Jenny Carter ([email protected]) LXO Basic Feasibility 15 July 2007 Basic Feasibility for the LXO...

Jenny Carter ([email protected])LXO Basic Feasibility

15 July 2007

Basic Feasibility for the LXO

Jenny Carter


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.


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


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.)


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


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


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.


15 July 2007

Results – using MOS response


15 July 2007

Results – response matrix adapted


15 July 2007

Results – off centre selection


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


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


15 July 2007

More images

1 ks, resultant,

smoothed


15 July 2007

More images (2)

10 ks

100 ks


15 July 2007


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

Jenny Carter ([email protected]) LXO Basic Feasibility 15 July 2007 Basic Feasibility for the LXO...

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