Of the neutron stars discovered so far, the lightest neutron star was found at the center of the HESS J1731-347 supernova remnant.
Dr. Victor Doroshenko, Dr. Gerd Pühlhofer, Dr. Valery Suleimanov 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 using x-ray telescopes in space.
According to the researchers’ calculations, this star has only about half the mass of an ordinary neutron star. As the basis for their calculations, the scientists applied new distance measurements to a companion star that the same team had previously detected. This allowed astrophysicists to stipulate the radius and mass of the neutron star with unparalleled precision.
Their findings were published in the latest issue of natural astronomy.
Neutron stars are born when regular stars with large masses “die” in a supernova explosion, says the study’s lead author, Victor Doroshenko. He designates them as extreme objects considered as celestial laboratories for the examination of fundamental physics.
“Neutron stars have as yet unknown properties of matter; they have a much higher density than atomic nuclei,” says Doroshenko. Such parameters cannot be simulated in terrestrial laboratories.
Space observations of neutron stars with extreme properties such as the one we have just found, using X-rays or other telescopes, will allow us to solve the mysteries of super-dense matter – at least if we can solve challenges such as the inaccuracy of measurements over such distances that arises during observations. That’s exactly what we managed to do: push the knowledge of these mysterious objects a little further.
Victor Doroshenko, Senior Study Author, Section of High Energy Astrophysics, Institute of Astronomy and Astrophysics, University of Tübingen
The neutron star at the center of supernova remnant HESS J1731-347 was one of the few objects detected during gamma-ray measurements with HESS Telescopes in Namibia, then explored using X-ray telescopes since space,” says Doroshenko.
“Only then did the cooling neutron star become visible. adds Gerd Pühlhofer.
The particularity of this object, as the researchers had previously observed, is that it is physically linked to another star. This star irradiates the dust cloud surrounding 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 researchers with precise distance measurements of the two objects. The Gaia mission includes a high-precision three-dimensional (3D) optical survey of the sky.
“This allowed us to address previous inaccuracies and improve our models,” says Pühlhofer.
The mass and radius of the neutron star could be determined much more precisely than before.
Valery Suleimanov, Theoretical Astrophysicist, High Energy Astrophysics Section, Institute of Astronomy and Astrophysics, University of Tübingen
Suleimanov says it’s still unclear how the rare item was created. Andrea Santangelo adds that there are also uncertainties as to whether it really is a neutron star or if the object is a candidate for an even more unusual object composed of odd-quark matter.
It is currently the most promising quark or strange matter star we know of to date, although its properties are consistent with those of a “normal” neutron star.
Professor Andrea Santangelo, Section of High Energy Astrophysics, Institute of Astronomy and Astrophysics, University of Tübingen
However, even though the object at the center of HESS J1731-347 is a neutron star, it is still a challenging and mysterious object.
It 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 pose valuable constraints on the equation of state of dense matter, which is used to describe its properties.
Professor Andrea Santangelo, Section of High Energy Astrophysics, Institute of Astronomy and Astrophysics, University of Tübingen
Journal reference
Doroshenko, V. et al. (2022) A strangely light neutron star in a supernova remnant. natural astronomy. doi.org/10.1038/s41550-022-01800-1.
Source: https://uni-tuebingen.de/en
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