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Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
Basic Feasibility for the LXO
Jenny Carter
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
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.
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
Selected areas
Select various FOV and calculate flux within the relevant solid angle
FOV
(º)
Solid Angle
(str)
Flux
keV s-1 cm-2 / ergs s-1 cm-2
5 x 5 0.007 0.049 / 7.90×10-11
9 x 9 0.024 0.144 / 2.31×10-10
20 x 20 0.123 0.551 / 8.83×10-10
30 x 30 0.284 1.06 / 1.70×10-9
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
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.)
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
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.
Line Energy (keV)C VI 0.37C VI 0.46O VII 0.56O VIII 0.65O VIII 0.81Ne IX 0.91Mg XI 1.34
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
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: wabs * (raymond + powerlaw + raymond) + vapec + raymondSky: MW-halo, local halo, cosmic bkg, local hot bubble
PB: powerlawPB: particle induced background
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
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.
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
Results – response matrix adapted
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
Results SummaryFOV
(º)
Pos Time
(ks)
CR – S
(ct s-1)
CR – Sky
(ct s-1)
CR – PB
(ct s-1)
S/N
9x9 C 10 2.96 5.60 0.06 103
C 100 319
C 1000 1009
30x30 C 10 21.8 66.2 0.75 231
C 1000 732
C 1000 2317
9x9 O 10 1.39 5.59 0.06 52
O 1000 165
O 1000 522
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
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
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
More images
1 ks, resultant,
smoothed
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
Jenny Carter ([email protected])LXO Basic Feasibility
15 July 2007
0
2
4
6
8
10
12
14
0 2 4 6 8 10E (keV)
Eff
ecti
ve a
rea (
cm2 )
f=100cm; L:D = 75:1
f=50cm; L:D = 50:1
f=37.5cm; L:D = 20:1
LOBSTER optic designed for primary science goal as an ASM so
optimises telescope grasp (fov x effective area)
For LXO we would enhance soft X-ray sensitivity:
f = 50 cm gives useful 90 x 90 fov in a compact form.
Eff. Area of nickel-coated glass MCP optic of varying focal lengths