[Last Change: 05 Apr 2011 (rev 2)]
Assessing the Chandra PSF Wings: On-Orbit Calibration
Version 1.0-Rev1
T. J. Gaetz
A deep observation of Her X-1 was analyzed to characterize the on-axis PSF wings of
Chandra's High Resolution Mirror Assembly (HRMA). Because of detector pileup, the fits are reliable only for distances greater than approximately 15". A full memo describing the analysis is available here:
1up 2up
This memo supercedes the
estimate based on ground calibration.
Summary of the observation
| ObsID |
Object |
Exposure |
Frame time |
Theta |
NH (cm-2) |
| 3662 |
Her X-1 high state |
50 ks |
3.1 s |
45" |
1.8E20 |
Fit with projected QE Map
Errors are purely statistical. These fits are to profiles flattened using a projected QE map and the effective area evaluated at the specular image of Her X-1. For further discussion, see the full memo:
1up 2up
The fit is to a function of the form:
ψ(θ) = a (θ/θ0)-γ exp(-c θ)
where
| ψ |
= |
normalized PSF (arcsec-2) |
| θ |
= |
angle from PSF center (in arcsec) |
| θ0 |
= |
reference θ (nominally 10 arcsec) |
| γ0 |
= |
powerlaw index |
| c |
= |
exponential cutoff (arcsec-1) |
| a |
= |
normalization factor |
Note that the fits were for θ ≥ 15". For smaller radii, pileup increasingly depresses the profile.
Table 2: Fit Coefficients
| Energy |
γ |
γerr |
a |
aerr |
c |
cerr |
| (keV) |
|
(arcsec-2) |
(arcsec-1) |
| 1.0-2.0 |
1.972 |
0.003 |
7.476e-06 |
3.739e-08 |
6.750e-04 |
4.915e-05 |
| 2.0-3.0 |
1.840 |
0.004 |
1.012e-05 |
7.033e-08 |
1.213e-03 |
5.971e-05 |
| 3.0-4.0 |
1.760 |
0.008 |
1.875e-05 |
1.618e-07 |
1.963e-03 |
5.236e-05 |
| 4.0-5.0 |
1.749 |
0.008 |
2.569e-05 |
2.177e-07 |
1.982e-03 |
5.061e-05 |
| 5.0-6.0 |
1.902 |
0.011 |
3.471e-05 |
3.693e-07 |
1.783e-03 |
7.361e-05 |
| 6.0-7.0 |
1.948 |
0.015 |
4.017e-05 |
5.875e-07 |
1.844e-03 |
1.159e-04 |
| 7.0-8.0 |
2.137 |
0.030 |
4.909e-05 |
1.280e-06 |
-3.332e-04 |
2.531e-04 |
Fit to a conventional exposure map
Errors are purely statistical. These fits are to profiles flattened using a conventional exposure map. For further discussion, see the full memo:
1up 2up
The fit is to a function of the form:
ψ(θ) = a (θ/θ0)-γ exp(-c θ)
where
| ψ |
= |
normalized PSF (arcsec-2) |
| θ |
= |
angle from PSF center (in arcsec) |
| θ0 |
= |
reference θ (nominally 10 arcsec) |
| γ0 |
= |
powerlaw index |
| c |
= |
exponential cutoff (arcsec-1) |
| a |
= |
normalization factor |
Note that the fits were for θ ≥ 15". For smaller radii, pileup increasingly depresses the profile.
Table 3: Fit Coefficients
| Energy |
γ |
γerr |
a |
aerr |
c |
cerr |
| (keV) |
|
(arcsec-2) |
(arcsec-1) |
| 1.0-2.0 |
1.967 |
0.003 |
7.443e-06 |
3.725e-08 |
5.641e-04 |
4.917e-05 |
| 2.0-3.0 |
1.841 |
0.004 |
1.013e-05 |
7.042e-08 |
1.075e-03 |
5.973e-05 |
| 3.0-4.0 |
1.764 |
0.008 |
1.884e-05 |
1.633e-07 |
1.836e-03 |
5.245e-05 |
| 4.0-5.0 |
1.757 |
0.008 |
2.591e-05 |
2.207e-07 |
1.823e-03 |
5.074e-05 |
| 5.0-6.0 |
1.924 |
0.011 |
3.533e-05 |
3.780e-07 |
1.473e-03 |
7.404e-05 |
| 6.0-7.0 |
2.002 |
0.016 |
4.166e-05 |
6.148e-07 |
1.057e-03 |
1.168e-04 |
| 7.0-8.0 |
2.264 |
0.032 |
5.303e-05 |
1.394e-06 |
-2.031e-03 |
2.555e-04 |
