HIGH-RESOLUTION 1.6 μm SPECTRA OF FeH IN M AND L DWARFS

Near-infrared bands due to the iron monohydride (FeH) molecule are a characteristic feature of late-M and -L dwarfs. We have created a line list at 2200 K for the FeH E 4Π-A 4Π electronic transition near 1.58 μm (6300 cm–1) based on laboratory spectra and an ab initio calculation of the band strength. A variety of M and L dwarfs were observed near 1.6 μm with high spectral resolution (R ~ 70,000) using the Phoenix spectrograph on the 8.1 m Gemini South telescope. The FeH E-A transition made a surprisingly strong contribution to the observed spectral energy distributions and needs to be included in modeling of late-M and L dwarfs.