The characteristics of an x-ray spectrum can greatly influence imaging and related tasks. In practice, due to the pile-up effect of the detector, it's difficult to directly measure the spectrum of a CT scanner using an energy resolved detector. An alternative solution is to estimate the spectrum using transmission measurements with a step phantom or another CT phantom. In this work, we present ...

We investigate the nature of the luminous X-ray source population detected in a (72 ks) Chandra ACISS observation of NGC 4038/39, the Antennae galaxies. We derive the average X-ray spectral properties of sources in different luminosity ranges, and we correlate the X-ray positions with radio, IR, and optical (HST) data. The X-ray sources are predominantly associated with young stellar clusters, ...

Chandra observations of the type 1.8, low-redshift (z 1⁄4 0:115), red (J KS 2) quasar 2MASSJ 104943+583750 (2M1049+5837) indicated an unusually hardX-ray spectrum (HR 0:6), suggesting obscuration ofNH 4 ; 10 cm 2 and a flat 0:4 power-law slope. A higher signal-to-noise ratio XMM-Newton observation reported here reveals a more complex spectrum, being extremely hard above 2 keV, 0:6, with a well-...