Confirmation of the presence of iron hydride in sunspots and cool stars

Abstract

A high-resolution sunspot spectrum clearly shows the presence of the 9896 Å and 8691 Å bands of iron hydride (FeH). At least 332 lines of the two bands, accounting for 80% of the lines registered in the laboratory, can be identified with certainty in the spot spectrum; most of these are unblended. Our estimate that the 9896 Å band is 2.0 ± 0.2 times stronger than the 8691 Å band supports the idea, suggested earlier by laboratory deuteride experiments, that the 9896 Å band is the (0, 0) transition. No evidence for FeH is found in the spectrum of the solar disk. Image-tube spectrograms of M dwarfs and S stars have been taken in the near-infrared at 86 Å mm^(-1) to examine the feature which Nordh, Lindgren, and Wing have proposed is due to the 9896 Å band of FeH. At this dispersion enough band structure is evident to confirm the identification in both kinds of stars.