The background noise of gravitational waves from orbiting white dwarf stars will be stronger than the noise from double black holes. That is what two Nijmegen master students and their supervisor predict in two publications ahead of the LISA space mission. Until now, that mission did not take noisy white dwarfs into account. Fortunately, the noise can be filtered out and even provide new information.
LISA , the Laser Interferometer Space Antenna, is scheduled to be launched in the mid-2030s by the European Space Agency (ESA). The Netherlands is building LISA’s ’eyes’, software, targeting mechanism and readout electronics, among other things. LISA will measure gravitational waves from compact binary stars, double white dwarfs, supermassive merging black holes and other exotic objects in the universe. As a side note, LISA will also pick up background noise from thousands of billions of black holes that merged with each other long ago.
Gijs Nelemans is an astronomer at Radboud University and is involved in the Dutch input for LISA. Together with now-graduated master students Seppe Staelens and Sophie Hofman , he created models to see if background noise from white dwarfs could be captured in addition to the background noise of black holes. Staelens, who came to Nijmegen as an exchange student from Leuven and is now doing his PhD in Cambridge, started with simple models. Hofman, who just graduated and is a trainee at a technical corporation, extended the models.
Override
The models show that the background noise of white dwarfs is stronger than the background noise of black holes. ’Our supervisor thought that LISA would never be able to detect the collective signal from white dwarf stars,’ says Staelens. ’And now our models show that the white dwarfs drown out the black holes. Ha!’
The astronomers see the background noise of white dwarfs as an opportunity to study the evolution of stars like our sun in distant galaxies. ’With telescopes you can only study white dwarfs in our own Milky Way, but with LISA we can listen to white dwarfs from other galaxies,’ says Nelemans. ’Moreover, next to the background noise of black holes and the noise of white dwarfs, perhaps other exotic processes from the early universe can also be captured.’
Hofman adds, ’I think it’s really cool that with my masters research we are contributing to such an important mission as LISA.’
Literature referenceOn the uncertainty of the white dwarf astrophysical gravitational wave background. Door: Sophie Hofman & Gijs Nelemans. Geaccepteerd voor publicatie in Astronomy & Astrophysics [ preprint ].
Likelihood of white dwarf binaries to dominate the astrophysical gravitational wave background in the mHz band. Door: Seppe Staelens & Gijs Nelemans. In: Astronomy & Astrophysics , 15 maart 2024 [ origineel (open access)].
