Frequently Asked Questions


General


Q1:I've found a bug! How can I find out if you know about it already?

A1: We will attempt to list all known bugs (and workarounds) on the Known Bugs page. If you do not see your particular issue there, or are even not certain it is the same problem as one listed, please let us know via the Feedback form. We will attempt to recreate the bug and let you know if we have a workaround or will need to release a new version.

Q2: I need a new feature! Who should I tell?

A2: Again, please let us know via the Feedback form. Please remember that Profit is not (yet) anyone's main priority, so clear explanations of your new feature request, especially including examples of how it should work and even how it might be implemented will be most appreciated. Most of Profit's new features are due to user requests, so please do not be shy!

Q3: What are the top ten items on your to-do list?

A3: We're glad you asked! Here they are:

  • 1. Use effective area file to present spectra in physical units.
  • 2. Add option to return flux instead of total counts in line fits.
  • 3. Allow variable abundances, rather than only Anders & Grevesse values.
  • 4. Allow user-selected label colors, sizes, fonts.
  • 5. Store results of fits to a latex file.
  • 6. Allow plots to be output as qdp files.
  • 7. Make the XSTAR database work more like the ATOMDB database, so that atomic data are available.
  • 8. Allow a wider range of axis units, such as nm or inverse cm.
  • 9. Improve look & feel of buttons and preferences window.
  • 10. Improve fitting to allow more options.
Q4: I want to read in a text file for a spectrum, rather than a FITS file. Is this possible?

A4: Yes! However, the file must include (before any data) two lines telling Profit how the data are formatted. The first line should read

FORMAT = profit

which tells Profit that this is a text spectrum file. The second line should read either

TTYPE = E_MIN E_MAX COUNTS

or

TTYPE = E_MIN COUNTS

The first style should be used when the file has three values per rows, listing the bin minimum (in keV), the bin maximum (in keV), and the counts in that bin. The second form is used when the file only gives the bin minimum and the counts; the last bin is then assumed to be the bin maximum and the counts in the last bin are ignored. Comments can also be included in the file, prefaced with an exclamation mark (!).


Fitting


Q1: I tried to fit but got an error message "Fit did not converge" even though it's a simple spectral region.

A1: Basically, it wasn't simple enough. The fitting algorithm currently used works especially poorly on low-count data or regions where the continuum is curved. Also, to avoid degeneracies, the maximum line width is 100 eV.

Q2: I'd like to do fits that include the detector response (.rmf) and effective area files (.arf).

A2: May we recommend XSPEC, a fine package that does this and far more. We are in close contact with the XSPEC developers, and may include more features like this in the future. At the moment, Profit should be used an exploratory tool.


ROOT


Q1: Why did you choose ROOT and not package XYZ?

A1: ROOT has the features we need and is actively supported by the high-energy physics community. Although different in many ways, both astronomers and high-energy physicists both use histograms and spectra as one of their primary data units, unlike (say) computer scientists or GUI designers who include histograms in their libraries only for completeness. Finally, we were familiar with ROOT and could rapidly develop Profit with it. However, we are not wedded to ROOT if a superior package is available.


Atomic Databases


Q1: What other atomic databases will you include?

A1: Plans are fluid on this. If you happen to know of an atomic database you would like to add, please let us know via the Feedback form.


Miscellaneous


Q1: How is profit different from XSPEC/Sherpa/ISIS?

A1:Profit is meant to be a GUI-based tool for exploring a spectrum, discovering what emission lines are present and if they show signs of doppler shift or broadening. XSPEC, Sherpa, and ISIS are primarily meant for fitting models to spectra. Profit is meant to complement, not replace, those tools.

Q2: How is the name pronounced? Pro'-fit or Prah'-fit?

A2: We accept either.


If you have any questions concerning Profit, please visit the Feedback form.


Return to Profit Home Page


HEASARC Home | Observatories | Archive | Calibration | Software | Tools | Students/Teachers/Public

Last modified: Thursday, 16-Aug-2007 11:00:29 EDT