Hunting for the Exoplanets in HD 100546's Protoplanetary Disk

The SPHERE view of the planet-forming disk around HD100546

Authors:

Garufi et al

Abstract:

We image with unprecedented spatial resolution and sensitivity disk features that could be potential signs of planet-disk interaction. Two companion candidates have been claimed in the disk around the young Herbig Ae/Be star HD100546. Thus, this object serves as an excellent target for our investigation of the natal environment of giant planets. We exploit the power of extreme adaptive optics operating in conjunction with the new high-contrast imager SPHERE to image HD100546 in scattered light. We obtain the first polarized light observations of this source in the visible (with resolution as fine as 2 AU) and new H and K band total intensity images that we analyze with the Pynpoint package. The disk shows a complex azimuthal morphology, where multiple scattering of photons most likely plays an important role. High brightness contrasts and arm-like structures are ubiquitous in the disk. A double-wing structure (partly due to ADI processing) resembles a morphology newly observed in inclined disks. Given the cavity size in the visible (11 AU), the CO emission associated to the planet candidate 'c' might arise from within the circumstellar disk. We find an extended emission in the K band at the expected location of 'b'. The surrounding large-scale region is the brightest in scattered light. There is no sign of any disk gap associated to 'b'.

HD 100546b is a SuperJovian and HD 100546c is a SuperJovian at 13 AU

Resolving the HD 100546 Protoplanetary System with the Gemini Planet Imager: Evidence for Multiple Forming, Accreting Planets

Authors:

Currie et al

Abstract:

We report Gemini Planet Imager H band high-contrast imaging/integral field spectroscopy and polarimetry of the HD 100546, a 10 Myr-old early-type star recently confirmed to host a thermal infrared bright (super)jovian protoplanet at wide separation, HD 100546 b. We resolve the inner disk cavity in polarized light, recover the thermal-infrared (IR) bright arm, and identify one additional spiral arm. We easily recover HD 100546 b and show that much of its emission originates an unresolved, point source. HD 100546 b likely has extremely red infrared colors compared to field brown dwarfs, qualitatively similar to young cloudy superjovian planets, however, these colors may instead indicate that HD 100546 b is still accreting material from a circumplanetary disk. Additionally, we identify a second point source-like peak at rproj ∼ 13 AU, located just interior to or at inner disk wall consistent with being a 10--20 MJ candidate second protoplanet-- "HD 100546 c" -- and lying within a weakly polarized region of the disk but along an extension of the thermal IR bright spiral arm. Alternatively, it is equally plausible that this feature is a weakly polarized but locally bright region of the inner disk wall. Astrometric monitoring of this feature over the next 2 years and emission line measurements could confirm its status as a protoplanet, rotating disk hot spot that is possibly a signpost of a protoplanet, or a stationary emission source from within the disk.

Are the gas Giants in HD 100546's Protoplanetary Disk Forming Sequentially?

Sequential planet formation in the HD 100546 protoplanetary disk?

Authors:

Pinilla et al

Abstract:

Context.

The disk around the Herbig Ae star, HD 100546, shows structures that suggest the presence of two companions in the disk at ∼10 and ∼70 AU. The outer companion seems to be in the act of formation.

Aims.

Our aims are to provide constraints on the age of the planets in HD 100546 and to explore the potential evidence for sequential planet formation in transition disks such as HD 100546.

Methods.

We compare the recent resolved continuum observations of the disk around HD 100546 with the results of dust evolution simulations using an analytical prescription for the shapes of gaps carved by massive planets.

Results.

An inner pressure bump must have been present since early in the disk lifetime to have good agreement between the dust evolution models and the continuum observations of HD 100546. This pressure bump may have resulted from the presence of a very massive planet (∼20MJup), which formed early in the inner disk (r∼10 AU). If only this single planet exists, the disk is likely to be old, comparable to the stellar age (∼5-10 Myr). Another possible explanation is an additional massive planet in the outer disk (r∼70 AU): either a low-mass outer planet (≲5MJup) injected at early times, or a higher mass outer planet (≳15MJup) formed very recently, traps the right amount of dust in pressure bumps to reproduce the observations. In the latter case, the disk could be much younger (∼3.0 Myr).

Conclusions.

In the case in which two massive companions are embedded in the disk around HD 100546, as suggested in the literature, the outer companion could be at least ≳2.5 Myr younger than the inner companion.

Protoplanetary Disks Including Radiative Feedback From Accreting Exoplanets

Protoplanetary disks including radiative feedback from accreting planets

Authors:

Montesinos et al

Abstract:

While recent observational progress is converging on the detection of compact regions of thermal emission due to embedded protoplanets, further theoretical predictions are needed to understand the response of a protoplanetary disk to the planet formation radiative feedback. This is particularly important to make predictions for the observability of circumplanetary regions. In this work we use 2D hydrodynamical simulations to examine the evolution of a viscous protoplanetary disk in which a luminous Jupiter-mass planet is embedded. We use an energy equation which includes the radiative heating of the planet as an additional mechanism for planet formation feedback. Several models are computed for planet luminosities ranging from 10−5 to 10−3 Solar luminosities. We find that the planet radiative feedback enhances the disk's accretion rate at the planet's orbital radius, producing a hotter and more luminous environement around the planet, independently of the prescription used to model the disk's turbulent viscosity. We also estimate the thermal signature of the planet feedback for our range of planet luminosities, finding that the emitted spectrum of a purely active disk, without passive heating, is appreciably modified in the infrared. We simulate the protoplanetary disk around HD 100546 where a planet companion is located at about 68 au from the star. Assuming the planet mass is 5 Jupiter masses and its luminosity is ∼2.5×10−4L⊙, we find that the radiative feedback of the planet increases the luminosity of its ∼5 au circumplanetary disk from 10−5L⊙ (without feedback) to 10−3L⊙, corresponding to an emission of ∼1mJy in L′ band after radiative transfer calculations, a value that is in good agreement with HD 100546b observations.

HD 100546b: a Protoplanet SuperJovian Gas Giant

Recovery of the Candidate Protoplanet HD 100546 b with Gemini/NICI and Detection of Additional (Planet-Induced?) Disk Structure at Small Separations

Authors:

Currie et al

Abstract:

We report the first independent, second-epoch (re-)detection of a directly-imaged protoplanet candidate. Using L′ high-contrast imaging of HD 100546 taken with the Near-Infrared Coronagraph and Imager (NICI) on Gemini South, we recover `HD 100546 b' with a position and brightness consistent with the original VLT/NaCo detection from Quanz et al, although data obtained after 2013 will be required to decisively demonstrate common proper motion. HD 100546 b may be spatially resolved, up to ≈ 12-13 AU in diameter, and is embedded in a finger of thermal IR bright, polarized emission extending inwards to at least 0.3". Standard hot-start models imply a mass of ≈ 15 MJ. But if HD 100546 b is newly formed or made visible by a circumplanetary disk, both of which are plausible, its mass is significantly lower (e.g. 1--7 MJ). Additionally, we discover a thermal IR-bright disk feature, possibly a spiral density wave, at roughly the same angular separation as HD 100546 b but 90 degrees away. Our interpretation of this feature as a spiral arm is not decisive, but modeling analyses using spiral density wave theory implies a wave launching point exterior to ≈ 0.45" embedded within the visible disk structure: plausibly evidence for a second, hitherto unseen wide-separation planet. With one confirmed protoplanet candidate and evidence for 1--2 others, HD 100546 is an important evolutionary precursor to intermediate-mass stars with multiple super-jovian planets at moderate/wide separations like HR 8799.