In-Class Assignment 27

In-Class Assignment 27#

Note due for credit, in-class participation only

The TP-AGB Phase#

Learning Objectives#

  • explore the 3DU event in intermediate mass stars

  • characterize the dredge-up efficiency

  • gain a qualitative understanding of the He-shell flash region and interpulse properties

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

Download the following model file locally. These data were produced using the c13_pocket test suite.

  • \(3 M_{\odot}\): 3m_to_3DU_history.data; - the model starts from core He-depletion.

  • \(3 M_{\odot}\): 3m_c13_pocket_history.data; - this data covers one full thermal pulse and captures the presence of a c13 pocket.

  • \(3 M_{\odot}\) LOGS: LOGS.zip; - this contains a LOG folder and one profile file during the above c13 pocket TP.

# load data and see which variables are available
#tp_agb_data = pd.read_csv('3m_to_3DU_history.data',sep=r'\s+',header=4)
#tp_agb_data.head(10)

a. - Thermally Pulsing AGB Star#

Using the \(3M_{\odot}\) 3m_to_3DU_history.data MESA history dataset:

  1. Plot the helium luminosity as a function of age. You may want to subtract the age at the star of the dataset from the x-axis. Recall that the timescale for this epoch is ~1e6 years, but the star has evolved previously for ~1.2 Gyr.

Using this plot answer the following:

How many pulses are covered over this range?

What is their qualitative properties over time?

What is the approximate time between pulses?

  1. To determine the point at which 3DU occurs, plot the surface c12, o16, and n14 as a function of age or model number.

Using this plot:

Determine how many pulses it takes until the first 3DU occurs.

Does this plot show evidence for hot bottom burning? If not, why?

b - 3DU efficiency and mass loss#

Using the \(3M_{\odot}\) 3m_c13_pocket_history.data MESA history dataset:

  1. Plot the log Helium luminosity as a function of star age (subtracting the previous age to recenter the data) and the mass loss rate on the same plot.

At what point does the star experience the strongest mass loss?

  1. Plot a Kippenhahn diagram using mesaPlot and zoom into the He-shell flash region (about 0.5-0.6 \(M_{\odot}\)) using yrng. Remember you need to move/copy and rename the file to the LOGS directory :).

Identify the following: the intershell convective zone, the helium shell, the hydrogen shell, and the location of the 3DU.

  1. Using this same plot, make a very approximate estimate of the dredge up efficiency:

\[ \lambda = \frac{\Delta m_{\rm{DU}}}{\Delta m_{\rm{H,intershell}}} \]

What is this value and does it suggest efficient or inefficient 3DU at this pulse?

## b results here

## b result here
#import mesaPlot as mp
#m=mp.MESA()
#p=mp.plot()
#m.loadHistory('LOGS')
#kip = p.plotKip(m,show_mass_loc=True,yrng=[...,...])

c. - the c13 pocket#

  1. Finally, use the Abund function in mesaPlot to confirm the presence of the formation of a c13 pocket during the interpulse phase for this model.

What does the presence of the c13 pocket imply about the observational characteristics of the AGB star?

# c result here
#m=mp.MESA()
#p=mp.plot()
#m.loadProfile(f='LOGS/profile38.data')
#p.plotAbun(m,
#           xmin=...,xmax=..., # set these based on the inspection of the Kipp above
#           cmap=plt.cm.inferno_r,num_labels=10)
Contents