Proposal Planning Toolkit: PIMMS Help PIMMS: Portable, Interactive Multi-Mission Simulator

• ASCA
• CHANDRA - The effective area curves are provided for the current and all previous NRAs, and can be viewed through the Effective Area File Viewer.
  More information is provided on the Chandra Proposal Planning Calibration Files page.
  Note that the CHANDRA effective area files include the sum of source count rates in positive and negative orders
  (i.e. the 1st order files contain orders +/-1 and the letghi file contains orders +/-2 through +/-11).
• EINSTEIN
• EXOSAT
• GINGA
• ROSAT
• SAX
• SWIFT
• SUZAKU
• XMM
• XTE

• its flux over a specified energy range;
• its flux density at a specified energy;
• the count rate it would produce in a selected instrument.

• Absorbed Flux (or Flux Density) - Use flux from the source spectrum at the telescope aperture (before application of instrumental effects, and including absorption in the ISM).
• Unabsorbed Flux (or Flux Density) - Use flux from the source spectrum at the telescope aperture (before application of instrumental effects, and as if there were no absorption in the ISM).

Energy Range

• Input Energy - Specify the energy bounds of the source spectrum, in keV. If you are normalizing the source spectrum by specifying the count rate it would produce in a selected instrument, you may elect to use the default energy range of the instrument. For flux density, specify the energy, in keV, at which the flux density is evaluated.
• Output Energy - Specify the output energy range of interest, in keV. You may elect to use the default energy range of the detecting instrument. For flux density, specify the energy, in keV, at which the flux density is evaluated.

• Power Law - The parameter is Photon Index, defined such that AE**(-(photon index)) is the flux in photons / cm**2 / s .
• Black Body - The parameter is energy (kT) in keV.
• Thermal Bremsstrahlung - The parameter is energy (kT) in keV. The model includes the Gaunt factor.
• Plasma - APEC/MEKAL/Raymond-Smith
  The parameters are temperature, abundance and NH.

  PIMMS v4.0 is distributed with APEC and Raymond-Smith models at 59 temperatures (logT of 5.60 to 8.50 in an increment of 0.05) times 5 abundance (0.2 to 1.0 in an increment of 0.2), while MEKAL has a narrower temperature range starting with logT of 6.0 (51 temperatures to logT=8.50). For MEKAL and APEC, ``solar'' abundances are those due to Anders & Grevesse, while the solar standard for the Raymond-Smith grid has become unclear due to passage of time. PIMMS will select the nearest temperature and abundance that is supported by the grid in use.

  The Raymond-Smith models provided through the GUI support up to a maximum energy of 8 keV. Any inputs exceeding 8 keV are reset within the code to 8 keV. [8 keV is used as the maximum energy for normalizing the source spectrum (i.e., as the maximum energy contributing to the "input" flux or count rate), and also as the maximum energy contributing to the "output" count rate. The errors caused by these truncations are opposite in sense (the input truncation overestimates the source, the output truncation underestimates the count rate that that source would produce). The errors are generally small, as the effective areas are diminishing rapidly at these high energies.]

The cts/frame output is the summation of the individual detect cell values.

Pileup warnings:

1. The pileup fraction assumes the user is calculating the flux over the *entire* bandpass of the ACIS-I or ACIS-S instrument. If the energy range is restricted, the pileup fraction calculated will be *under*-estimated because fewer photons will be included in the pileup calculation than the full bandpass. The severity of the effects of pileup depends upon the spectral energy distribution (SED) of a source; however, the PIMMS calculation does not take the SED into account.

2. The current pileup model begins to break down and becomes increasingly invalid as a predictor for pileup fractions greater than about 75%. 75% pileup is reached approximately when the PIMMS output is equivalent to about 3 counts/frame or higher. Because the model does break down above 75%, the "cts/frame" and "cts/s" results may appear anomalous when the pileup percentage is this high. Please refer to the Proposers' Observatory Guide for information on mitigating the pileup effect.

3. For grating observations, the pileup estimate is an upper limit based on the undispersed 1st order count rate. Improved pileup estimates may be obtained by reducing the energy range being considered; however, users who need accurate simulations in order to ensure pileup will not be a problem are advised to use the MARX simulation tool.