X-rays around “Magnificent 7” can be traces of theoretical particles

Researchers say they may have found evidence of theoretical actions, and possibly dark matter, around a group of neutron stars.

A new study, led by a theoretical physicist from the U.S. Department of Energy, Lawrence Berkeley National Laboratory (Berkeley Lab), suggests that particles that have never been mentioned before can be the source of unexplained, high-energy X-ray emissions around a group of neutron stars.

The actions that were first theorized in the 1970s as part of a solution to a fundamental particle physics problem are expected to produce actions in the core of stars and converted into light particles, called photons, in the presence of a magnetic field.

Actions can also constitute dark matter – the mysterious things that make up an estimated 85 percent of the total mass of the universe, but so far we have only seen its gravitational effects on ordinary matter. Even though it seems that the excess of X-ray is not action or dark matter, it can still reveal new physics.

A collection of neutron stars, known as the Magnificent 7, provides an excellent test bed for the possible presence of actions, as these stars have powerful magnetic fields, are relatively close within hundreds of light years and are only expected to have low energy X-rays and ultraviolet light.

“They are known to be very ‘boring’,” and in this case it’s a good thing, said Benjamin Safdi, a divisional member of the theoretical group Berkeley Lab Physics Division, who led a study, 12 January published in the magazine. Physical overview letters, in which the statement of action for the excess is set out.

Christopher Dessert, a subsidiary of Berkeley Lab Physics Division, contributed greatly to the study, which was also conducted by researchers at UC Berkeley, University of Michigan, Princeton University, and the University of Minnesota.

If the neutron stars were of a type known as pulses, they would have an active surface that emits radiation at different wavelengths. This radiation would appear across the electromagnetic spectrum, Safdi noted, and could drown out this X-ray signature that the researchers found, or deliver radio frequency signals. But the Magnificent 7 are not pulsators, and no such radio signal has been noticed. Other general astrophysical explanations also do not seem to hold up to the observations, Safdi said.

If the X-ray excess detected around the Magnificent 7 was generated from an object or objects hiding behind the neutron stars, it would probably have shown in the datasets used by researchers from two space satellites: the European Space Agency’s XMM-Newton en NASA‘s Chandra X-ray telescopes.

Safdi and co-workers say it is still quite possible that a new, non-action statement will emerge to take into account the observed X-ray excess, although they remain hopeful that such a statement goes beyond the standard model of particle physics. and the new ground will lie. and space-based experiments will confirm the origin of the high-energy X-ray signal.

“We are pretty confident that this excess exists, and very confident that there is something new among this excess,” Safdi said. ‘If we were 100% sure that what we were seeing was a new particle, it would be big. It would be revolutionary in physics. “Although it seems that the discovery is not related to a new particle or dark matter, he said: ‘It will tell us so much more about our universe, and there will be much to learn.’

Raymond Co, a postdoctoral researcher from the University of Minnesota who collaborated on the study, said: ‘We are not yet claiming that we discovered the action, but we are saying that the extra X-ray photons can be explained. by actions. It’s an exciting discovery of the excess in the X – rays, and it’s an exciting possibility that already matches our interpretation of actions. ”

If actions exist, they will be expected to behave like neutrinos in a star, as both will have very small masses and are only very rarely and weakly related to each other. They could be produced in abundance inside stars. Uncharged particles called neutrons move around within neutron stars, sometimes alternating by scattering apart and releasing a neutrino or possibly an action. The neutrino-emitting process is the dominant way neutron stars cool down over time.

Like neutrinos, the actions could move outside the star. The incredibly strong magnetic field that surrounds the Magnificent 7 stars – billions of times stronger than magnetic fields that can be produced on Earth – can cause emerging actions to be converted into light.

Neutron stars are incredibly exotic objects, and Safdi noted that many modeling, data analysis, and theoretical work participated in the latest study. In recent work, researchers have widely used a bank of supercomputers, known as the Lawrencium Cluster at Berkeley Lab.

Some of this work has been done at the University of Michigan, where Safdi previously worked. “Without the high-performance supercomputer work in Michigan and Berkeley, none of this would have been possible,” he said.

‘There is a lot of data processing and data analysis that has gone into this. You need the inside of a neutron star to predict how many actions should be produced inside the star. ”

Safdi noted that as a next step in this investigation, white dwarf stars would be an excellent place to look for actions, as they also have very strong magnetic fields and are expected to be ‘X-ray free environments’.

“It starts out pretty convincing that it’s something out of the standard model if we also see an excess of the x-ray there,” he said.

Researchers could also invoke another X-ray space telescope called NuStar to help solve the redundant mystery.

Safdi said he is also excited about experiments on the ground like CAST at CERN, which works as a solar telescope to detect actions converted by a strong magnet into X-rays, and ALPS II in Germany, which would use a powerful magnetic field to transform actions into light particles on one side of a barrier if laser light hits the other side of the barrier.

Axions received more attention because a sequence of experiments could not show the WIMP (poor interaction with massive particles), another promising candidate for dark matter. And the action picture is not that simple – it could actually be a family album.

There can be hundreds of action-like particles, or ALPs, that form dark matter, and string theory – a candidate theory to describe the forces of the universe – holds open the possible existence of many types of ALPs.

Reference: “Axion Emission May Explain ‘New Hard X-Ray Surplus of Nearby Isolated Neutron Stars’ by Malte Buschmann, Raymond T. Co, Christopher Dessert and Benjamin R. Safdi, January 12, 2021, Physical overview letters.
DOI: 10.1103 / PhysRevLett.126.021102

The study was supported by the U.S. Department of Energy Office of Science Early Career Research Program; Advanced Research Computing and the Leinweber Graduate Fellowship at the University of Michigan, Ann Arbor; the National Science Foundation; the Mainz Institute for Theoretical Physics (MITP) of the Cluster of Excellence PRISMA +; the Munich Institute for Astro- and Particle Physics (MIAPP) of the DFG Excellence Cluster Origins; and the CERN theory section.