The architecture of the LkCa 15 transitional disk revealed by high-contrast imaging

Abstract

We present four new epochs of K s -band images of the young pre-transitional disk around LkCa 15 and perform extensive forward modeling to derive the physical parameters of the disk. We find indications of strongly anisotropic scattering (Henyey-Greenstein g = 0.67 +0.18 −0.11 ) and a significantly tapered gap edge ("round wall") but see no evidence that the inner disk, whose existence is predicted by the spectral energy distribution, shadows the outer regions of the disk visible in our images. We marginally confirm the existence of an offset between the disk center and the star along the line of nodes; however, the magnitude of this offset (x = 27 +19 −20 mas) is notably lower than that found in our earlier H-band images. Intriguingly, we also find an offset of y = 69 +49 −25 mas perpendicular to the line of nodes at high significance. If confirmed by future observations, this would imply a highly elliptical -or otherwise asymmetric -disk gap with an effective eccentricity of e ≈ 0.3. Such asymmetry would most likely be the result of dynamical sculpting by one or more unseen planets in the system. Finally, we find that the bright arc of scattered light we see in direct imaging observations originates from the near side of the disk and appears brighter than the far side because of strong forward scattering.

Near-infrared imaging polarimetry of LkCa 15: A possible warped inner disk

“…The inclinations of the two disks are similar (∼44 • ), but that of the gap shows larger angle (∼52 • ). Note that Thalmann et al (2014) reported eccentricities from the shape of the gap associated with LkCa 15, thus the inclination based on the ellipse fit only could be biased. Figure 3 shows the radial surface brightness profiles on the major and minor axes with a power-law fit at each slope.…”

The Matryoshka Disk: Keck/Nirc2 Discovery of a Solar-System-Scale, Radially Segregated Residual Protoplanetary Disk Around Hd 141569a

“…From inspection, the disk signal and its self-subtraction footprints, not residual speckles, dominate the pixels at r ∼0 27-0 55, thereby biasing the estimate of the noise profile and yielding an underestimated disk SNRE (see also Thalmann et al 2014;Currie et al 2015a). Masking a rectangular "evaluation region" with dimensions 0 54 by 1 08 centered on the star and defining the radial noise profile from pixels outside this region, we derive a disk SNRE in the Keck image to ∼8-10 at most separations.…”

“…To identify the best-fitting disk models, we closely follow the methods from Thalmann et al (2014). Briefly, we bin down the Keck image, the model image, and the noise profile to the Keck/NIRC2 spatial resolution to compare the data and model at effectively independent data points and compute 2 c from the residuals of the binned image over the angular separation where the disk detection is significant and negligibly contaminated by residual speckles (r ∼ 0 27-0 55).…”

Very deep images of the innermost regions of theβPictoris debris disc atL′

“…iterations as in Lagrange et al (2012a) in order to obtain images that have the least biases from ADI; 2. forward modelling to constrain the dust density distribution as in Thalmann et al (2014), presented in Sect. 4.2; and 3. injection of model discs in the data to calibrate the morphological parameters measured in the images, as in Boccaletti et al (2012).…”

“…The merit function is a reduced chi squared computed in the part of the image where the disc is detected 3 . Thalmann et al (2014) used this forward modelling approach as well to study the disc of LkCa 15.…”