Technical: Putting it all together: More on the flux issue

As mentioned previously, my best fit to the HETG flux Fx(1.5-9.5 keV) = 3.7 ph/cm^2/s

The HRC response was calculated using weights from 0.5-9.8 keV, although it drops off to < 5% for E > 5.5 keV.  The flux below 1.5 keV is negligible.

Of course, this value includes the scattered flux since the HETG data are in CC mode; in reality, only 80-85% of this is truly from the source, the other 15-20% is scattered and not seen directly. So we add a correction to make it just be the true direct source rate.  I get this 15-20% value from a halo calculation which gives 5% scattering for 1e22 cm^-2 worth of MRN77-type dust, so for 3-4 x10^22 (exact value unknown) it's 15-20%.  I get slightly lower values for some of the reasonable ZDA04 values.  Taking 15% as 'typical', though, this 3.7 ph/cm^2/s becomes 3.1 ph/cm^2/s of direct flux.

Now, within 2" of the GX5-1, there are 500795 cts.  The 'ONTIME' is 4785 s, for a total count rate is 104.6 cts/s, and this should correspond to 90% of the total direct counts, or to 116.3 cts/s total.  Note that I have not taken deadtime into account yet. The effective area here is 62.2 cm^2 (taken from the exposure map), so that means the flux required to get the total observed count rate is 116.3/62.2 = 1.87 ph/cm^2/s.   This is an OK match with the HETG results.  If the deadtime is 30.5%, that can be treated as either reducing the observation time (which increases the measured count rate). Alternatively, if we wish to compare to the 1.87 ph/cm^2/s, we can simply decreasing the estimated flux we got from other sources.  This then converts 3.1 ph/cm^2/s to 2.1 ph/cm^2/s, which is 12%  higher than the 1.87 value.  That's within the range I'm expecting between the  HETG flux and the HRC flux based on the RXTE ASM data.


So, I will use 1.87 ph/cm^2/s as the 'flux' of my HRC-I source, since I only care about the post-deadtime-corrected value, not the actual flux.