A high spectral resolution observation of the soft X-ray diffuse background with thermal detectors

D. McCammon*, R. Almy, E. Apodaca, W. Bergmann Tiest, W. Cui, S. Deiker, M. Galeazzi, M. Juda, A. Lesser, T. Mihara, J. P. Morgenthaler, W. T. Sanders, J. Zhang, E. Figueroa-Feliciano, R. L. Kelley, S. H. Moseley, R. F. Mushotzky, F. S. Porter, C. K. Stahle, A. E. Szymkowiak

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

286 Scopus citations


A high spectral resolution observation of the diffuse X-ray background in the 60-1000 eV energy range has been made using an array of 361 mm2 microcalorimeters flown on a sounding rocket. Detector energy resolution ranged from 5 to 12 eV FWHM, and a composite spectrum of ∼1 sr of the background centered at l = 90°, b = +60° was obtained with a net resolution of ∼9 eV. The target area includes bright 1/4 keV regions but avoids Loop I and the North Polar Spur. Lines of C VI, O VII, and O VIII are clearly detected with intensities of 5.4 ± 2.3, 4.8 ± 0.8, and 1.6 ± 0.4 photons cm-2 s-1 sr-1, respectively. The oxygen lines alone account for a majority of the diffuse background observed in the ROSAT R4 band that is not due to resolved extragalactic discrete sources. We also have a positive detection of the Fe-M line complex near 70 eV at an intensity consistent with previous upper limits that indicate substantial gas-phase depletion of iron. We include a detailed description of the instrument and its detectors.

Original languageEnglish (US)
Pages (from-to)188-203
Number of pages16
JournalAstrophysical Journal
Issue number1 I
StatePublished - Sep 1 2002


  • Instrumentation: detectors
  • Instrumentation: spectrographs
  • Intergalactic medium
  • Space vehicles: instruments
  • X-rays: ISM
  • X-rays: diffuse background

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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