|
|
|
|
HRC-S Quantum Efficiency Verification
|
For this study we employed the supernova remnant Cas A to perform cross-calibration of HRC-S (ObsID 172) with ACIS-S3 (ObsID 214), over the energy range of 0.7 - 2.5 keV.
Dick Edgar provided a line flux source model which we fit to
the ACIS-S3 observations (see model below).
Using the current state of the HRC-S QE model (version 1.1),
Dick built/formatted the HRC response function with which
we were able to generate predicted HRC-S counts using
the "fakeit" command in XSPEC (version 10).
The predicted counts with total model uncertainties are:
783063 ± 16.0%
The HRC-S observed counts were extracted from a circle around the source
[in sky coords: cir(xcen,ycen,r)=cir(33356,32292,1680);
1 HRC-S pixel = 6.429um],
corresponding to the size of the ACIS circle
[in tdet coords: cir(4380,4045,450); 1 ACIS-S pixel = 24.0um].
A very large HRC-S background region was defined as the active detector
minus the source region.
The background-subtracted observed counts are: 793482
± 0.1%
The source model derived from ACIS-S3 has an uncertainty of ~5%.
The HRC-S QE over this range has an additional uncertainty of ~10-15%.
Thus, the total model uncertainty resulting from convolving the source model
with the model of the HRC-S response becomes ~16.0%.
So even though HRC-S actually sees 1.3% more
(absolute difference)
than predicted by our model, the observed matches the predicted within
the 16.0% total model uncertainty.
1) MODEL for Cas A derived from ACIS-S3 (casa.xcm)
mo = ( gaussian[1] + ( gaussian[2] + gaussian[3] + gaussian[4] + gaussian[5]
+ gaussian[6] + gaussian[7] + gaussian[8] + gaussian[9] + gaussian[10]
+ gaussian[11] + gaussian[12] + gaussian[13] + gaussian[14]
+ gaussian[15] + gaussian[16] + gaussian[17] + gaussian[18]
+ gaussian[19] + powerlaw[20] )wabs[21] ) + powerlaw/b[22]
Model Fit Model Component Parameter Unit Value
par par comp
1 1 1 gaussian LineE keV 0.3323 frozen
2 2 1 gaussian Sigma keV 2.8582E-02 frozen
3 3 1 gaussian norm 6.1720E-03 +/- 0.1572E-03
4 4 2 gaussian LineE keV 1.060 frozen
5 5 2 gaussian Sigma keV 0. frozen
6 6 2 gaussian norm 8.5412E-02 +/- 0.1580E-02
7 7 3 gaussian LineE keV 0.9457 +/- 0.2475E-02
8 8 3 gaussian Sigma keV 0. frozen
9 9 3 gaussian norm 6.3098E-02 +/- 0.2119E-02
10 10 4 gaussian LineE keV 1.129 frozen
11 11 4 gaussian Sigma keV 0. frozen
12 12 4 gaussian norm 1.3506E-02 +/- 0.9180E-03
13 13 5 gaussian LineE keV 1.385 frozen
14 14 5 gaussian Sigma keV 0. frozen
15 15 5 gaussian norm 2.3193E-02 +/- 0.4451E-03
16 16 6 gaussian LineE keV 1.515 frozen
17 17 6 gaussian Sigma keV 0. frozen
18 18 6 gaussian norm 7.0877E-03 +/- 0.3877E-03
19 19 7 gaussian LineE keV 1.893 frozen
20 20 7 gaussian Sigma keV 0. frozen
21 21 7 gaussian norm 0.1170 +/- 0.4270E-03
22 22 8 gaussian LineE keV 2.047 frozen
23 23 8 gaussian Sigma keV 0. frozen
24 24 8 gaussian norm 2.1968E-02 +/- 0.2537E-03
25 25 9 gaussian LineE keV 2.370 frozen
26 26 9 gaussian Sigma keV 0. frozen
27 27 9 gaussian norm 8.9934E-03 +/- 0.2790E-03
28 28 10 gaussian LineE keV 2.218 +/- 0.2619E-02
29 29 10 gaussian Sigma keV 0. frozen
30 30 10 gaussian norm 9.9173E-03 +/- 0.2589E-03
31 31 11 gaussian LineE keV 2.487 frozen
32 32 11 gaussian Sigma keV 0. frozen
33 33 11 gaussian norm 4.3544E-02 +/- 0.3162E-03
34 34 12 gaussian LineE keV 2.618 frozen
35 35 12 gaussian Sigma keV 0. frozen
36 36 12 gaussian norm 6.8336E-03 +/- 0.2343E-03
37 37 13 gaussian LineE keV 2.954 frozen
38 38 13 gaussian Sigma keV 0. frozen
39 39 13 gaussian norm 3.5371E-03 +/- 0.2055E-03
40 40 14 gaussian LineE keV 3.164 frozen
41 41 14 gaussian Sigma keV 0. frozen
42 42 14 gaussian norm 6.9491E-03 +/- 0.1668E-03
43 43 15 gaussian LineE keV 3.925 frozen
44 44 15 gaussian Sigma keV 0. frozen
45 45 15 gaussian norm 1.8196E-03 +/- 0.1489E-03
46 46 16 gaussian LineE keV 6.658 frozen
47 47 16 gaussian Sigma keV 0. frozen
48 48 16 gaussian norm 2.7364E-03 +/- 0.1772E-03
49 49 17 gaussian LineE keV 6.839 frozen
50 50 17 gaussian Sigma keV 0. frozen
51 51 17 gaussian norm 1.3231E-03 +/- 0.1892E-03
52 52 18 gaussian LineE keV 7.030 +/- 0.2732E-01
53 53 18 gaussian Sigma keV 0. frozen
54 54 18 gaussian norm 3.7170E-04 +/- 0.1686E-03
55 55 19 gaussian LineE keV 7.971 frozen
56 56 19 gaussian Sigma keV 0. frozen
57 57 19 gaussian norm 1.8948E-04 +/- 0.2383E-03
58 58 20 powerlaw PhoIndex 2.935 +/- 0.6447E-02
59 59 20 powerlaw norm 1.560 +/- 0.1094E-01
60 60 21 wabs nH 10^22 0.9214 +/- 0.2898E-02
61 61 22 powerlaw/b PhoIndex 0. frozen
62 62 22 powerlaw/b norm 7.2173E-02 frozen
---------------------------------------------------------------------------
---------------------------------------------------------------------------
Chi-Squared = 10842.07 using 2048 PHA bins.
Reduced chi-squared = 5.359403 for 2023 degrees of freedom
Null hypothesis probability = 0.
source model uncertainty of ~ 5%
Last modified: 09/25/12
 |
The Chandra X-Ray
Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA. Email: cxcweb@head.cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2004. All rights reserved. |