Are the axes behind the extreme X-ray of the Seven Brave Neutron Stars?
XMM-Newton X-ray Observatory. Credit: D. Ducros; ESA / XMM-Newton.
–
At a distance of over 400 light-years from Earth, there is a wonderful group of young and really hot neutron stars. Astronomers christened them the “Magnificent Seven,” or the Seven Brave. In a somewhat drier professional slang, these are XDINS (X-ray Dim Isolated Neutron Stars) or also XINS. All seven were discovered at the turn of the millennium by the German space observatory ROSAT.
It’s not just a luxury nickname. Seven brave neutron stars emit extremely energetic X-rays that scientists can’t handle. Benjamin Safdi of the American Lawrence Berkeley National Laboratory and his colleagues suggest an interesting explanation. It is said that there could be axions, hypothetical particles with a very low mass, which should change into photons in the presence of a magnetic field. Needless to say, axions are now among the leading candidates for dark matter particles, although they are certainly still quite controversial. Axions have been talked about since the 1970s, but have never been observed or confirmed by any experiment.
Benjamin Safdi.
Credit: LBNL.
–
Safdi’s team used supercomputers to model the behavior of axions in neutron stars. According to their idea, axions form inside neutron stars and then change into photons in their strong magnetic field. According to their results, axions should behave similarly to other very light particles, neutrinos.
The research of the Seven Brave represents a remarkable opportunity. As Safdi says, the extreme X-rays of the Seven Brave undoubtedly exist. Whether there are axions behind it or not, it is undoubtedly a remarkable phenomenon, behind which is probably some new physics or at least a hitherto unknown mechanism.
Lawrence Berkeley National Laboratory, logo.
–
Due to their age, the neutron stars of the Seven Brave should emit UV rays and low-energy X-rays. However, astronomers have detected an influx of high-energy X-rays. We would expect such radiation from pulsars, which are actually neutron stars, just in, say, “beacon” mode. However, none of the Seven Brave Neutron Stars is a pulsar. The researchers went even further to see if a group of the Seven Brave was blocking a more distant source of high-energy X-rays. They searched the area with the XMM-Newton and Chandra space X-ray telescopes, but found nothing like it.
Safdi and colleagues emphasize that they do not announce the discovery of axions. They just say they can explain the observed mysterious high-energy X-rays of the Seven Brave with the help of axions. In the future, they intend to look for similar phenomena in white dwarfs, for example. Even these nuclei of burnt smaller stars should not emit high-energy X-rays, but Safdi’s team believes that axions could form there as well.
Literature
Physical Review Letters 126: 021102.
– .
