Mapping H-band scattered light emission in the mysterious SR21 transitional disk

Katherine B. Follette, Motohide Tamura, Jun Hashimoto, Barbara Whitney, Carol Grady, Laird Close, Sean M. Andrews, Jungmi Kwon, John Wisniewski, Timothy D. Brandt, Satoshi Mayama, Ryo Kandori, Ruobing Dong, Lyu Abe, Wolfgang Brandner, Joseph Carson, Thayne Currie, Sebastian E. Egner, Markus Feldt, Miwa GotoOlivier Guyon, Yutaka Hayano, Masahiko Hayashi, Saeko Hayashi, Thomas Henning, Klaus Hodapp, Miki Ishii, Masanori Iye, Markus Janson, Gillian R. Knapp, Tomoyuki Kudo, Nobuhiko Kusakabe, Masayuki Kuzuhara, Michael W. McElwain, Taro Matsuo, Shoken Miyama, Jun Ichi Morino, Amaya Moro-Martin, Tetsuo Nishimura, Tae Soo Pyo, Eugene Serabyn, Hiroshi Suto, Ryuji Suzuki, Michihiro Takami, Naruhisa Takato, Hiroshi Terada, Christian Thalmann, Daigo Tomono, Edwin L. Turner, Makoto Watanabe, Toru Yamada, Hideki Takami, Tomonori Usuda

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64 Scopus citations


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 technique. We resolve the disk in scattered light at H-band for stellocentric 0.″1 ≤ r ≤ 0.″6 (12 ≲ r ≲ 75 AU). We compare our results with previously published spatially resolved 880 μm continuum Submillimeter Array images that show an inner r ≲ 36 AU 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 (δ = 0.1, 0.01 relative to an undepleted disk) than those that reproduce the sub-mm cavity (δ ∼ 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 36 AU 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 ∼ 10-20 AU, 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.

Original languageEnglish (US)
Article number10
JournalAstrophysical Journal
Issue number1
StatePublished - Apr 10 2013

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • planetary systems
  • protoplanetary disks
  • stars: individual (SR21)
  • stars: pre-main sequence
  • techniques: polarimetric


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