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log(N ) | ||||||||||

kT | 0.0 | 18.0 | 18.7
| 19.0 | 19.7 | 20.0
| 20.7 | 21.0 | 21.7
| 22.0 |

0.01 | 3.91e-2 | 3.76e-2 | 3.21e-2 | 2.64e-2 | 5.94e-3 | 1.13e-3 | 2.53e-5 | 1.00e-9 | 1.00e-9 | 1.00e-9 |

0.03 | 1.18e-1 | 1.15e-1 | 1.04e-1 | 9.21e-2 | 3.94e-2 | 1.77e-2 | 6.83e-4 | 6.07e-5 | 1.00e-9 | 1.00e-9 |

0.05 | 1.69e-1 | 1.66e-1 | 1.53e-1 | 1.40e-1 | 7.57e-2 | 4.28e-2 | 3.42e-3 | 4.67e-4 | 2.10e-6 | 1.00e-8 |

0.10 | 2.12e-1 | 2.09e-1 | 1.98e-1 | 1.86e-1 | 1.21e-1 | 8.05e-2 | 1.22e-2 | 3.50e-3 | 1.50e-4 | 1.82e-5 |

0.30 | 2.05e-1 | 2.03e-1 | 1.96e-1 | 1.88e-1 | 1.42e-1 | 1.10e-1 | 4.16e-2 | 2.62e-2 | 6.02e-3 | 1.93e-3 |

0.50 | 1.98e-1 | 1.96e-1 | 1.91e-1 | 1.85e-1 | 1.50e-1 | 1.24e-1 | 6.51e-2 | 4.78e-2 | 1.48e-2 | 5.73e-3 |

1.00 | 1.86e-1 | 1.85e-1 | 1.82e-1 | 1.78e-1 | 1.53e-1 | 1.35e-1 | 8.81e-2 | 7.06e-2 | 2.67e-2 | 1.17e-2 |

3.00 | 1.68e-1 | 1.68e-1 | 1.65e-1 | 1.63e-1 | 1.47e-1 | 1.35e-1 | 9.95e-2 | 8.36e-2 | 3.59e-2 | 1.72e-2 |

5.00 | 1.63e-1 | 1.63e-1 | 1.60e-1 | 1.58e-1 | 1.44e-1 | 1.33e-1 | 1.01e-1 | 8.55e-2 | 3.77e-2 | 1.83e-2 |

log(N ) | ||||||||||

| 0.0 | 18.0 | 18.7
| 19.0 | 19.7 | 20.0
| 20.7 | 21.0 | 21.7
| 22.0 |

0.0 | 1.44e-1 | 1.43e-1 | 1.42e-1 | 1.41e-1 | 1.32e-1 | 1.25e-1 | 1.03e-1 | 8.93e-2 | 4.25e-2 | 2.17e-2 |

0.5 | 1.64e-1 | 1.63e-1 | 1.61e-1 | 1.58e-1 | 1.41e-1 | 1.29e-1 | 9.45e-2 | 7.96e-2 | 3.50e-2 | 1.71e-2 |

1.0 | 1.81e-1 | 1.80e-1 | 1.75e-1 | 1.70e-1 | 1.41e-1 | 1.21e-1 | 7.52e-2 | 6.02e-2 | 2.42e-2 | 1.12e-2 |

1.5 | 1.90e-1 | 1.90e-1 | 1.81e-1 | 1.73e-1 | 1.32e-1 | 1.05e-1 | 5.09e-2 | 3.79e-2 | 1.36e-2 | 5.97e-3 |

2.0 | 1.88e-1 | 1.86e-1 | 1.77e-1 | 1.67e-1 | 1.16e-1 | 8.50e-2 | 3.06e-2 | 2.05e-2 | 6.41e-3 | 2.65e-3 |

2.5 | 1.78e-1 | 1.76e-1 | 1.66e-1 | 1.54e-1 | 9.85e-2 | 6.68e-2 | 1.75e-2 | 1.01e-2 | 2.67e-3 | 1.04e-3 |

3.0 | 1.64e-1 | 1.61e-1 | 1.51e-1 | 1.39e-1 | 8.20e-2 | 5.19e-2 | 9.92e-3 | 4.76e-3 | 1.04e-3 | 3.74e-4 |

log(N ) | ||||||||||

kT | 0.0 | 18.0 | 18.7
| 19.0 | 19.7 | 20.0
| 20.7 | 21.0 | 21.7
| 22.0 |

0.01 | 5.17e-1 | 4.98e-1 | 4.29e-1 | 3.56e-1 | 8.75e-2 | 1.86e-2 | 1.59e-5 | 2.00e-7 | 1.00e-9 | 1.00e-9 |

0.03 | 3.39e-1 | 3.28e-1 | 2.90e-1 | 2.50e-1 | 8.41e-2 | 2.80e-2 | 4.09e-4 | 3.20e-5 | 1.00e-9 | 1.00e-9 |

0.05 | 2.97e-1 | 2.92e-1 | 2.73e-1 | 2.51e-1 | 1.43e-1 | 8.16e-2 | 5.50e-3 | 6.24e-4 | 2.70e-6 | 1.00e-7 |

0.10 | 2.74e-1 | 2.72e-1 | 2.63e-1 | 2.52e-1 | 1.88e-1 | 1.38e-1 | 2.54e-2 | 7.27e-3 | 2.69e-4 | 2.91e-5 |

0.30 | 1.92e-1 | 1.92e-1 | 1.89e-1 | 1.86e-1 | 1.68e-1 | 1.52e-1 | 1.02e-1 | 7.82e-2 | 1.75e-2 | 3.95e-3 |

