Highlights for each version of marx¶
Marx 5.5.2 (Dec 2022)¶
This release just upgrades the CalDB files that are shipped with marx. There are no code changes.
Marx 5.5.1 (Dec 2020)¶
This release just upgrades the CalDB files that are shipped with marx. There are no code changes.
Marx 5.5 (Dec 2019)¶
Change column type of PHA and PI columns written by
marx2fits to float32
to match the files that CIAO writes.
User-compiled sources (
SourceType="USER") have a function called
user_create_ray which is called with a pointer to ray properties
(direction, time, and energy). All ray properties used to be undefined before
calling this function and the user function could return
-1 for energy and
time to have marx assign energy and time. Now,
energy is initialized
user_create_ray is called, to allow user code that assigns
locations based on the ray energy. With this change, marx.par must contain a
valid specification for the source spectrum, since an energy will be drawn,
even if the user source later assigns a different value. For
user_create_ray sets the energy to a negative
value, marx will assign the energy drawn before to the variable again.
Marx 5.4 (Dec 2018)¶
The HRC detector PSF has some blur in it. See https://cxc.cfa.harvard.edu/twiki/bin/view/HrcCal/DetectorPSF for how the parameters used in previous versions of marx are determined. However, we recently found that the PSFs are wider than observed. Thus, in this version we change the values of the default marx.par file to use a single Gaussian instead. This change is most important for the profile of the wings in very bright HRC sources. We continue to investigate this and expect another change in the next marx release.
Marx 5.3.3 (Dec 2017)¶
Small bug fix to the source code to allow compilation with clang (which is the default compiler on Macs).
Marx 5.3.2 (Dec 2016)¶
Update CalDB files that are shipped with marx. No changes to the source code.
Marx 5.3.1 (Aug 2016)¶
This fixes two bugs for users of SIMPUT sources; all other runs are unaffected.
Marx 5.3 (Apr 2016)¶
Important bug-fix for off-axis sources: Please upgrade!¶
MARX 5.0, 5.1, and 5.2 contain a bug that affects the PSF for simulations of off-axis sources; this is fixed in 5.3. The root cause for this bug was that the entrance aperture of the Chandra mirrors was chosen to match the size of the mirror opening as seen an on-axis source exactly. For an off-axis source that means that the generated photons hit only part of the mirror, leading to gaps in the simulated PSF. Now, the entrance aperture has been increased to allow sources anywhere in the field-of-view to fill the detector. This necessarily increases the run time of all marx simulations, because more photons need to be generated. See https://github.com/Chandra-MARX/marx/issues/21 for a detailed description of the issue.
New source type: SIMPUT¶
marx now supports the new SIMPUT standard, which is a fits based
description of sources, which allows a large number of source with different
spectra, light curves, and shapes on the sky. This file format is supported by a
number of other simulators (e.g. for ATHENA), so integrating it in marx
allows users to use the same source specification for different X-ray missions.
The support in marx is through the SIMPUT code which needs to be installed
separately and is linked dynamically at runtime if
Marx 5.2 (Dec 2015)¶
There are only minor enhancements, calibration updates, and bug fixes in this version.
Change in default parameters¶
PointingOffsetZ to 0 to match the
values in current Chandra observations (was
This defines the difference between RA/DEC_NOM and RA/DEC_PNT in the
fits headers of event files; it is not used in the code except to output
the RA/DEC_PNT values by
Match use of long and double types in fits output to standard CIAO products.
Previously an ASOL file name > 63 characters would crash
marx2fits. Now, it cuts the pathname to shorten the string.
Marx 5.1 (Apr 2015)¶
marx version 5.1 is a maintenance release. Since more than two years have gone by since release 5.0, there are major changes in the Chandra calibration data that marx uses, particularly in the soft energy response of ACIS. In addition there are several minor changes, some of which are listed below (see the commit log of the git repository for complete details):
marx now compiles with
clang, the compiler that is shipped with Max OS X-code. (Apple sets an alias called
gcc, but this really points to
Enhanced support for dithered SAOTrace rays on input. In particular, that means that the parameter
SAOSAC_Color_Raysis no longer needed. Setting it currently has no effect and this parameter will be removed in the next version.
The HRC blur model has been improved. Simulations with HRC-I and HRC-S will give slightly different PSF shapes. In order to describe the HRC blur properly, new parameters have been added to
marx.par. These parameters should not be changed by the user; instead we strongly recommend to just copy and modify the version of
marx.parthat comes with the installation which includes those new parameters.
marx now includes the LEG misalignment compared to the ACIS chips. Handling this required changes to the default values of the
legTheta. These parameters should not be changed by the user; instead we strongly recommend to just copy and modify the version of
marx.parthat comes with the installation which includes those updated values.
marx 5.0 is a major new release. This page is devoted to the new features.
The EDSER subpixel algorithm was incorporated into CIAO 4.3. When computing Sky coordinates, acis_process_events first converts the integer-valued chip coordinate to a floating point value. There are several ways in which this may be done. One way is to simply cast the integer to a float, e.g,, the integer 2 becomes 2.0. The problem with this approach is that it can cause aliasing artifacts in the resulting Sky image. For this reason, the default up until CIAO 4.3 was to simply add a uniform random deviate from -0.5 to 0.5 to the integer value so that 2 would become a random real number in the semi-open interval [1.5, 2.5). The default was changed in CIAO 4.3 to use a discrete probability distribution based upon flight grade and energy, known as the EDSER method.
