XSTAR Home Page

Two component XSTAR model fit to the 800 ks Chandra HETG observation of NGC 3783. Model fit performed in xspec11 using the warmabs analytic model.

XSTAR model fit to the HST/COS combined emission and absorption line spectrum of Mrk 290. Top panel: data and model fit; lower panels: emission and absorption model components (Zhang et al. 2014).

XSTAR model fit to the Hitomi observation of the Perseus cluster.

What is XSTAR?

XSTAR is a computer program for calculating the physical conditions and emission spectra of photoionized gases.

How Do I Get XSTAR?

Xstar is avaible in several different ways.

The XSTAR package is now integrated and distributed with the HEASARC's standard HEASOFT package, so if your facility has this package installed then you already have access to xstar.

XSTAR is also available as a standalone package. The standalone XSTAR (or the full HEASOFT), is available in either source or binary versions and it can be downloaded from here .

Current develop version

The known issues page

A utility has been created for extracting atomic data and rates from the xstar database. This utility is a standalone fortran program, which calls many of the xstar routines, and returns the rate (forward and reverse) and raw atomic data for a single type of rate for a single ion. It can be found here

Warmabs, an analytic model for calculating warm absorber and emitter spectra within xspec is available. This has the advantage that it avoids the intrinsic approximations associated with use of tables for absorption with variable abundances treated as multiplicative parameters, and the intrinsic clumsiness of the use of tables. It also allows the use of arbitrary spectral resolution, not limited by the internal xstar spectral resolution. To use it, download the tarfile, unzip and untar in your user area, and follow the installation instructions contained in the README. This includes the analogous routine which simulates the absorption (and emission) by a gas in coronal equilibrium.

An older release of warmabs, which used a simpler system of saved quantities, is here

A version of xstar which allows for parallel computation of a grid of models has been developed by Michael Noble of MIT. pvm_xstar fosters parallel execution of XSTAR over large, time-consuming sets of parameters.

A php tool for making the xstinitable.par file needed by xstar2xspec is provided by D. Maitra of the University of Michigan here. This is a GUI form which produces the file in ascii. No error checking is provided.

An analytic model for calculating interstellar absorption within xspec is available. This utilizes the same atomic data as xstar and warmabs but allows the column densities of the ions to be free parameters rather than being prescribed by ionization equilibrium. It also allows the use of arbitrary spectral resolution, not limited by the internal xstar spectral resolution. To use it, download the tarfile, unzip and untar in your user area, and follow the installation instructions contained in the README. A paper describing the tool in more detail is available here.

Online Documentation

XSTAR documentation is included as part of the standard source distribution and is also viewable here or can be downloaded as a pdf. The doxygen pages are ohere

Sample xstar output from optically thin photoionized model, alpha=1 power law, line opacities

Sample xstar output from optically thin photoionized model, alpha=1 power law, RRC emissivities

Sample xstar output from optically thin photoionized model, alpha=1 power law, RRC opacities

Sample XSPEC table models

Postscript plots of atomic rates(42 Mbytes).

An ascii version of the xstar database (28 Mbytes).

The xstar database sorted according to process. (16 Mbytes).

Sample output: Lexington H II region.