What's newΒΆ

Following is a brief list of important updates to the COMPAS code. A complete record of changes can be found in the file changelog.h.

03.18.00 Apr 14, 2025

New command line option:

  • --timestep-multipliers to enable more granular, phase-dependent, timestep multipliers

03.17.03 Apr 14, 2025

  • Neutron stars are now labelled as RecycledNS when undergoing mass transfer through common envelope (when --neutron-star-accretion-in-ce is not set to ZERO).

  • Removed output option RLOF_ONTO_NS as it can be retrieved from existing RLOF output info.

03.17.00 Mar 22, 2025

  • Added ENVELOPE_STATE_PRESCRIPTION::CONVECTIVE_MASS_FRACTION (default threshold of convective envelope by mass to label envelope convective is 0.1, can be set with --convective-envelope-mass-threshold)

  • Stable mass transfer now conserves angular momentum after accounting for the rotational angular momentum lost or gained by the stars

  • Imposed Keplerian rotation limit on mass-gaining stars: response depends on the new --response-to-spin-up option, with possible values:

    • TRANSFER_TO_ORBIT (default) allows the star to accrete, but excess angular momentum is deposited in the orbit

    • KEPLERIAN_LIMIT forces mass transfer to become non-conservative once star (approximately) reaches super-critical rotation

    • NO_LIMIT allows arbitrary super-critical accretion, to match legacy choices

03.16.02 Mar 19, 2025

New output options for supernova, which allow for full characterization of the binary orientation post-SN:

  • ORBITAL_ANGULAR_MOMENTUM_VECTOR_X

  • ORBITAL_ANGULAR_MOMENTUM_VECTOR_Y

  • ORBITAL_ANGULAR_MOMENTUM_VECTOR_Z

  • SYSTEMIC_VELOCITY_X

  • SYSTEMIC_VELOCITY_Y

  • SYSTEMIC_VELOCITY_Z

03.15.00 Mar 5, 2025

Changes to the treatment of Neutron Star evolution.

New command line options:

  • --neutron-star-accretion-in-ce to determine how a NS accretes mass in a common envelope

  • --pulsar-birth-magnetic-field-distribution-mean and --pulsar-birth-magnetic-field-distribution-sigma to determine the birth distribution of the pulsar magnetic field (only relevant when the --pulsar-birth-magnetic-field-distribution option value is NORMAL or LOGNORMAL)

  • --pulsar-birth-spin-period-distribution-mean and --pulsar-birth-spin-period-distribution-sigma to determine the birth distribution of the pulsar period (only relevant when the --pulsar-birth-spin-period-distribution option value is `NORMAL or LOGNORMAL)

Changed command line option values and defaults:

  • --pulsar-birth-spin-period-distribution option value ZERO is now deprecated.

  • --pulsar-birth-magnetic-field-distribution option value ZERO is now deprecated.

  • --pulsar-birth-spin-period-distribution default option value is now NORMAL (was ZERO)

  • --pulsar-birth-magnetic-field-distribution default option value is now LOGNORMAL (was ZERO)

Changes to the NS-related values in log files:

  • The pulsar magnetic field strength is now recorded in Gauss (was Tesla)

  • The pulsar spin down rate now tracks the pulsar spin period derivative (was spin frequency derivative).

  • The SSE/BSE_Pulsar_Evolution file default record now includes the pulsar spin period (s) instead of spin frequency. Spin frequency is still tracked and can be added using the logfile-definitions option

  • The period of non-spinning neutron stars is now reported as infinity instead of zero

03.14.00 Mar 3, 2025

  • Updates to improve convergence without sacrificing computational speed, including updates to default mass and radial change fractions per time step and their usage

  • Capped total wind mass loss rate at MAXIMUM_WIND_MASS_LOSS_RATE (set to 0.1 Msol/yr) for all prescriptions

  • Changed order of calls in SSE evolution to better match BSE evolution

03.13.02 Feb 19, 2025

  • Replaced name of SHIKAUCHI main sequence core mass prescription with BRCEK.

