scientific abstract mass-loss from intermediate mass stars is the major ingredient in our understanding not only of stellar evolution but also of the galactic chemical evolution as a whole. it is known that the large mass-loss takes place at the latest stage of stellar evolution represented by red (super)giants and agb stars, but the origin of the mass-loss in these stages is poorly understood. for clarifying the origin of mass-loss, the first step should be to understand the physical structure of the upper atmosphere-inner circumstellar envelope (or outer atmosphere) where mass-loss outflow originates in these stars. this outer atmosphere can best be probed directly by the rich spectra due to atoms (including f-f continuum), gaseous molecules (vib-rot and pure rot) and dusts in the thermal infrared region to be observed by the iso sws. the infrared radiation in the thermal infrared region between 2.4 and 45 micron includes the contributions from the upper photosphere, stellar chromosphere, and inner circumstellar envelopes. to better interpret these complicated spectra, we think it useful to do systematic survey of infrared spectra of cool evolved stars with different characteristics, and we propose to observe red supergiants including bright oh/ir sources in lmc, red giants and mira variables, carbon stars of different characteristics (n-,j-,cs-,ch- types), and some peculiar carbon stars including transition objects to pne. observation summary we use the low resolution mode of sws (sws01-1) to see the global structure of the infrared radiation. this mode is ideal to map the thermal structure of the gas/dust envelopes. we apply this mode to observe some 30 objects that may sample the major objects in the temperature - luminosity - o/c ratio - metallicity - peculiarity space of cool evolved stars. for 10 representative objects in the parameter space, we use the normal grating mode of sws (sws06) to observe the full sws range with the expected resolution of about 2,000, which will be necessary to resolve the molecular bands. the results of these observations will provide the basic data to model the physical structure of the photosphere and outer atmospheres of cool evolved stars. we also apply the normal grating mode (sws06) to the restricted spectral region for some additional objects, and we further try the high resolution observation by the fp mode (sws07). here, we explore some possibilities to observe the molecular lines of the circumstellar origin. for carbon-rich objects, the major interests are the hcn nu2 (14.0 micron) and c2h2 nu5 (13.7 micron) bands whose strong q-branch complex can be identified by the medium resolution of the grating scan (sws06). for oxygen-rich stars, oh pure rotation lines are the major possibility, but high resolution of the fp mode is needed to resolve these lines. we focus our attention to the quartets at 14.6micron and 16.8 micron (sws07). we can expect to observe the photospheric component if thermal emission is not strong, but otherwise we expect to observe those originating in the circumstellar envelopes, either as emission or as absorption against the continuum due to the dust thermal emission. we also hope to measure radial velocity and to clarify the kinematics of inner circumstellar envelopes, which may be difficult to probe by the millimeter spectroscopy. this observation is restricted to a few very bright objects.
Instrument
SWS01 , SWS06 , SWS07
Temporal Coverage
1996-06-10T09:33:26Z/1998-03-05T20:29:09Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the worlds first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, TAKASHI et al., 1999, 'Mass-Loss in the Late Stage of Stellar Evolution: I. Structure of the Outer Atmosphere of Cool Evolved Stars ', 1.0, European Space Agency, https://doi.org/10.5270/esa-y1eenhv
