High Resolution Near-Infrared Spectroscopy of FUors and FUor-like stars

TL;DR

This study provides high-resolution near-infrared spectra of FU Orionis stars and FUor-like objects, revealing spectral features and similarities that support the accretion disk model and suggest FUor-like stars are more common than previously thought.

Contribution

It offers new high-resolution near-infrared spectral data for FUors and FUor-like stars, analyzing their spectral features and similarities to support the accretion disk model.

Findings

FUors and FUor-like stars show similar spectral features and colors.

Spectra are inconsistent with late-type dwarfs, giants, or embedded protostars.

FUor-like objects may be more common than previously believed.

Abstract

We present new high resolution (R=18,000) near-infrared spectroscopic observations of a sample of classical FU Orionis stars (FUors) and other young stars with FUor characteristics that are sources of Herbig-Haro flows. Spectra are presented for the region 2.203 - 2.236 microns which is rich in absorption lines sensitive to both effective temperatures and surface gravities of stars. Both FUors and FUor-like stars show numerous broad and weak unidentified spectral features in this region. Spectra of the 2.280 - 2.300 micron region are also presented, with the 2.2935 micron v=2-0 CO absorption bandhead being clearly the strongest feature seen in the spectra all FUors and Fuor-like stars. A cross-correlation analysis shows that FUor and FUor-like spectra in the 2.203 - 2.236 micron region are not consistent with late-type dwarfs, giants, nor embedded protostars. The cross-correlations also show that the observed FUor-like Herbig-Haro energy sources have spectra that are substantively similar to those of FUors. Both object groups also have similar near-infrared colors. The large line widths and double-peaked nature of the spectra of the FUor-like stars are consistent with the established accretion disk model for FUors, also consistent with their near-infrared colors. It appears that young stars with FUor-like characteristics may be more common than projected from the relatively few known classical FUors.