The following document lists the file abstract/DLAMBERT_DLL004.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
======================================================================= ==> In this proposal, more time is being requested for DLAMBERT.DLL002 ======================================================================= This proposal is a continuation of another one already performed by ISO. It deals with the atmospheres of cool dwarf stars whose chemical compositions are unique clues to the early evolution of the Galaxy. Contemporary analyses of spectra depend on model stellar atmospheres computed usually from a set of simplifying assumptions, and only few attempts have been made to derive atmospheric structures as directly as possible from observations, i.e. to construct empirical atmospheres. This study is motivated by the power of ISO photometry to measure the temperature in the upper photospheric layers: the opacity in the infrared is provided by the free-free transitions of the H- ion and scales as wavelength-squared. Hence, a large range of depths is sampled by the flux between 3 to 120 micron. Previous studies of optical line and continuous spectra suggest that theoretical model atmospheres do not yet adequately represent the real atmospheres of cool dwarf stars. The cool metal-poor star Gmb1830 (HD103095) was observed in 3.6, 4.85, 7.3, 11, 16, and 60 micron by our group with ISOPHOT (proposal DLL002), providing very good data for the shorter wavelength filters, and showing that it was possible to detect this very faint source in the longest wavelength filter. We propose now to complement these data by observing the metal-rich star Epsilon Eri (HD22049, with similar stellar parameters than Gmb1830) in these six filters plus the 25 and 90 micron filters, for making a direct comparison of the IR flux distribution in both objects and having a detailed photometric information of Epsilon Eri. Most of these observations were already included in the former proposal, but it was not possible to carry them out within the allocated observing time due to the errors contained in the cookbook for computing exposure times, and to the change of sensitivity of the ISOPHOT detectors once in orbit compared to their pre-flight values.