galapy.XRayBinaries

The XRayBinaries module implements the contribution to the X-band emission from stellar binary systems.

This module provides classes for modeling X-ray emission from both High Mass Stars (HMXRB) and Low Mass Stars (LMXRB).

Module Attributes

xrb_tunables

Dictionary with the tunable parameters of the X-ray contribution from binary star systems

Functions

xrb_build_params(startype, **kwargs)

Builds the parameters dictionary for a given star type.

Classes

HMXRB(lmin, lmax, **kwargs)	Class for handling X-ray emission from High Mass Stars.
LMXRB(lmin, lmax, **kwargs)	Class for handling X-ray emission from Low Mass Stars.
XRB(lmin, lmax, **kwargs)	Class for handling X-ray emission from both High and Low Mass Stars.

galapy.XRayBinaries.xrb_tunables = {'hm': ['psi', 'Zstar'], 'lm': ['Mstar', 'age']}

Dictionary with the tunable parameters of the X-ray contribution from binary star systems

1. hm : High Mass Star

2. lm : Low Mass Stars

galapy.XRayBinaries.xrb_build_params(startype, **kwargs)

Builds the parameters dictionary for a given star type.

Parameters:

• startype (str) – Type of star (‘hm’ for High Mass Star, ‘lm’ for Low Mass Star).

• **kwargs (dict) – Additional keyword arguments for specifying parameters. The galapy.XRayBinaries.xrb_tunables contains the available free-parameters for the 2 different types of Xray Binaries: high and low mass stars.

Returns:

Dictionary containing the parameters for the specified star type.

Return type:

dict

class galapy.XRayBinaries.HMXRB(lmin, lmax, **kwargs)

Class for handling X-ray emission from High Mass Stars.

Distributes the X-ray luminosity on a power-law spectrum with exponential cut-off

\[L_\Gamma^X(\lambda)\propto E^{-\Gamma+3}(\lambda)\, e^{-E(\lambda)/E_\text{cut}}\]

with \(E(\lambda)=h_P\, \nu_\lambda=h_P\, c/\lambda\) the energy of a photon with wavelength \(\lambda\), \(E_\text{cut}\) the characteristic energy of the exponential cut-off and \(\Gamma = 2\) (Fabbiano, 2006) the photon index.

The normalisation factor of the exponential cut-off emission is given by

\[\begin{split}\log(L_\text{HMXB}/\text{erg}\,s^{-1}) \approx\\ \log({\dot M_\star/M_\odot}\text{yr}^{-1}) + 40.28-62.12\, Z_\star\\+569.44\,Z_\star^2-1883.80\,Z_\star^3+1968.33\, Z_\star^4\end{split}\]

where \({\dot M_\star} \equiv \psi(\tau)\) is the star formation rate and \(Z_\star\) is the stellar absolute metallicity.

The emission is therefore computed as

\[L(\lambda, Z_\star) = L_{\Gamma=2}^X(\lambda) \cdot L_\text{HMXB}\]

Parameters:

• lmin (float) – Minimum wavelength for the X-ray emission.

• lmax (float) – Maximum wavelength for the X-ray emission.

• **kwargs (dict) – Additional keyword arguments for specifying parameters.

Keyword Arguments:

• psi (float) – star formation rate, default is 1.

• Zstar (float) – stellar average absolute metallicity, default is 0.02

set_parameters(**kwargs)

Set parameters for HMXRB model.

Keyword Arguments:

• psi (float) – star formation rate.

• Zstar (float) – stellar average absolute metallicity.

class galapy.XRayBinaries.LMXRB(lmin, lmax, **kwargs)

Class for handling X-ray emission from Low Mass Stars.

Distributes the X-ray luminosity on a power-law spectrum with exponential cut-off

\[L_\Gamma^X(\lambda)\propto E^{-\Gamma+3}(\lambda)\, e^{-E(\lambda)/E_\text{cut}}\]

with \(E(\lambda)=h_P\, \nu_\lambda=h_P\, c/\lambda\) the energy of a photon with wavelength \(\lambda\), \(E_\text{cut}\) the characteristic energy of the exponential cut-off and \(\Gamma = 1.6\) (Fabbiano, 2006) the photon index.

The normalisation factor of the exponential cut-off emission is given by

\[\begin{split}\log(L_\text{LMXB}/\text{erg}\,s^{-1}) \approx\\ \log(M_\star/M_\odot) + 40.276-1.503\, \theta-0.423\,\theta^2+0.425\,\theta^3+0.136\, \theta^4\end{split}\]

where \(M_\star\) is the stellar mass and \(\theta \equiv \log(\tau/\text{Gyr})\) is the logarithm of the stellar population age.

Assuming \(\Gamma = 1.6\) (Fabbiano, 2006) the emission is computed as

\[L(\lambda, Z_\star) = L_{\Gamma=1.6}^X(\lambda) \cdot L_\text{LMXB}\]

Parameters:

• lmin (float) – Minimum wavelength for the X-ray emission.

• lmax (float) – Maximum wavelength for the X-ray emission.

• **kwargs (dict) – Additional keyword arguments for specifying parameters.

Keyword Arguments:

• age (float) – age of the stellar populations, default is 1.e+8

• Mstar (float) – total stellar mass of the stellar populations, default is 1.e+10

set_parameters(**kwargs)

Set parameters for LMXRB model.

Keyword Arguments:

• age (float) – age of the stellar populations

• Mstar (float) – total stellar mass of the stellar populations

class galapy.XRayBinaries.XRB(lmin, lmax, **kwargs)

Class for handling X-ray emission from both High and Low Mass Stars.

The total emission is given as

\[L_\text{XRB}(\lambda, Z_\star, \tau) = L_\text{HMXB}(Z_\star) L_{\Gamma=2}^X(\lambda) + L_\text{LMXB}(\tau) L_{\Gamma=1.6}^X(\lambda)\]

where the first term gives the contribution from High Mass binaries and the second term that from Low Mass binaries.

Parameters:

• lmin (float) – Minimum wavelength for the X-ray emission.

• lmax (float) – Maximum wavelength for the X-ray emission.

• **kwargs (dict) – Additional keyword arguments for specifying parameters.

Keyword Arguments:

• psi (float) – star formation rate, default is 1.

• Zstar (float) – stellar average absolute metallicity, default is 0.02

• age (float) – age of the stellar populations, default is 1.e+8

• Mstar (float) – total stellar mass of the stellar populations, default is 1.e+10

set_parameters(**kwargs)

Set parameters of the model.

Keyword Arguments:

• psi (float) – star formation rate.

• Zstar (float) – stellar average absolute metallicity.

• age (float) – age of the stellar populations

• Mstar (float) – total stellar mass of the stellar populations

emission(ll)

Compute X-ray emission due to X-Ray Binaries for the given wavelengths.

Parameters:

ll (array-like) – Wavelengths at which to compute the X-ray emission.

Returns:

X-ray emission values corresponding to the input wavelengths.

Return type:

array-like