Sebastian Egner

Discovery of Small-scale Spiral Structures in the Disk of SAO 206462 (HD 135344B): Implications for the Physical State of the Disk from Spiral Density Wave Theory

We present high-resolution, H-band imaging observations, collected with Subaru/HiCIAO, of the scattered light from the transitional disk around SAO 206462 (HDxa0135344B). Although previous sub-mm imagery suggested the existence of a dust-depleted cavity at r ≤ 46 AU, our observations reveal the presence of scattered light components as close as 02 (~ 28 AU) from the star. Moreover, we have discovered two small-scale spiral structures lying within 05 (~ 70 AU). We present models for the spiral structures using the spiral density wave theory, and derive a disk aspect ratio of h ~ 0.1, which is consistent with previous sub-mm observations. This model can potentially give estimates of the temperature and rotation profiles of the disk based on dynamical processes, independently from sub-mm observations. It also predicts the evolution of the spiral structures, which can be observable on timescales of 10-20 years, providing conclusive tests of the model. While we cannot uniquely identify the origin of these spirals, planets embedded in the disk may be capable of exciting the observed morphology. Assuming that this is the case, we can make predictions on the locations and, possibly, the masses of the unseen planets. Such planets may be detected by future multi-wavelength observations.

Direct Imaging of a Cold Jovian Exoplanet in Orbit around the Sun-like Star GJ 504

Several exoplanets have recently been imaged at wide separations of >10?AU from their parent stars. These span a limited range of ages ( 0.5?mag), implying thick cloud covers. Furthermore, substantial model uncertainties exist at these young ages due to the unknown initial conditions at formation, which can lead to an order of magnitude of uncertainty in the modeled planet mass. Here, we report the direct-imaging discovery of a Jovian exoplanet around the Sun-like star GJ 504, detected as part of the SEEDS survey. The system is older than all other known directly imaged planets; as a result, its estimated mass remains in the planetary regime independent of uncertainties related to choices of initial conditions in the exoplanet modeling. Using the most common exoplanet cooling model, and given the system age of 160?Myr, GJ 504b has an estimated mass of 4 Jupiter masses, among the lowest of directly imaged planets. Its projected separation of 43.5?AU exceeds the typical outer boundary of ~30?AU predicted for the core accretion mechanism. GJ 504b is also significantly cooler (510 K) and has a bluer color (J ? H = ?0.23?mag) than previously imaged exoplanets, suggesting a largely cloud-free atmosphere accessible to spectroscopic characterization. Thus, it has the potential of providing novel insights into the origins of giant planets as well as their atmospheric properties.

SPIRAL ARMS IN THE ASYMMETRICALLY ILLUMINATED DISK OF MWC 758 AND CONSTRAINTS ON GIANT PLANETS

We present the first near-IR scattered light detection of the transitional disk associated with the Herbig Ae star MWC 758 using data obtained as part of the Strategic Exploration of Exoplanets and Disks with Subaru, and 1.1 {

Direct Imaging of Fine Structures in Giant Planet Forming Regions of the Protoplanetary Disk around AB Aurigae

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Direct Imaging Discovery of a "Super-Jupiter" around the Late B-type Star κ And

}m Hubble Space Telescope/NICMOS data. While submillimeter studies suggested there is a dust-depleted cavity with r = 0.35, we find scattered light as close as 0.1 (20-28 AU) from the star, with no visible cavity at H, K, or K

Discovery of the Coldest Imaged Companion of a Sun-like Star

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Imaging of a Transitional Disk Gap in Reflected Light: Indications of Planet Formation Around the Young Solar Analog LkCa 15

. We find two small-scaled spiral structures that asymmetrically shadow the outer disk. We model one of the spirals using spiral density wave theory, and derive a disk aspect ratio of h ~{} 0.18, indicating a dynamically warm disk. If the spiral pattern is excited by a perturber, we estimate its mass to be 5

The Missing Cavities in the SEEDS Polarized Scattered Light Images of Transitional Protoplanetary Disks: A Generic Disk Model

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Subaru imaging of asymmetric features in a transitional disk in upper Scorpius

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