White dwarfs are stellar remnants resulting from the evolution of solar-mass stars. Like most stars, the progenitor may have belonged to a multiple system, with a companion at a different stage of evolution. To find out how the evolution of the host star affects the companion, a theoretical investigation of systems formed by white dwarfs and brown dwarfs, substellar objects that are not massive enough, and therefore cannot sustain continuous nuclear reactions of hydrogen fusion in their core, was carried out. The second author of this work is Matthias Schreiber, director of the Nucleus Millennium of Planetary Formation (NPF).
The research, published in the prestigious scientific journal Monthly Notices of the Royal Astronomical Society, concluded that sub-stellar objects can survive this evolution even if they are relatively close to the host star.
“Upon survival, mass is transferred from the host star to the brown dwarf, leading to a brief evolutionary phase in which both the future white dwarf and the grown dwarf orbit in the envelope of the progenitor white dwarf. In contrast to previous findings, we show that this special evolutionary phase does not depend on whether the companion is a star or a brown dwarf,” emphasizes Schreiber, who is also an academic at Universidad Santa María.
To carry out the research, previous knowledge about stellar evolution and the interaction between two stars (or a star and a substellar object) was used. Based on this, computational models were used.
The main result of this work, the astrophysicist points out, is that the evolution of the common envelope does not depend on whether the companion star is a brown dwarf or a star.
“The next steps of this research are to relate our result to the formation of substellar objects and the evolution of binary stars,” concludes Schreiber.
Image credit: Sheffield University