We performed a photodynamical modeling of the HARPS and PFS RVs, along with transit photometry from the Transiting Exoplanet Survey Satellite (TESS) and the TESS Follow-up Observing Program (TFOP). We determined the planet masses and radii of TOI-1130 b and TOI-1130 c to be Mb = 19.28 ± 0.97Mâ and Rb = 3.56 ± 0.13 Râ, and Mc = 325.59 ± 5.59Mâ and Rc = 13.32-1.41+1.55 Râ, respectively. We have spectroscopically confirmed the existence of TOI-1130 b, which had previously only been validated. We find that the two planets have orbits with small eccentricities in a 2:1 resonant configuration. This is the first known system with a hot Jupiter and an inner lower mass planet locked in a mean-motion resonance. TOI-1130 belongs to the small, yet growing population of hot Jupiters with an inner low-mass planet that poses a challenge to the pathway scenario for hot Jupiter formation. We also detected a linear RV trend that is possibly due to the presence of an outer massive companion
TOI-1130: A photodynamical analysis of a hot Jupiter in resonance with an inner low-mass planet
The TOI-1130 is a known planetary system around a K-dwarf consisting of a gas
giant planet, TOI-1130 c, on an 8.4-day orbit, accompanied by an inner
Neptune-sized planet, TOI-1130 b, with an orbital period of 4.1 days. We
collected precise radial velocity (RV) measurements of TOI-1130 with the HARPS
and PFS spectrographs as part of our ongoing RV follow-up program. We perform a
photodynamical modeling of the HARPS and PFS RVs, and transit photometry from
the Transiting Exoplanet Survey Satellite (TESS) and the TESS Follow-up
Observing Program. We determine the planet masses and radii of TOI-1130 b and
TOI-1130 c to be Mb = 19.28 0.97 M and Rb = 3.56 0.13
R, and Mc = 325.59 5.59 M and Rc = 13.32+1.55-1.41
R, respectively. We spectroscopically confirm TOI-1130 b that was
previously only validated. We find that the two planets orbit with small
eccentricities in a 2:1 resonant configuration. This is the first known system
with a hot Jupiter and an inner lower mass planet locked in a mean-motion
resonance. TOI-1130 belongs to the small yet increasing population of hot
Jupiters with an inner low-mass planet that challenges the pathway for hot
Jupiter formation. We also detect a linear RV trend possibly due to the
presence of an outer massive companion.Comment: 19 pages, Accepted to A&
TOI-1130: A photodynamical analysis of a hot Jupiter in resonance with an inner low-mass planet
The TOI-1130 is a known planetary system around a K-dwarf consisting of a gas giant planet, TOI-1130 c on an 8.4-day orbit that is accompanied by an inner Neptune-sized planet, TOI-1130 b, with an orbital period of 4.1 days. We collected precise radial velocity (RV) measurements of TOI-1130 with the HARPS and PFS spectrographs as part of our ongoing RV follow-up program. We performed a photodynamical modeling of the HARPS and PFS RVs, along with transit photometry from the Transiting Exoplanet Survey Satellite (TESS) and the TESS Follow-up Observing Program (TFOP). We determined the planet masses and radii of TOI-1130 b and TOI-1130 c to be Mb = 19.28 \ub1 0.97Mâ and Rb = 3.56 \ub1 0.13 Râ, and Mc = 325.59 \ub1 5.59Mâ and Rc = 13.32-1.41+1.55 Râ, respectively. We have spectroscopically confirmed the existence of TOI-1130 b, which had previously only been validated. We find that the two planets have orbits with small eccentricities in a 2:1 resonant configuration. This is the first known system with a hot Jupiter and an inner lower mass planet locked in a mean-motion resonance. TOI-1130 belongs to the small, yet growing population of hot Jupiters with an inner low-mass planet that poses a challenge to the pathway scenario for hot Jupiter formation. We also detected a linear RV trend that is possibly due to the presence of an outer massive companion
The impact of planet wakes on the location and shape of the water ice line in a protoplanetary disk
International audienc
How much does turbulence change the pebble isolation mass for planet formation?
Context. When a planet becomes massive enough, it gradually carves a partial gap around its orbit in the protoplanetary disk. A pressure maximum can be formed outside the gap where solids that are loosely coupled to the gas, typically in the pebble size range, can be trapped. The minimum planet mass for building such a trap, which is called the pebble isolation mass (PIM), is important for two reasons: it marks the end of planetary growth by pebble accretion, and the trapped dust forms a ring that may be observed with millimetre observations.
Aims. We study the effect of disk turbulence on the PIM and find its dependence on the gas turbulent viscosity, aspect ratio, and particles Stokes number.
Methods. By means of 2D gas hydrodynamical simulations, we found the minimum planet mass to form a radial pressure maximum beyond the orbit of the planet, which is the necessary condition to trap pebbles. We then carried out 2D gas plus dust hydrodynamical simulations to examine how dust turbulent diffusion impacts particles trapping at the pressure maximum. We finally provide a semi-analytical calculation of the PIM based on comparing the radial drift velocity of solids and the root mean square turbulent velocity fluctuations around the pressure maximum.
Results. From our results of gas simulations, we provide an expression for the PIM vs. disk aspect ratio and turbulent viscosity. Our gas plus dust simulations show that the effective PIM can be nearly an order of magnitude larger in high-viscosity disks because turbulence diffuse particles out of the pressure maximum. This is quantified by our semi-analytical calculation, which gives an explicit dependence of the PIM with Stokes number of particles.
Conclusions. Disk turbulence can significantly alter the PIM, depending on the level of turbulence in regions of planet formation
Effect of levamisole in steroid-dependent nephrotic syndrome
Introduction. Childhood idiopathic nephrotic syndrome is characterized by frequent relapsing courses or steroid dependency. Levamisole is a popular drug for treatment of these patients. The purpose of this study was to evaluate levamisole in children with steroid-dependent nephrotic syndrome. Materials and Methods. We retrospectively studied 304 children with a diagnosis of steroid-dependent nephrotic syndrome or frequently relapsing nephrotic syndrome. The mean age at the time of diagnosis was 4.84 years. Following induction of complete remission with steroid therapy based on the International Study of Kidney Disease in Children's protocol and when they were taking alternative days of steroid, 2.5 mg/kg of levamisole was administered. Results. The steroid dose was significantly decreased (mean reduction of 0.39 ñ 0.46 g to 0.33 ñ 0.38 g) after treatment with levamisole (P <.001). The number of relapses also significantly decreased (mean reduction of 0.92 ñ 0.98 episodes to 1.07 ñ 1.20 relapses per year; P <.001). The 14.5-month administration of levamizole had a sensitivity of 67.5 and a specificity of 71.9 to reach a dose reduction of more than 50 in steroid therapy. The duration of levamizole treatment was associated with more than 50 reduction in the number of relapses (P <.001). A 14.5-month treatment with levamizole had a sensitivity of 62.3 and a specificity of 63.6 to reach a relapse reduction of more than 50. Conclusions. Levamisole appears to be effective in prolonging the duration of remission and decreasing the steroid dose in children with steroid-dependent nephrotic syndrome