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Grady C.,Eureka Scientific and Goddard Space Flight Center | Fukagawa M.,Osaka University | Maruta Y.,Osaka University | Ohta Y.,Osaka University | And 59 more authors.
Astrophysics and Space Science | Year: 2015

Spatially-resolved imaging of Herbig stars and related objects began with HST, but intensified with commissioning of high-contrast imagers on 8-m class telescopes. The bulk of the data taken from the ground have been polarized intensity imagery at H-band, with the majority of the sources observed as part of the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) survey. Sufficiently many systems have been imaged that we discuss disk properties in scattered, polarized light in terms of groups defined by the IR spectral energy distribution. We find novel phenomena in many of the disks, including spiral density waves, and discuss the disks in terms of clearing mechanisms. Some of the disks have sufficient data to map the dust and gas components, including water ice dissociation products. © 2014, Springer Science+Business Media Dordrecht.

Janson M.,University of Toronto | Carson J.,College of Charleston | Thalmann C.,Max Planck Institute for Astronomy | McElwain M.W.,Princeton University | And 47 more authors.
Astrophysical Journal | Year: 2011

GJ 758 B is a cold (∼600 K) companion to a Sun-like star at 29 AU projected separation, which was recently detected with high-contrast imaging. Here, we present photometry of the companion in seven photometric bands from Subaru/HiCIAO, Gemini/NIRI, and Keck/NIRC2, providing a rich sampling of the spectral energy distribution in the 1-5 μm wavelength range. A clear detection at 1.58 μm combined with an upper limit at 1.69 μm shows methane absorption in the atmosphere of the companion. The mass of the companion remains uncertain, but an updated age estimate indicates that the most likely mass range is ∼30-40 Mjup. In addition, we present an updated astrometric analysis that imposes tighter constraints on GJ 758 B's orbit and identifies the proposed second candidate companion, "GJ 758 C," as a background star. © 2011. The American Astronomical Society. All rights reserved. Printedin the U.S.A.

Hashimoto J.,Japan National Astronomical Observatory | Tamura M.,Japan National Astronomical Observatory | Muto T.,Tokyo Institute of Technology | Kudo T.,Subaru Telescope | And 51 more authors.
Astrophysical Journal Letters | Year: 2011

We report high-resolution 1.6 μm polarized intensity (PI) images of the circumstellar disk around the Herbig Ae star AB Aur at a radial distance of 22 AU (015) up to 554 AU (385), which have been obtained by the high-contrast instrument HiCIAO with the dual-beam polarimetry. We revealed complicated and asymmetrical structures in the inner part (≲140 AU) of the disk while confirming the previously reported outer (r ≳ 200 AU) spiral structure. We have imaged a double ring structure at 40 and 100 AU and a ring-like gap between the two. We found a significant discrepancy of inclination angles between two rings, which may indicate that the disk of AB Aur is warped. Furthermore, we found seven dips (the typical size is 45 AU or less) within two rings, as well as three prominent PI peaks at 40 AU. The observed structures, including a bumpy double ring, a ring-like gap, and a warped disk in the innermost regions, provide essential information for understanding the formation mechanism of recently detected wide-orbit (r > 20 AU) planets. © 2011. The American Astronomical Society. All rights reserved.

Benisty M.,University Grenoble Alpes | Juhasz A.,French National Center for Scientific Research | Boccaletti A.,Institute of Astronomy | Avenhaus H.,University Pierre and Marie Curie | And 29 more authors.
Astronomy and Astrophysics | Year: 2015

Context. The study of dynamical processes in protoplanetary disks is essential to understand planet formation. In this context, transition disks are prime targets because they are at an advanced stage of disk clearing and may harbor direct signatures of disk evolution. Aims. We aim to derive new constraints on the structure of the transition disk MWC 758, to detect non-axisymmetric features and understand their origin. Methods. We obtained infrared polarized intensity observations of the protoplanetary disk MWC 758 with VLT/SPHERE at 1.04 μm to resolve scattered light at a smaller inner working angle (0.093′′) and a higher angular resolution (0.027′′) than previously achieved. Results. We observe polarized scattered light within 0.53′′ (148 au) down to the inner working angle (26 au) and detect distinct non-axisymmetric features but no fully depleted cavity. The two small-scale spiral features that were previously detected with HiCIAO are resolved more clearly, and new features are identified, including two that are located at previously inaccessible radii close to the star. We present a model based on the spiral density wave theory with two planetary companions in circular orbits. The best model requires a high disk aspect ratio (H/r ~ 0.20 at the planet locations) to account for the large pitch angles which implies a very warm disk. Conclusions. Our observations reveal the complex morphology of the disk MWC 758. To understand the origin of the detected features, the combination of high-resolution observations in the submillimeter with ALMA and detailed modeling is needed. © ESO, 2015.

Thalmann C.,Max Planck Institute for Astronomy | Grady C.A.,Eureka Scientific and Goddard Space Flight Center | Goto M.,Max Planck Institute for Astronomy | Wisniewski J.P.,University of Washington | And 51 more authors.
Astrophysical Journal Letters | Year: 2010

We present H- and Ks-band imaging data resolving the gap in the transitional disk around LkCa 15, revealing the surrounding nebulosity. We detect sharp elliptical contours delimiting the nebulosity on the inside as well as the outside, consistent with the shape, size, ellipticity, and orientation of starlight reflected from the far-side disk wall, whereas the near-side wall is shielded from view by the disk's optically thick bulk. We note that forward scattering of starlight on the near-side disk surface could provide an alternate interpretation of the nebulosity. In either case, this discovery provides confirmation of the disk geometry that has been proposed to explain the spectral energy distributions of such systems, comprising an optically thick disk with an inner truncation radius of ∼46 AU enclosing a largely evacuated gap. Our data show an offset of the nebulosity contours along the major axis, likely corresponding to a physical pericenter offset of the disk gap. This reinforces the leading theory that dynamical clearing by at least one orbiting body is the cause of the gap. Based on evolutionary models, our high-contrast imagery imposes an upper limit of 21MJup on companions at separations outside of 0. ″1 and of 13MJup outside of 0. ′2. Thus, we find that a planetary system around LkCa 15 is the most likely explanation for the disk architecture. © 2010. The American Astronomical Society.

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