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Next: Examples Up: FEASIBILITY: XMA + HRI Previous: Point Source Sensitivity

Expected Count Rates

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.

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

For each spectral model we calculate the factor by which the unabsorbed source flux (in units of tex2html_wrap_inline2420  ergs cm tex2html_wrap_inline1930  s tex2html_wrap_inline1894 ) has to be multiplied in order to obtain the expected HRI on-axis count rate within the 5'' detect cell as a function of the spectral parameter ( tex2html_wrap_inline2288 or kT), and the interstellar absorption column density tex2html_wrap_inline2416 .

The curves shown in Figures 11.4 gif - 11.7 gif (or Tables 11.2gif - 11.5gif) should be used as follows:

  1. Calculate the expected source flux tex2html_wrap_inline2506 (in units of tex2html_wrap_inline2420  ergs cm tex2html_wrap_inline1930  s tex2html_wrap_inline1894 ) in the ROSAT pass band 0.1 - 2.4 keV assuming no interstellar absorption.
  2. Determine the expected interstellar absorption column density.
  3. With the assumed values of tex2html_wrap_inline2416 and spectral parameter ( tex2html_wrap_inline2288 or kT) read from the figures or tables the resulting energy-to-counts conversion factor ECF.
  4. Multiply tex2html_wrap_inline2506 and ECF to obtain the expected ROSAT HRI count rate.

 

ROSAT HRI Energy to Count Conversion Factors
log( tex2html_wrap_inline2416 )
kT 0.0 18.0 18.7 19.0 19.7 20.0 20.7 21.0 21.7 22.0
0.013.91e-23.76e-23.21e-22.64e-25.94e-31.13e-32.53e-51.00e-91.0 0e-91.00e-9
0.031.18e-11.15e-11.04e-19.21e-23.94e-21.77e-26.83e-46.07e-51.0 0e-91.00e-9
0.051.69e-11.66e-11.53e-11.40e-17.57e-24.28e-23.42e-34.67e-42.1 0e-61.00e-8
0.102.12e-12.09e-11.98e-11.86e-11.21e-18.05e-21.22e-23.50e-31.5 0e-41.82e-5
0.302.05e-12.03e-11.96e-11.88e-11.42e-11.10e-14.16e-22.62e-26.0 2e-31.93e-3
0.501.98e-11.96e-11.91e-11.85e-11.50e-11.24e-16.51e-24.78e-21.4 8e-25.73e-3
1.001.86e-11.85e-11.82e-11.78e-11.53e-11.35e-18.81e-27.06e-22.6 7e-21.17e-2
3.001.68e-11.68e-11.65e-11.63e-11.47e-11.35e-19.95e-28.36e-23.5 9e-21.72e-2
5.001.63e-11.63e-11.60e-11.58e-11.44e-11.33e-11.01e-18.55e-23.7 7e-21.83e-2
Table: 11.2   Thermal Bremsstrahlung

 

ROSAT HRI Energy to Count Conversion Factors
log( tex2html_wrap_inline2416 )
tex2html_wrap_inline2288 0.0 18.0 18.7 19.0 19.7 20.0 20.7 21.0 21.7 22.0
0.01.44e-11.43e-11.42e-11.41e-11.32e-11.25e-11.03e-18.93e-24.25 e-22.17e-2
0.51.64e-11.63e-11.61e-11.58e-11.41e-11.29e-19.45e-27.96e-23.50 e-21.71e-2
1.01.81e-11.80e-11.75e-11.70e-11.41e-11.21e-17.52e-26.02e-22.42 e-21.12e-2
1.51.90e-11.90e-11.81e-11.73e-11.32e-11.05e-15.09e-23.79e-21.36 e-25.97e-3
2.01.88e-11.86e-11.77e-11.67e-11.16e-18.50e-23.06e-22.05e-26.41 e-32.65e-3
2.51.78e-11.76e-11.66e-11.54e-19.85e-26.68e-21.75e-21.01e-22.67 e-31.04e-3
3.01.64e-11.61e-11.51e-11.39e-18.20e-25.19e-29.92e-34.76e-31.04 e-33.74e-4
Table: 11.3   Power Law

 

ROSAT HRI Energy to Count Conversion Factors
log( tex2html_wrap_inline2428 )
kT 0.0 18.0 18.7 19.0 19.7 20.0 20.7 21.0 21.7 22.0
0.015.17e-14.98e-14.29e-13.56e-18.75e-21.86e-21.59e-52.00e-71.0 0e-91.00e-9
0.033.39e-13.28e-12.90e-12.50e-18.41e-22.80e-24.09e-43.20e-51.0 0e-91.00e-9
0.052.97e-12.92e-12.73e-12.51e-11.43e-18.16e-25.50e-36.24e-42.7 0e-61.00e-7
0.102.74e-12.72e-12.63e-12.52e-11.88e-11.38e-12.54e-27.27e-32.6 9e-42.91e-5
0.301.92e-11.92e-11.89e-11.86e-11.68e-11.52e-11.02e-17.82e-21.7 5e-23.95e-3
0.502.41e-12.40e-12.38e-12.35e-12.22e-12.12e-11.75e-11.47e-14.2 9e-21.14e-2
1.002.27e-12.26e-12.22e-12.17e-11.95e-11.83e-11.51e-11.31e-15.3 3e-22.08e-2
3.001.75e-11.74e-11.72e-11.69e-11.54e-11.44e-11.11e-19.50e-24.2 7e-22.05e-2
5.001.66e-11.66e-11.64e-11.61e-11.48e-11.38e-11.06e-19.07e-24.0 8e-21.99e-2
Table: 11.4   Raymond-Smith

 

ROSAT HRI Energy to Count Conversion Factors
log( tex2html_wrap_inline2416 )
kT 0.0 18.0 18.7 19.0 19.7 20.0 20.7 21.0 21.7 22.0
0.015.59e-25.38e-24.65e-23.88e-29.98e-32.35e-34.80e-61.00e-71.0 0e-91.00e-9
0.032.02e-11.98e-11.85e-11.71e-19.85e-25.79e-24.62e-35.61e-49.0 0e-71.00e-9
0.052.48e-12.45e-12.35e-12.23e-11.55e-11.08e-11.66e-24.00e-37.0 7e-53.50e-6
0.101.89e-11.87e-11.83e-11.78e-11.47e-11.21e-15.07e-23.05e-24.4 0e-39.29e-4
0.301.77e-11.77e-11.76e-11.76e-11.71e-11.66e-11.44e-11.25e-15.4 5e-22.52e-2
0.501.39e-11.39e-11.39e-11.38e-11.36e-11.34e-11.21e-11.09e-15.5 2e-22.88e-2
1.001.04e-11.04e-11.03e-11.03e-11.02e-11.01e-19.29e-28.49e-24.7 2e-22.65e-2
3.008.48e-28.48e-28.47e-28.46e-28.38e-28.29e-27.71e-27.11e-24.1 3e-22.41e-2
5.008.18e-28.17e-28.17e-28.16e-28.09e-28.00e-27.45e-26.88e-24.0 3e-22.37e-2
Table: 11.5   Blackbody




next up previous contents
Next: Examples Up: FEASIBILITY: XMA + HRI Previous: Point Source Sensitivity

Michael Arida
Tue Jun 11 16:18:41 EDT 1996