Introduction to PROS

PROS is a multi-mission x-ray analysis software system designed to run under the Image Reduction and Analysis Facility (IRAF).

The analysis of x-ray data differs from that of other wavelengths due to the nature of x-ray data. The scarcity of data, the low signal-to-noise ratio and the large gaps in exposure time make data screening and masking an important part of the analysis process.

The PROS software includes spatial, spectral, timing, data I/O and conversion routines, plotting applications, and general algorithms for performing arithmetic operations with imaging data.

A more complete description of PROS can be found in the PROS User's GUIDE (PUG).

How PROS is organized

Programs in PROS are called tasks. Tasks are grouped by function into packages. The major packages in PROS include:

xdataio - Tasks to convert data to/from FITS format
xplot - Plotting routines for XRAY data
ximages - Additions to IRAF images package
xspatial - X-ray spatial analysis package
xspectral - X-ray spectral analysis package
xtiming - X-ray timing analysis package

A diagram of the current package organization is available.

Brief Overview of PROS analysis tasks

tv display
Tasks display and xdisplay will produce a TV display of the data.

sky grids
The imcontour task calculates and graphs the iso-intensity areas of the images and displays them on a skygrid.

Support for the World Coordinate System (WCS) is provided in all the IRAF and PROS tasks. PROS provides additional interfaces to facilitate conversions, including an interactive mode from the image display.

All non-image output data files from PROS analysis are produced in TABLE format which can be graphed either with the TABLES sgraph task or with the Interactive Graphics Interpreter (igi).

source detection
The detect package is designed to perform Maximum Likelihood Source detection on data exhibiting Poisson statistics. It uses a signal-to-noise threshold calculation.

PRF modeling
The imcalc, immodel and imsmooth tasks provide the ability to generate complex Point Response Function model images that can be convolved with observations.

data extraction
The imcnts task is a utilitarian tool used to extract background subtracted counts from complex regions.

timing corrections
The timcor package provides the conversions from spacecraft clock to UTC and calculation of the barycenter timing correction.

periodic analysis
The tasks ltcurv and fft provide general capabilities to examine periodic data. The period and fold tasks include a provision for a decaying period. The qpphase task generates a QPOE files with an additional event attribute, phase, that then allows the data to be split according to phase.

spectrum extraction
The qpspec task allows users to extract a background corrected spectrum from a QPOE file for use in PROS or for export to other analysis systems.

model specification and fitting
PROS has a flexible spectral model specification language which allows multi-component model fitting. Also, the fit task allows fitting of multiple data sets.

flux conversion
Fluxes for any object can be calculated from the xflux task.

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