Beginners should start here. The Introductory threads explain how to start Sherpa and provide an overview of using the application.
To quickly access the scripts used in each of the Sherpa threads, visit the Sherpa Quick Scripts page.
Sherpa provides extensive facilities for modeling and fitting data. The topics here range from basic fits using source spectra and responses to more advanced areas, such as simultaneous fits to multiple data sets, accounting for the effects of pileup, and fitting spatial and grating data.
Before fitting ACIS spectral data sets with limited pulse-height ranges, please read the CIAO caveat "Spectral analyses of ACIS data with a limited pulse-height range."
Spectral (1-D) Data
- Introduction to Fitting PHA Spectra (15 Dec 2020)
- Changing the grouping scheme of a data set within Sherpa (15 Dec 2020)
- Simultaneously Fitting Two Data Sets
- Fitting a PHA Data Set with Multiple Responses
- Simulating X-ray Spectral Data (PHA): the fake_pha command (22 Dec 2020)
- Simulating Chandra ACIS-S Spectra with Sherpa
- Simulating Chandra ACIS-S LETG Spectra with Sherpa
- Simulating NuSTAR X-Ray Spectra with Sherpa
- Fitting PHA Data with Multi-Component Source Models
- Calculating Uncertainties by Simulating Flux Distributions
- Calculating Model Flux and Flux Uncertainty
- Simultaneously Fitting Source and Background Spectra (17 Dec 2020)
- Using A Pileup Model
- Sherpa User Models
- Sherpa Table Models
- Sherpa Template Models
- Creating an Input Spectrum for MARX and ChaRT Simulations
- Bayesian Analysis in Sherpa (21 Dec 2020)
Spatial (2-D) Data
- Fitting FITS Image Data
- Radial and elliptical profiles of Image Data
- Using an Exposure Map in Fitting Image Data
- Accounting for PSF Effects in 2D Image Fitting
- Fitting Image Data with Convolved and Unconvolved Model Components
- See also: the Obtain and Fit a Radial Profile CIAO thread
- Sherpa User Models
- Fitting Grating Data (21 Dec 2020)
- Fitting Multiple Orders of HRC-S/LETG Data (21 Dec 2020)
- Measuring Line Parameters with an HETG/ACIS-S Spectrum (22 Dec 2020)
- Measuring Line Parameters with an LETG/ACIS-S Spectrum
These threads involve data analysis which is not specific to X-ray spectral or spatial modeling, therefore they can be followed using simple ASCII files as input, or other non-X-ray data.
Sherpa allows the user to plot data, fits, statistics, ARFs, contours, and more. These threads describe the basics of plotting as well as various methods for customizing plots.
Sherpa provides numerous tools for determining goodness of fit, errors in parameter values, confidence intervals, and other statistical measures of a model's validity. These threads describe how to use these tools in your analysis.
The Sherpa fake_pha command is available for simulating a Chandra PHA data set with an input instrument response and source model expression. These threads describe how to produce simulated data appropriate for your analysis.
These threads demonstrate miscellaneous tasks in Sherpa which you may find useful in your scientific analysis, and which are not specific to the other thread categories.