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By NASA // September 17, 2018
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This animation shows a neutron star (RX J0806.4-4123) with a hot dust disk that produces an infrared signature detected by NASA's Hubble Space Telescope. The disc was not photographed directly, but one of the ways to explain the data is to hypothesize an 18-billion-kilometer disk structure. The disc would be composed of materials falling on the neutron star after the explosion of the supernova that created the stellar rest. (Image of NASA)
(NASA) – An unusual infrared light emission from a nearby neutron star detected by NASA's Hubble Space Telescope could point to new features never seen before.
One possibility is that there is a dusty disc surrounding the neutron star; another is that there is an energetic wind coming out of the object and slamming in the gas in the interstellar space through which the neutron star passes.
Although neutron stars are generally studied in radio and high energy emissions, such as X-rays, this study demonstrates that new and interesting information about neutron stars can also be obtained by studying infrared light.
The observation, by a team of researchers from the Pennsylvania State University, University Park, Pennsylvania; Sabanci University, Istanbul, Turkey; and the University of Arizona, in Tucson, Arizona, could help astronomers better understand the evolution of neutron stars – the incredibly dense remains after the explosion of one. massive star in supernova. Neutron stars are also called pulsars, because their very fast rotation (typically a fraction of a second, in this case of 11 seconds) causes a variable emission of time from light-emitting regions.
An article describing the research and two possible explanations for the unusual discovery appears on September 17, 2018 in the Astrophysical Journal.
"This neutron star belongs to a group of seven near-X-ray pulsars – nicknamed" the seven gorgeous "- which are warmer than they should be considering their age and reservoir. available energy provided by the loss of rotational energy, "said Bettina. Posselt, associate professor of astronomy and astrophysics research at Pennsylvania State and lead author of the paper.
"We observed an extended infrared emission zone around this neutron star – called RX J0806.4-4123 – whose total size translates to about 200 astronomical units (about 18 billion kilometers) at the assumed distance pulsar. "
This is an illustration of a pulsar wind nebula produced by the interaction of neutron star exit particles with gaseous materials in the interstellar medium that crosses the neutron star. Such an infrared pulsar nebula is unusual because it involves a rather weak energy of particles accelerated by the intense magnetic field of the pulsar. This hypothetical model would explain the unusual infrared signature of the neutron star detected by NASA's Hubble Space Telescope. (Image of NASA)
It is the first neutron star in which an extended signal has been observed only in infrared light. The researchers suggest two possibilities that could explain the extended infrared signal seen by Hubble. The first is that there is a disc of matter – perhaps mostly dust – surrounding the pulsar.
"One theory is that there could be a so-called" fallback disc "of the material that fused around the neutron star after the supernova," Posselt said. "Such a disc would be composed of material from the massive star of the ancestor. Its subsequent interaction with the neutron star could have heated the pulsar and slowed its rotation. If confirmed as a supernova backup disk, this result could change our general understanding of the evolution of neutron stars. "
The second possible explanation for the extended infrared emission of this neutron star is a "pulsar wind nebula".
"A pulsar wind nebula would require the neutron star to have a pulsar wind," Posselt said.
"A pulsar wind can be produced when particles are accelerated in the electric field produced by the rapid rotation of a neutron star with a strong magnetic field. As the neutron star passes through the interstellar medium at a speed greater than that of the sound, a shock can occur where the interstellar medium and the pulsar wind interact. The shocked particles would then emit synchrotron radiation, causing the extended infrared signal that we see. As a general rule, pulsar wind nebulae are seen in X-rays and an all-infrared pulsar wind nebula would be very unusual and exciting.
With NASA's upcoming James Webb Space Telescope, astronomers will be able to explore this newly opened discovery space in the infrared to better understand the evolution of neutron stars.
In addition to Posselt, the research team included George Pavlov and Kevin Luhman from the state of Pennsylvania; Ünal Ertan and Sirin Çaliskan at Sabanci University; and Christina Williams at the University of Arizona. The research was funded by NASA, the Turkish Council for Scientific and Technological Research, the US National Science Foundation, the State of Pennsylvania, the Penn State Eberly College of Science and the Pennsylvania Space Grant Consortium.
The Hubble Space Telescope is an international cooperation project between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, operates the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts scientific operations on Hubble. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, DC.
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