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Post Info TOPIC: HD 135344B
Blobrana


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RE: HD 135344B
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Title: Constraining the structure of the transition disk HD 135344B (SAO 206462) by simultaneous modelling of multi-wavelength gas and dust observations
Author: A. Carmona (1), C. Pinte (2,1), W.F. Thi (1), M. Benisty (1), F. Ménard (2,1), C. Grady (3,4,5), I. Kamp (6), P. Woitke (7), J. Olofsson (8), A. Roberge (5), S. Brittain (9), G. Dűchene (10,1), G. Meeus (11), C. Martin-Zaďdi (1), B. Dent (12), J.B. Le Bouquin (1), J.P. Berger (13,1) ((1) IPAG, Université Joseph Fourier Grenoble, (2) UMI-FCA Universidad de Chile, (3) Eureka Scientific, (4) ExoPlanets and Stellar Astrophysics Laboratory, Goddard Space Flight Center, (5) Goddard Centre for Astrobiology, Goddard Space Flight Centre, (6) Kapteyn Astronomical Institute, Groningen, (7) University of St Andrews, (8) Max Planck Institut für Astronomie, Heidelberg, (9) Clemson University, (10) University of California, Berkeley, (11) Universidad Autónoma de Madrid, (12) Joint ALMA Observatory, Santiago, (13) European Southern Observatory)

HD 135344B is an accreting (pre-) transition disk which displays emission of warm CO extending tens of AU inside its 30 AU dust cavity. We employ the dust radiative transfer code MCFOST and the thermo-chemical code ProDiMo to derive the disk structure from the simultaneous modeling of the spectral energy distribution (SED), VLT/CRIRES CO P(10) 4.75 micron, Herschel/PACS [O I] 63 micron, Spitzer-IRS, and JCMT 12CO J=3-2 spectra, VLTI/PIONIER H-band visibilities, and constraints from (sub-)mm continuum interferometry and near-IR imaging. We found a disk model able to describe simultaneously the current observations. This disk has the following structure: (1) to reproduce the SED, the near-IR interferometry data, and the CO ro-vibrational emission, refractory grains (we suggest carbon) are present inside the silicate sublimation radius (0.08<R<0.2 AU); (2) the dust cavity (R<30 AU) is filled with gas, the surface density of this gas must increase with radius to fit the CO P(10) line profile, a small gap of a few AU in the gas is compatible with current data, a large gap in the gas is not likely; (4) the gas/dust ratio inside the cavity is > 100 to account for the 870 micron continuum upper limit and the CO P(10) line flux; (5) the gas/dust ratio at 30<R<200 AU is < 10 to simultaneously describe the [O I] 63 micron line flux and the CO P(10) line profile; (6) in the outer disk most of the mass should be located in the mid-plane and a significant fraction of the dust is in large grains. Conclusions: Simultaneous modeling of the gas and dust it is required to break the model degeneracies and constrain the disk structure. An increasing gas surface density with radius in the inner dust cavity echoes the effect of a migrating jovian planet. The global low gas mass (a few Jupiter masses) in the HD 135344B's disk suggests that it is an evolved disk that has already lost a large fraction of its mass.

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Blobrana


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Title: 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
Authors: T. Muto, C. A. Grady, J. Hashimoto, M. Fukagawa, J. B. Hornbeck, M. Sitko, R. Russell, C. Werren, M. Cure, T. Currie, N. Ohashi, Y. Okamoto, M. Momose, M. Honda, S. Inutsuka, T. Takeuchi, R. Dong, L. Abe, W. Brandner, T. Brandt, J. Carson, S. Egner, M. Feldt, T. Fukue, M. Goto, O. Guyon, Y. Hayano, M. Hayashi, S. Hayashi, T. Henning, K. W. Hodapp, M. Ishii, M. Iye, M. Janson, R. Kandori, G. R. Knapp, T. Kudo, N. Kusakabe, M. Kuzuhara, T. Matsuo, S. Mayama, M. W. McElwain, S. Miyama, J.-I. Morino, A. Moro-Martin, T. Nishimura, T.-S. Pyo, E. Serabyn, H. Suto, R. Suzuki, M. Takami, N. Takato, H. Terada, C. Thalmann, D. Tomono, E. L. Turner, M. Watanabe, J. P. Wisnewski, T. Yamada, H. Takami, T. Usuda, M. Tamura

We present high-resolution, H-band, imaging observations, collected with Subaru/HiCIAO, of the scattered light from the transitional disk around SAO 206462 (HD 135344B). Although previous sub-mm imagery suggested the existence of the dust-depleted cavity at r~46AU, our observations reveal the presence of scattered light components as close as 0.2" (~28AU) from the star. Moreover, we have discovered two small-scale spiral structures lying within 0.5" (~70AU). 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-wavelengths observations.

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Blobrana


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Posts: 131433
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HD 135344
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Planetary disk image could indicate planet formation



Simulations of young stellar systems suggest that planets embedded in a circumstellar disk can produce many distinctive structures, including rings, gaps and spiral arms. This video compares computer simulations of hypothetical systems to the image of SAO 206462, produced by the the Strategic Exploration of Exoplanets and Disks with Subaru project that involves University of Washington astronomer John Wisniewski. (Credit: NASA's Goddard Space Flight Center/NCSA)



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Blobrana


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Posts: 131433
Date:
SAO 206462
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Spiral Arms Point to Possible Planets in a Star's Dusty Disk
 
A new image of the disk of gas and dust around a sun-like star is the first to show spiral-arm-like structures. These features may provide clues to the presence of embedded but as-yet-unseen planets

HD135344.jpg
Two spiral arms emerge from the gas-rich disk around SAO 206462, a young star in the constellation Lupus. This image, acquired by the Subaru Telescope and its HiCIAO instrument, is the first to show spiral arms in a circumstellar disk. The disk itself is some 14 billion miles across, or about twice the size of Pluto's orbit in our own solar system. (Credit: NAOJ/Subaru)

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Blobrana


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Posts: 131433
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HD 135344B
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Title: HD 135344B: a young star has reached its rotational limit
Authors: André Müller (ESO, MPIA), Mario van den Ancker (ESO), Ralf Launhardt (MPIA), Jörg-Uwe Pott (MPIA), Davide Fedele (Johns Hopkins University), Thomas Henning (MPIA)

We search for periodic variations in the radial velocity of the young Herbig star HD 135344B with the aim to determine a rotation period. We analysed 44 high-resolution optical spectra taken over a time range of 151 days. The spectra were acquired with FEROS at the 2.2m MPG/ESO telescope in La Silla. The stellar parameters of HD 135344B are determined by fitting synthetic spectra to the stellar spectrum. In order to obtain radial velocity measurements, the stellar spectra have been cross-correlated with a theoretical template computed from determined stellar parameters. We report the first direct measurement of the rotation period of a Herbig star from radial-velocity measurements. The rotation period is found to be 0.16 d (3.9 hr), which makes HD 135344B a rapid rotator at or close to its break-up velocity. The rapid rotation could explain some of the properties of the circumstellar environment of HD 135344B such as the presence of an inner disk with properties (composition, inclination), that are significantly different from the outer disk.

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