scientific abstract long-period and mira variables are important stages in the late stellar evolution of low and intermediate mass stars. in fact, they are the main sources of galactic dust production and of a large variety of chemical species originating from their circumstellar shells. a reliable quantitative diagnostic and interpretation of these objects demands both, appropriate theoretical models and specific detailed observations, in particular in the infrared regime. we propose periodic isophot observations of long--period variables (lpvs) at different wavelengths in the mid-- and far--infrared range. these measurements will yield informations about the temporal variation of the physical conditions in different spatial regions of the circumstellar dust shells and will allow a comparison with detailed dynamical model calculations. it is the aim of this project to study the wavelength--dependence of certain structures appearing in already observed near--infrared lightcurves and in theoretical lightcurves as well. the data obtained with this investigation, combined with ground-based monitoring, will also allow an interpretation of the long--term behaviour of miras and lpvs in different wavelength regimes. observation summary **** important note: **** photometric observations will be performed for only two objects from the list given below. we use 3 filters for pht03 aot at 25 microns (52.. aperture), 60 microns (120.. aperture), and 100 microns (180.. aperture). each observation is concatenated to a background measurement with the same instrument setting in order to get a proper reference level. all observations will be performed in staring mode, because the source--to--background contrast is high and because the reference position must be independent of the s/c roll angle. using 32 s integration time per filter allows to measure our objects with s/n > 100 so t...hat brightness variations on a few percent level can be sufficiently well assessed. both sources will be observed periodically in the 3 proposed filter bands at 6 fixed dates (three times during two observation periods). the decision as to which 2 objects will be observed can only be made once the satallite has been launched, since it depends on the visibility of the objects at the time required for the observations and we anticipate that it will be possible for only 2 from the list to be observable. these specialised fixed time observations should not preclude more general photometry proposals being accepted. the calculations of the time required for the observations were performed using phtaot v1.3.
Instrument
PHT03
Temporal Coverage
1996-02-04T18:43:17Z/1997-08-21T07:48:09Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the world's 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, 1999, Variability Of Circumstellar Dust Shells Around Long-Period Variables , 1.0, European Space Agency, https://doi.org/10.5270/esa-8rkjp82
