The origin of the unfocused XMM-Newton background, its variability and lessons learned for ATHENA

Abstract

We analyzed the unexposed to the sky outFOV region of the MOS2 detector on board XMM-Newton covering 15 years of data amounting to 255 Ms. We show convincing evidence that the origin of the unfocused background in XMM-Newton is due to energetic protons, electrons and hard X-ray photons. Galactic Cosmic Rays are the main contributors as shown by the tight correlation (2.6% of total scatter) with 1 GeV protons data of the SOHO EPHIN detector. Tight correlations are found with a proxy of the Chandra background rate, revealing the common source of background for detectors in similar orbits, and with the data of the EPIC Radiation Monitor (ERM), only when excluding Solar Energetic Particles events (SEPs). The entrance to the outer electron belts is associated to a sudden increase in the outFOV MOS2 rate and a spectral change. These facts support the fact that MeV electrons can generate an unfocused background signal. The correlation between MOS2 outFOV data and the SOHO EPHIN data reveals a term constant in time and isotropic similar to the one found in the study of the pn data. The most plausible origin of this component is hard unfocused X-ray photons of the Cosmic X-ray Background (CXB) Compton-scattering in the detector as supported by the strength of the signal in the two detectors with different thicknesses. Based on this physical understanding a particle radiation monitor on board ATHENA has been proposed and it is currently under study. It will be able to track different species with the necessary accuracy and precision to guarantee the challenging requirement of 2% reproducibility of the background.

14 pages, 15 figures, accepted for publication in ApJ

References in corpus (15)

• Some Aspects of Measurement Error in Linear Regression of Astronomical Data
• A Catalog of Galaxy Clusters Observed by XMM-Newton
• Radial temperature profiles for a large sample of galaxy clusters observed with XMM-Newton
• Probing the Dark Matter and Gas Fraction in Relaxed Galaxy Groups with X-ray observations from Chandra and XMM
• The XMM-Newton EPIC Background and the production of Background Blank Sky Event Files
• The EXTraS Project: Exploring the X-ray transient and variable sky
• Monte Carlo simulations of soft proton flares: testing the physics with XMM-Newton
• A systematic analysis of the XMM-Newton background: IV. Origin of the unfocused and focused components
• A Systematic Analysis of the XMM-Newton Background: I. Dataset and Extraction Procedures
• Analysis of the unconcentrated background of the EPIC-pn camera on board XMM-Newton
• Prediction and understanding of soft proton contamination in XMM-Newton: a machine learning approach
• A systematic analysis of the XMM-Newton background: III. Impact of the magnetospheric environment
• Fifteen years of the Advanced CCD Imaging Spectrometer
• Prediction of soft proton intensities in the near-Earth space using machine learning
• The role of the background in past and future X-ray missions

Cited by in corpus (2)

• The Planck clusters in the LOFAR sky. III. LoTSS-DR2: Dynamic states and density fluctuations of the intracluster medium
• CHEX-MATE: pressure profiles of 6 galaxy clusters as seen by SPT and Planck