We have calculated the relativistic reflection component of the X-ray spectra of accretion disks in active galactic nuclei （AGN）. Our calculations have shown that the spectra can be significantly modified by the mot...We have calculated the relativistic reflection component of the X-ray spectra of accretion disks in active galactic nuclei （AGN）. Our calculations have shown that the spectra can be significantly modified by the motion of the accretion flow, and the gravity and rotation of the central black hole. The absorption edges in the spectra suffer severe en- ergy shifts and smearing, and the degree of distortion depends on the system parameters, in particular, the inner radius of the accretion disk and the disk viewing inclination angles. The effects are significant. Fluorescent X-ray emission lines from the inner accretion disk could be a powerful diagnostic of space-time distortion and dynamical relativistic effects near the event horizons of accreting black holes. However, improper treatment of the reflection component in fitting the X-ray continuum could give rise to spurious line-like features. These features mimic the true fluorescent emission lines and may mask their relativistic signatures. Fully relativistic models for reflection continua together with the emission lines are needed in order to extract black-hole parameters from the AGN X-ray spectra.展开更多
We discuss a novel use of the Geant4 simulation toolkit to model molecular transport in a vacuum environment,in the molecular flow regime.The Geant4 toolkit was originally developed by the high energy physics communit...We discuss a novel use of the Geant4 simulation toolkit to model molecular transport in a vacuum environment,in the molecular flow regime.The Geant4 toolkit was originally developed by the high energy physics community to simulate the interactions of elemen-tary particles within complex detector systems.Here its capabilities are utilized to model molecular vacuum transport in geometries where other techniques are impractical.The techniques are verified with an application representing a simple vacuum geometry that has been studied previously both analytically and by basic Monte Carlo simulation.We discuss the use of an application with a very complicated geometry,that of the Large Synoptic Survey Telescope camera cryostat,to determine probabilities of transport of contaminant molecules to optical surfaces where control of contamination is crucial.展开更多
基金supported by the Nuffield Foundation through the Research Bursary program
文摘We have calculated the relativistic reflection component of the X-ray spectra of accretion disks in active galactic nuclei （AGN）. Our calculations have shown that the spectra can be significantly modified by the motion of the accretion flow, and the gravity and rotation of the central black hole. The absorption edges in the spectra suffer severe en- ergy shifts and smearing, and the degree of distortion depends on the system parameters, in particular, the inner radius of the accretion disk and the disk viewing inclination angles. The effects are significant. Fluorescent X-ray emission lines from the inner accretion disk could be a powerful diagnostic of space-time distortion and dynamical relativistic effects near the event horizons of accreting black holes. However, improper treatment of the reflection component in fitting the X-ray continuum could give rise to spurious line-like features. These features mimic the true fluorescent emission lines and may mask their relativistic signatures. Fully relativistic models for reflection continua together with the emission lines are needed in order to extract black-hole parameters from the AGN X-ray spectra.
基金supported in part by the National Science Foundation through Governing Cooperative Agreement 0809409 managed by the Association of Universities for Research in Astronomy(AURA)the Department of Energy under contract DE-AC02-76-SFO0515 with the SLAC National Accelerator Laboratory.
文摘We discuss a novel use of the Geant4 simulation toolkit to model molecular transport in a vacuum environment,in the molecular flow regime.The Geant4 toolkit was originally developed by the high energy physics community to simulate the interactions of elemen-tary particles within complex detector systems.Here its capabilities are utilized to model molecular vacuum transport in geometries where other techniques are impractical.The techniques are verified with an application representing a simple vacuum geometry that has been studied previously both analytically and by basic Monte Carlo simulation.We discuss the use of an application with a very complicated geometry,that of the Large Synoptic Survey Telescope camera cryostat,to determine probabilities of transport of contaminant molecules to optical surfaces where control of contamination is crucial.