03.13.01 Feb 13, 2025

  • Enabled nuclear timescale mass transfer from evolved donors

03.13.00 Feb 13, 2025

  • Added pulsar evolution and output (SSE_Pulsar_Evolution) for SSE mode

  • Changed stopping condition for single stars to continue evolving pulsars if --evolve-pulsars is TRUE

  • Updated documentation for new output

03.12.04 Feb 8, 2025

  • Replaced name of COMPAS PPISN prescription with WOOSLEY; COMPAS is now deprecated

03.12.00 Jan 16, 2025

  • Added convective core mass prescription for main sequence stars from Shikauchi+ (2024), describing how the core mass evolves under mass loss and mass gain.

  • New command line option --main-sequence-core-mass-prescription with arguments SHIKAUCHI (new prescription), MANDEL (replaces the functionality of --retain-core-mass-during-caseA-mass-transfer), and ZERO (core mass set to zero, no treatment).

  • Updated stellar tracks with added luminosity prescription for main sequence stars from Shikauchi+ (2024).

  • Added treatment for rejuvenation of main sequence accretors when the new prescription is used.

03.10.00 Nov 29, 2024

Added functionality to log stellar mergers in the BSE switchlog file. Switchlog merger records come in pairs (one for each star) so that the stellar type of each star is recorded.

03.09.00 Nov 28, 2024

Improved nuclear timescale mass transfer: the nuclear timescale mass transfer rate is now set by the requirement that the star ends the time step just filling its Roche lobe. Fixed several significant mass-transfer issues, such as accretors not gaining mass appropriately and failures in the root solver for fitting the star into the Roche lobe that were leading to artificial common envelopes and mergers.

03.08.02 Nov 18, 2024

Updated implementation of the mass transfer stability critical mass ratio tables from the team of Hongwei Ge. We now use all the most up to do date tables they've produced (public or otherwise) from Papers I-V, including variations for adiabatic and isentropic treatments, variable accretion efficiency, and two different metallicities, as well as for He stars (albeit only for adiabatic, fully conservative, solar metallicity stars).

03.08.00 Nov 18, 2024

Improved the treatment of stellar rotation (with further corrections in 03.08.01):

  • Assume rigid body rotation

  • Keep the angular moment of a star constant when there is no mass loss

  • When a star with radius r and angular frequency omega loses mass dm through winds or mass transfer, it loses angular momentum dL = (2/3) dm r^2 omega

  • (However, angular momentum never drops below zero)

  • When a star loses its envelope, the remaining core is assumed to rotate with the same rotation rate as the preceding star

  • When a star of mass m and radius r gains mass dm through accretion, it gain angular momentum dL = dm sqrt{G m r}

  • If initial binary rotation is fast enough for a star to be CHE, it is set to that rotation frequency without regard for the tidal prescription; CHE stars remain tidally locked if the tidal prescription is NONE

03.07.01 Oct 23, 2024

Resolved (and reverted) performance degradation introduced in v03.00.00.

03.07.00 Oct 16, 2024

Added new critical mass ratio tables from Ge et al. 2024.

03.06.00 Oct 14, 2024

Incorporated the Maltsev+ (2024) prescription for supernova remnant masses.

03.03.00 Sep 24, 2024

Added new functionality to improve modelling of chemically homogeneous evolution (CHE). The default behaviour remains unchanged.

  • New command line option --enable-rotationally-enhanced-mass-loss to enable rotationally enhanced mass loss following Langer (1998)

  • New command line option --enhance-CHE-lifetimes-luminosities to enhance CHE lifetimes and luminosities following detailed models from Szecsi et al. (2015)

  • New command line option --scale-CHE-mass-loss-with-surface-helium-abundance to switch from OB to WR mass loss for CH stars towards the end of the main sequence

  • New command line option --scale-terminal-wind-velocity-with-metallicity-power to scale the terminal wind velocity with the metallicity

03.02.00 Sep 19, 2024

Added recording of MASS_TRANSFER_TIMESCALE (NONE, NUCLEAR, THERMAL, CE). Now continuing evolution on mergers at birth (stars touching) if --resolve-main-sequence-merger. Changed Sabhahit+ 2023 VMS winds to default to current OB wind prescription if Gamma threshold is not met Correct the behaviour of the second stage of 2-stage CE to first transfer mass from the star that initiated RLOF; now ensuring that the accretor's mass is correctly adjusted Update the fits for the convective envelope mass and radial extent to ensure smooth behaviour Updated treatment of 2-stage common envelope for intermediate mass stars, to smoothly reduce from Hirai & Mandel above 8 solar masses to classical "full envelope" removal for stars below 2 solar masses.

