How large is the effective area of one XRT?
The effective area (including the detector efficiency) at launch was about 330 and 370 cm2 on the FI and BI at 1.5 keV. The detector efficiency has been decreasing due to the contamination accumulating on the optical blocking filters. The user is referred to Section 2.1 of the technical description for further details. • How big is the effect of straylight from nearby bright sources? Stray light is equal to or less than three orders of magnitude of the effective area at on-axis, depending on the off-axis angle and the energy of the stray source. For more details, please eee Section 5.2.6 of the technical description. • How large is the difference in the pointing direction between XIS and HXD? Although the average optical axis of XIS and that of HXD-PIN differ by about 5 arcmin, the XIS field of view is entirely covered by the HXD-PIN field of view. Users therefore always obtain both XIS and HXD data simultaneously. Taking into account this difference, we prepared the two default pointi
