Detection of solid ammonia, methanol, and methane with ISOPHOT^*

¹ Astrophysikalisches Institut und Universitäts-Sternwarte, Schillergäßchen 2-3, 07745 Jena, Germany
² Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
³ Konkoly Observatory of the Hungarian Academy of Sciences, PO Box 67, 1525 Budapest, Hungary
⁴ Brunnersweg 12, 64380 Roßdorf, Germany

Corresponding author: J. Gürtler, guertler@astro.uni-jena.de

Received: 30 March 2001
Accepted: 16 May 2002

Abstract

We report on a search for the NH inversion band at 9.0 μm, the CH₄ band at 7.7 μm, and the CH₃OH band at 9.7 μm in the spectra of 10 heavily obscured stellar objects taken with the spectrophotometer ISOPHOT-S aboard the Infrared Space Observatory (ISO). Four of them show indications of the NH₃ inversion band at 9.0 μm superimposed on the always strong silicate band. The results show that ammonia ice may be abundant in some cool and dense molecular circumstellar regions. The 9.7 μm band of solid CH₃OH was detected in 5 of the sources, and also the 7.7 μm band of solid CH₄ was found in 5 sources. The PHT-S detections were cross-checked against ISO-SWS spectra from archive data. Considering the different beam sizes (24 24  versus 14 20 ), there is good agreement.