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New PSFs available for the ASCA XRT

   Point Spread Function datasets for the ASCA XRT available

There are new images giving the Point Spread Function of the ASCA XRT
available in the Calibration Database on legacy.gsfc.nasa.gov. These
datasets have been provided by Keith Arnaud of the ASCA GOF. 

There are 11 new files within the directory:
one file for each of 11 different positions in the focal plane, with a 
naming scheme psf_*_*.fits. Each file contains 10 psf images appropriate 
for 10 different energy bands. Further information is provided in the 
README file within the above directory (and appended below).

These datasets supercede all previous XRT PSF datasets available, namely the:
  - ray-tracing simulations astrod_image_*_*.fits, which have been 
	MOVED at the request of the ASCA GOF to
  - the xrt_psf_isas1.fits file, which has been 
	MOVED at the request of the ASCA GOF to
  - the xrt_eef_220693.fits file, which has been 
	MOVED at the request of the ASCA GOF to

Ian M George

README for ASCA XRT Point Spread Function datasets

This directory contains files containing PSF images for the ASCA XRT.
The file naming scheme is psf_X_Y.fits, where each file contains PSF
images for a given position in the focal plane, with X giving the 
off-axis angle (theta, in arcmins) and Y giving the azimuthal angle 
(phi, in degrees). The following positions are currently available:
	pos. 1: theta= 1.8 arcmin, phi= 5 deg
	pos. 2: theta= 3.8 arcmin, phi=10 deg
	pos. 3: theta= 6.0 arcmin, phi= 9 deg
	pos. 4: theta= 6.0 arcmin, phi=19 deg	
	pos. 5: theta= 8.1 arcmin, phi=34 deg
	pos. 6: theta=13.0 arcmin, phi= 0 deg
	pos. 7: theta=13.0 arcmin, phi=22 deg
	pos. 8: theta=13.0 arcmin, phi=40 deg
	pos. 9: theta=17.0 arcmin, phi= 0 deg
	pos.10: theta=17.0 arcmin, phi=18 deg
	pos.11: theta=17.0 arcmin, phi=39 deg

Each file contains 10 PSF images (the Primary Array + 9 IMAGE extensions)
appropriate for 10 different energy bands (1-2-3-4-5-6-7-8-9-10-12 keV).

Each image is 63 x 63 pixels, where 1 image pixel = 1 arcmin (= 4 GIS pixels), 
and were constructed from observations of Cyg X-1 using the GIS. The images 
have been smoothed to compensate for the GIS energy-dependent detector 

In all cases:
- The peak brightness is at the center of the pixel (32,32). 
- The images are normalized to have 1 photon within the 6 arcmin off-peak 
- Background is subtracted. 
- The images are smoothed before binning with the position-independent 
	Gaussian with sigma=0.85, 1.35, 1.51, 1.54, 1.64, 1.67, 1.66, 
	1.60, 1.46, 1.18 GIS pixels for the 10 energy bands, respectively, 
- Have the final resolution of sigma=0.5 arcmin in all energy bands. 

For further details on the construction of the datasets, contact 
Maxim Markevitch <maxim@astro.isas.ac.jp>