Abstract FU Orionis objects (FUors) are thought to be described by a steady-state Keplerian disk. However, the characteristic double-peaked Keplerian line profile is not readily seen in most near-infrared spectra of FUors. In this paper, we measure the near-infrared line profiles of 15 FUors and FUor-like objects by convolving model cool atmosphere spectra with a linear combination of Gaussians. The models are fit to high-resolution spectra obtained with iSHELL on the NASA Infrared Telescope Facility. Five of the targets are found to have double-peaked line profiles in K band, which can also be fitted by a Keplerian line profile. For eight targets that were also observed in J band, we find that the line profiles are well correlated to what is observed in K band, but the line width does not clearly appear to decrease with wavelength. We find that a double-peaked line profile can be difficult to see for several reasons, which include blending with extraneous molecular features and potential absorption from a disk wind or infalling material. The CO lines in M band are morphologically different from their counterparts in K band, so they are probably of a different origin.
Lee et al. (Wed,) studied this question.