beecee Posted September 5, 2018 Share Posted September 5, 2018 (edited) https://phys.org/news/2018-09-radio-superfast-jet-material-neutron.html Radio observations confirm superfast jet of material from neutron star merger: September 5, 2018, National Radio Astronomy Observatory Precise measurement using a continent-wide collection of National Science Foundation (NSF) radio telescopes has revealed that a narrow jet of particles moving at nearly the speed of light broke out into interstellar space after a pair of neutron stars merged in a galaxy 130 million light-years from Earth. The merger, which occurred in August of 2017, sent gravitational waves rippling through space. It was the first event ever to be detected both by gravitational waves and electromagnetic waves, including gamma rays, X-rays, visible light, and radio waves. The aftermath of the merger, called GW170817, was observed by orbiting and ground-based telescopes around the world. Scientists watched as the characteristics of the received waves changed with time, and used the changes as clues to reveal the nature of the phenomena that followed the merger. Read more at: https://phys.org/news/2018-09-radio-superfast-jet-material-neutron.html#jCp <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> the paper: https://www.nature.com/articles/s41586-018-0486-3 Superluminal motion of a relativistic jet in the neutron-star merger GW170817 Abstract The binary neutron-star merger GW1708171 was accompanied by radiation across the electromagnetic spectrum and localized to the galaxy NGC 4993 at a distance of about 41 megaparsecs from Earth. The radio and X-ray afterglows of GW170817 exhibited delayed onset a gradual increase in the emission with time (proportional to t0.8) to a peak about 150 days after the merger event, followed by a relatively rapid decline. So far, various models have been proposed to explain the afterglow emission, including a choked-jet cocoon and a successful-jet cocoon (also called a structured jet). However, the observational data have remained inconclusive as to whether GW170817 launched a successful relativistic jet. Here we report radio observations using very long-baseline interferometry. We find that the compact radio source associated with GW170817 exhibits superluminal apparent motion between 75 days and 230 days after the merger event. This measurement breaks the degeneracy between the choked- and successful-jet cocoon models and indicates that, although the early-time radio emission was powered by a wide-angle outflow8 (a cocoon), the late-time emission was most probably dominated by an energetic and narrowly collimated jet (with an opening angle of less than five degrees) and observed from a viewing angle of about 20 degrees. The imaging of a collimated relativistic outflow emerging from GW170817 adds substantial weight to the evidence linking binary neutron-star mergers and short γ-ray bursts. :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: The aftermath of this Neutron Stars merger is now actually a BH. It is illustrated at the link as follows..... Aftermath of the merger of two neutron stars. Ejecta from an initial explosion formed a shell around the black hole formed from the merger. A jet of material propelled from a disk surrounding the black hole first interacted with the ejecta material to form a broad "cocoon." Later, the jet broke through to emerge into interstellar space, where its extremely fast motion became apparent. Credit: Sophia Dagnello, NRAO/AUI/NSF Read more at: https://phys.org/news/2018-09-radio-superfast-jet-material-neutron.html#jCp Edited September 5, 2018 by beecee 1 Link to comment Share on other sites More sharing options...
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