D. E. McKenzie (Montana State University), S. Gburek (Space Research Centre, Polish Academy of Sciences), L. W. Acton, P. C. Martens (Montana State University) The Point Spread Function of the Yohkoh Soft X-ray Telescope Poster preparation for AAS meeting

Abstract The point spread function (PSF) of the Yohkoh solar observatory's Soft X-ray Telescope has two primary components, a sharply defined core and a diffuse wing due to photon scattering. Because the extent of the PSF is significantly wider than a single pixel, its characterization is useful for improvement of the quality of the SXT images. We will present results from analyses of the two PSF components, and demonstrate our best model of the core and scattering wing of the SXT point spread function. An example of PSF deconvolution to remove the effects of photon scattering will be given

Core part of the SXT PSF Properties: Size – about 5 pixels from the peak FWHM – approx. 1.5 pixels Depends on wavelength, position on the CCD

Calibration series to consider BX42_APR25 49 C K (0.28 keV/44.7 A) Best_Defoc XY Scan -> X,-11,500 to -2,500; Y, -6,500 to 2,500; Step 1,500 BX02_APR23 49 Al K (1.49 keV/8.34 A) Best_Defoc XY Scan -> X,-11,500 to -2,500; Y, -6,500 to 2,500 Step 1,500 BX51_APR25 49 Ag L (3.00 keV/4.16 A) Best_Defoc XY Scan -> X,-11,500 to -2,500; Y, -6,500 to 2,500; Step 1,500 Could be also BX21_APR24 49 C K Best_Defoc XY Scan -> X,-11,500 to -2,500; Y, -6,500 to 2,500; Step 1,500

bx42_apr25 calibration series

bx02_apr23 calibration series The image above shows 49 images of bx01_apr23 ground calibration series. Enlarged contour plots of their peak portions in the image bellow.

bx51_apr25 calibration series

Elipticity of the core calibration series bx42_apr25 bx02_apr23 bx51_apr25 The PSF core gets elliptically deformed with the distance from the CCD center. In the CCD corners can be even double peaked.

averaged core cross sections calibration series bx42_apr25 bx02_apr23 bx51_apr25 Solid line peak x-cross sections (upper row) and y-cross sections (the bottom row) for average PSF core for WSMR calibration series. The average PSF shape was determined from images 7-49 for each of (mentioned above) series respectively. Error bars show absolute errors for the selected images

Comparison of cross sections of averaged PSF core for different energies x-cross sections y-cross sections Al-K C-K Ag-L Al-K C-K Ag-L

Core aplications Aplications: Deconvolution of the SXT Flare images, mainly in horizontal belt shown to the left where eliptical deformation of the core PSF part is small. Above, a coverage map of the CCD detector surface by full resolution SXT frames. Gray intensity says how many times a given pixel was captured within a full resolution frame during year 2000.

SXT flare frame 8-MAY-00 at 10:50:21 Deconvolved image SXT flare frame (Log10 scale) Deconvolved image (Log10 scale) Example of deconvolution of SXT Flare images

PSF approximation from steepest descent method Calibration beam seen in Al.-K line Deconvolved PSF PSF cross sections (x-cross section in the left panel, to the right y-cross section. Thin solid line – cross sections of the PSF found by steepest descents method Thick solid line – cross sections of the calibration beam Diamonds – deconvolved PSF cross-sections