Mass Loss Models - arsenal-popsynth/arsenal_gear GitHub Wiki

In this page we will detail all of the Mass Loss models employed for stellar wind and SNe mass loss by various stellar population synthesis (SPS) codes as well as stellar evolutionary codes. We provide links to the relevant source material where appropriate.

To be described (Lachlan): New X-Shooting ULLYSES observations showing no signs of a bi-stability jump in wind mass loss rates.

Starburst99

In terms of mass loss the main reference here is Leitherer et al. 1992

  • Stellar Tracks: They use the "old" Geneva tracks of Maeder & Meynet 1988 and Maeder 1990
  • OB Stars:
    • Use Equations 1 & 2 of Leitherer et al. 1992 which are based on fits to their own stellar wind models.
    • They define O & B stars as all stars with $\log_{10}\left( T_{\rm eff}/{\rm K}\right)> 3.9$ and $X>0.4$ where $X$ is the surface Hydrogen mass fraction
  • LBV Stars:
    • $\dot{M} = 10^{-3.9}$ $M_{\odot}$ ${\rm yr}^{-1} \left(Z/Z_{\odot}\right)^{0.8}$ and $V_w = 200$ ${\rm km/s} \left(Z/Z_{\odot}\right)^{0.13}$
    • Define LBV Stars by $3.75 < \log_{10}\left( T_{\rm eff}/{\rm K}\right)> 4.4$ and $\log_{10}\left( \dot{M}/M_{\odot}/{\rm yr}\right)> -3.5$ in the M90 Tracks.
    • They also tested the mass loss prescriptions of de Jager 1988 which are empirical and meant to be used over the whole CMD.
  • RSG Stars:
    • Defined a $\log_{10}\left( T_{\rm eff}/{\rm K}\right) < 3.9$ unless it's an LBV as above
    • $\dot{M}$ from Reimers 1975 (given as Eq. 5 in Leitherer et al. 1992)
    • $V_w = 200$ ${\rm km/s} \left(Z/Z_{\odot}\right)^{0.13}$
  • WR Stars:
  • Supernovae:
    • All stars above $8 M_{\odot}$ explode as SN at the end of their lives according to the M90 tracks
    • Each SN gets $10^{51}$ ergs in energy
    • The ejecta mass is given by the mass of the star at the end of central carbon burning (according to the M90 tracks) with an assumed remnant mass of 1.4 $M_{\odot}$ taken out

SLUG

References: on SLUG overall are Paper I, Paper II, Paper III, and Paper IV

SLUG seems to really be mostly focused on observers and the radiation budget but Jeong-Gyu found winds mentioned in this commit to the SLUG2 bitbucket repository which is from July of 2022, more recent than any of the above papers. Looks like the implementation is here. Basically, they just follow the default MIST prescription. MIST gets the mass loss right but doesn’t really care about the wind velocity being correct (it is mostly correct in the optically thick wind regime) so there are some additions to deal with the wind velocity, detailed below.

  • Stellar Tracks: They use MIST (talked about further below)
  • AGB & RGB Stars: Uses MIST mass loss from empirical values given by Reimers 1975 & Bloecker 1995 with wind velocities from Elitzur & Ivezic 2001
  • OB Stars:
    • Uses Vink et al. 2000, 2001 with $V_w \propto Z^{0.13}$
    • As with everyone else, their implementation assumes $\Gamma_e = 0.434$ for calculating the effective temperature of the bi-stability jump according to Equation 15 of Vink et al. 2001. rather than taking into account the variation of $\Gamma_e$ over the CMD
  • WR Stars:
    • Decide whether or not its a WR based on the MIST flag which according to Choi et al. 2016 is basically the SB99 decision except $T_{\rm eff} > 10, {\rm kK}$).
    • They calculate the velocity by using the MIST $\dot{M}$ and setting the wind momentum to $L_{\rm bol}/c$. MIST mass loss come from the empirical Nugis & Lamers 2000.
  • Supernovae:

BoOST

The GRIFFIN Project uses the Bonn Optimized Stellar Tracks (BoOST) described in Szécsi et al. 2022 which takes special care in tracking the evolution of massive stars. They only look at stars with masses between 9-500 solar masses. Actually, they have their own SPS code that they call SYNSTARS which might be worth checking out (also detailed in the BoOST paper).