03.01.06 Aug 30, 2024

Added functionality to allow users to specify if WD-binaries should be included in the BSE DCO file via new option --include-WD-binaries-as-DCO. When enabled, --include-WD-binaries-as-DCO changes the definition of "Double Compact Object" from a binary comprised of any two of {Neutron Star, Black Hole} to a binary star comprised of any two of {Helium White Dwarf, Carbon-Oxygen White Dwarf, Oxygen-Neon White Dwarf, Neutron Star, Black Hole}.

The default value for the new option is FALSE.

03.01.04 Aug 28, 2024

  • New option 'HENDRIKS' for --pulsational-pair-instability-prescription implementing the prescription for pulsational pair instability mass-loss from Hendricks et al. 2023 (https://arxiv.org/abs/2309.09339).

  • New command line option --PPI-CO-Core-Shift-Hendriks for use with the above prescription (see Hendriks+ for an explanation)

03.01.00 Aug 24, 2024

  • New option to emit gravitational radiation at each timestep of binary evolution: --emit-gravitational-radiation. The effects of radiation are approximated by the change in semimajor axis and eccentricity from Peters 1964 equations 5.6 and 5.7. Reduce timestep if required to keep orbital separation change per step due to GW radiation within ~ 1%.

03.00.00 Jul 26, 2024

This is a major release of COMPAS. There are some significant changes in COMPAS operation and functionality in this release. The major change, and the impetus for the release, is the implementation of a new, coherent, robust, error handling strategy.

Early versions of COMPAS (versions prior to v03.00.00) did not have a coherent, robust, error-handling strategy. In those versions, errors were typically displayed as either errors or warnings (depending on the severity) as they occurred, and evolution of the star (SSE mode) or binary (BSE mode) continued - users were expected to check errors or warnings displayed and use results with appropriate caution. This was not ideal.

In addition, earlier versions of COMPAS did not handle floating-point errors (divide-by-zero, invalid-parameters (e.g. \(\sqrt{-2.0}\)), etc.) well - in fact the code effectively ignored these errors (for a detailed explanation of why this was so, refer to the Error Handling documentation in the Developer Guide (See Floating-point errors in C++).

In COMPAS version 03.00.00 the error handling philosophy has changed, and more coherent and robust error-handling code implemented. The new error-handling philosophy is to stop evolution of a star or binary if an error occurs (including, optionally by a program option, floating-point errors), and record in the (SSE/BSE) system parameters file the fact that an error occurred, and an error number identifying the error that occurred. This way users can check the system parameters file at the completion of a run for the disposition of a star or binary and, if the evolution of that star or binary was stopped because an error occurred, the actual error that occurred.

Users should refer to the Error Handling documentation in the User Guide (See Handling COMPAS errors). Developers should refer to the Error Handling documentation in the Developer Guide (See Error handling service).

In addition to the new error handling strategy, a number of program options have been deprecated and replaced by new program options that are more consistent with the naming convention we are trying to maintain. The program options deprecated, and their replacements, are:

  1. --mass-transfer , replaced by --use-mass-transfer (to be consistent with --use-mass-loss)

  2. --luminous-blue-variable-prescription , replaced by --LBV-mass-loss-prescription (to be consistent with other 'prescription'-type options)

  3. --OB-mass-loss , replaced by --OB-mass-loss-prescription (to be consistent with other 'prescription'-type options)

  4. --RSG-mass-loss , replaced by --RSG-mass-loss-prescription (to be consistent with other 'prescription'- type options)

  5. --VMS-mass-loss , replaced by --VMS-mass-loss-prescription (to be consistent with other 'prescription'- type options)

  6. --WR-mass-loss , replaced by --WR-mass-loss-prescription (to be consistent with other 'prescription'- type options)

