Characterization of the Advanced Satellite for Cosmology and Astrophysics x-ray telescope: preflight calibration and ray tracing

Abstract

The x-ray properties of multinested thin-foil mirror x-ray telescopes (XRT's) on board ASCA, the Advanced Satellite for Cosmology and Astrophysics, were fully evaluated with an x-ray pencil beam.Scanning over the telescope aperture of 35 cm in diameter with an x-ray pencil beam, we found the effective area of a set of XRT's to be 325, 200, and 113 cm(2) at energies of 1.5, 4.5, and 8.0 keV, respectively. We derive the point-spread functions (PSF's) of the XRT's by measuring the image profile at the focal plane with an x-ray CCD. The PSF is found to exhibit a sharp core concentrated within 30 arcsec and a broad wing extended to 3 arcmin in half-power diameter. We also evaluate the contribution of stray light, which is caused by the single reflection of x rays by primary or secondary mirrors and by the backside reflection of the mirrors. To obtain the characteristics of the XRT in the energy region of 0.5-10.0 keV, incorporated with the measurements at discrete energies, we develop a ray-tracing method with the telescope design parameter, the PSF, and optical constants. In particular, we obtain the optical constants around the gold-atom M shell (Au-M) absorption-edge energies by measuring the reflectivity of our mirror sample, with monochromatized x-rays in the energy range of 2.0-3.5 keV from synchrotron radiation. Taking into account the PSF's and optical constants, we find that our ray-tracing program can reproduce all these XRT performances.

A Filament between Galaxy Clusters A3391 and A3395

“…There are three independent causes of light scattering (Tsusaka et al 1995) : (1) nonideal optical paths, (2) broadening owing to reÑector misalign -FIG. 4.ÈThe GIS image of the region between A3391 and A3395.…”

“…They have, at their core, the same legacy routines developed for preÑight characterization of the ASCA XRT. Those routines were able to reproduce the scattered light to better than 10% for a source 1¡ o †-axis (Tsusaka et al 1995). In-Ñight validation of the ray-tracing software has been sparse.…”

Detection of a Temperature Structure in the Coma Cluster of Galaxies with [ITAL]ASCA[/ITAL]

“…The systematic error in the estimation of the stray-light effect should affect our spectral results. The "ray-tracing" method (Tsusaka et al 1995) is used to estimate the XRT response in the present analysis. We compare the observed spectra of the Crab Nebula at different offset angles (0Ј-80Ј) and those produced by the ray-tracing code (Ishisaki 1996).…”

Development of thin-foil substrates for a large X-ray telescope

“…The figure error of <10 lm enables us to make a smooth surface using several methods, for example, by using a replication method (Furuzawa et al, 1998). We applied improvements of the ASCA type mirror to the new type mirror, because we have a good understanding of the characteristics of the ASCA type mirror (Tsusaka et al, 1994(Tsusaka et al, , 1995, and this type of mirror satisfies the weight constraints of Japanese satellites. The design of our prototype of the substrate is shown in Fig.…”