It seems like the mass loss prescriptions are described in the most detail by Szécsi et al. 2015. Section 2.3

  • OB Stars: They use the prescription of Vink et al. 2000 with the bi-stability jump (included incorrectly as in SLUG) and the metallicity dependence of Vink et al. 2001
  • LBV Phase: They seem to try to account for short periods of high mass losses by, during the OB phase, changing to the mass loss to the prescription of Nieuwenhuijzen & de Jager 1990 if it is great than the Vink prediction
  • RSG Stars:
    • Defined by $T_{\rm eff} < 12$ ${\rm kK}$
    • Use the Mass loss prescription of Nieuwenhuijzen & de Jager 1990
    • Include an additional $\propto Z^{0.85}$ dependence, as in the Vink prescription
  • WR Stars:
    • For stars with a surface mass fraction of Helium $Y \ge 0.7$ they include the prescription of Hamann et al. 1995 with a reduction by a factor of 10 as recommended by Yoon et al. 2006
    • They also include an additional $\propto Z^{0.85}$ dependence, as in the Vink prescription
    • They interpolate linearly between this prescription and that of Vink for $0.55 \le Y \le 0.7$
  • They say that overall a mass-loss enhancement is included for star rotating close to critical rotation (accounting for the Eddington factor) but they don’t give specifics. This is probably similar to the one given in MIST, which is detailed below.

MIST/MESA

MIST is the Modules for Experiments in Stellar Astrophysics (MESA) Isochrone and Stellar Tracks (MIST altogether). The main website is here. The main references are

  1. The main MIST Paper Choi et al. 2016 Section 3.7 contains most of the details of stellar mass loss.
  2. The main MESA Paper Paxton et al. 2011

The MIST prescription for $M_* > 10$ $M_{\odot}$ is called the DUTCH prescription, given all the dutch authors of wind-related codes. This prescription is used in a lot of the other SPS calculations. They also include a prescription for rotation that boosts the mass losses.

  • OB Stars:

    • Defined by $T_{\rm eff} > 1.1 \times 10^4$ ${\rm K}$ and $X>0.4$
    • Uses Vink et al. 2000, 2001 with metallicity dependence
    • Assumes $\Gamma_e = 0.434$ for calculating the effective temperature of the bi-stability jump according to Equation 15 of Vink et al. 2001. as stated above for SLUG.

  • WR Stars:

    • Defined by $T_{\rm eff} > 10^4$ ${\rm K}$ and $X<0.4$ (as given above for SLUG)
    • Nugis & Lamers 2000 prescription for mass loss that should extend to all WR types.

  • RSG Stars:

    • Defined as all stars with $T_{\rm eff} < 10^4$ ${\rm K}$
    • They use the de Jager et al. 1988 mass loss prescription (Eq. 20 of Choi et al. 2016) and mention that Mauron & Josselin 2011 recommend an additional metallicity scaling that they don’t include of $\propto Z^{0.7}$

  • Rotational Enhancement: For rotating stars they include a wind mass loss enhancement factor given by $(1 - \Omega/\Omega_{\rm crit})^{-0.43}$ where $\Omega$ is the rotational velocity of the star and $\Omega_{\rm crit} = \sqrt{(1 - L/L_{\rm Edd})GM/R_*^3}$ is the critical angular velocity at the stellar surface. They cap the rotational boost to $< 10^4$

BPASS

The “Binary Population and Spectral Synthesis” (BPASS) code was developed especially to keep in mind the effects of massive star binaries, or really just binaries in general on Stellar population synthesis. As far as I can tell, all wind stuff is done within the stellar modeling which comes from the "Cambridge" models, which seem to be quite old, so I'm not sure how much I would trust these. Probably a good idea to ask someone with more BPASS experience if there is a better place to look for these.

Modern Mass Loss Prescriptions

In trying to put together the most up to date mass loss prescriptions I read over Jorick Vink's recenter review article (Vink 2022) where I found references to some of the mass loss prescriptions mentioned below. The other most recent review article on this is Smith 2014

  • Björklund et al. 2021: CMF RHD simulations using the FASTWIND code meant for OB Stars.
  • Vink & Sander 2021: An update to the Vink 2000, 2001 calculation. These calculations are still done using the ISA-WIND code ISA stands for "Improved Sobolev Approximation".
  • Sander & Vink 2020: The first theoretically based predictions for Wolf-Rayet star Mass Loss using the Potsdam Wolf-Rayet (POWR) code for doing CMF RHD simulations.