Characterization and evolution of the Swift X-ray Telescope instrumental background

C. Pagani, D. C. Morris, J. Racusin, D. Grupe, L. Vetere, M. Stroh, A. Falcone, J. A. Kennea, D. N. Burrows, J. A. Nousek, A. F. Abbey, L. Angelini, A. P. Beardmore, S. Campana, M. Capalbi, G. Chincarini, O. Citterio, G. Cusumano, P. Giommi, O. GodetJ. E. Hill, V. LaParola, V. Mangano, T. Mineo, A. Moretti, J. P. Osborne, K. L. Page, M. Perri, P. Romano, G. Tagliaferri, F. Tamburelli

Research output: Chapter in Book/Report/Conference proceedingConference contribution

8 Scopus citations


The X-ray telescope (XRT) on board the Swift Gamma Ray Burst Explorer has successfully operated since the spacecraft launch on 20 November 2004, automatically locating GRB afterglows, measuring their spectra and lightcurves and performing observations of high-energy sources. In this work we investigate the properties of the instrumental background, focusing on its dynamic behavior on both long and short timescales. The operational temperature of the CCD is the main factor that influences the XRT background level. After the failure of the Swift active on-board temperature control system, the XRT detector now operates at a temperature range between -75C and -45C thanks to a passive cooling Heat Rejection System. We report on the long-term effects on the background caused by radiation, consisting mainly of proton irradiation in Swift's low Earth orbit and on the short-term effects of transits through the South Atlantic Anomaly (SAA), which expose the detector to periods of intense proton flux. We have determined the fraction of the detector background that is due to the internal, instrumental background and the part that is due to unresolved astrophysical sources (the cosmic X-ray background) by investigating the degree of vignetting of the measured background and comparing it to the expected value from calibration data.

Original languageEnglish (US)
Title of host publicationUV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XV
StatePublished - 2007
EventUV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XV - San Diego, CA, United States
Duration: Aug 26 2007Aug 27 2007

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherUV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XV
Country/TerritoryUnited States
CitySan Diego, CA

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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