XTGRID Stellar Spectroscopic Diagnostics

Version 32

XTGRID is a multi-purpose, multi-wavelength spectral fitting procedure for TLUSTY/SYNSPEC. The idea of a new steepest-descent χ2 minimization program came up in Ondrejov in the fall of 2010. After having done spectral analysis for novae in the X-rays by interpolating in a precalculated grid, a new, more flexible and reliable procedure became necessary. A proper χ2 minimization spectral analysis of classical novae is difficult with a precalculated grid due to the many free parameters these spectra require. Developing a new method for something we don't really know is, at least, risky. Fortunately, a large set of subdwarf data were available in our group at that time. These evolved stars were not only good for developing the method, they opened a way for testing and validating the new and quite general spectral fitting interface. In its first application H/He/CNO model atmospheres and binary spectral decomposition were included in the modeling of ~170 hot subdwarfs from the GALEX survey.
The program is under continuous developement to accomplish its original task and fit supersoft X-ray sources. Among many necessary improvements an appropriate ISM absorption model is needed in the fitting algorithm, currently the standalone XSPEC ISM model is under consideration.
The code has a potential to do direct exoplanet spectroscopy with COOLTLUSTY, a field what needs to be explored in the future.
XTGRID is offered to the community through the Astroserver.org framework. For a review on the most recent version of the code, see: