High-resolution spectroscopy of the diffuse x-ray background using an array of microcalorimeters

We have flown a microcalorimeter array on a suborbital sounding rocket to observe the soft x-ray background in the 70 eV to 1000 eV energy range. The array consisted of thirty-six 0.5mm x 2.0mm x-ray detectors with ion implanted silicon thermistors and HgTe absorbers, operated at 60 mK. Each pixel viewed approximately the same 1 steradian field of view centered on 1 = 90, b = +60. The spectra from each pixel were gal in corrected and combined to produce a composite spectrum with better statistics. Although the 8 best detectors had resolution better than 10 eV FWHM at 3.3 keV, the composite spectrum had a resolution that varied from 14 eV at 277 eV to 21 eV at 677 eV. An O VII emission line was observed, and this, combined with the absence of an O VIII line allowed us to put constraints on absorbed thermal mechanisms as a source of M band emission.