  7. --kick-direction , replaced by --kick-direction-distribution (to be consistent with other 'distribution'-type options)

  8. --mass-transfer-thermal-limit-accretor, replaced by --mass-transfer-thermal-limit-accretor-multiplier (for consistency and to better describe the option)

  9. --black-hole-kicks , replaced by --black-hole-kicks-mode (for consistency and to better describe the option)

  10. --chemically-homogeneous-evolution , replaced by --chemically-homogeneous-evolution-mode (for consistency and to better describe the option)

Deprecated program options will still be available, in tandem with their replacements, for some time (at least six months from the release date of v03.00.00), after which time the deprecated options will be removed and only their replacements will be valid options. Appropriate warning messages will be displayed in the period of deprecation if deprecated program options are used.

As well as deprecating some program options, some program option values have been deprecated and replaced by new values that are more consistent with the naming convention we are trying to maintain. The program option value deprecated, and their replacements, are:

  1. --LBV-mass-loss-prescription , value NONE replaced by ZERO

  2. --luminous-blue-variable-prescription, value NONE replaced by ZERO

  3. --OB-mass-loss , value NONE replaced by ZERO

  4. --OB-mass-loss-prescription , value NONE replaced by ZERO

  5. --RSG-mass-loss , value NONE replaced by ZERO

  6. --RSG-mass-loss-prescription , value NONE replaced by ZERO

  7. --VMS-mass-loss , value NONE replaced by ZERO

  8. --VMS-mass-loss-prescription , value NONE replaced by ZERO

  9. --WR-mass-loss , value NONE replaced by ZERO

  10. --WR-mass-loss-prescription , value NONE replaced by ZERO

Deprecated program option values will still be available, in tandem with their replacements, for some time (at least six months from the release date of v03.00.00), after which time the deprecated option values will be removed and only their replacements will be valid option values. Appropriate warning messages will be displayed in the period of deprecation if deprecated program option values are used.

Finally, for program option --mt-rejuvenation-prescription, the value NONE was replaced by HURLEY

02.48.01 May 24, 2024

  • changed functionality of --output-path option so that missing directories in the specified path are created.

  • Added "Quick Links" to online documentation.

02.48.00 May 22, 2024

  • added options --mass-transfer-jloss-macleod-linear-fraction-degen and --mass-transfer-jloss-macleod-linear-fraction-non-degen to allow for different accretor AM response for degenerate and non-degenerate companions.

  • removed option --mass-transfer-jloss-macleod-linear-fraction (no longer required - see above).

02.46.00 May 13, 2024

  • added options --radial-change-fraction and --mass-change-fraction, as approximate desired fractional changes in stellar radius and mass on phase when setting SSE and BSE timesteps

  • the recommended values for both parameters are 0.005, but the default remains 0, which reproduces previous timestep choices

  • mass transfer from main sequence donors (including HeMS) can now proceed on nuclear timescales -- approximated as the radial expansion timescales -- if equilibrium zetas are greater than Roche lobe zetas

02.45.00 Apr 09, 2024

  • Changed compiler standard in Makefile from c++11 to c++17. This is required for boost v1.82 and above. c++11 can still be used if boost version is below v1.82, but moving to c++17 and boost v1.8x is preferred (and will eventually be mandatory). Tested with Ubuntu v20.04, g++ v11.04, and boost v1.74; and macOS v14.1.1, clang v15.0.0, and boost v1.85.

02.44.00 Apr 04, 2024

  • Added 'realistic' tides option, which implements dynamical and equilibrium tides using the formalism described in Kapil et al. (2024).

  • Functionality enabled with new option --tides-prescription KAPIL2024 (default is NONE).

  • Removed old option --enable-tides, which can now be enabled by setting --tides-prescription PERFECT.

02.43.00 Mar 29, 2024

  • Implementation of the neutrino rocket kick.

02.42.00 Jan 04, 2023

  • Timesteps are now quantised to an integral multiple of 1e-12Myr.

  • New option provided to allow user-defined timesteps: --timesteps-filename (See Timestep files).

  • Code changes to make SSE and BSE evolution more consistent (See PR 1052).

