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IPCPHOT - Einstein IPC Photon Event Data



The IPCPHOT database contains information from the Imaging Proportional Counter aboard HEAO-2, the Einstein Observatory, in Event List Format. Einstein incorporated a high-resolution X-ray telescope and a focal plane assembly capable of positioning at its focus one of four instruments: a high-resolution imaging detector (HRI), a broader-field imaging proportional counter (IPC), a solid state spectrometer (SSS), and a Bragg crystal spectrometer (FPCS). Einstein (HEAO-2) was launched on November 13, 1978, and operated successfully until April 1981.


The Imaging Proportional Counter has been described by Gorenstein, et al. (TRANS. IEEE Nuc. Sci., NS-28 , 869, 1981), and by Giacconi, et al. (Ap.J. 230 , 540, 1979).


The IPC is a flow type proportional counter that uses pulse rise time information from the induced cathode signal to determine the Y-Z coordinates of an event. There are two gas-filled counters with different thicknesses for detecting X-rays in the 0.2 to 3.5 keV region. The mirror ceases to reflect X-rays above about 4.5 keV. Time resolution is 63 microseconds. It has a 75 X 75 arcmin FOV with a spatial resolution of 1 arcmin, an effective area of 100 cm**2, and a sensitivity of 1 count per sec per UFU. The energy resolution (E/delta E) of the IPC was 0.5 at 0.25 keV and >1 at 1.5-4 keV. Background was 3 x 10**-3 cts arcmin**-2 sec**-1. For the instrument, the corresponding conversion factor was: 1 IPC ct s**-1 = 1 UHURU ct s**-1.


Start time of observation in the format yy.ddd

Stop time of observation in the format yy.ddd

The RA reference point value of the FITS image file. The right ascension (1950.0) in decimal degrees of the center of the image.

The DEC reference point value of the FITS image file. The declination (1950.0) in decimal degrees of the center of the image.

Galactic Longitude of field center of the FITS image file.

Galactic Latitude of field center of the FITS image file.

The detector roll angle in degrees

The number of photons collected during the exposure.

Satellite On-Time (sec)

Observation mode of current observation (point, slew or scan)

Information on the nature of the target. Entries include catalog names (e.g., 4U0248-85) and observer's notes.


The file name of the original XPR file used to create the FITS file. The XPR files conform to a standard of Ixxxx.XPR in which xxxx is the observation sequence number.

File name of the FITS image file in the database system. The files have the format `ihhmmDdd.xp*`. The letters `hhmm` denote the RA hour and minute. The `D` is either `N` or `S` for North or South, and `dd` is the declination in degrees. The `*` is a letter such as A, B, C, etc., to distinguish the files when the rest of the file name is not unique. This occurs when more than one pointing was made at a given position.

Contact Person

Questions regarding the IPCPHOT database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Tuesday, 09-Nov-2004 20:07:59 EST