Utility Bugs: eflux

Bugs

1. In ARF-less analysis, it is possible to calculate fluxes but not flux densities.

2. Problems calculating flux and counts over a range.

Bugs

1. In ARF-less analysis, it is possible to calculate fluxes but not flux densities.

   sherpa> dataspace (0.1:10:0.01) histogram
   sherpa> paramprompt off
   Model parameter prompting is off
   sherpa> source = powlaw1d * xsphabs
   sherpa> eflux (0.5:2.0)
   Flux for source dataset 1: 1.92335e-09 counts
   sherpa> eflux (0.5)
   Error: applying the current filter yields an empty dataset.
   

   create a dummy ARF filled with zeroes:

   sherpa> erase all
   sherpa> x = [0.1:10.0:0.01]
   sherpa> arf = struct { _filename, ENERG_LO, ENERG_HI, SPECRESP }
   sherpa> arf._filename = "a1"
   sherpa> arf.ENERG_LO = typecast( x[[:-2]], Float_Type );
   sherpa> arf.ENERG_HI = typecast( x[[1:]], Float_Type );
   sherpa> arf.SPECRESP = arf.ENERG_LO * 0.0f;
   sherpa> () = load_arf("a1",arf )
   sherpa> instrument 1 = a1
   
   (continue from above)
   

   Note that this ARF adds no value to the session since it equals 0.0 at each energy; it is only used to allow the flux-density to be calculated.

2. Problems calculating flux and counts over a range.

   The behavior described in this bug applies to the following commands:

   • [B]EFLUX,
   • [B]PFLUX,
   • [B]DCOUNTS,
   • [B]MCOUNTS,
   • and the corresponding "get" commands (e.g. get_eflux).

   Given x > 0:

   1. "EFLUX (0:x)" returns the same value as "EFLUX" (i.e. the flux over the full range of the dataset), when it should return the flux integrated from the start of the dataset to x.
   2. "EFLUX (x:0)" returns the same value as "EFLUX (x)." This should return an error since x > 0, so the range isn't sensible.

   Workaround:

   replace 0 with a small decimal, e.g. 0.001. Then case 1 gives the correct answer (flux from the start of the dataset to x), and case 2 gives 0 (which at least tells you that you did something wrong).