Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userCircumplanetary disk or circumplanetary envelope?
68
0
0.0
(
0
)
Added by
Judit Szul\\'agyi Dr.
Publication date
2016
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We present three-dimensional simulations with nested meshes of the dynamics of the gas around a Jupiter mass planet with the JUPITER and FARGOCA codes. We implemented a radiative transfer module into the JUPITER code to account for realistic heating and cooling of the gas. We focus on the circumplanetary gas flow, determining its characteristics at very high resolution ($80%$ of Jupiters diameter). In our nominal simulation where the temperature evolves freely by the radiative module and reaches 13000 K at the planet, a circumplanetary envelope was formed filling the entire Roche-lobe. Because of our equation of state is simplified and probably overestimates the temperature, we also performed simulations with limited maximal temperatures in the planet region (1000 K, 1500 K, and 2000 K). In these fixed temperature cases circumplanetary disks (CPDs) were formed. This suggests that the capability to form a circumplanetary disk is not simply linked to the mass of the planet and its ability to open a gap. Instead, the gas temperature at the planets location, which depends on its accretion history, plays also fundamental role. The CPDs in the simulations are hot and cooling very slowly, they have very steep temperature and density profiles, and are strongly sub-Keplerian. Moreover, the CPDs are fed by a strong vertical influx, which shocks on the CPD surfaces creating a hot and luminous shock-front. In contrast, the pressure supported circumplanetary envelope is characterized by internal convection and almost stalled rotation.
rate research
Read More
PDS70 is a unique system in which two protoplanets, PDS70b and c, have been discovered within the dust-depleted cavity of their disk, at $sim$22 and 34au respectively, by direct imaging at infrared wavelengths. Subsequent detection of the planets in the H$alpha$ line indicates that they are still accreting material through circumplanetary disks. In this Letter, we present new Atacama Large Millimeter/submillimeter Array (ALMA) observations of the dust continuum emission at 855$mu$m at high angular resolution ($sim$20mas, 2.3au) that aim to resolve the circumplanetary disks and constrain their dust masses. Our observations confirm the presence of a compact source of emission co-located with PDS70c, spatially separated from the circumstellar disk and less extended than $sim$1.2au in radius, a value close to the expected truncation radius of the cicumplanetary disk at a third of the Hill radius. The emission around PDS70c has a peak intensity of $sim$86$pm$16 $mu mathrm{Jy}~mathrm{beam}^{-1}$ which corresponds to a dust mass of $sim$0.031M$_{oplus}$ or $sim$0.007M$_{oplus}$, assuming that it is only constituted of 1 $mu$m or 1 mm sized grains, respectively. We also detect extended, low surface brightness continuum emission within the cavity near PDS70b. We observe an optically thin inner disk within 18au of the star with an emission that could result from small micron-sized grains transported from the outer disk through the orbits of b and c. In addition, we find that the outer disk resolves into a narrow and bright ring with a faint inner shoulder.
Large dips in the brightness for a number of stars have been observed, for which the tentative explanation is occultation of the star by a transiting circumplanetary disk or ring system. In order for the circumplanetary disk/rings to block the host stars light, the disk must be tilted out of the planets orbital plane, which poses stability problems due to the radial extent of the disk required to explain the brightness dip durations. This work uses N-body integrations to study the structure and stability of circumplanetary disk/ring systems tilted out of the planets orbital plane by the spinning planets mass quadrupole. Simulating the disk as a collection of test particles with orbits initialized near the Laplace surface (equilibrium between tidal force from host star and force from planets mass quadrupole), we find that many extended, inclined circumplanetary disks remain stable over the duration of the integrations (~3-16 Myr). Two dynamical resonances/instabilities excite the particle eccentricities and inclinations: the Lidov-Kozai effect which occurs in the disks outer regions, and ivection resonance which occurs in the disks inner regions. Our work places constraints on the maximum radial extent of inclined circumplanetary disk/ring systems, and shows that gaps present in circumplanetary disks do not necessarily imply the presence of exomoons.
