Solar Wind Charge Exchange Contribution to the Rosat All Sky Survey Maps

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 • , b = 0 • , where the DXL path crosses the Galactic plane is 33% ± 6%(statistical) ± 12%(systematic) for R1, 44% ± 6% ± 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.

MAXI/SSC all-sky maps from 0.7 keV to 4 keV

“…One of the objectives of the present study has been to observe the ROSAT-discovered EXS under a condition wherein the variable and anisotropic SWCX contribution ( §3.2.1) is considered to be much lower than in the ROSAT R5 band (0.56-1.21 keV), where the SWCX contribution is estimated (Uprety et al 2016) to be 6% ± 4% (statistical) ±4% (systematic). The present SSC results are expected to satisfy this requirement, for the following reasons.…”

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

“…10). Nevertheless, recent results from the December 2012 Diffuse X-rays from the Local galaxy (DXL) rocket flight have conclusively demonstrated that ∼ 40% of background emissions in a direction of very low cosmic background intensity originate from the He focusing cone and not the local hot bubble surrounding the heliosphere Uprety et al 2016;Liu et al 2017). Koutroumpa et al (2007) employed a dynamic model to simulate the effects of a propagating corotating interaction region on line of sight soft X-ray emissions.…”

“…The Diffuse X-ray emission from the Local galaxy (DXL) sounding rocket flight was designed to isolate the spatial variation of soft X-ray emissions from the He focusing cone (Galeazzi et al 2011Uprety et al 2016). The look direction of the local midnight launch on 2012 December 13 from the White Sands Missile Range in New Mexico avoided soft X-rays from charge exchange in the vicinity of the Earth's magnetosphere and pointed antisunward through the maximum emission region of the heliospheric He focusing cone, a direction towards the galactic anti-center which avoids bright galactic soft X-ray sources.…”

A High Spectral Resolution Study of the Soft X-Ray Background with the X-Ray Quantum Calorimeter

“…As mentioned in Section 5.2, at high latitudes we are unable to separate the local plasma from the low temperature component of the halo, which affects our derived values for emission measure, as well as possibly temperature. Liu et al (2017) combined SWCX maps from Uprety et al (2016) with data from Snowden et al (1998) to estimate the local and distant astrophysical contributions to the R12 band. In Table 9, we compare the results of our spectral model fits to that work.…”

“…Combined contribution of fast and slow SWCX model components inTables 3 and 4to the ROSAT energy bands R1 and R2, compared to estimates for the RASS R1 and R2 maps given byUprety et al (2016). All uncertainties are reported at 90% confidence level.…”