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The Common Envelope (CE) interaction is an intricate problem. To-date, only individual aspects of
CE physical processes have been investigated analytically, suggesting what
physics cannot be overlooked, e.g., magnetic fields, or the internal energy of the gas.
Numerical simulations have taken a more comprehensive look at the problem with
promising yet sparse results. Today, there is an unprecedented opportunity to
use existing techniques to create a benchmark of results which will not only
unify past results, but will also provide a much needed quantitative description
of the CE phenomenon to be used in population syntheses and the interpretation
of stellar classes.
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The common envelope interaction is an inherently 3D phenomenon, and 3D hydrodynamic simulations are the best tool to takle this interaction. This does not mean it is easy, as achieving sufficient resolution remains a problem. Starting with the nested grid code of Burkert and Bodenheimer, I moved to the 3D code Enzo and eventually to the SPH code Phantom. Check out the publication list below for an idea of this work.
Some aspects of the common envelope interaction can be also studied analytically and with 1D code. The efficiency paramter, called alpha, is a single number used to express how much of the orbital energy of the companion is available to eject the envelope. From part simulations (and common sense), we know that alpha is not a constant but is dependent on paramters. The problem is that alpha might not be the best way to paramterize the common envelope problem. So, while continuing our work on hydrodynamics simulations, we are also studying the physics of the common envelope interaction in an analytical way. Thanks to the work of graduate student Jean-Claude Passy, this work has revealed that, as previously suspected by, e.g., Nelemans et al. (2001), alpha is a misleading paramter. The analytical paper is here.
I have been working with observed objects as well. I have participated in the detection and characterization of post-CE systems (see this list of papers) as well as used them as simulation constraints here.
There are other groups intent on applying a diversity of codes to the CE problem. When I started, the only other researchers occupied with this topic were Paul Ricker and Ron Tam, but this is not so any longer. An approximate list of current and past common envelope simulation efforts can be found here.
Finally we are starting a new project to include dust into CE simulations in collaboration with Lionel Siess (Universite Libre de Bruxelles), Daniel Price (Monash University) and Mansi Kasliwal (Caltech). This is to determine the impact of dust formation on envelope dynamics and on thelight properties. We are hiring at the moment (February 2021), so send me a mail if you are interested.
Publicatons
For a list of publications relevant to this topic see
here
      
Last Update: 8 February 2021
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