Line Structure in the Spectrum of FU Orionis

Abstract

New high-resolution spectra of FU Ori, obtained with the HIRES spectrograph at the Keck I telescope in 2003-2006, make it possible to compare the optical line profiles with those predicted by the self-luminous accretion disk model. A dependence of line width on excitation potential and on wavelength, expected for a Keplerian disk, is definitely not present in the optical region, nor is the line duplicity due to velocity splitting. The absorption lines observed in the optical region of FU Ori must originate in or near the central object, and here their profiles are shown to be those expected of a rigidly rotating object. They can be fitted by a rapidly rotating (v sin i = 70 km/s) high-luminosity G-type star having a large dark polar spot, with axis inclined toward the line of sight. Over these years, the radial velocity of FU Ori has remained constant to within +/-0.3 km/s, so there is no indication that the star is a spectroscopic binary. These results apply to the optical region ($\lambda <8800$ Å); more distant, cooler regions of the disk contribute in the infrared.

14 pages, 11 figures, accepted by AJ

References in corpus (7)

• High-Resolution Spectroscopy of FUors
• The photometric evolution of FU Orionis objects: disc instability and wind-envelope interaction
• New insights on the AU-scale circumstellar structure of FU Orionis
• FU Orionis: A Binary Star?
• High Resolution Near-Infrared Spectroscopy of FUors and FUor-like stars
• Spectra and Line Profiles of FU Orionis Objects: Comparisons Between Boundary Layer Models and Observations
• Long-term evolution of FU Orionis objects at infrared wavelengths

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