Free Access
Astron. Astrophys. Suppl. Ser.
Volume 120, Number 1, November_II 1996
Page(s) 187 - 193
Published online 15 November 1996
The energy-dependent temporal variation of the ROSAT PSPC gain DOI: 10.1051/aas:1996284

Astronomy and Astrophysics Supplement Series, Vol. 120, November II 1996, 187-193

The energy-dependent temporal variation of the ROSAT PSPC gain

M.A. Prieto , G. Hasinger and S.L. Snowden
Send offprint requests to: M.A. Prieto

Max-Plank-Inst. für extraterrestrische Physik, Germany
Astrophysikalisches Institut Potsdam, Germany
USRA/Goddard Space Flight Center

Received August 29, 1995; accepted February 24, 1996


The existence of systematic spectral-fit residuals in ROSAT PSPC spectra, and their dependence on time, is by now a well established fact. This paper describes how those residuals may be related to second order variations of the gain of the PSPC as a function of energy and time. As a result, the energy scale used for the interpretation of PSPC spectra can be incorrect producing significant systematic effects, in particular at energies where the effective area of the instrument changes rapidly. A monotonic gain decay of per year is measured at 1 keV. A quantitative description of the PSPC gain-time variation as a function of energy is provided. The functional dependence of this variation is found to be well represented by a second order polynomial.

Key words: instrumentation: detectors --- methods: data analysis --- methods: observational --- X-rays: general --- space vehicles

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