Discovering new physics in debris from colliding neutron stars – Source

Neutron star mergers are a treasure trove of new physical signals, with implications for determining the true nature of dark matter, according to research from Washington University in St. Louis.

On August 17, 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States, and the Virgo, detector in Italy, detected gravitational waves. Collision of two neutron stars. For the first time, this astronomical phenomenon was not only heard in gravitational waves, but seen in light by dozens of telescopes on the ground and in space.


Physicist Bhupal Dev Arts and Sciences used observations from this neutron star merger — an event identified in astronomical circles as GW170817 — to derive new constraints on axon-like particles. These hypothetical particles have not been observed directly, but they appear in many extensions of the Standard Model of physics.

Axes and ax-like particles lead to candidates for making up some or all of the universe's „missing” matter, or dark matter, that scientists haven't yet been able to quantify. At the very least, these weakly interacting particles could act as a sort of portal that connects the visible realm that humans are most familiar with to the unknown dark realm of the universe.

„We have good reason to suspect that new physics beyond the standard model may be lurking around the corner,” said Dev, first author of the study. Physical review letters and Faculty Fellow of the University McDonnell Center for Space Sciences.

When two neutron stars merge, a hot, dense remnant forms for a short period of time. This residue is an excellent breeding ground for exotic particle production, Dev said. „Depending on the initial mass, before settling into a massive neutron star or black hole, the remnant gets much hotter than individual stars for about a second,” he said.

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Defunct neutron stars spiral toward their doom in this animation, which represents events observed up to nine days after GW170817. (Video: NASA Goddard)

These new particles quietly escape the debris of the collision and, far from their source, decay into known particles, usually photons. Dev and his team — WashU alum Steven Harris (now an NP3M fellow at Indiana University), and Jean-Francois Fortin, Kuver Sinha, and Yongchao Zhang — show that these escaped particles produce unique electromagnetic signals that can be detected by gamma rays. – Ray telescopes like NASA Fermi-LAD.

The research team analyzed the spectral and temporal information from these electromagnetic signals and determined that the signals could be distinguished from the known astrophysical background. They then used Fermi-LAT data on GW170817 to calculate new constraints on the axial-photon coupling as a function of axial mass. Complement those coming from laboratory experiments such as these astrophysical constraints A.D.M.KIt examines a different part of the axis parameter space.

In the future, scientists may use gamma-ray space telescopes such as Fermi-Lot or proposed gamma-ray missions such as the WashU-led Advanced Particle-Astronomy Telescope (APT) to take other measurements during neutron star collisions. It will help improve their understanding of particles like mold.

„Extreme astrophysical environments like neutron star mergers offer a new opportunity in our search for dark-field particles like axons, which may hold the key to understanding the missing 85% of all matter in the universe,” Dev said.

This work was supported by the Department of Energy's Office of Science.

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