In-Class Assignment 15

In-Class Assignment 15#

Note due for credit, in-class participation only

Wolf-Rayet Stars#

Learning Objectives#

  • explore HR properties of WR stars

  • classify subclasses of WR stars

import numpy as np
import matplotlib.pyplot as plt
import pandas as pd

a. - Mass loss evolution of WR stars#

Download the following model files locally. These data were produced using the 80m_zams_to_cc test suite. This model was only evolved to core He-depletion.

Individually/with the person next to you:#

Using the \(80M_{\odot}\) MESA history dataset:

  1. Plot an HR diagram of the model as a scatter plot, but color the data according to the log of the absolute value of the mass loss rate log_abs_mdot value at a given HR data pair.

  2. Label a vertical line of log effective temperature where the star becomes a WR star and label that region.

# load data and see which variables are available
#wr_80m_history = pd.read_csv('##',sep=r'\s+',header=4)
#list(wr_80m_history)
#wr_80m_history.head(10)

# load vars
#wr_80m_log_Teff = wr_80m_history['##']
#wr_80m_log_L = wr_80m_history['##']
#wr_80m_log_abs_Mdot = wr_80m_history['##']

## a results here
#fig, ax = plt.subplots()

#sc = ax.scatter(wr_80m_log_Teff,
#           wr_80m_log_L, 
#           c=wr_80m_log_abs_Mdot, 
#           cmap='inferno')

#ax.invert_xaxis()

#plt.colorbar(sc,label=r'$\left | \dot{M} \right | \ (M_{\odot} \ \rm{yr}^{-1})$')

# label the WR phase
#plt.axvline(X,color='k',ls='-',lw=1)
#ax.text(X,Y, 'WR', rotation=90)


#plt.legend()
#plt.xlabel(r'$\rm{log}~T_{\rm{eff}} \ (K)$')
#plt.ylabel(r'$\rm{log}~L \ (L_{\odot})$')

#plt.show()

With your larger group, try to answer the following:#

  1. Does this star become a blue supergiant? If so, when?

Your groups response here.

  1. Does this star experience an LBV outburst? If so, how can we tell?

Your groups response here.

  1. Does the star become a red supergiant? If so, why or why not?

Your groups response here.

  1. Describe in a few words qualitatively, the path of the model after it leaves the MS.

Your groups response here.

b. - WR subclasses#

Wolf-Rayet stars (\(M\gt\sim25M_{\odot}\))#

Very hot, luminous stars with with bright emission lines in their spectra, mass loss rates of \(\dot{M}\approx 10^{-5}\) to \(10^{-4}\) \(M_{\odot} \textrm{yr}^{-1}\).

WNL stars: some H present on their surface (\(X_{\rm{H}}\lt0.4\)) and increased He and N abundances consistent with CNO cycle burning.

WNE stars: similar to WNL but they lack hydrogen (\(X_{\rm{H}}=0\))

WC stars: no H, little or no N, some He/C/O suggest partial H burning

WO stars: similar to WC stars but strongly increased O suggesting nearly complete helium burning

Individually/with the person next to you:#

  1. Plot the surface abundances of he4, c12, o16, the hydrogen envelope mass fraction left (envelope_fraction_left- \(X_{H}\)) as a function of model number.

# load additional vars
#wr_80m_model_number = wr_80m_history['##']
#wr_80m_surface_he4 = wr_80m_history['surface_##']
#wr_80m_surface_c12 = wr_80m_history['surface_##']
#wr_80m_surface_n14 = wr_80m_history['surface_##']
#wr_80m_surface_o16 = wr_80m_history['surface_##']
#wr_80m_envelope_fraction_left = wr_80m_history['##']

## 1 result here
#plt.title('80$M_{\odot}$ Model During MS and Core He-Burning')

#plt.plot(#,
#         #,label=r'$X_{\rm{env}}(H)$')

#plt.plot(#,
#         #,label=r'$X_{\rm{surface}}(^{4}\rm{He})$')

#plt.plot(#,
#         #,label=r'$X_{\rm{surface}}(^{12}\rm{C})$')

#plt.plot(#,
#         #,label=r'$X_{\rm{surface}}(^{16}\rm{O})$')

#plt.legend()
#plt.xlabel(r'$\rm{Model \ Number}$')
#plt.ylabel(r'Variable')

With your larger group, try to answer the following:#

  1. What subclass of WR stars does the model become at the last model number (this corresponds to core He-depletion) and why?

Respond here.

  1. After the star has left the main-sequence but before core He-depletion what other subclass of WR stars does the star appear as before its final?

Hint: look around model number of 800 to answer this.

Respond here.

  1. What will be the evolutionary fate of this star? Will it blow up? What type of supernova will it be?

Respond here.

Contents