(News from Nanowerk) The lightest neutron star found to date is located at the center of supernova remnant HESS J1731-347. Dr. Victor Doroshenko, Dr. Valery Suleimanov, Dr. Gerd Pühlhofer and Professor Andrea Santangelo from the High Energy Astrophysics Section of the Institute of Astronomy and Astrophysics at the University of Tübingen discovered the object unusual using x-ray telescopes in space.
According to the research team’s calculations, it has only about half the mass of a typical neutron star. As the basis for their calculations, they used new measurements of the distance to a companion star that the same team had discovered earlier. This allowed astrophysicists to specify the neutron star’s mass and radius with unprecedented precision.
Their study was published in the last natural astronomy (“A strangely light neutron star in a supernova remnant”).
Neutron stars are born when normal stars with large masses “die” in a supernova explosion, says lead author Victor Doroshenko. He calls them extreme objects that can be considered celestial laboratories for studying fundamental physics.
“Neutron stars have as yet unknown properties of matter; they have a much higher density than atomic nuclei,” explains the researcher. Such conditions could not be reproduced in terrestrial laboratories. “Space observations of neutron stars with extreme properties such as the one we just found, the use of X-rays or other telescopes will allow us to solve the mysteries of super-dense matter – at least if we can solving challenges such as the inaccuracy of measurements over such distances that occurs during observations.We have now succeeded in doing just that – taking the knowledge of these mysterious objects a step further.
Precise calculations
The neutron star at the center of supernova remnant HESS J1731-347 was one of the few objects discovered during gamma-ray measurements with the HESS telescopes in Namibia and then studied by X-ray telescopes from space, reports Doroshenko.
“Only then did the cooling neutron star become visible,” adds Gerd Pühlhofer. The peculiarity of this object, as the same research team noted earlier, is that it is physically connected to another star. This star illuminates the dust cloud around the neutron star, heating it and causing it to glow in infrared light. The companion star was recently observed by the European Space Agency’s Gaia Space Telescope, which provided the research team with precise distance measurements to the two objects. The Gaia mission involves a high-precision three-dimensional optical survey of the sky.
“This allowed us to address previous inaccuracies and improve our models,” Pühlhofer said. The mass and radius of the neutron star could be determined much more accurately than before,” says theoretical astrophysicist Valery Suleimanov.
It is not yet known how the unusual object formed, he said. There are also doubts as to whether it really is a neutron star or whether the object is a candidate for an even more exotic object made of quark strange matter, says Andrea Santangelo, adding: “C is currently the most promising quark or strange matter. candidate star we know of so far, although its properties are consistent with those of a “normal” neutron star. But even though the object at the center of HESS J1731-347 is a neutron star, it’s still an interesting and puzzling object. “This allows us to probe the still unexplored part of the parameter space in the mass-radius plane of neutron stars. This will allow us to put valuable constraints on the equation of state of dense matter, which is used to describe its properties,” explains Santangelo.
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