Data-oriented diagnostics of pileup effects on the suzaku XIS

Shin'ya Yamada, Hideki Uchiyama, Tadayasu Dotani, Masahiro Tsujimoto, Satoru Katsuda, Kazuo Makishima, Hiromitsu Takahashi, Hirofumi Noda, Shunsuke Torii, Soki Sakurai, Teruaki Enoto, Takayuki Yuasa, Shu Koyama, Aya Bamba

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


We present the results of a systematic study of pileup phenomena seen in the X-ray Imaging Spectrometer, an X-ray CCD instrument, onboard the Suzaku observatory. Using a data set of observed sources in a wide range of brightness and spectral hardness, we characterized the pileup fraction, spectral hardening, and grade migration as a function of the observed count rate in a frame per pixel. Using the pileup fraction as a measure of the degree of pileup, we found that the relative spectral hardening (the hardness ratio normalized to the intrinsic spectral hardness), branching ratio of split events, and that of detached events increase monotonically as the pileup fraction increases, despite the variety of brightness and hardness of the sample sources. We derived the pileup fraction as a function of radius used for event extraction. Upon practical considerations, we found that events outside of the radius with a pileup fraction of 1% or 3% are useful for spectral analysis. We present relevant figures, tables, and software for the convenience of users who wish to apply our method for their data reduction of piled-up sources.

Original languageEnglish
Pages (from-to)531-5312
Number of pages4782
JournalPublications of the Astronomical Society of Japan
Issue number3
Publication statusPublished - 2012 Jun 25
Externally publishedYes


  • Instrumentation: detectors
  • X-rays: general-X-rays: individual (Cygnus X-1)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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