Models

Models#

NMMA will be under continuous development meaning that new astrophysical models such as for kilonovae, supernovae, gamma-ray bursts and so on will be implemented over time. Therefore, it is worthwhile to check out the model_parameters_dict in models.py from time to time.

We make the interpolated models available here: Theodlz/nmma-models which are automatically downloaded upon their first request.

Kilonovae#

These are optical counterparts to binary neutron star mergers generated by r-process material produced (Metzger 2017). In this framework, we use a few different sources for the models:

Kasen et al. 2017#

We use a model from Kasen et al. 2017. The model is named Ka2017 in the code. The parameters are:

  • ejecta mass \(M_{\rm ej}\)

  • ejecta velocity \(v_{\rm ej}\)

  • lathanide fraction \(X_{\rm lan}\)

The original light curves are available on GitHub here.

Dietrich et al. 2020#

We use a model from Dietrich et al. 2020, which is derived from POSSIS, spanning the plausible binary neutron star parameter space. The model is named Bu2019lm in the code. The model parameters are:

  • dynamical ejecta mass \(M^{\rm dyn}_{\rm ej}\)

  • disk wind ejecta mass \(M_{\rm ej}^{\mathrm{wind}}\)

  • half opening angle \(\Phi\)

  • observation angle \(\Theta_{\rm{obs}}\)

The original light curves are available on GitHub here.

Anand & Coughlin et al. 2021#

We use a model from Anand & Coughlin et al. 2021, which is derived from POSSIS, spanning the plausible neutron star - black hole space. The model is named Bu2019nsbh in the code. The model parameters are:

  • the dynamical ejecta \(M^{\rm dyn}_{\rm ej}\)

  • disk wind ejecta \(M_{\rm ej}^{\mathrm{wind}}\)

  • observation angle \(\Theta_{\rm{obs}}\)

The half opening angle \(\Phi\) is fixed to 30 deg. The original light curves are available on GitHub here.

Anand et al. 2023#

We use a model from Anand et al. 2023, which is derived from POSSIS, spanning the plausible binary neutron star parameter space. The model is named Bu2022mv in the code. The model parameters are:

  • dynamical ejecta mass \(M^{\rm dyn}_{\rm ej}\)

  • dynamical ejecta velocity \(v^{\rm dyn}_{\rm ej}\)

  • disk wind ejecta mass \(M^{\rm wind}_{\rm ej}\)$

  • disk wind ejecta velocity $\(v^{\rm wind}_{\rm ej}\)

  • observation angle \(\Theta_{\rm{obs}}\)

The original light curves are available on GitHub here.

Wollaeger et al. 2021#

We use a model from Wollaeger et al. 2021 spanning the plausible binary neutron star parameter space. The models are named LANLTS1, LANLTS2, LANLTP1, and LANLTP2 in the code, representing the different geometries to choose from (see here for LANL list). The model parameters are:

  • dynamical ejecta mass \(M^{\rm dyn}_{\rm ej}\)

  • dynamical ejecta velocity \(v^{\rm dyn}_{\rm ej}\)

  • disk wind ejecta mass \(M^{\rm wind}_{\rm ej}\)

  • disk wind ejecta velocity \(v^{\rm wind}_{\rm ej}\)

  • observation angle \(\Theta_{\rm{obs}}\)

The original light curves are available on Zenodo here.

r-process generation in collapsars#

We use a model from Anand et al. 2023, which is derived from the model presented in Barnes & Metzger 2022, studying r-process generation in broadlined stripped-envelope (Ic-BL) supernovae associated with collapsars. The model is named AnBa2022 in the code. The model parameters are:

  • total mass \(M_{\rm ej}\)

  • Nickel 56 mass \(M_{\rm 56}\)

  • ejecta velocity \(v_{\rm ej}\)

  • r-process mass \(M_{\rm rp}\)

  • fraction of r-process material mixed into the ejecta \(x_{\rm mix}\)

Gamma-ray burst afterglows#

We use afterglowpy (Ryan et al. 2020), an open-source computational tool modeling forward shock synchrotron emission from relativistic blast waves as a function of jet structure and viewing angle. The model is named TrPi2018 in the code. The model parameters are:

  • isotropic kinetic energy \(E_{\mathrm{K,iso}}\)

  • jet collimation angle \(\theta_c\)

  • viewing angle \(\theta_v\)

  • circumburst constant density \(n\)

  • spectral slope of the electron distribution \(p\)

  • fraction of energy imparted to the electrons by the shock \(\epsilon_e\)

  • fraction of energy imparted to the magnetic field \(\epsilon_B\)

Shock Cooling supernovae#

We use a model from Piro et al. 2021. Following shock breakout, the radiation of shock heated material expands and cools, known as shock cooling emission. The model parameters are:

  • mass of extended material \(M_e\)

  • radius of extended material \(R_e\)

  • energy of material as the shock passes through it \(E_e\)

Supernovae#

We rely on models for supernovae from sncosmo. For example, the nugent-hyper model (Levan et al. 2005) used for SN Ib/c supernovae with the stretch and scale set to match the intrinsic (dereddened, rest frame) \(R\)-band luminosity of SN 1998bw at maximum light. The main free parameter is the absolute magnitude.

All models listed here can be used. We provide a prior file called sncosmo-generic.prior that only provides:

  • luminosity distance

  • timeshift

  • supernova_mag_boost

The latter parameter shifts the absolute magnitude up and down.