Mapping H-band Scattered Light Emission in the Mysterious SR21 Transitional Disk
Abstract
We present the first near infrared (NIR) spatially resolved images of the circumstellar transitional disk around SR21. These images were obtained with the Subaru HiCIAO camera, adaptive optics and the polarized differential imaging (PDI) technique. We resolve the disk in scattered light at H-band for stellocentric 0.1"<r<0.6" (12<r<75AU). We compare our results with previously published spatially-resolved 880 micron continuum Submillimeter Array (SMA) images that show an inner r<36AU cavity in SR21. Radiative transfer models reveal that the large disk depletion factor invoked to explain SR21's sub-mm cavity cannot be "universal" for all grain sizes. Even significantly more moderate depletions (delta=0.1, 0.01 relative to an undepleted disk) than those that reproduce the sub-mm cavity (delta~10^-6) are inconsistent with our H-band images when they are assumed to carry over to small grains, suggesting that surface grains scattering in the NIR either survive or are generated by whatever mechanism is clearing the disk midplane. In fact, the radial polarized intensity profile of our H-band observations is smooth and steeply inwardly-increasing (r^-3), with no evidence of a break at the 36AU sub-mm cavity wall. We hypothesize that this profile is dominated by an optically thin disk envelope or atmosphere component. We also discuss the compatibility of our data with the previously postulated existence of a sub-stellar companion to SR21 at r~10-20AU, and find that we can neither exclude nor verify this scenario. This study demonstrates the power of multiwavelength imaging of transitional disks to inform modeling efforts, including the debate over precisely what physical mechanism is responsible for clearing these disks of their large midplane grains.
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@article{arxiv.1302.5705,
title = {Mapping H-band Scattered Light Emission in the Mysterious SR21 Transitional Disk},
author = {Katherine B. Follette and Motohide Tamura and Jun Hashimoto and Barbara Whitney and Carol Grady and Laird Close and Sean M. Andrews and Jungmi Kwon and John Wisniewski and Timothy D. Brandt and Satoshi Mayama and Ryo Kandori and Ruobing Dong and Lyu Abe and Wolfgang Brandner and Joseph Carson and Thayne Currie and Sebastian E. Egner and Markus Feldt and Miwa Goto and Olivier Guyon and Yutaka Hayano and Masahiko Hayashi and Saeko Hayashi and Thomas Henning and Klaus Hodapp and Miki Ishii and Masanori Iye and Markus Janson and Gillian R. Knapp and Tomoyuki Kudo and Nobuhiko Kusakabe and Masayuki Kuzuhara and Michael W. McElwain and Taro Matsuo and Shoken Miyama and Jun-Ichi Morino and Amaya Moro-Martin and Tetsuo Nishimura and Tae-Soo Pyo and Eugene Serabyn and Hiroshi Suto and Ryuji Suzuki and Michihiro Takami and Naruhisa Takato and Hiroshi Terada and Christian Thalmann and Daigo Tomono and Edwin L. Turner and Makoto Watanabe and Toru Yamada and Hideki Takami and Tomonori Usuda},
journal= {arXiv preprint arXiv:1302.5705},
year = {2013}
}