Statistics – Computation
Scientific paper
Sep 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...432..367s&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 432, no. 1, p. 367-372
Statistics
Computation
41
Astronomical Interferometry, Brightness, Cepheid Variables, Diameters, Distance, Stellar Atmospheres, Emission Spectra, Line Spectra, Local Thermodynamic Equilibrium, Radial Velocity, Very Long Base Interferometry
Scientific paper
We discuss several theoretical issues concerning the application of optical interferometry to angular diameter and distance measurement of pulsating stars. Among the pulsating stars, Cepheids are most notable because of their importance for establishing the primary distance scale. Accurate determination of Cepheid angular diameters using long-baseline interferometer measurements combined with appropriate disk brightness distribution models should improve significantly the accuracy of the distance scale. We present time- and wavelength-dependent Cepheid brightness distributions computed using dynamical non-local thermodynamic equilibrium (non-LTE) atmosphere models in plane-parallel and spherical geometry, and we discuss the resulting improvement in angular diameter determination. With angular diameter measurements provided by interferometry, an independent measure of the distance to the Cepheid can be acquired using the radial velocity measurements. It is essential to use appropriate transformations between the radial and pulsational velocities, and to be consistent with the interferometric measurements. This requires the selection of spectral lines of corresponding line-forming regions, as well as knowledge of the line profile changes and their effect on the radial velocity measurements. Our dynamical computations provide the input needed for a consistent solution.
Karovska Margarita
Sasselov Dimitar
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