The Einstein (HEAO-2) FPCS Instrument

artist concept of HEAO-2 Most of the 389 FPCS observations were designed to search for specific spectral features: lines, absorption edges, and recombination edges. There were about 40 aperture-map observations of the strong point sources Cyg X-1, Cyg X-2, and Sco X-1, whose purpose was to determine, in flight, the position of the aperture relative to the spacecraft pointing direction. This information is particularly relevant to the detailed analysis of data from extended sources (i.e., supernova remnants and clusters of galaxies, etc.). Finally, there were three spectral surveys of compact objects, the purpose of which was to combine a large number of individual observations, made at about the same time, in order to obtain the equivalent of a fairly large spectral scan. The three sources surveyed were AM Her and Her X-1 on the range ~200-300 eV and Sco X-1 in the range ~700-1200 eV.

The procedure used to analyze FPCS data can be summarized as follows. Timing, pulse-height, and position discrimination are used to remove much of the background. The residual background is then determined and subtracted, yielding the net signal from the source. Finally, the incident flux is determined by taking into account the known efficency of the instrument.

* High Level Data Products: These data files were produced at MIT in FITS format. Data from this instrument are also available on the HEASARC CD-ROM entitled "The Einstein Observatory SSS, MPC, and FPCS Data Products" dated 1 June 1992. There exists integrated spectra derived from one or more of the photon event list files. The three digit number used as the filename extension for the spectra files corresponds to the observation number used by Lum et al., Ap. J. Suppl. Series, 78, 423, 1992. There are 389 observations but only 336 of them had sufficent quality for the spectrum to be included.

* Raw data: There are 436 photon event files listing every photon detected in each observation. There are two calibration files contained in the same directory as the photon events: is a FITS file containing tables of the FPCS efficency parameter as a function of energy for all 6 crystals, is a FITS file containing tables of the spectral resolution of each of the 6 FPCS crystals.

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