On Fri, 14 Jun 2002, Daryl Haggard wrote:
> Hello all,
>
> I have a question that falls in the same general category as the one
> discussed earlier today (below).
>
> I have run wavdetect on my ACIS-I field and created a source list. I have
> also have computed psf's to determine the 95% encircled energy radii (as a
> function of off-axis angle at 1.4967keV) that I will use for count
> extraction. To determine appropriate fluxes for my sources I would also
> like to correct for the differing effective area of the HRMA/ACIS-I, again
> as a function of off-axis angle, using appropriate exposure maps. So,
>
> (1) I am wondering if there is a "standard" effective area that I can use
> to normalize my counts after I have adjusted them using the exposure maps.
I would either use standard responses that are released for proposals
or extract a dummy spectrum from a 2" region on-axis and generate an arf for
that.
>
> (2) In part I am interested because I want to use the PIMMS tool to
> convert counts/s to x-ray fluxes (erg/cm^2/s) and I imagine some effective
> area is assumed by that tool. Does anyone know what effective area PIMMS
> uses (at 1.4967keV) or where to find that information?
>
If you download the code for pimms, there is a data directory that has
simple text files for energy vs. eff. area. In the version I am using for
acis-i at 1.5 keV the area is ~ 655 cm^2. But the approach I prefer is to
extract spectra and generate arfs even for sources without enough counts
for fitting, and then use the arf to compute the flux for a power-law
spectrum. I have a simple c++ program to read in an arf and compute the
flux for a power-law if you are interested (it used by the pipeline
software I have that does this for every source in a field).
Cheers,
Andy Ptak
This archive was generated by hypermail 2b29 : Tue Feb 12 2013 - 01:00:11 EST