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Chandra X-Ray Observatory

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1E0102.2-7219 as a Standard Candle for X-ray Astronomy

Paul Plucinsky, Joseph DePasquale, Steven Snowden
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Why Use E0102 as a Calibration Source for X-ray Astronomy?
Well-characterized spectrum, both the Chandra HETG and XMM RGS have observed the object · The spectrum is relatively simple by astrophysical standards, no or very little Fe, strong lines of O, Ne, and Mg · Extended source so pileup effects are minimized · Constant source · The O and Ne lines sample an energy range in which the on-board calibration source does not have strong lines · Low-energy part of the bandpass is always a challenge to calibrate

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We are VERY close to agreeing on the model spectrum !!!
Paul Plucinsky 2

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Gratuitous Pretty Pictures of E0102
S3 Summed Data ~100 ks True Color Image

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Paul Plucinsky

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Spectral Model: Calibration vs. Astrophysics
Primary Objectives are to measure the gain, the spectral redistribution function, and detection efficiency in the 0.5 -2.0 keV range · Our immediate concern is to develop a model useful for calibration, not to develop an astrophysically-meaningful model, · We use a model consisting of Gaussians for the lines identified by the HETG and RGS, a bremsstrahlung for the continuum, and a two component absorption (Galactic and SMC) · Line energies are fixed at the true values and the widths of the Gaussians are fixed at zero, so the only parameter which varies is the normalization · Pollock has added recombination edges to the RGS model and has non-zero widths for some of the lines · When fitting CCD spectra, ratios of the F-I-R lines in a triplet are fixed to the RGS and/or HETG value
Paul Plucinsky 4

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RGS Spectrum from Pollock
OVIII

OVII NeIX NeX

OVIII

OVII

CVI

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Pollock RGS vs. Flanagan (2004) HETG

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Adopt line widths from Pollock

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OVII For OVII Res

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Pollock RGS vs. Flanagan (2004)HETG (O line region)

OVIII Ly-

OVIII Ly-

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Pollock RGS vs. Flanagan (2004) HETG (Ne line region)

Ne X Ly-

Ne IX triplet

Ne X Ly-

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Pollock RGS vs. Flanagan (2004) HETG Line Fluxes
Line OVII For OVII Res O VIII Ly- O VIII Ly- Ne IX triplet Ne X Ly- Ne X Ly- Flanagan Flux 13.95 24.38 37.31 6.37 23.18 9.72 2.07
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Pollock Flux 11.53 27.23 40.65 7.78 21.15 12.70 1.87

(10-4 photons cm-2 s-1) (10-4 photons cm-2 s-1)

Difference +17.3% -11.7% -8.9% -15.9% +8.8% -30.7% +9.7%

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S3(BI)
Ne X Ly-

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Mg XI triplet OVIII Ly- OVII triplet Ne IX triplet

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I3(FI)
OVIII Ly- OVII triplet Mg XI triplet

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Ne IX Ne X Ly- triplet

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Thick Filter Large Window

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MOS 1 MOS 2

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PN Thick Filter Small Window

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Pollock RGS vs. SPIE Plucinsky (2006)
Plucinsky Add some lines from Pollock but keeps Bremsstrahlung continuum

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Joint Fit With Line Energies Frozen
pn S3, S3 MOS1

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Independent Fits: SMC NH=5.65 e20 cm-2 Bremsstrahlung kT=0.95 keV and Ne line complexes energies free, Normalizations free

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S3: OBSID 3545, Red 2=1.27

S3: OBSID 6765, Red 2=1.48

pn, Red 2=2.69

MOS1, Red 2=2.51

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O VII Ly and Ne X Ly Normalization Results
Data sets fit independently, O and Ne line complexes are free to vary as a group SMC NH=5.65x1020 cm-2, Bremsstrahlung kT=0.95 keV
Instrumen t ACIS S3 (node 1) ACIS S3 (node 0) O VIII Ly Norm (x 10-3 photons cm-2 s) 6.58 [6.44,6.94] 6.92 [6.79,7.36] 6.14 [6.09,6.19] 6.42 [6.35,6.53] Ne X Ly Norm (x 10-3 photons cm-2 s) 1.80 [1.73,1.88] 1.77 [1.69,1.84] 1.74 [1.72,1.76] 1.71 [1.68,1.73] Red 2 1.27 1.48 2.69 2.51 DOF 95 93 279 92

OBSID 3545 [90% CL] 6765 [90% CL]

0135720801 pn [90% CL] 0135720601 MOS1 [90% CL]

· Ne X Ly a normalizations agree within ~6.0% for ACIS, pn, & MOS1

· Early S3 and MOS1 agree within ~2.0% for O VIII Ly normalizations
· Most recent S3 and pn disgree by ~18.0% for O VIII Ly normalizations
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Let's Agree on a Model !!!!!!!
Purpose: to improve the low-energy response model of ACIS, MOS and pn CCD instruments

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1) 2) 3) 4) 5) 6)

RGS and HETG agree on flux of bright lines RGS and HETG compromise on existence of weak lines RGS and HETG agree on widths for the lines Select a continuum model and absorption HETG team must analyze second epoch observations of E0102 Fit ACIS, MOS, and pn with the same model

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