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

Research output: Contribution to journalArticlepeer-review

296 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
Externally publishedYes


  • 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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