Unidentified molecular features in the red spectrum (5800 to 7300 Å) of PI Gruis

Abstract

Moderate dispersion (46 Å mm–1 at H) image-tube spectrum (5800–7300 Å) of the S star 1 Gru is found to exhibit several unidentified molecular features, in addition to the well-known bands of the oxides ofs-process elements. A list is presented of 28 measured unidentified red-degraded bands, of which six, at 5998, 6128, 6143, 6223, 6257, and 6557 Å, are prominent. Of the reported 28 bands, 22 are observed for the first time. A discussion is included on the expected molecular sources of the unidentified features. The possible presence of two new molecules, Pr O and Nd O, in 1 Gru is suggested.