A team in which researchers from the Higher Council for Scientific Research (CSIC) participate has observed for the first timea new kind of pulsating star, detectable by variations in its luminosity due to changes in its atmosphere, in our galaxy. The results, which appear published in the latest issue of the journalNature, open anew window for the study and understanding of the conditions in which low-mass white dwarfs form, that is, stars that are the remnant of giant red stars altered by exotic stellar objects, such as binary millisecond pulsars and other systems.
The detected star is part of thebinary system J0247-25, composed of the core of a red giant star about to become a low-mass white dwarf, and a star similar to the Sun. Both, discovered by the network of SuperWasp telescopes at the Roque de los Muchachos observatory on La Palma, (Islas Canarias) and by the South African Astronomical Observatory (South Africa), overshadow each other when observed from Earth.
Scientists have determined with great precision the luminosity, radius and mass of both stars. Comparing the observational data with theoretical models of stellar evolution in binary systems, they have discovered that the precursor to white dwarfnot only does it pulse radially, like a balloon that inflates and deflates, but also has non-radial pulsations, which are observed in the form of waves in all directions of the stellar surface.
“Low-mass white dwarfs form in binary systems, through mass transfer episodes to their companion. The discovery of this new pulsating class of stars, in an evolutionary stage immediately after the completion of the mass transfer phase, will make it possible to determine the internal structure of these objects and thus reconstruct their evolution during the formation process ”, explained the CSIC researcher Aldo Serenelli, who works at the Institute of Space Sciences.
Based on the star’s pulsations, the outer hydrogen layer of the forming white dwarf is much thicker than in most white dwarfs of this type.The thickness of the envelope allows the elevated temperatures at its base (around 107 degrees Kelvin) to give rise to nuclear hydrogen fusion reactions. This additional source of energy results in a much slower cooling of the white dwarf than if the only available source of energy was its internal heat.
