High Resolution Optical And NIR Spectra Of HBC 722

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Date

2015-07

Authors

Lee, Jeong-Eun
Park, Sunkyung
Green, Joel D.
Cochran, William D.
Kang, Wonseok
Lee, Sang-Gak
Sung, Hyun-Il

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Abstract

We present the results of high resolution (R >= 30,000) optical and near-IR spectroscopic monitoring observations of HBC 722, a recent FU Orionis object that underwent an accretion burst in 2010. We observed HBC 722 in the optical/near-IR with the Bohyunsan Optical Echelle Spectrograph, Hobby-Eberly Telescope-HRS, and Immersion Grating Infrared Spectrograph, at various points in the outburst. We found atomic lines with strongly blueshifted absorption features or P Cygni profiles, both evidence of a wind driven by the accretion. Some lines show a broad double-peaked absorption feature, evidence of disk rotation. However, the wind-driven and disk-driven spectroscopic features are anti-correlated in time; the disk features became strong as the wind features disappeared. This anti-correlation might indicate that the rebuilding of the inner disk was interrupted by the wind pressure during the first 2 years. The half-width at half-depth of the double-peaked profiles decreases with wavelength, indicative of the Keplerian rotation; the optical spectra with the disk feature are fitted by a G5 template stellar spectrum convolved with a rotation velocity of 70 km s(-1) while the near-IR disk features are fitted by a K5 template stellar spectrum convolved with a rotation velocity of 50 km s(-1). Therefore, the optical and near-IR spectra seem to trace the disk at 39 and 76 R-circle dot, respectively. We fit a power-law temperature distribution in the disk, finding an index of 0.8, comparable to optically thick accretion disk models.

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Lee, Jeong-Eun, Sunkyung Park, Joel D. Green, William D. Cochran, Wonseok Kang, Sang-Gak Lee, and Hyun-Il Sung. "High Resolution Optical and NIR Spectra of HBC 722." arXiv preprint arXiv:1505.03206 (Jul., 2015).