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Characterizing the IYJ Excess Continuum Emission in T Tauri Stars

Fischer, William and Edwards, Suzan and Hillenbrand, Lynne and Kwan, John (2011) Characterizing the IYJ Excess Continuum Emission in T Tauri Stars. Astrophysical Journal, 730 (2). Art. No. 73. ISSN 0004-637X.

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We present the first characterization of the excess continuum emission of accreting T Tauri stars between optical and near-infrared wavelengths. With nearly simultaneous spectra from 0.48 to 2.4 μm acquired with HIRES and NIRSPEC on Keck and SpeX on the Infrared Telescope Facility, we find significant excess continuum emission throughout this region, including the I, Y, and J bands, which are usually thought to diagnose primarily photospheric emission. The IYJ excess correlates with the excess in the V band, attributed to accretion shocks in the photosphere, and the excess in the K band, attributed to dust in the inner disk near the dust sublimation radius, but it is too large to be an extension of the excess from these sources. The spectrum of the excess emission is broad and featureless, suggestive of blackbody radiation with a temperature between 2200 and 5000 K. The luminosity of the IYJ excess is comparable to the accretion luminosity inferred from modeling the blue and ultraviolet excess emission and may require reassessment of disk accretion rates. The source of the IYJ excess is unclear. In stars of low accretion rate, the size of the emitting region is consistent with cooler material surrounding small hot accretion spots in the photosphere. However, for stars with high accretion rates, the projected area is comparable to or exceeds that of the stellar surface. We suggest that at least some of the IYJ excess emission arises in the dust-free gas inside the dust sublimation radius in the disk.

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Additional Information:© 2011 American Astronomical Society. Received 2010 August 21; accepted 2011 January 21; published 2011 March 7. We are grateful to Scott Dahm for flexibility in the scheduling of his HIRES time and for acquiring our HIRES spectra. We acknowledge stimulating conversations with Nuria Calvet, Laura Ingleby, and Scott Gregory, and we thank the anonymous referee for helpful comments. This work was partially supported by NASA grant NNG506GE47G issued through the Office of Space Science. The authors reverently acknowledge the cultural significance of the Mauna Kea summit to the indigenous Hawaiian community. We are most fortunate to have had the opportunity to conduct observations with IRTF and the Keck telescopes from this mountain.
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Subject Keywords:accretion; accretion disks; protoplanetary disks; stars: formation; stars: pre-main sequence
Issue or Number:2
Classification Code:PACS: 97.21.+a; 95.30.Ky; 97.10Ri; 97.10.Gz; 97.10Ex
Record Number:CaltechAUTHORS:20110414-085412533
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Official Citation:Characterizing the IYJ Excess Continuum Emission in T Tauri Stars William Fischer, Suzan Edwards, Lynne Hillenbrand and John Kwan doi: 10.1088/0004-637X/730/2/73
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23327
Deposited By: Ruth Sustaita
Deposited On:14 Apr 2011 21:05
Last Modified:03 Oct 2019 02:45

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