0.50 | 2.41e-1 | 2.40e-1 | 2.38e-1 | 2.35e-1 | 2.22e-1 | 2.12e-1 | 1.75e-1 | 1.47e-1 | 4.29e-2 | 1.14e-2 |

1.00 | 2.27e-1 | 2.26e-1 | 2.22e-1 | 2.17e-1 | 1.95e-1 | 1.83e-1 | 1.51e-1 | 1.31e-1 | 5.33e-2 | 2.08e-2 |

3.00 | 1.75e-1 | 1.74e-1 | 1.72e-1 | 1.69e-1 | 1.54e-1 | 1.44e-1 | 1.11e-1 | 9.50e-2 | 4.27e-2 | 2.05e-2 |

5.00 | 1.66e-1 | 1.66e-1 | 1.64e-1 | 1.61e-1 | 1.48e-1 | 1.38e-1 | 1.06e-1 | 9.07e-2 | 4.08e-2 | 1.99e-2 |

log(N ) | ||||||||||

kT | 0.0 | 18.0 | 18.7
| 19.0 | 19.7 | 20.0
| 20.7 | 21.0 | 21.7
| 22.0 |

0.01 | 5.59e-2 | 5.38e-2 | 4.65e-2 | 3.88e-2 | 9.98e-3 | 2.35e-3 | 4.80e-6 | 1.00e-7 | 1.00e-9 | 1.00e-9 |

0.03 | 2.02e-1 | 1.98e-1 | 1.85e-1 | 1.71e-1 | 9.85e-2 | 5.79e-2 | 4.62e-3 | 5.61e-4 | 9.00e-7 | 1.00e-9 |

0.05 | 2.48e-1 | 2.45e-1 | 2.35e-1 | 2.23e-1 | 1.55e-1 | 1.08e-1 | 1.66e-2 | 4.00e-3 | 7.07e-5 | 3.50e-6 |

0.10 | 1.89e-1 | 1.87e-1 | 1.83e-1 | 1.78e-1 | 1.47e-1 | 1.21e-1 | 5.07e-2 | 3.05e-2 | 4.40e-3 | 9.29e-4 |

0.30 | 1.77e-1 | 1.77e-1 | 1.76e-1 | 1.76e-1 | 1.71e-1 | 1.66e-1 | 1.44e-1 | 1.25e-1 | 5.45e-2 | 2.52e-2 |

0.50 | 1.39e-1 | 1.39e-1 | 1.39e-1 | 1.38e-1 | 1.36e-1 | 1.34e-1 | 1.21e-1 | 1.09e-1 | 5.52e-2 | 2.88e-2 |

1.00 | 1.04e-1 | 1.04e-1 | 1.03e-1 | 1.03e-1 | 1.02e-1 | 1.01e-1 | 9.29e-2 | 8.49e-2 | 4.72e-2 | 2.65e-2 |

3.00 | 8.48e-2 | 8.48e-2 | 8.47e-2 | 8.46e-2 | 8.38e-2 | 8.29e-2 | 7.71e-2 | 7.11e-2 | 4.13e-2 | 2.41e-2 |

5.00 | 8.18e-2 | 8.17e-2 | 8.17e-2 | 8.16e-2 | 8.09e-2 | 8.00e-2 | 7.45e-2 | 6.88e-2 | 4.03e-2 | 2.37e-2 |

The expected HRI count rates depend sensitively on the assumed incident spectrum, which is not well known for many sources. In general, the convolution of the effective area and incident spectrum needs to be calculated to predict the HRI counting rate. Since the effective area is not a simple analytic function, the convolution is not straight-forward. In order to facilitate count rate calculations we provide a series of tables and graphs which give the energy-to-counts conversion factor (ECF) for several spectral models and various spectral parameters. These are based upon the counts collected in a detect cell which is assumed to contain 50% of the total source counts that fall on the HRI detector. (Note that other estimation techniques may use the total counts and hence may differ by a factor of two from the results obtained by following the procedures described here.)

Tables for computing the expected count rates in the ROSAT\ HRI were generated for four spectral models. These are:

- Thermal Bremsstrahlung (Exponential plus Gaunt Factor) Spectrum (Table 11.2, Figure 11.4 of Appendix F), where kT is in keV.
- Power Law Spectrum (Table 11.3, Figure 11.5 of Appendix F), where is the energy index.
- Raymond-Smith Plasma Spectrum (Table 11.4, Figure 11.6 of Appendix F), where kT is in keV.
- Blackbody Spectrum (Table 11.5, Figure 11.7 of Appendix F), where kT is in keV

For each spectral model we calculate the factor by which the unabsorbed source flux (in units of erg cm s ) has to be multiplied in order to obtain the expected HRI on-axis count rate within the detect cell. The conversion factor is as a function of the intrinsic source spectrum (characterized by or kT), and the interstellar absorption column density .

The curves shown in Appendix F Figures 11.4 - 11.7 (or Tables 5.10 - 5.13 reproduced here for convenience) should be used as follows:

- Estimate the
**un**absorbed source flux (in units of ergs cm s ) in the ROSAT pass band 0.1 - 2.4 keV. This is the flux which would have been incident on the Earth in the absence of any absorption. - Estimate the interstellar absorption column density.
- With the assumed values of and spectral parameter ( or kT) read from the figures or tables the resulting energy-to-counts conversion factor ECF.
- Multiply and ECF to obtain the expected ROSAT HRI count rate.