User's Guide to SPECTRAL

EGRET/SU/PLN/93/MAR/23

SPECTRAL is a program for analyzing the energy spectra of point sources. The user chooses the form of the model that is to be fitted to the observed spectrum. The program then calculates the best fit of the model to the data. SPECTRAL is actually a shell which manages two main programs. One calculates a matrix that represents the response of EGRET to an incident spectrum; this part is called SPECMAT. SPECNLYZ uses this matrix in calculating the most likely incident flux.

Changes from version 2.2 to 2.3 (March 1993)

• Class A+B+C events can now be used for pulsars, as well as DC sources.
• A pulsar data file with an energy-dependent selection cone can be analyzed, as well as a fixed cone.
• When analyzing a pulsar it is possible to read a file containing a background spectrum rather than counting background photons during a portion of the phase interval.

Changes from version 2.1 to 2.2 (January 1993)

• The response matrix file has been augmented and is now in FITS format.
• The correct event classes are now used in pulsar mode.
• Class C events are now handled, although it appears that the response functions are incorrect.
• Empirical fudge factors for the effective area have been added to pulsar mode.
• In DC source analysis either Class A or Class A+B+C events can be analyzed.
• Bugs were fixed in the reporting of standard errors and correlation coefficients.
• In pulsar moded events are screened correctly for zenith angle and TASC minimum energy.
• Times are now represented as MJD.
• There are small changes in the various data displays.
• The results of fitting are put into a FITS format file.

Changes from version 2.0 to 2.1 (August 1992).

• The program now handles both the old and new types of PSRSPEC files.
• The program now works with the new-format timeline file.
• Graphs can now be produced for broken power law models.
• Minor bug fixes.

Changes from version 1.0 (January 1991) to 2.0 (May 1992).

• There are now two different modes of operation. The program can do pulse-phase spectroscopy of a pulsar or it can analyze a DC source. In the latter case, the data comes from a likelihood analysis.
• The diffuse background model has been removed. It is no longer needed. When analyzing a pulsar, the off-pulse phase region performs the role of a background. For a DC source, the likelihood analysis subtracts the background before SPECTRAL sees the data.
• The number of observed energy bins is now set by a data file.
• The response matrix now takes into account the events which are rejected because of a zenith angle cutoff.
• The correct names of the calibration files are found by an automatic search.
• The default parameters for fitting and for pulsar angle binning are now found in two files, which may have system defaults.