Using SRG/eROSITA to estimate soft proton fluxes at the ATHENA detectors

TL;DR

This study estimates soft proton fluxes at the ATHENA X-ray detectors using eROSITA data and simulations, suggesting the flux levels are manageable with minor adjustments to detector filters, ensuring mission safety.

Contribution

It introduces a model-independent method to estimate soft proton fluxes at ATHENA using eROSITA data and simulations, bypassing external flux modeling.

Findings

Soft proton fluxes at ATHENA could be near the mission's background requirement.

eROSITA experienced no detrimental soft proton fluxes during its all-sky survey.

A 30% increase in optical blocking filter thickness could mitigate soft proton impacts.

Abstract

Context: Environmental soft protons have affected the performance of the X-ray detectors on board Chandra and XMM-Newton, and they pose a threat for future high energy astrophysics missions with larger aperture, such as ATHENA. Aims: We aim at estimating soft proton fluxes at the ATHENA detectors independently of any modelisation of the external fluxes in the space environment.We analysed the background data measured by eROSITA on board SRG, and with the help of simulations we defined a range of values for the potential count-rate of quiet-time soft protons focused through the mirror shells. We used it to derive an estimate of soft proton fluxes at the ATHENA detectors, assuming ATHENA in the same L2-orbit as SRG. Results: The scaling, based on the computed proton transmission yields of the optics and optical/thermal filters of eROSITA and ATHENA, indicates that the soft proton induced WFI and X-IFU backgrounds could be expected close to the requirement. Conclusions: No soft proton fluxes detrimental to the observations have been suffered by eROSITA during its all-sky survey in orbit around L2. Regardless of where ATHENA will be placed (L1 or L2), our analysis suggests that increasing somewhat the thickness of the WFI optical blocking filter, e.g. by 30%, would help to reduce the soft proton flux onto the detector, in case the planned magnetic diverters perform worse than expected due to soft proton neutralisation at the mirror level.