02.41.03 Dec 28, 2023

  • The functions BaseBinaryStar::CalculateAngularMomentum(), BaseBinaryStar::CalculateTotalEnergy(), and BaseStar::AngularMomentum() changed to use moment of inertia instead of gyration radius.

  • Changed CalculateMomentOfInertia() to properly implement Hurley et al., 2000 eq 109.

  • This change may change DCO yields slightly when compared to previous versions of the code.

02.41.00 Nov 02, 2023

  • Added a naive tides implementation.

  • Added program option enable-tides to enable the tides implementation (default is false).

02.40.00 Oct 20, 2023

  • Added FLEXIBLE2023 as a new default, and BELCZYNSKI2010 as a replacement for the previous VINK mass loss prescription. The following new sub-wrappers are overridden when selecting BELCZYNSKI2010:

  • Added --OB-mass-loss program option, applying to main sequence stars, with default VINK2021, and options NONE, VINK2001 (previous default), BJORKLUND2022, and KRTICKA2018.

  • Added --RSG-mass-loss program option, applying to stars below 8kK in giant branch stellar types, with default DECIN2023, and options NONE, VINISABHAHIT2023, BEASOR2020, YANG2023, KEE2021, NJ90 (previous default).

  • Added --VMS-mass-loss program option, applying to stars over 100 Msol, with default SABHAHIT2023, and options NONE, VINK2011, and BESTENLEHNER2020.

  • Added --WR-mass-loss program option, with default SANDERVINK2023, and options BELCZYNSKI2010, and SHENAR2019.

  • Changed default value for option --wolf-rayet-multiplier from 0.1 to 1.0

02.39.00 Jul 4, 2023

  • Added 'Evolution_Status' columns to both SSE and BSE default system parameters records - records final status of evolution (reason evolution stopped).

02.38.03 Apr 20, 2023

  • Changed some of the default options, see issue # 957 and PR # 961 for explanations

02.37.00 Mar 26, 2023

  • Added functionality for WDs to accrete in different regimes.

  • New supernova types: SNIA (Type Ia), and HeSD (Helium shell detonation).

02.36.00 Mar 15, 2023

  • Added functionality to automatically create COMPAS YAML file - adds two new options: --create-YAML-file and YAML-template. See documentation for details.

    Note: From this release, the default COMPAS YAML file (compasConfigDefault.yaml), as distributed, has all COMPAS option entries commented so that the COMPAS default value for the option is used by default. To use a value other than the COMPAS default value, users must uncomment the entry and change the option value to the desired value.

02.35.03 Feb 27, 2023

Added mass accretion prescription during CE CHEVALIER for option --common-envelope-mass-accretion-prescription, following model 2 from van Son + 2020

02.35.02 Feb 19, 2023

  • Changed BINARY_PROPERTY::ROCHE_LOBE_RADIUS_1 and BINARY_PROPERTY::ROCHE_LOBE_RADIUS_2 to be the Roche lobe radius as computed at periapsis, in units of \(R_\odot\).

  • Changed header string for BINARY_PROPERTY::ROCHE_LOBE_RADIUS_1 from 'RocheLobe(1)|a' to 'RocheLobe(1)' - same change made for BINARY_PROPERTY::ROCHE_LOBE_RADIUS_2.

  • Removed BINARY_PROPERTY::STAR_TO_ROCHE_LOBE_RADIUS_RATIO_1 (header string 'Radius(1)|RL') and BINARY_PROPERTY::STAR_TO_ROCHE_LOBE_RADIUS_RATIO_2 (header string 'Radius(2)|RL') from BSE_DETAILED_OUTPUT_REC (BSE detailed output file default record). Note that both variables are still selectable for output via the logfile-definitions file.

    Note: These changes will affect post-processing code that consumes the affected variables - users should check their post-processing code.

02.35.00 Dec 8, 2022

  • Added critical mass ratios from Ge+ 2020 for determining if MT is unstable.

02.34.01 Dec 7, 2022

  • Fixed Time<MT in BSE_RLOF, which previously was identical with Time>MT.

