Dear MESA Users,

To coincide with the new mesa instrument paper we’re happy to announce a new public release of MESA: version 11532. We refer the reader to the paper for the largest and most significant changes. Here we give a brief overview of the changes from the MESA paper as well as document the changes which did not make it to the instrument paper.


https://arxiv.org/abs/1903.01426

Inlists available on mesastar.org and https://zenodo.org/communities/mesa/


Thanks,
Rob (on behalf of the MESA developer team)


MESA 11532 Release Notes:


We welcome the following new MESA developers:

Adam Jermyn

Radek Smolec


RSP is a new functionality in MESAstar that models the non-linear radial stellar pulsations that characterize RR Lyrae, Cepheids, and other classes of variable stars. See the rsp_* examples in the test suite.


We significantly enhance numerical energy conservation capabilities, including during mass changes. For example, this enables calculations through the He flash that conserve energy to better than 0.001%. Most test cases now have this enabled, for instance 1.3M_ms_high_Z, 25M_pre_ms_to_core_collapse, and wd as examples.


To improve the modeling of rotating stars in MESA, we introduce a new approach to modifying the pressure and temperature equations of stellar structure, and a formulation of the projection effects of gravity darkening. The latter are controlled by the grav_dark options in history_columns.list;  see high_rot_darkening for an example of its use.


A new scheme for tracking convective boundaries, called Convective Pre-Mixing (CPM), yields reliable values of the convective-core mass, and allows the natural emergence of adiabatic semiconvection regions during both core hydrogen- and helium-burning phases. Examples for this can be found in the inlists provided with the mesa 5 paper.


We have updated the equation of state and nuclear reaction physics modules.


There are an increased number of warnings for when MESA goes beyond the validity of the input physics (for instance the nuclear reactions rates from REACLIB are ill-defined when logT>10.0). These warnings are controlled by the warn_* options.  


The definition of eps_nuc has slightly changed (see MESA V, Section 3.2) in order to be suitable for use with the new energy equation.  If you are running models using the dLdm form that includes eps_grav, you should consult the controls option include_composition_in_eps_grav and its associated documentation.


A new set of tests (gyre_in_mesa_*) demonstrate how to call GYRE on the fly during a MESA run.


The astero module now allows users to define model parameters (my_param[123]) that will be optimised in a similar way to the standard options (M, Y, FeH, alpha, f_ov). These are defined in the subroutine set_my_params in run_star_extras.f in a similar way to how users can define their own observables (my_var[123]).


The astero module now has controls normalize_chi2_* that allow the user to decide whether or not to normalize each component of χ² by the number of terms that contributed to that component.


The format of the OP_MONO opacity table cache has changed.  If you have used these files in a previous version of MESA then you should do:

   rm $MESA_OP_MONO_DATA_CACHE_FILENAME

before installing MESA.  If you use multiple MESA versions, this means that you cannot share the cache file between old and new versions.  Therefore, you should make sure to use a different cache file in each case. This may be more easily accomplished using the controls option op_mono_data_cache_filename rather than the environment variable.

The version of GYRE bundled with MESA has been updated to version 5.2


Binaries can now model “twins”, where we can skip the calculation of the companion as its assumed to be identical to the primary. This is controlled by the binary_job parameter *_model_twins_flag


There is a new way to treat convection in a model, via the convective_velocity_flag. This adds an equation to solve the velocity of convective motion, instead of using the value derived from MLT. This is useful for models evolving on fast timescales and is a replacement for min_T_for_acceleration_limited_conv_velocity


Two new test cases (hydro_Ttau_solar and hydro_Ttau_evolve) demonstrate the use of mixing length parameters and T(tau) relations calibrated to 3D radiation-coupled hydrodynamics (RHD) simulations computed by Trampedach et al. (2014). More details are provided in Mosumgaard et al. (2018). MESA also includes low-temperature opacity tables that match those used in the 3D RHD simulations, which can be used by setting kappa_lowT_prefix = 'lowT_rt14_ag89'


There have been many bug fixes and performance enhancements to MESA. Reports of bugs or suggested improvements are welcome on the mesa-users mailing list.


A reminder to please share your inlists and run_star_extras on mesastar.org upon publication of your science papers!