High Resolution Optical and NIR Spectra of HBC 722

Lee, Jeong-Eun and Park, Sunkyung and Green, Joel D. and Cochran, William D. and Kang, Wonseok and Lee, Sang-Gak and Sung, Hyun-Il. (2015) High Resolution Optical and NIR Spectra of HBC 722. ASTROPHYSICAL JOURNAL, 807 (1). ISSN 1538-4357

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Abstract

We present the results of high resolution (R≥30,000) optical and near-IR spec- troscopic monitoring observations of HBC 722, a recent FU Orionis object that underwent an accretion burst in 2010. We observed HBC 722 in optical/near-IR with the BOES, HET-HRS, and IGRINS spectrographs, 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. How- ever, 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 inter- rupted by the wind pressure during the first two years. The Half-Width at Half-Depth (HWHD) 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 op- tical and near-IR spectra seem to trace the disk at 39 and 76 R⊙, 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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