We present the first observational evidence for a circumplanetary disk around the protoplanet PDS~70~b, based on a new spectrum in the $K$ band acquired with VLT/SINFONI. We tested three hypotheses to explain the spectrum: Atmospheric emission from the planet with either (1) a single value of extinction or (2) variable extinction, and (3) a combined atmospheric and circumplanetary disk model. Goodness-of-fit indicators favour the third option, suggesting circumplanetary material contributing excess thermal emission --- most prominent at $lambda gtrsim 2.3 mu$m. Inferred accretion rates ($sim 10^{-7.8}$--$10^{-7.3} M_J$ yr$^{-1}$) are compatible with observational constraints based on the H$alpha$ and Br$gamma$ lines. For the planet, we derive an effective temperature of 1500--1600 K, surface gravity $log(g)sim 4.0$, radius $sim 1.6 R_J$, mass $sim 10 M_J$, and possible thick clouds. Models with variable extinction lead to slightly worse fits. However, the amplitude ($Delta A_V gtrsim 3$mag) and timescale of variation ($lesssim$~years) required for the extinction would also suggest circumplanetary material.
I calculate the spectral energy distributions (SEDs) of accreting circumplanetary disks using atmospheric radiative transfer models. Circumplanetary disks only accreting at $10^{-10} M_{odot} yr^{-1}$ around a 1 M$_{J}$ planet can be brighter than the planet itself. A moderately accreting circumplanetary disk ($dot{M}sim 10^{-8}M_{odot} yr^{-1}$; enough to form a 10 M$_{J}$ planet within 1 Myr) around a 1 M$_{J}$ planet has a maximum temperature of $sim$2000 K, and at near-infrared wavelengths ($J$, $H$, $K$ bands), this disk is as bright as a late M-type brown dwarf or a 10 M$_{J}$ planet with a hot start. To use direct imaging to find the accretion disks around low mass planets (e.g., 1 M$_{J}$) and distinguish them from brown dwarfs or hot high mass planets, it is crucial to obtain photometry at mid-infrared bands ($L$, $M$, $N$ bands) because the emission from circumplanetary disks falls off more slowly towards longer wavelengths than those of brown dwarfs or planets. If young planets have strong magnetic fields ($gtrsim$100 G), fields may truncate slowly accreting circumplanetary disks ($dot{M}lesssim10^{-9} M_{odot} yr^{-1}$) and lead to magnetospheric accretion, which can provide additional accretion signatures, such as UV/optical excess from the accretion shock and line emission.
We present Karl G. Jansky Very Large Array (VLA) observations of the 7 mm continuum emission from the disk surrounding the young star LkCa 15. The observations achieve an angular resolution of 70 mas and spatially resolve the circumstellar emission on a spatial scale of 9 AU. The continuum emission traces a dusty annulus of 45 AU in radius that is consistent with the dust morphology observed at shorter wavelengths. The VLA observations also reveal a compact source at the center of the disk, possibly due to thermal emission from hot dust or ionized gas located within a few AU from the central star. No emission is observed between the star and the dusty ring, and, in particular, at the position of the candidate protoplanet LkCa 15 b. By comparing the observations with theoretical models for circumplanetary disk emission, we find that if LkCa~15~b is a massive planet (>5 M_J) accreting at a rate greater than 1.e-6 M_J yr^{-1}, then its circumplanetary disk is less massive than 0.1 M_J, or smaller than 0.4 Hill radii. Similar constraints are derived for any possible circumplanetary disk orbiting within 45 AU from the central star. The mass estimate are uncertain by at least one order of magnitude due to the uncertainties on the mass opacity. Future ALMA observations of this system might be able to detect circumplanetary disks down to a mass of 5.e-4 M_J and as small as 0.2 AU, providing crucial constraints on the presence of giant planets in the act of forming around this young star.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
