Hot subdwarfs' models with rotation, internal magnetic fields and accretion

Hot subdwarfs' models with rotation, internal magnetic fields and accretion:

Overview

This repository contains stellar evolutionary tracks of rotating hot subdwarfs including internal magnetic fields and accretion. All the models were computed with MESA (version 24.08.1, SDK version x86_64-linux-24.7.1, all computations were made in CentOS Linux release 7.4.1708). The needed initial parameters' files and software modifications necessary to reproduce our results are provided as well.

In addition, we provide the stellar evolutionary tracks of models evolved from the zero age main sequence until the tip of the red giant branch used to construct our rotating hot subdwarf models. These models include rotation and internal magnetic fields, and are tailored to reproduce asteroseismic rotation rates of red giant branch stars.

Repository structure

Hot subdwarfs models:

The sdB models are provided in different folders depending on whether they include accretion and whether the accretion was included until the core (or envelope) spins up to a given rotation rate given in nanoHertz. These are specified by the keyword "core" or "env" and the number next to it. For example, the file "sdb_accretion_env200.tar.gz" contains sdB models where the envelope is spun up to 200 nHz by accretion whereas the file "sdb.tar.gz" contains sdB models without accretion.

The individual folders containing the sdB models are named depending on the properties of their progenitors and the hydrogen-rich envelope mass of the sdB. For the properties of the progenitor, the folders are named according to the initial mass at the ZAMS, and their initial rotation period (in days) or rate (in microHertz) also at the ZAMS. The hydrogen-rich envelope mass is given in Msun for each model.

For example:

M12_5d_menv5e-4/ : initial ZAMS mass of 1.2 Msun and initial rotation period of 5 days. The sdB model has a hydrogen-rich envelope mass of 5 x 10^-4 Msun.

M16_10muhz_menv1e-3/ : initial ZAMS mass of 1.6 Msun and initial rotation rate of 10 microHertz. The sdB model has a hydrogen-rich envelope mass of 1 x 10^-3 Msun.

In addition to the standard columns provided by MESA, the following columns are given:

nu_max:              Frequency of maximum oscillation power [muhz]
om_g:                  Mean core angular velocity as sensed by g-modes    [rad/s]
om_p:                  Mean envelope angular velocity as sensed by p-modes [rad/s]
delta_nu:             Large frequency separation [muhz]
delta_pi1:            Period spacing of g-modes [s]
mixmod_freq:     Mixed mode density
omegadotmag:  Rate of angular velocity decrease by magnetised winds [rad/s^2]
total_mass_h:    Total mass of hydrogen [Msun]
macc:                  Mass accreted [Msun] (only in sdB models with accretion)

Among these, the only relevant ones for sdB models are om_g, om_p, delta_pi1, total_mass_h, and macc (only for sdB models with accretion)

ZAMS to RGB tip models: are provided in the file "zamstorgb.tar.gz", which contains stellar evolutionary tracks of models evolved with rotation and internal magnetic fields from the ZAMS until the RGB tip. Each folder is named according to their mass and initial rotation as explained above. 

Inputs and software needed to recompute models:

The file source.tar.gz  contains the necessary input files to recompute the models presented in the work, from the ZAMS until the sdB phase including both rotation and internal magnetic fields (and optionally accretion). Each folder within this file contains the specific files with the input parameters and the necessary software modifications to account for internal magnetic fields and accretion. All files are already configured to compute a model with Mzams= 1 Msun, initial rotation period Prot,zams=1 day, and an sdB model with a hydrogen-rich envelope mass Menv=10^-3 Msun. Each specific folder contains:

• run_sdb_accretion: input files needed to run sdB models with accretion
• run_sdb_deg: input files needed to run sdB models from the RGB tip for sdB's whose progenitors ignite helium in degenerate conditions
• run_sdb_nondeg: input files needed to run sdB models from the RGB tip for sdB's whose progenitors ignite helium in non-degenerate conditions
• run_zamstorgb: input files needed to run models from the ZAMS to the RGB tip. The resulting RGB tip models are then used then to construct the sdB models

In addition to the standard input parameters to change the initial mass and the initial angular velocity of the model provided by MESA by default, the  parameter x_ctrl(9) in the file run_sdb_deg/inlist_postcee_presdb or run_sdb_nondeg/inlist_cee should be changed to compute sdB models with different envelope masses, by default it is set to 10^-3 Msun and reads as shown below:

x_ctrl(9) = 1d-3 ! target hydrogen-rich envelope mass [Msun]

To compute sdB models whose rotation is affected by accretion the target rotation rate can be modified in the source files, namely in the function extras_check_model through the variables omp_target or omg_target.

To compute the whole evolution from ZAMS to the sdB phase the models should be computed in the following order:

From the ZAMS until the RGB tip. Use the files provided in the folder run_zamstorgb. If needed change the initial parameters in inlist_msrgb.

From the RGB tip until the sdB phase: use the files in the folders run_sdb_deg or run_sdb_nondeg depending on whether the RGB models ignite helium in degenerate or non-degenerate conditions. In the degenerate case, use the inlists in the order:

1. inlist_cee: this will remove the outer hydrogen-rich envelope until it has only 10^-2 Msun and save a model for the next step
2. inlist_postcee_presdb: this will load the model produced by inlist_cee and continue the evolution with smaller mass-loss rates until the core-helium ignition. To compute models with different hydrogen-rich envelope masses, the parameter x_ctrl(9) can be modified at this step so the first step (inlist_cee) does not have to be repeated for each model with similar initial conditions.
3. inlist_sdb: this will load the model produced by inlist_postcee_presdb and compute the core-helium burning phase of the sdB model. It will stop once the central helium mass fraction drops below 10^-6 in mass fraction.

For models with non-degenerate helium ignition, the second step is skipped and the hydrogen-rich envelope mass can be modified in inlist_cee.

To compute sdB models with accretion, use the files given in the folder run_sdb_accretion, for which you will need the zero-age sdB model, which can be computed following the previously mentioned steps.

If you have any questions or additional requests please only contact the corresponding author (Facundo D. Moyano).