[Mesa-users] rsp_Cepheid Questions

Wallace, Alexander aawallace at mail.smu.edu
Fri Jul 19 18:54:49 EDT 2019

July 19 2019

Hello, Dr. Smolec and/or anyone else who can help,

Thank you for the instructions the last time you spoke; they were very informative and helped me to understand the simulator.

I read the relevant sections of the MESA Instrument Paper V, but I have a few more questions after having ran rsp_Cepheid according to your instructions.

In your instructions for rsp_Cepheid, you said to ensure that the simulation was at constant pulsation/large-amplitude pulsation. I was able to do so and generated a light curve by converting luminosity to bolometric magnitude and phasing part of the constant-pulsation data using outside software. However, I started examining the data before the large-amplitude pulsation section.

What exactly is happening in this section, physically speaking? If I understand the instrument paper correctly, is RSP checking to see whether a set of initial conditions or combination of eigenvectors unique to each pulsation cycle stabilizes to a constant period of pulsation/large amplitude pulsation? Could a stable Cepheid star exist with these conditions (before the models converge to large amplitude pulsation), or is it unlikely/impossible? Is there any way to determine how long MESA will take to produce a model with a steady period of pulsation, or what set of initial conditions would give a steady period of pulsation? Lastly, how exactly do the unconverged models differ from each other and from the models where large amplitude pulsations have been reached?

I do not know if this may help you answer any of my questions, but the reason I am asking for all this information is that I am trying to develop a simulator for Cepheid (both types 1 and 2) light curves for my professor, who is trying to calibrate his telescope at an observatory to detect minute changes in Cepheid periods as they evolve. The first step in this calibration would be to simulate real light curves, a process which involves physics that is more sophisticated than I know (as a 2nd year undergraduate) to start from scratch, which is why I am using MESA.

Many thanks for your patience,

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