Simulation Study of Pulse Height Difference Between Pixel Patterns of X-ray CCDs Onboard the XRISM Satellite
Y. Aoki*, Y. Ito, M. Nobukawa, Y. Kanemaru, K. Miyazaki, K. Kusunoki,
K. Mori, T. Yoneyama, T. Tamba, H. Tomida, H. Nakajima, H. Matsumoto, H. Noda, K. Hayashida, H. Uchida, T. Tanaka, H. Suzuki, T. Yoshida, H. Murakami, M. Yamauchi, I. Hatsukade, K. Hagino, T. Kohmura, H. Uchiyama, K. Yamaoka, M. Ozaki, T. Dotani, H. Tsunemi, K. Nobukawa, T. Tsuru, S. Kobayashi and J. Hiragaet al. (click to show)
March 16, 2023
We have developed a soft X-ray telescope system Xtend onboard Japan’s new X-ray astronomical satellite XRISM. Xtend employs X-ray CCDs, which have basically the same design as those used in the previous X-ray astronomical satellite Hitomi. Monochromatic X-ray line spectra of the CCDs onboard Hitomi showed offsets of centroids between different pixel patterns or different good grades; the spectral centroids of charge-sharing events are higher than those of single-pixel events. The spectral offset, which we call “Goffset”, can cause large uncertainties in X-ray energy determination accuracy. In this paper, confirming the CCDs onboard XRISM also have Goffset, we performed a simulation study that takes into account the two factors; charge sharing and readout noise. Goffset of the flight model CCD is successfully reproduced by the simulation with a certain readout noise. We investigate how charge sharing and readout noise cause Goffset based on the simulation results.
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