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Basic Feasibility for the LXO

This study aims to model the instrument concept of LXO using Xspec to determine expected count rates, signal-to-noise, and flux within the relevant solid angle. The study is based on the model of Robertson and Cravens and builds upon previous work to improve MCP optic and adapt the MOS effective area curve. The results include simulated images of the field of view and enhanced soft X-ray sensitivity.

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Basic Feasibility for the LXO

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  1. Basic Feasibility for the LXO Jenny Carter

  2. Basis for this study • Base on model of Robertson and Cravens, GeoPhys Res. Letters, Vol. 30, No. 8, 1439, X-ray emission from the terrestrial magnetosheath • Max – 8.8 keV cm-2 s-1 sr-1 • MCP optic plus MOS type CCD cameras at focal plane • Plan to model this instrument concept using Xspec to find expected count rates, signal-to-noise etc.

  3. Selected areas • Select various FOV and calculate flux within the relevant solid angle

  4. Effective area • Create arf using LOBSTER bkg effective area curve (Simon Vaughan, www.star.le.ac.uk/lwft/poster.pdf) • (Improvement on previous work, adapting MOS arf for MCP optic, lack of RGA etc.)

  5. Model basis • Snowden et al., HDFN and SWCX, ApJ, 610, 1182, 2004 • Use Snowden response matrix initially • SWCX lines, plus use background components • Relative normalisations taken from Snowden paper.

  6. Spectra and Bkg • Fake spectra, sky bkg and particle background separately • Use MOS response matrix and lobster effective area • Scale each spectrum to match the flux in Robertson and Cravens model between 0.2 and 2 keV • Sky background assumed to be 10 photons cm-2 s-1 sr-1 at 1 keV, approx. value from Lumb et al., 389, 93, 2002, scale accordingly • Scale particle background so that crosses sky background at 5 keV Sky: MW-halo, local halo, cosmic bkg, local hot bubble Sky: wabs * (raymond + powerlaw + raymond) + vapec + raymond PB: particle induced background PB: powerlaw

  7. Limitations, extra bkg • No lunar background considered • Instrumental lines, depending on instrument used etc. • Local and temporal variations in the sky background • Specifics of particle induced background dependent on instrumental set up etc.

  8. Results – using MOS response

  9. Results – response matrix adapted

  10. Results – off centre selection

  11. Results Summary

  12. Simulated images of fov • Andy Read; based on predicted count rates and distribution of model, distribute photons for different exposure times 1 ks, magnetosheath, sky bkg

  13. More images 1 ks, resultant, smoothed

  14. More images (2) 10 ks 100 ks

  15. LOBSTER optic designed for primary science goal as an ASM so optimises telescope grasp (fov x effective area) Eff. Area of nickel-coated glass MCP optic of varying focal lengths For LXO we would enhance soft X-ray sensitivity: f = 50 cm gives useful 90 x 90 fov in a compact form.

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