Twenty-five years of XMM-Newton EPIC-MOS2 Unfocused Particle Background: Solar Cycle Modulation, Galactic Cosmic-Ray Correlation, and Implications for NewAthena
Abstract
We present a study of the unfocused particle-induced background measured by the XMM-Newton EPIC-MOS2 detector, extending previous analyses to the end of 2025 and covering approximately twenty-five years of observations. Using out-of-field-of-view (outFOV) data, we investigate the long-term evolution of the particle background over two complete solar cycles and compare it with independent tracers of the Galactic cosmic-rays. We find an extremely tight correlation between the MOS2 outFOV count rate and the AMS proton flux, with an intrinsic scatter of only about 1.1\%, confirming that variations in the unfocused background are primarily driven by changes in the Galactic cosmic-rays flux. The extended temporal baseline clearly reveals the modulation associated with the solar cycle and the characteristic signatures of the 22 year Hale cycle. A Lomb-Scargle analysis identifies a dominant periodicity at 11.28 yr, while structure-function and wavelet analyses reveal a persistent ∼27 day modulation associated with solar rotation. We also confirm the presence of a residual background component that does not scale with the Galactic cosmic-ray flux, consistent with previous studies and possibly associated with Compton-scattered high-energy X-ray photons. This work places the particle-induced background measured by the XMM-Newton EPIC-MOS2 detector in the broader context of Galactic cosmic-ray studies, while also providing direct implications for the development of background-monitoring and mitigation strategies for future X-ray missions such as \textit{NewAthena}.
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BibTeX
@misc{vaia2026twentyfive,
title = {{Twenty-five years of XMM-Newton EPIC-MOS2 Unfocused Particle Background: Solar Cycle Modulation, Galactic Cosmic-Ray Correlation, and Implications for NewAthena}},
author = {B. Vaia and F. Gastaldello and S. Molendi and I. Bartalucci and M. Balboni and S. Ghizzardi and L. Lovisari and M. Marelli and M. Rossetti and A. Tiengo and C. Macculi and S. Lotti and V. Fioretti and T. Mineo and G. Schellenberger and C. E. Grant},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.27121},
eprint = {2610.27121},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.27121},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Twenty-five years of XMM-Newton EPIC-MOS2 Unfocused Particle Background: Solar Cycle Modulation, Galactic Cosmic-Ray Correlation, and Implications for NewAthena
AU - B. Vaia
AU - F. Gastaldello
AU - S. Molendi
AU - I. Bartalucci
AU - M. Balboni
AU - S. Ghizzardi
AU - L. Lovisari
AU - M. Marelli
AU - M. Rossetti
AU - A. Tiengo
AU - C. Macculi
AU - S. Lotti
AU - V. Fioretti
AU - T. Mineo
AU - G. Schellenberger
AU - C. E. Grant
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.27121
UR - https://arxiv.org/abs/2610.27121
AB - We present a study of the unfocused particle-induced background measured by the XMM-Newton EPIC-MOS2 detector, extending previous analyses to the end of 2025 and covering approximately twenty-five years of observations. Using out-of-field-of-view (outFOV) data, we investigate the long-term evolution of the particle background over two complete solar cycles and compare it with independent tracers of the Galactic cosmic-rays. We find an extremely tight correlation between the MOS2 outFOV count rate and the AMS proton flux, with an intrinsic scatter of only about 1.1\%, confirming that variations in the unfocused background are primarily driven by changes in the Galactic cosmic-rays flux. The extended temporal baseline clearly reveals the modulation associated with the solar cycle and the characteristic signatures of the 22 year Hale cycle. A Lomb-Scargle analysis identifies a dominant periodicity at 11.28 yr, while structure-function and wavelet analyses reveal a persistent ∼27 day modulation associated with solar rotation. We also confirm the presence of a residual background component that does not scale with the Galactic cosmic-ray flux, consistent with previous studies and possibly associated with Compton-scattered high-energy X-ray photons. This work places the particle-induced background measured by the XMM-Newton EPIC-MOS2 detector in the broader context of Galactic cosmic-ray studies, while also providing direct implications for the development of background-monitoring and mitigation strategies for future X-ray missions such as \textit{NewAthena}.
ER -