===================================================================== ==> in this proposal, more time is being requested for tonaka.timvar_1 ==> this proposal requests an upgrade from priority 3 for tonaka.timvar_1 ===================================================================== mass loss of agb stars is an important process for the evolution of matter in the galaxy. however, there are a number of unknowns involved in it. the largest uncertainties reside in the formation process and optical properties of the dust grains. model analysis of infrared observations often suggests a low temperature of silicate dust formation compared to theoretical predictions, indicating a reconsideration of dust formation and mass loss process. the interpretation of observations requires the photon absorption efficiency of silicate dust to be much higher than that of any known silicate existing on the earth (dirty silicate model). the amount of increase of the absorptivity is arbitrarily assumed. both problems interrelate with each other and are difficult to be investigated separately by analyses solely based on an ir spectrum of the dust shell. we propose to elucidate these problems by observing spectra of optically thin dust shell around two oxygen-rich mira variables periodically by iso. periodic spectroscopic observations from near to far infrared will provide the information of the reaction of dust shell to different incident radiations from the photosphere. these results and the energy balance consideration enable us to derive the absorptivity of silicate dust quantitatively and identify the dust forming region. iso will provide a unique opportunity to make such periodic observations of the wide ir region with stable accuracy, which are essential for this kind of study. the results will lead to a better understanding of the late stellar evolution and the circulation of the matter in the galaxy. we have been given the observing time in the first call and this proposal is to extend the variability coverage as well as to upgrade the far-infrared observations.
Instrument
PHT03 , SWS01
Temporal Coverage
1997-08-08T12:20:38Z/1997-12-01T06:32:45Z
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, T. Onaka, 1999, 'TIME VARIATION OF SPECTRA OF CIRCUMSTELLAR ENVELOPES', 1.0, European Space Agency, https://doi.org/10.5270/esa-lq7ou4c
