THE GOODNESS OF SIMULTANEOUS FITS IN ISIS

Matthias Kühnel, Sebastian Falkner, Christoph Grossberger, Ralf Ballhausen, Thomas Dauser, Fritz-Walter Schwarm, Ingo Kreykenbohm, Michael A. Nowak, Katja Pottschmidt, Carlo Ferrigno, Richard E. Rothschild, Silvia Martínez-Núñez, José Miguel Torrejón, Felix Fürst, Dmitry Klochkov, Rüdiger Staubert, Peter Kretschmar, Jörn Wilms

Abstract


In a previous work, we introduced a tool for analyzing multiple datasets simultaneously, which has been implemented into ISIS. This tool was used to fit many spectra of X-ray binaries. However, the large number of degrees of freedom and individual datasets raise an issue about a good measure for a simultaneous fit quality. We present three ways to check the goodness of these fits: we investigate the goodness of each fit in all datasets, we define a combined goodness exploiting the logical structure of a simultaneous fit, and we stack the fit residuals of all datasets to detect weak features. These tools are applied to all RXTE-spectra from GRO 1008−57, revealing calibration features that are not detected significantly in any single spectrum. Stacking the residuals from the best-fit model for the Vela X-1 and XTE J1859+083 data evidences fluorescent emission lines that would have gone undetected otherwise.

Keywords


Methods: data analysis; X-rays: binaries

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This work is licensed under a Creative Commons Attribution 4.0 International License.

ISSN 1210-2709 (Print)
ISSN 1805-2363 (Online)
Published by the Czech Technical University in Prague