Software Packages

Profile Fitting (FITS6P)

The profile fitting program FITS6P is a descendant of the program FITS2, which was originally put together by D. Davis and D. Welty (from parts of similar programs written by A. Vidal-Madjar and W. Morton) in the summer of 1976, for analysis of UV line profiles observed by the Copernicus satellite. It is written in Fortran, and originally ran in batch mode on an IBM mainframe; it has since been significantly modified to run interactively on UNIX and VMS workstations (e.g., SUN OS, Solaris 2, LINUX, VMS). Graphics are handled by the PGPLOT plotting package (typically using an xterm or xserve window), which is available via anonymous ftp from deimos.caltech.edu or via the web: pgplot5.2.tar.gz (thanks to Tim Pearson).

In brief, FITS6P performs iterative multicomponent Voigt profile fits to interstellar absorption line profiles. Any or all of the column densities, line widths, and velocities of the N components contributing to the profile may be varied in the fit. Approximate 1-sigma uncertainties for those parameters are also computed. The program can handle multiplets (such as the hyperfine-split Na I D lines) -- i.e., keeping the column densities, line widths, and velocities the same for all members of the multiplet during the fit.

Further description of the program and examples of its use may be found in:

Welty, D.E., Hobbs, L.M., & York, D.G. 1991, ApJS, 75, 425,
Predicted Profiles of Ultraviolet Interstellar Absorption Lines.
Welty, D.E., Hobbs, L.M., & Kulkarni, V.P. 1994, ApJ, 436, 152,
A High Resolution Survey of Interstellar Na I D1 Lines.
Welty, D.E., Morton, D.C., & Hobbs, L.M., 1996, ApJS, 106, 533,
A High Resolution Survey of Interstellar Ca II Absorption.
Welty, D. E., Lauroesch, J.T., Blades, J.C., Hobbs, L.M., & York, D.G., 1997, ApJ, 489, 672,
Interstellar Abundances in the Magellanic Clouds. I. GHRS Observations of the SMC Star Sk 108.
Welty, D. E., Frisch, P. C., Sonneborn, G., & York, D. G., 1999, ApJ, 512, 636,
Interstellar Abundances in the Magellanic Clouds. II. The Line of Sight to SN 1987A in the LMC.
Welty, D. E., Hobbs, L. M., Lauroesch, J. T., Morton, D. C., Spitzer, L., & York, D. G. 1999, ApJS, 124, 465,
The Diffuse Interstellar Clouds toward 23 Orionis.

Versions of the program also exist for fitting QSO absorption line system profiles (with lines from different redshift systems) and for simultaneously fitting multiple line profiles with the same set of velocity components (e.g., three different Fe II lines and two different Si II lines).

To obtain the program: please contact me if you would like to obtain a version of FITS6P; currently available versions are for SUN OS 5.7 (Solaris) and for Fedora (LINUX). The tar file includes a file with complete installation instructions, as well as a file describing the program structure, variables, and flow.

Please let me know if you use the program, so that I can alert you to bugs, as they are found, and to enhancements, as they are made.

Some of the more recent development of the program was done in connection with the Local ISM Workshop project at the University of Chicago, which was supported by NASA grants NAG5-704, NAG5-1303, and NAG5-286.

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Remote Observing with IUE

IUEREMOTE is an IRAF-based package for remote observing with the IUE satellite, written by D. Welty and M. Crawford at the University of Chicago. The program's original incarnation included two main modules. One ran on a SUN workstation at Goddard Space Flight Center -- which read and decoded the data stream from the satellite, identified the image and engineering data, then packaged the data for transmission to the remote observing station (initially at the U of C). The second module, running on another SUN workstation at the U of C, read the data transmitted from GSFC, then provided quick-look analysis tools (within the IRAF environment) to allow early assessment of exposure quality for planning subsequent exposures during the observing shift.

The IRAF-based quick-look analysis tools were made available to other sites by the IUE project during the last several years of IUE operations.

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Spectrum Analysis (specp)

specp is a Fortran program containing modules for various spectrum manipulation and analysis tasks, extending code originally developed by L. Hobbs; PGPLOT is used for the graphics. The program can read various kinds of input data files (ascii, integer FITS), then has several sets of options for processing and analysis:

A number of the routines have been incorporated in several more specialized spectrum analysis programs (e.g., arcexam; see below).

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Semi-automated DIB Measurement (arcexam)

arcexam is a Fortran program designed to allow semi-automated measurement of the equivalent widths of the many diffuse interstellar bands (DIBs) observed in ARC echelle spectra. The program uses some routines from the spectral analysis code specp (see above); PGPLOT is used for the graphics. Using an input table of line centers and (rough) widths based on the DIB surveys of Hobbs et al. (2008, 2009), the program steps through the target star spectrum, fits a local continuum around each potential DIB, then measures the equivalent width, wavelength, and several higher moments of the profile. Also plotted are the corresponding spectral intervals from the two DIB atlas stars (HD 183143, HD 204827) and from a lightly reddened star of similar spectral type (to reveal any stellar lines). The user can either approve the choices of fitted continuum and limits over which the DIB is measured or perform interactive continuum fits and integration limits. Descriptions of the code and examples of its use may be found in Fan et al. (2017, 2019). I have also adapted the code to measure atomic and molecular absorption lines in HST/STIS echelle spectra.

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Dan Welty / dwelty@stsci.edu

Last modified 08 Jun 2020