EDP Sciences
Free access
Volume 414, Number 2, February I 2004
Page(s) 767 - 776
Section Physical and chemical processes
DOI http://dx.doi.org/10.1051/0004-6361:20031687

A&A 414, 767-776 (2004)
DOI: 10.1051/0004-6361:20031687

Properties of the background of EPIC-pn onboard XMM-Newton

H. Katayama1, I. Takahashi2, Y. Ikebe3, K. Matsushita3 and M. J. Freyberg3

1  Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, 560-0043 Osaka, Japan
    e-mail: hkatayam@ess.sci.osaka-u.ac.jp
2  Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-0033 Tokyo, Japan
3  Max-Planck-Institut für Extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany

(Received 30 September 2002 / Accepted 29 July 2003 )

We have investigated the background properties of EPIC-pn onboard XMM-Newton to establish the background subtraction method. Count rates of the background vary violently by two orders of magnitude at the maximum, while during the most quiet period, these are stable within 8% at a 1 $\sigma$ level. The overall spectrum is dominated by particle events above 5 keV, and its spatial variation is also found. The long-term variation of the background is also investigated with CAL CLOSED data, where the filter wheel was in closed position with the internal calibration source illuminating the sensitive area. The average background count rate decreased by 20% from March 2000 to January 2001, but it regained in February 2001. For the modeling of the background spectrum, we investigate relations between the 2.0-7.0 keV count rate and some characteristic parameters. The 2.0-7.0 keV background count rate shows a good correlation with the count rate of events outside the field of view. This correlation is usable for the modeling of the background.

Key words: X-rays: general -- instrumentation: detectors

Offprint request: K. Matsushita, matsushita@rs.kagu.tus.ac.jp

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