Alma reveals for the first time millimeter radiation from kilonovae

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Une étoile à neutrons est un astre très dense résultant de l'effondrement gravitationnel d'une grosse étoile explosant en supernova SN II. Lorsqu'elles sont en couple, les étoiles à neutrons peuvent finir par entrer en collision et fusionner, engendrant une bouffée d'ondes gravitationnelles et une puissante émission d'ondes électromagnétiques dans toutes les longueurs d'onde, dont le visible ; cette émission est détectable sous forme de sursauts gamma. © Dana Berry, SkyWorks Digital

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[EN VIDÉO] Gamma Ray Bursts: Neutron Star Collisions Light Up the Universe Gamma ray bursts are the Universe’s brightest events in the field of electromagnetic waves. We can observe one per day on average in the sky and they occur in distant galaxies. There are two types, short and long. This video explains the nature of short bursts. Many advances in astronomy have resulted from the opening of a new window of observation in a new band of the electromagnetic spectrum. X-rays revealed stellar black holes, infrared rays the interior of stellar nurseries, and decimeter radio waves the structure of the Milky Way’s arm. This is one of the reasons for the design of the Atacama Large Millimeter/submillimeter Array (Alma). Another, complementary, is that the network of radio telescopes constructed in this way makes it possible to carry out the aperture synthesis and, therefore, to have a very large virtual instrument without the need to create it. Today we learn that the Alma radio telescope network will be used for a great first, observing in the millimeter and submillimetre radio range the astrophysical processes associated with kilonovae. Remember, these are neutron star collisions that were first discovered in the form of short bursts of gamma rays, and whose nature we have only been able to determine for decades, although we are not sure. The energy released is colossal, making gamma-ray bursts among the brightest phenomena in the cosmos. In this artist video, two low-dimensional but very high-density neutron stars are about to merge and break apart. This particularly rare event causes the emission of gravitational waves and short bursts of gamma rays. The two emissions were actually observed on August 17, 2017, respectively by Ligo-Virgo and Fermi/Integral. Several detailed observations made with ESO telescopes have confirmed the nature of this object, a kilonova, located in the galaxy NGC 4993 about 130 million light years from Earth. This type of object is the main source of heavy chemical elements, such as gold and platinum, in the Universe. © ESOL The key to this determination was the rise of multi-messenger astronomy with the simultaneous detection by Ligo and Virgo of gravitational waves coming from the source GW170817, clearly associated with the celestial vault with emissions of electromagnetic waves both in the X domain as in gamma (GRB 170817A) -observed by the Chandra and Fermi satellites-, than in the visible domain with the Las Cumbres Observatory to name only these instruments. Neutron star collisions that produce gold and platinum Now, astrophysicists have published a paper in The Astrophysical Journal Letters, a version of which is open access on arXiv, that discusses the brief burst of gamma rays that GRB 211106A observed – as its name suggests Gamma Ray Burst, on November 6, 2021. As in the case of the source of gravitational waves (Gravitational Wave). ) observed on August 17, 2017, the collision between the neutron stars comes from the fact that the two compact stars have lost u rapidly growing energy in the form of gravitational waves, which led them to fall inexorably and faster towards each other. Fusion was not only supposed to produce thermonuclear reactions at the origin of the birth of heavy elements such as gold and platinum, but also a beam of particles collimated at very high speeds producing also a beam of equally collimated gamma photons at high energies. Earth happened to pass through this beam like an observer illuminated by a lighthouse. The beam of particles and gamma photons injected into the interstellar medium excites it and forces the matter it contains to glow in response . It is this remnant radiation that was first detected in the spectral band accessible to Alma. Before this instrument, millimeter telescopes were not sensitive enough to detect these glows, as GRBs are often observed billions of light-years from the Milky Way. So we only look at old GRBs, and we also suspect that for some still unknown reason, they were more abundant during the first billion years of the cosmos’ history. In fact, GRB 211106A occurred when the observable Universe was only 40% of its current age. However, even if the kilonovae are clearly visible from far in gamma, this is no longer the case for the remnant radiation which is much less luminous Initially, when only the X-ray counterpart of GRB 211106A had been discovered to that of the Swift satellite, astrophysicists thought the kilonova could still come from a nearby galaxy, even though we couldn’t associate one with visible observations with Hubble, likely due to the near line-of-sight presence of the GRB of a large amount of But finally, thanks to Alma, it was possible to find a faint and distant galaxy where the gamma-ray burst occurred. The determined distance, it was necessary to conclude that it was one of the most powerful GRBs detected so far… Alma, together with the observations of the JWST (James Webb Space Telescope) should allow to go even further in the study. of short bursts of gamma rays. The saga of the detection of GW170817. For a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © Science vs Cinema Are you interested in what you just read?
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