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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 postscript memo describing the analysis is available here: 1up 2up or the PDF version.
This memo supercedes the estimate based on ground calibration.
| ObsID | Object | Exposure | Frame time | Theta | NH (cm-2) |
|---|---|---|---|---|---|
| 3662 | Her X-1 high state | 50 ks | 3.1 s | 45" | 1.8E20 |
Errors are purely statististical. 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 postscript memo: 1up 2up or the PDF version.
The fit is to a function of the form:
| &psi | = | normalized PSF (arcsec-2) |
| &theta | = | angle from PSF center (in arcsec) |
| &theta0 | = | reference &theta (nominally 10 arcsec) |
| &gamma0 | = | powerlaw index |
| c | = | exponential cutoff (arcsec-1) |
| a | = | normalization factor |
Note that the fits were for &theta &ge 15". For smaller radii, pileup increasingly depresses the profile.
| Energy | gamma | gamma_err | a | a_err | c | c_err |
|---|---|---|---|---|---|---|
| (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 |
The fit is to a function of the form:
| &psi | = | normalized PSF (arcsec-2) |
| &theta | = | angle from PSF center (in arcsec) |
| &theta0 | = | reference &theta (nominally 10 arcsec) |
| &gamma0 | = | powerlaw index |
| c | = | exponential cutoff (arcsec-1) |
| a | = | normalization factor |
Note that the fits were for &theta &ge 15". For smaller radii, pileup increasingly depresses the profile.
| Energy | gamma | gamma_err | a | a_err | c | c_err |
|---|---|---|---|---|---|---|
| (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 |
Last modified: 2008 Jul 18
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