Solar Wind Charge Exchange contribution to the ROSAT All Sky Survey Maps

TL;DR

This study quantifies the Solar Wind Charge Exchange (SWCX) contribution to the ROSAT All Sky Survey maps using data from the DXL mission, revealing significant SWCX influence across multiple X-ray bands and enabling improved correction of diffuse X-ray background measurements.

Contribution

It provides the first direct comparison between DXL and ROSAT data to quantify SWCX contributions across all RASS bands, improving background correction methods.

Findings

SWCX contributes up to 44% in R2 band at specific sky regions.

Average SWCX contribution across the sky is about 26-30% in R1 and R2 bands.

SWCX contribution is negligible in R6 and R7 bands.

Abstract

DXL (Diffuse X-ray emission from the Local Galaxy) is a sounding rocket mission designed to estimate the contribution of Solar Wind Charge eXchange (SWCX) to the Diffuse X-ray Background (DXB) and to help determine the properties of the Local Hot Bubble (LHB). The detectors are large-area thin-window proportional counters with a spectral response similar to that of the PSPC used in the ROSAT All Sky Survey (RASS). A direct comparison of DXL and RASS data for the same part of the sky viewed from quite different vantage points in the Solar system and the assumption of approximate isotropy for the Solar wind allowed us to quantify the SWCX contribution to all 6 RASS bands (R1-R7, excepting R3). We find that the SWCX contribution at l=140 deg, b=0 deg, where the DXL path crosses the Galactic plane is 33%+-6% (statistical)+-12%(systematic) for R1, 44%+-\%+-5% for R2, 18%+-12%+-11% for R4, 14%+-11%+-9% for R5, and negligible for R6 and R7 bands. Reliable models for the distribution of neutral H and He in the Solar system permit estimation of the contribution of interplanetary SWCX emission over the the whole sky and correction of the RASS maps. We find that the average SWCX contribution in the whole sky is 26%+-6%+-13% for R1, 30%+-4%+-4% for R2, 8%+-5%+-5% for R4, 6%+-4%+-4% for R5, and negligible for R6 and R7.