Heasim is a multi-mission high-energy astrophysics simulation tool. 
Heasim utilizes a pseudo Monte-Carlo approach that redistributes the 
source photons in position and energy according to the input files 
appropriate to the chosen telescope/detector system. The output is 
a FITS event file, from which data products may be extracted and 
analyzed using, e.g., XSELECT, XSPEC, etc.

For detail, see
https://heasarc.gsfc.nasa.gov/lheasoft/ftools/headas/heasim.html


The following files may be used for heasim simulations as explained
below. For additional information and examples, please go to

https://heasarc.gsfc.nasa.gov/docs/xrism/proposals/

Heasim is part of the standard HEASoft distribution.

*RESOLVE*

Normalized XRISM Resolve response matrix (RMF) files including only
the gaussian core of the line spread function (LSF). Pairs of
responses are provided for "high", h7ev ("medium", m8ev) resolution
grade with 7eV (8eV) FWHM LSF.

 resolve_h7ev_2019a.rmf
 resolve_m8ev_2019a.rmf

XRISM Resolve effective area (ARF) files that include the quantum
efficiency and the optical blocking filter transmission of the Hitomi
SXS detector. The ARFs range over energies 0.11-25 keV.
The filename descriptors "pnt" refer to point-like sources.

 resolve_pnt_heasim_noGV_20190611.arf      

Note that these are scaled from the ARF files used in spectral
simulations, and the latter must be used in analysis of spectra
extracted from heasim event files.

New high statistics XRISM Resolve Non-X-ray (NXB) background spectra,
likewise convolved with LSFs of 7 and 8 eV for use with the
corresponding RMF, are based on Hitomi pre-launch estimates with the
addition of MnK-alpha and K-beta features with fluxes estimated by the
instrument team. These are consistent with in-flight Hitomi SXS NXB
spectra derived using the "sxsnxbgen' ftool. The Resolve NXB, at ~0.01
ct/s over the Resolve array, is negligible in most cases of interest.

 resolve_h7ev_2019a_rslnxb.pha         -- use with resolve_h7ev_2019a.rmf
 resolve_m8ev_2019a_rslnxb.pha         -- use with resolve_m8ev_2019a.rmf

The PSF (EEF), vignetting, and instrument map, and are the same that
were used for pre-launch Hitomi (Astro-H) SXS files.

 ah_sxs_instmap_20131001v004.fits
 eef_from_sxs_psfimage_20140618.fits
 SXT_VIG_140618.txt

*XTEND* 

The following Hitomi (Astro-H) pre-launch (ARF, RMF, and background
spectrum) files are provided to be used for Xtend heasim
simulations:

 sxt-i_140505_ts02um_int01.8r_intall_140618psf.arf
 ah_sxi_20120702.rmf
 eef_from_sxi_psfimage_20140618.fits
 ah_sxi_instmap_20131001v004.fits
 ah_sxi_pch_nxb_full_20110530.pi

As with Resolve, these are scaled from the ARF files used in spectral
simulations, and the latter must be used in analysis of spectra
exracted from heasim event files.

*EXAMPLE ON-AXIS ABSORBED BLACKBODY SPECTRUM POINT SOURCE RESOLVE AND XTEND SIMULATIONS*

heasim mission=hitomi instrume=sxs rapoint=81.5 decpoint=-69.5 roll=0.0 exposure=100000. insrcdeffile=heasim_source_sample.txt outfile=resolve.evt psffile=eef_from_sxs_psfimage_20140618.fits vigfile=SXT_VIG_140618.txt rmffile=resolve_h7ev_2019a.rmf arffile=resolve_pnt_heasim_noGV_20190611.arf intbackfile=resolve_h7ev_2019a_rslnxb.pha mdbfile=heasim.local.mdb

heasim mission=hitomi instrume=sxi rapoint=81.5 decpoint=-69.5 roll=0.0 exposure=100000. insrcdeffile=heasim_source_sample.txt outfile=xtend.evt psffile=eef_from_sxi_psfimage_20140618.fits vigfile=SXT_VIG_140618.txt rmffile=ah_sxi_20120702.rmf arffile=sxt-i_140505_ts02um_int01.8r_intall_140618psf.arf intbackfile=ah_sxi_pch_nxb_full_20110530.pi mdbfile=heasim.local.mdb

where heasim.local.mdb is the mission database file to be used when
the instrument files are in the local directory, and
heasim_source_sample.txt is an example source definition file.

*EXTRACTING PRODUCTS FROM HEASIM SIMULATIONS*

One may read events into xselect and extract images, light curves, and spectra by first issuing following the command, or its equivalent:

 setenv XSELECT_MDB xselect.mdb.heasim