The marx 5 version of
marx2fits introduces a
line parameter that allows the user to select one of several pixel
randomization methods. Simply running
marx2fits without any command
line arguments will display its usage message:
marx2fits v5.0.0: Usage: marx2fits [options] marxdir outfile Options: --pileup Process a marxpileup simulation --pixadj=EDSER Use a subpixel algorithm (default) --pixadj=RANDOMIZE Randomize within a detector pixel --pixadj=NONE Do not randomize within a detector pixel --pixadj=EXACT Use exact chip coordinates
The effect of these randomization methods may be seen in the following plot, which shows that the EDSER distribution approaches the exact limit.
New dither model¶
The EDSER subpixel algorithm necessitated numerous changes to the
marx aspect code. In particular, aspect reconstruction blur
had to be cleanly separated into its independently contributing
pieces, namely the telescope pointing uncertainty, the blur introduced
by pixel quantization/truncation, and the blur associated with pixel
randomization. Previous versions of marx incorporated these blurs
under the guise of a single parameter,
DitherBlur, whose value
was the RSS sum of the contributing blurs. This was the source of a
lot of confusion among users resulting in numerous help desk inquiries
about how this value was obtained and why it was so large.
For these reasons, the
DitherBlur parameter was removed from marx
and replaced by one called
AspectBlur whose value represents
just the telescope pointing uncertainty,
0.07 arc-seconds. One consequence of this change is that marx 4.x
parameter files cannot be used with marx 5.0.
It was also necessary to remove the blur parameters from
which computes an aspect solution file for use in reprocessing a
marx2fits generated event file. Hence any scripts that pass blur
parameter values to
marxasp will need to be modified.
As mentioned above, the
DitherBlur parameter’s value reflected
more that just that associated with the aspect uncertainty. It was
also tweaked to get the marx PSF to better match Chandra grating line
profiles. With this parameter gone, the marx HRMA blur parameters
had to be re-calibrated to get the widths of the marx simulated
grating line profiles to match those in the Chandra CALDB.
There was a long standing issue of a relative rotation between the
LETG and the ACIS detector. The root of this problem was tracked down
(with the help of marx) to a rotation offset between the aspect
coordinate system and the focal plane detector system. This offset
was masked by compensating rotations of the detectors from astrometric
analysis, and manifested itself as a small rotation of the LEG
dispersion arm on the ACIS detector. Changes were added to CIAO 4.3
that effectively adds an additional rotation to the LETG when used
with ACIS. The corresponding change in marx 5.0 is implemented via a
new parameter called
The marx calibration data have been brought up to date with the Chandra CALDB 4.4.7.
Marx Parameter File Updates¶
The parameter files for earlier versions of marx (e.g., the marx.par
file for version 4.5) cannot be used with marx 5.0. The recalibrations
that were necessary for subpixel support resulted in changes to all of
the HRMA blur parameters, as well as the introduction of the new
AspectBlur parameter discussed above.
The following marx.par parameter values have changed since marx 4.5:
P1Blur: 0.18129215 --> 0.303427 H1Blur: 0.13995037 --> 0.0051428 P3Blur: 0.11527828 --> 0.0951899 H3Blur: 0.16360829 --> 0.0713614 P4Blur: 0.1289134 --> 0.178899 H4Blur: 0.098093014 --> 0.0101367 P6Blur: 0.076202759 --> 0.151085 H6Blur: 0.079767401 --> 0.0239287 MEGRowlandDiameter: 8632.65 --> 8632.48 HEGRowlandDiameter: 8632.65 --> 8632.48 HETG_Shell1_Period: 0.400141 --> 0.400195 HETG_Shell3_Period: 0.400141 --> 0.400195 LETG_Shell1_Theta: -0.07 --> 0.07 LETG_Shell3_Theta: -0.07 --> 0.07 LETG_Shell4_Theta: -0.07 --> 0.07 LETG_Shell6_Theta: -0.07 --> 0.07 legCoarseNumOrders: 11 --> 121
The following parameters have been removed:
The following parameters have been added:
AspectBlur: 0.07 LETG_ACIS_dTheta: -0.0867 Use_This_Order: 0 DetExtendFlag: no
The latter two parameters were added for the purposes of calibration.
MARX 4.0 represents a major upgrade since the previous release. Where possible, MARX now uses CIAO CALDB data files directly for detector responses and quantum efficiencies thus providing the ability to transparently analyze simulations using standard CIAO tools. In addition to calibration changes, a number of improvements and enhancements to MARX’s functionality have been made. These include:
Simplified source position specification
Direct CALDB interface for calibration information
Direct use of FEF files for ACIS spectral response
New ACIS photon pileup tool
Enhancements to support processing CHART rayfiles
Improved compatibility with CIAO data analysis tools
Miscellaneous bug fixes
As with previous updates, most of these changes should be completely transparent to the returning user.