02.33.00 Aug 28, 2022

  • Added simplified (constant per stellar type) critical mass ratios from Claeys+ 2014 for determining if MT is unstable

02.32.00 Aug 27, 2022

  • Added 'record type' functionality to all standard log files. Note: This changes default behaviour: only Detailed Output log files affected in this release

  • Added/rationalised Detailed Output records printed for binary systems

  • Added new program option for each standard log file to allow specification of which record types to print. See e.g. --logfile-detailed-output-record-types

  • Changed case on column header strings for switch log files (SSE and BSE. SWITCHING_FROM, SWITCHING_TO, and STAR_SWITCHING are now Switching_From, Switching_To, and Star_Switching respectively). Note: This could affect post-processig code that consumes the switch log files - users should check that their code will recognise the new header strings.

  • Added new section to online documentation: 'What's new'

02.31.10 Aug 12, 2022

  • Added option to set the Temperature boundary between convective/radiative giant envelopes

02.31.09 Aug 9, 2022

  • Max evolution time and max number of timesteps now read in from gridline as well as commandline

02.31.08 Aug 3, 2022

  • Added Accretion Induced Collapse (AIC) of ONeWD as another type of SN

02.31.07 Aug 1, 2022

02.31.06 Aug 2, 2022

  • Added stellar merger to default BSE_RLOF output

02.31.05 July 25, 2022

  • Renamed program option --allow-H-rich-ECSN to allow-non-stripped-ECSN

  • Fixed check for non-interacting ECSN progenitors to consider MT history instead of H-richness

02.31.04 Jun 10, 2022

  • Changed MT_TRACKER values to be clearer and complementary to each other

  • Updated the relevant section in the detailed plotter that uses MT_TRACKER values

  • Removed end states from detailed plotter (Merger, DCO, Unbound) so that they don't over compress the rest

02.31.03 May 20, 2022

  • Fixed MS+MS unstable MT not getting flagged as a CEE

02.31.00 May 14, 2022

  • Added new program option --retain-core-mass-during-caseA-mass-transfer to preserve a larger donor core mass following case A MT, set equal to the expected core mass of a newly formed HG star with mass equal to that of the donor, scaled by the fraction of its MS lifetime

02.30.00 May 8, 2022

  • Added MACLEOD_LINEAR specific angular momentum gamma loss prescription for stable mass transfer (see --mass-transfer-angular-momentum-loss-prescription)

02.29.00 May 5, 2022

  • Added new program option to allow for H-rich ECSN (--allow-H-rich-ECSN, defaults to FALSE). When the option is TRUE, non-interacting ECSN progenitors do not contribute to the single pulsar population. Addresses issue https://github.com/TeamCOMPAS/COMPAS/issues/596

02.28.00 May 11, 2022

  • Added new remnant mass prescription: Fryer+ 2022

  • Added new program options --fryer-22-fmix and --fryer-22-mcrit

02.27.09 Apr 25, 2022

  • Added new program option --muller-mandel-sigma-kick

02.27.08 Apr 12, 2022

02.27.07 Apr 5, 2022

02.27.06 Apr 5, 2022

  • Fixed StarTrack PPISN prescription: previously it was doing the same thing as the COMPAS PPISN prescription

02.27.05 Feb 17, 2022

  • Added new program option --hmxr-binaries, which tells COMPAS to store high-mass x-ray binaries in BSE_RLOF output file

  • Added columns for pre- and post-timestep ratio of stars to Roche Lobe radius to BSE_RLOF output file (addressing issue https://github.com/TeamCOMPAS/COMPAS/issues/746)

02.27.04 Feb 15, 2022

02.27.03 Feb 8, 2022

v02.27.02 Feb 3, 2022

v02.27.01 Feb 3, 2022

  • Fixed condition for envelope type when using ENVELOPE_STATE_PRESCRIPTION::FIXED_TEMPERATURE (previously, almost all envelopes were incorrectly declared radiative)

v02.27.00 Jan 12, 2022

  • Added enhanced Nanjing lambda option that continuously extrapolates beyond radial range

  • Added Nanjing lambda option to switch between calculation using rejuvenated mass and true birth mass

  • Added Nanjing lambda mass and metallicity interpolation options

  • No change in default behaviour