Herschel-SPIRE FTS spectroscopy of the carbon-rich objects AFGL?2688, AFGL?618, and NGC?7027

摘要

We present far-infrared and submillimetre spectra of three carbon-richevolved objects, AFGL2688, AFGL618 andNGC7027. The spectra were obtained with the SPIREFourier-transform spectrometer on board the HerschelSpace Observatory, and cover wavelengths from 195-670m, a regionof the electromagnetic spectrum hitherto difficult to study in detail.The far infrared spectra of these objects are rich and complex, and wemeasure over 150lines in each object. Lines due to 18different species are detected. We determine physical conditions fromobservations of the rotational lines of several molecules, and presentinitial large velocity gradient models for AFGL618. We detectwater in AFGL2688 for the first time, and confirm itspresence in AFGL618 in both ortho and para forms. Inaddition, we report the detection of the J=1-0 lineof CH+ in NGC7027.Key words: astrochemistry - line:identification - circumstellar matter - stars: evolution - stars:general - infrared: stars