The following document lists the file abstract/HIZUMIUR_REDSTAR2.abs
from catalogue VI/111.
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SCIENTIFIC ABSTRACT We propose to obtain deep images of dust shells around bright AGB stars in the solar neighbourhood at far-infrared wavelengths with ISOPHOT in order to investigate mass-loss history in the AGB evolution by determining geometrical structure of the circumstellar dust shells. With the results we will be able to examine the mass-loss history on time scales from a few thousand to a hundred thousand years. They will open a new way for investigating non-steady mass-loss which is now drawing increasing attention. Modulation in the rates of mass-loss, which may be caused by thermal pulses, will be observed if they are really present. The issues posed by IRAS will be elucidated by ISO. OBSERVATION SUMMARY For most sources rectangular maps of 6.5'x30' and of 7.5'x30' will be obtained with C_90 and C_160 filters, respectively, using the AOT PHT32. One or two of the most extended sources will be observed with the wider spatial coverage of 6.5'x45' and 7.5'x45' in order to obtain their full brightness profiles. In addition, an area of 30'x30' will be mapped with the staring raster mode with C_160. The positions of map center for the observation numbers 7-10 and 23-26 in the autumn launch target list and 5-8 and 24-27 in the spring launch list are for the case that the space craft y-axis is aligned to the direction of either Right Ascension or Declination. Since the direction of raster scans will be chosen parallel to the space craft Y-axis in our observations, those positions will be rotated on the sky about the positions of the central stars according to the orientation of the space craft, and unpredictable now. The observation times given in the target lists are calculated using the observer's manual for ISOPHOT. Observation modes for each AGB object are briefly summarized in the following tables. We choose integration time per each raster point of 16sec for all the observations having consulted an ESA astronomer. This is appropriate since our observations are concentrated on regions having rather low and smooth brightness distribution.