MINILAB3 - Mass Loss

In MINILAB2, we calculated thermal timescales (both globally and locally as a function of mass coordinate) for stars evolved with different assumptions about convective efficiency. At the end, we began to think about the thermal mass loss rate, which is the rate at which the star would lose all of its mass in one thermal time. This is related to another interesting question - "How much mass can the star lose in a thermal timescale while being able to adjust its structure?"  

Here in MINILAB3, we will explore this concept of "thermal" mass loss in greater detail. We will also explore the structure of these stars as they lose mass. We will focus on two physical relationships: The relationship between stellar structure and total mass lost (or, if you prefer, the remaining envelope mass), and the star's response to increasing mass loss rates (relative to the thermal timescale).  

Both of these relationships are relevant for many subdisciplines in astrophysics involving massive stars. For example, this lab will hopefully give some physical intuition for the star's response to mass loss from interaction during binary stellar evolution (see also Thursday's labs!), as well as some intuition for the fully- and partially- stripped-envelope products of mass loss, be it via binary interaction, or intrinsic mass loss through well-understood processes or through eruptive mass loss episodes. One may also consider stellar feedback into the surrounding material from mass loss, and correlations with ionizing radiation due to changing surface temperatures in stripped-envelope stars. Moreover, the envelope mass and radius (as well as the density profile!) determine the shock-cooling emission of these stars when they explode as Type II (Hydrogen-rich) Supernovae. In order to map observed supernova emission back onto the properties of stars throughout their lives, it is necessary to understand what produces a given envelope mass and radius to begin with (within the scope of, and even as influenced by, our stellar evolution modeling assumptions). 

While going through this lab, it will be good to keep in mind the following guiding questions: 

1. What are the  relevant timescales in each layer of the star (especially the thermal timescale)? Does the star have enough time to respond to the mass loss?

2. How much mass is left in the star's H-rich envelope?

3. Is that envelope radiative or convective?

4. How does the energy transport in the envelope (i.e. convective vs. radiative) influence the star's radius and general structure?   

5. And, is this related to the mass loss rate? The mass lost or the mass remaining? How so and/or why not? 

From here, please navigate to Minilab 3 Task 1: Constant Mass Loss!