Ragland, S. and Ohnaka, K. and Hillenbrand, L. and Ridgway, S. T. and Colavita, M. M. and Akeson, R. L. and Cotton, W. and Danchi, W. C. and Hrynevych, M. and Millan-Gabet, R. and Traub, W. A. (2012) First Keck Nulling Observations of a Young Stellar Object: Probing the Circumstellar Environment of the Herbig Ae Star MWC 325. Astrophysical Journal, 746 (2). Art. No. 126. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20120328-075728944
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We present the first N-band nulling plus K- and L-band V^2 observations of a young stellar object, MWC 325, taken with the 85 m baseline Keck Interferometer. The Keck nuller was designed for the study of faint dust signatures associated with debris disks, but it also has a unique capability for studying the temperature and density distribution of denser disks found around young stellar objects. Interferometric observations of MWC 325 at K, L, and N encompass a factor of five in spectral range and thus, especially when spectrally dispersed within each band, enable characterization of the structure of the inner disk regions where planets form. Fitting our observations with geometric models such as a uniform disk or a Gaussian disk show that the apparent size increases monotonically with wavelength in the 2-12 μm wavelength region, confirming the widely held assumption based on radiative transfer models, now with spatially resolved measurements over a broad wavelength range, that disks are extended with a temperature gradient. The effective size is a factor of about 1.4 and 2.2 larger in the L band and N band, respectively, compared to that in the K band. The existing interferometric measurements and the spectral energy distribution can be reproduced by a flat disk or a weakly shadowed nearly flat disk model, with only slight flaring in the outer regions of the disk, consisting of representative "sub-micron" (0.1 μm) and "micron" (2 μm) grains of a 50:50 ratio of silicate and graphite. This is in marked contrast to the disks previously found in other Herbig Ae/Be stars, suggesting a wide variety in the disk properties among Herbig Ae/Be stars.
|Additional Information:||© 2012 American Astronomical Society. Received 2010 December 15; accepted 2011 October 30; published 2012 February 1. The Keck Interferometer is funded by the National Aeronautics and Space Administration (NASA). Observations presented were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. KI observations were taken through Keck Director’s time. We thank E. Appleby, A. Cooper, C. Felizardo, J. Herstein, D. Medeiros, D. Morrison, T. Panteleeva, B. Parvin, B. Smith, K. Summers, K. Tsubota, C. Tyau, E. Wetherell, P. Wizinowich, and J. Woillez for their contributions to KI operations. CHARA observations were taken through NOAOTAC time. We thank Gail Schaefer, P. J. Goldfinger, Chris Farrington, and Theo ten Brummelaar for support of the CHARA observing program and Tabetha Boyajian for advice on data reductions. S.T.R. acknowledges partial support from NASA grant NNH09AK731.|
|Subject Keywords:||circumstellar matter; radiative transfer; stars: individual (MWC 325); stars: pre-main sequence; stars: variables: T Tauri, Herbig Ae/Be; techniques: interferometric|
|Official Citation:||First Keck Nulling Observations of a Young Stellar Object: Probing the Circumstellar Environment of the Herbig Ae Star MWC 325 S. Ragland et al. 2012 ApJ 746 126|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||28 Mar 2012 15:41|
|Last Modified:||26 Dec 2012 14:59|
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