Variable dynamics in the inner disk of HD 135344B revealed with multi-epoch scattered light imaging

Variable dynamics in the inner disk of HD 135344B revealed with multi-epoch scattered light imaging

 

Authors:

Stolker et al

Abstract:

We present multi-epoch VLT/SPHERE observations of the protoplanetary disk around HD 135344B (SAO 206462). The J-band scattered light imagery reveal, with high spatial resolution (∼41 mas, 6.4 au), the disk surface beyond ∼20 au. Temporal variations are identified in the azimuthal brightness distributions of all epochs, presumably related to the asymmetrically shading dust distribution in the inner disk. These shadows manifest themselves as narrow lanes, cast by localized density enhancements, and broader features which possibly trace the larger scale dynamics of the inner disk. We acquired visible and near-infrared photometry which shows variations up to 10% in the JHK bands, possibly correlated with the presence of the shadows. Analysis of archival VLTI/PIONIER H-band visibilities constrain the orientation of the inner disk to i=18.2deg+3.4−4.1 and PA=57.3deg±5.7deg, consistent with an alignment with the outer disk or a minor disk warp of several degrees. The latter scenario could explain the broad, quasi-stationary shadowing in N-NW direction in case the inclination of the outer disk is slightly larger. The correlation between the shadowing and the near-infrared excess is quantified with a grid of radiative transfer models. The variability of the scattered light contrast requires extended variations in the inner disk atmosphere (H/r≲0.2). Possible mechanisms that may cause asymmetric variations in the optical depth (Δτ≲1) through the atmosphere of the inner disk include turbulent fluctuations, planetesimal collisions, or a dusty disk wind, possibly enhanced by a minor disk warp. A fine temporal sampling is required to follow day-to-day changes of the shadow patterns which may be a face-on variant of the UX Orionis phenomenon.

The Inner Debris Structure in the Fomalhaut Planetary System

The Inner Debris Structure in the Fomalhaut Planetary System

Authors:

Su et al

Abstract:

Fomalhaut plays an important role in the study of debris disks and small bodies in other planetary systems. The proximity and luminosity of the star make key features of its debris, like the water ice-line, accessible. Here we present ALMA cycle 1, 870 \mu m (345 GHz) observations targeted at the inner part of the Fomalhaut system with a synthesized beam of 0.45"x0.37" (~3 AU linear resolution at the distance of Fomalhaut) and a rms of 26 \mu Jy/beam. The high angular resolution and sensitivity of the ALMA data enable us to place strong constraints on the nature of the warm excess revealed by Spitzer and Herschel observations. We detect a point source at the star position with a total flux consistent with thermal emission from the stellar photosphere. No structures that are brighter than 3\sigma\ are detected in the central 15 AU x 15 AU region. Modeling the spectral energy distribution using parameters expected for a dust-producing planetesimal belt indicates a radial location in the range ~8-15 AU. This is consistent with the location where ice sublimates in Fomalhaut, i.e., an asteroid-belt analog. The 3\sigma\ upper limit for such a belt is less than 1.3 mJy at 870 \mu m. We also interpret the 2 and 8-13 \mu m interferometric measurements to reveal the structure in the inner 10 AU region as dust naturally connected to this proposed asteroid belt by Poynting-Robertson drag, dust sublimation, and magnetically trapped nano grains.

The Evolution of Inner Disk Gas in Transition Disks

The Evolution of Inner Disk Gas in Transition Disks

Authors:

Hoadley et al

Abstract:

Investigating the molecular gas in the inner regions of protoplanetary disks provides insight into how the molecular disk environment changes during the transition from primordial to debris disk systems. We conduct a small survey of molecular hydrogen (H2) fluorescent emission, using 14 well-studied Classical T Tauri stars at two distinct dust disk evolutionary stages, to explore how the structure of the inner molecular disk changes as the optically thick warm dust dissipates. We simulate the observed HI-Lyman α-pumped H2 disk fluorescence by creating a 2D radiative transfer model that describes the radial distributions of H2 emission in the disk atmosphere and compare these to observations from the Hubble Space Telescope. We find the radial distributions that best describe the observed H2 FUV emission arising in primordial disk targets (full dust disk) are demonstrably different than those of transition disks (little-to-no warm dust observed). For each best-fit model, we estimate inner and outer disk emission boundaries (rin and rout), describing where the bulk of the observed H2 emission arises in each disk, and we examine correlations between these and several observational disk evolution indicators, such as n13−31, rin,CO, and the mass accretion rate. We find strong, positive correlations between the H2 radial distributions and the slope of the dust SED, implying the behavior of the molecular disk atmosphere changes as the inner dust clears in evolving protoplanetary disks. Overall, we find that H2 inner radii are ∼4 times larger in transition systems, while the bulk of the H2 emission originates inside the dust gap radius for all transitional sources.

Studying the Inner Protoplanetary Disk (sub AU) of HD 85567

Study of the sub-AU disk of the Herbig B[e] star HD 85567 with near-infrared interferometry

Authors:

Vural et al

Abstract:

Context:

The structure of the inner disk of Herbig Be stars is not well understood. The continuum disks of several Herbig Be stars have inner radii that are smaller than predicted by models of irradiated disks with optically thin holes.

Aims:

We study the size of the inner disk of the Herbig B[e] star HD 85567 and compare the model radii with the radius suggested by the size-luminosity relation.

Methods:

The object was observed with the AMBER instrument of the Very Large Telescope Interferometer. We obtained K-band visibilities and closure phases. These measurements are interpreted with geometric models and temperature-gradient models.

Results:

Using several types of geometric star-disk and star-disk-halo models, we derived inner ring-fit radii in the K band that are in the range of 0.8 - 1.6 AU. Additional temperature-gradient modeling resulted in an extended disk with an inner radius of 0.67+0.51−0.21 AU, a high inner temperature of 2200+750−350 K, and a disk inclination of 53+15−11∘.

Conclusions:

The derived geometric ring-fit radii are approximately 3 - 5 times smaller than that predicted by the size-luminosity relation. The small geometric and temperature-gradient radii suggest optically thick gaseous material that absorbs stellar radiation inside the dust disk.