25 research outputs found
Three-dimensional Global Simulations of Type-II Planet-disk Interaction with a Magnetized Disk Wind: I. Magnetic Flux Concentration and Gap Properties
Giant planets embedded in protoplanetary disks (PPDs) can create annulus
density gaps around their orbits in the type-II regime, potentially responsible
for the ubiquity of annular substructures observed in PPDs. Despite of
substantial amount of works studying type-II planet migration and gap
properties, they are almost exclusively conducted under the viscous accretion
disk framework. However, recent studies have established magnetized disk winds
as the primary driving disk accretion and evolution, which can co-exist with
turbulence from the magneto-rotational instability (MRI) in the outer PPDs. We
conduct a series of 3D global non-ideal magneto-hydrodynamic (MHD) simulations
of type-II planet-disk interaction applicable to the outer PPDs. Our
simulations properly resolve the MRI turbulence and accommodate the MHD disk
wind. We found that the planet triggers the poloidal magnetic flux
concentration around its orbit. The concentrated magnetic flux strongly
enhances angular momentum removal in the gap, which is along the inclined
poloidal field through a strong outflow emanating from the disk surface outward
of the planet gap. The resulting planet-induced gap shape is more similar to an
inviscid disk, while being much deeper, which can be understood from a simple
inhomogeneous wind torque prescription. The corotation region is characterized
by a fast trans-sonic accretion flow that is asymmetric in azimuth about the
planet and lacking the horseshoe turns, and the meridional flow is weakened.
The torque acting on the planet generally drives inward migration, though the
migration rate can be affected by the presence of neighboring gaps through
stochastic, planet-free magnetic flux concentration.Comment: 42 pages, 24 figures, Accepted for publication in the Astrophysical
Journa
Comparison of Planetary Hα-emission Models: A New Correlation with Accretion Luminosity
Accreting planets have been detected through their hydrogen-line emission, specifically Hα. To interpret this, stellar-regime empirical correlations between the Hα luminosity LHα and the accretion luminosity Lacc or accretion rate have been extrapolated to planetary masses, however without validation. We present a theoretical Lacc–LHα relationship applicable to a shock at the surface of a planet. We consider wide ranges of accretion rates and masses and use detailed spectrally resolved, nonequilibrium models of the postshock cooling. The new relationship gives a markedly higher Lacc for a given LHα than fits to young stellar objects, because Lyα, which is not observable, carries a large fraction of Lacc. Specifically, an LHα measurement needs 10 to 100 times higher Lacc and than previously predicted, which may explain the rarity of planetary Hα detections. We also compare the –LHα relationships coming from the planet-surface shock or implied by accretion-funnel emission. Both can contribute simultaneously to an observed Hα signal, but at low (high) the planetary-surface shock (heated funnel) dominates. Only the shock produces Gaussian line wings. Finally, we discuss accretion contexts in which different emission scenarios may apply, putting recent literature models in perspective, and also present Lacc–Lline relationships for several other hydrogen lines
Resolved near-UV hydrogen emission lines at 40-Myr super-Jovian protoplanet Delorme 1 (AB)b: Indications of magnetospheric accretion
We have followed up on our observations of the ~ 40-Myr, and still accreting,
PMC Delorme 1 (AB)b. We used high-resolution spectroscopy to characterise the
accretion process further by accessing the wealth of emission lines in the
near-UV. With VLT/UVES, we obtained R ~ 50000 spectroscopy at 330--452 nm.
After separating the emission of the companion from that of the M5 low-mass
binary, we performed a detailed emission-line analysis, which included
planetary accretion shock modelling. We reaffirm ongoing accretion in Delorme 1
(AB)b and report the first detections in a (super-Jovian) protoplanet of
resolved hydrogen line emission in the near-UV (H-gamma, H-delta, H-epsilon, H8
and H9). We tentatively detect H11, H12, He I and Ca II H/K. The analysis
strongly favours a planetary accretion shock with a line-luminosity-based
accretion rate dMp/dt = 2e-8 MJ/yr. The lines are asymmetric and well described
by sums of narrow and broad components with different velocity shifts. Overall
line shapes are best explained by a pre-shock velocity v0 = 170+-30 km/s,
implying a planetary mass Mp = 13+-5 MJ, and number densities n0 ~ 1e13/cc or
n0 ~ 1e11/cc. The higher density implies a small line-emitting area of ~ 1%
relative to the planetary surface. This favours magnetospheric accretion, a
case potentially strengthened by the presence of blueshifted emission in the
asymmetrical profiles.High-resolution spectroscopy offers the opportunity to
resolve line profiles, crucial for studying the accretion process in depth. The
super-Jovian protoplanet Delorme 1 (AB)b is still accreting at ~ 40 Myr. Thus,
Delorme 1 belongs to the growing family of Peter Pan disc systems with
protoplanetary and/or circumplanetary disc(s) far beyond the typically assumed
disc lifetimes. Further observations of this benchmark companion, and its
presumed disc(s), will help answer key questions about the accretion geometry
in PMCs.Comment: Published in A&A 669, L12, 11 pages, abbreviated abstrac
Constraining PDS 70b’s Formation Mechanism with Multi-hydrogen-emission Observations
We present our Keck/OSIRIS observations of the Paβ emission line (1.282 μm) to investigate accretion mechanisms of PDS 70 planetary system. Our spectral differential imaging reduction to remove the stellar PSF resulted in null detection of Paβ at the locations of PDS 70b and c. The 5σ detection limit of Paβ compared with the theoretical model of Aoyama & Ikoma (2019) indicates the gas velocity onto PDS 70b is smaller than 70 km s⁻¹, which suggests MUSE-based Hα studies overestimated the gas velocity and the mass of PDS 70b