How does the Occultation Technique work?

The BATSE Earth Occultation Monitoring results for various hard X-ray/gamma ray sources are given as a list of detections and non-detections in the full list of sources. Sources from this list which show bright persistent emission and those which are bright transient sources are described in more detail in tabular form.

In selecting interfering sources for this catalog, the aim was to provide the cleanest possible light curves for the full catalog of sources while minimizing data loss. This selection may not always be optimal for each individual source and residual features in the light curves can remain both from known and unknown interfering sources.

Occultation step fitting was occasionally affected by variable sources above the Earth's horizon, especially those that varied on timescales similar to the 220-second occultation fitting window. An example was the extremely bright giant outburst of the pulsar A 0535+262. The outburst peaked around TJD 9400, where both its large amplitude pulses and proximity to the Crab in the sky can be seen to disturb the Crab light curve around this time period.

During the final two years of the CGRO mission problems with automatic gain control of one detector have some effect on the following results This can be easily seen in the 4-band light curve for the Crab.

A detailed discussion of systematic factors that affect this analysis is found in the earth occultation method paper (preprint).

More

• Other Publications - Articles in refereed publications with BATSE GRA team members in author list.


• Data in FITS Format - One-day averaged lightcurves (20-100 keV) and spectra (16-channel) available for download. These can be used to generate pha files for xspec. Single-step data are now available in FITS format for each source. Please be aware of problems with detector 7 gain control during the final two years of the mission when looking at these data.


• Software to generate occultation lightcurves


• Conversion factors from BATSE 4-Band to photon and energy flux:

  Energy Band (keV)	Multiplier (ph/cm^2/s/keV)	Multiplier (ergs/cm^2/s)
  20 - 40	8.508 x 10^-3	7.567 x 10^-9
  40 - 70	2.323 x 10^-3	5.830 x 10^-9
  70 - 160	5.514 x 10^-4	8.079 x 10^-9
  160 - 430	6.261 x 10^-5	6.887 x 10^-9