Presently an analytical representation of the point spread function is available for the experiment ROSAT PSPC and ROSAT HRI. For ROSAT WFC it is not included in this release of EXSAS.
For ROSAT PSPC a Gaussian representation of the point spread function as a function of off-axis-angle and energy is available. This function is used in the EXSAS spatial analysis commands (including Source Detection commands).
There is also a more complicated presentation available (Gaussian + exponential + Lorentzian function). The surface brightness of the point spread function is normalized to 1,
The on-axis point spread function PSF(E,r), with energy E (in keV) and distance from the center of the point spread function r (in arcsec) can be calculated from the relations given below.
with
BR1 = 39.95 / E
BR2 = 861.9 / E
F1 = A1 / (2. 
)
F2 = A2 / (2. 
)
F3 = A3 / ( 
) -
log(BR1 
BR1) + 2. / (ALPHA-2.)))
ARG1 = 0.5 
ARG2 = r / RC
SIGMA = 
RC = 
ALPHA = 2.119 + 0.212 
E
A1 = 1.0 - A2 - A3
A2 = 
A3 = 0.059 
The ring integrated surface normalized on-axis point spread function for ROSAT PSPC is plotted for energies of 0.1, 0.3, 0.5, 0.8, 1.0, 1.2 and 1.5 keV in Figure 5.13. It is also available in form of a table file, EXSAS_CAL:psf.tbl and EXSAS_CAL:psf_pspc_00.tbl, in the energy range 0.1 to 1.7 keV.
For off-axis angles of 5 to 50 arcmin (in steps of 5 arcmin) the point spread function is available in table form as well (EXSAS_CAL:psf_pspc_05.tbl, ..., EXSAS_CAL:psf_pspc_50.tbl).
For ROSAT HRI the point spread function is available in table form (EXSAS_CAL:psf_hri_05.tbl, EXSAS_CAL:psf_hri_10.tbl, ..., EXSAS_CAL:psf_hri_20.tbl) for off-axis angles of 0 (on-axis), 5, ..., 20 arcmin.
Figure 5.13:
On-axis ROSAT PSPC surface brightness of the point spread function
for energies of 0.1, 0.3, 0.5, 0.8, 1.0, 1.2 and 1.5 keV and
distances to the center of the point spread function up to about
3000 arcsec. The normalization is as given in
section 5.4.1
including a multiplicative factor of 3600.