Looking inside a neutron star

A merger of neutron stars. Credit: NASA Goddard Space Flight Center/CI Laboratory

The oscillations in binary neutron stars before they merge could have big implications for the insights scientists can gain from detecting gravitational waves.

The oscillations in binary neutron stars before they merge could have big implications for the insights scientists can gain from detecting gravitational waves.

Researchers at the University of Birmingham have shown how these unique vibrations, caused by interactions between the tidal fields of the two stars as they approach each other, affect gravitational-wave observations. The study is published in Physical Review Letters.

Taking these motions into account could make a big difference in our understanding of data taken by the Advanced LIGO and Virgo instruments, set to detect gravitational waves (ripples in time and space) produced by the merger of black holes and neutron stars. .

The researchers aim to have a new model ready for the next Advanced LIGO observing series and even more advanced models for the next generation of Advanced LIGO instruments, called A+, which will begin their first observing series in 2025.

Since the LIGO Scientific Collaboration and the Virgo Collaboration detected the first gravitational waves in 2016, scientists have focused on advancing their understanding of the massive collisions that produce these signals, including the physics of a neutron star at supranuclear densities.

Dr. Geraint Pratten, from the University of Birmingham’s Institute for Gravitational-Wave Astronomy, is the paper’s lead author. He said: “Scientists can now get a lot of crucial information about neutron stars from the latest gravitational wave detections. Details like the ratio of the star’s mass to its radius, for example, provide crucial insights into the fundamental physics behind neutron stars. If we neglect these additional effects, our understanding of the structure of the neutron star as a whole can be profoundly skewed.”

Dr. Patricia Schmidt, co-author of the paper and Associate Professor at the Institute for Gravitational-Wave Astronomy, added: “These refinements are really important. Within individual neutron stars we can begin to understand what happens deep inside the star’s core, where matter exists at temperatures and densities that we cannot produce in ground-based experiments. At this point, we might start to see atoms interacting with each other in ways we haven’t seen yet, which might require new laws of physics.”

The refinements devised by the team represent the latest contribution from the University of Birmingham to the Advanced LIGO programme. Researchers at the University’s Institute for Gravitational-Wave Astronomy have been deeply involved in the design and development of the detectors since the early stages of the program. Looking to the future, Ph.D. student Natalie Williams is already working on the calculations to further refine and calibrate the new models.

Journal Reference:

  1. Geraint Pratten, Patrica Schmidt and Natalie Williams. Impact of Dynamical Tides on the Reconstruction of the Neutron Star Equation of State. Phys. Rev. Lett. 129, 081102 – Published 18 August 2022. DOI: 10.1103/PhysRevLett.129.081102