# ASCA and ROSAT observations of NGC5548: discrepant spectral indices

Source: [ASCA and ROSAT observations of NGC5548: discrepant spectral indices](<https://www.sota2.com/research/paper/68fa24b52c2a3760193a7d33>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-24T09:26:34.495Z

Authors: K. Iwasawa, A.C. Fabian, K. Nandra

Published: 1999-04-06T11:35:10.000Z

## Abstract

We report on simultaneous ASCA and ROSAT observations of the Seyfert galaxy NGC5548 made during the ASCA Performance Verification phase. Spectral features due to a warm absorber and reflection are clearly seen in the X-ray spectra. We find that the continuum spectral shape differs between the ASCA and ROSAT datasets. The photon-index obtained from the ROSAT PSPC exceeds that from the ASCA SIS about 0.4. The discrepancy is clear even in the 0.5-2 keV energy band over which both detectors are sensitive. The spectra cannot be made consistent by choosing a more complex model. The problem likely lies in the response curve (estimated effective area) of one, or both, detectors. There may be important consequences for a wide range of published results.

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/astro-ph/9904071>)

[PDF](<https://arxiv.org/pdf/astro-ph/9904071.pdf>)