========================================================================== IX/24 The Einstein Observatory HRI Source List (Giacconi+, 1979) The following files can be converted to FITS (extension .fit .fgz or .fiZ) hrifield.dat hrisrc.dat obsnames.dat ========================================================================== Query from: http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=IX/24 ==========================================================================
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Beginning of ReadMe : IX/24 The Einstein Observatory HRI Source List (Giacconi+, 1979) ================================================================================ The Einstein Observatory HRI Source List Giacconi et al. <The Einstein Observatory (HEAO-2) (1979)> ================================================================================ ADC_Keywords: X-ray sources ; Surveys ; Observatory log Mission_Name: Einstein Description: The Einstein Observatory is the second of NASA's three High Energy Astrophysical Observatories, HEAO-2, renamed Einstein after launch, and was the first fully imaging X-ray telescope put into space. It observed in the energy range 0.2-20keV. It was launched on 12 November 1978, and remained in operation until April 1981. The High Resolution Imager (HRI) is one fo the four instruments aboard the Einstein Observatory, operating in the 0.2-3.0keV energy range, with a spatial resolution of a few arcseconds, and a field of view of 25arcmin. Field and source parameters observed with this instrument are given here. The HRI Instruments: The High Resolution Imager (HRI) has been described by Henry et al (Proc. SPIE, 106, 196, 1977) and by Giacconi, et al (1979ApJ...230..540G). The following summary is meant only as a convenient reference for features of the HRI with which users should be familiar. The Instrument: --------------- The performance characteristics of the telescope-HRI combination included: spatial resolution (FWHM): 3 arcsec at the telescope focus field of view: 24 arcmin on a side temporal resolution: 7.8125 microsec background in orbit: 0.46 cts/sec/arcmin**2 (away from the South Atlantic Anomaly) quantum efficiency: 10% at 1 keV maximum event rate: 100 counts/sec. (telemetry limited) dead time correction: median of 1.02 for mission energy range: 0.15-3.0 keV (HRI-2) 0.15-3.5 keV (HRI-3) The mirror effective area decreased as a function of off-axis angle to 0.9 at 15 arcminutes. This "vignetting" must be taken into account when calculating count rates. The quantum efficiency of the microchannel plates varied by +/-5% across the field of view of the HRI, which must also be allowed for in determining source strengths. The two-dimensional HRI used a pair of cascaded microchannel plates (MCPs) as an X-ray image converter and photoelectron multiplier, and a crossed-wire grid as a two-dimensional position-sensitive charge detector. Position determination was accomplished by electronic interpolation between the coarse grid wires. The detector provided the arrival time and position of each X-ray event which occurred within the field of view. The MCP photocathode surface was shielded from ultraviolet light and ions by a thin, metallized self-supporting plastic filter. This UV/ion shield was the only component to differ among the three HRIs on-board the Einstein Observatory. HRI-2 showed a splotchy artifact early in the mission; from December 15, 1978, therefore, HRI-3 was used instead. An Objective Grating Spectrometer (OGS) could be used in conjunction with the HRI. 53 sequences were observed with this configuration. These sequences have not been included in the current HRI source list. Point Response Function: ------------------------ An analytical approximation to the Point Response Function (PRF) for the HRI at 1.5 keV has been given by J.P. Henry: PSF(r) = 0.02885 x [ exp (-r/1.96") + 0.01 exp (-r/12.94") ] /arcsec**2 This was derived from long exposures of point sources on axis, and appears to be a reasonably accurate description within 5 arcminutes of the field center for sources such as Cyg X-2 and 3C273 (i.e., for sources with non-pathological spectra). The formula is also a good fit to the 1.5 keV ground calibration data. It is valid for r < 1'.