. | . |
Observations of a rare hypernova complete the picture of the death of the massive stars by Staff Writers Granada, Spain (SPX) Jan 18, 2019
The end of a star's life can occur in a tranquil manner in the case of low mass stars, such as the Sun. This is not the case, however, for very massive stars, which suffer such extreme explosive events that they can outshine the brightness of the whole galaxy that hosts them. An international group of astronomers has published a detailed study of the death of a high-mass star that produced a gamma-ray burst (GRB) and a hypernova, in which they have detected a new component in this type of events. The study, published in Nature, provides a link that completes the scenario that relates hypernovae with GRBs. "The first hypernova was detected in 1998 as a very energetic type of supernova that followed a gamma-ray burst. This was the first evidence of the connection between both phenomena" says Luca Izzo, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC), and leader the study. The scenario that has been proposed to explain the phenomena involves a star over 25 times more massive than the Sun that, once it has exhausted its fuel, suffers the collapse of its core. During this collapse, the nucleus of the star transforms either into a neutron star or a black hole, and at the same time, two polar jets of matter are ejected. These jets drill through the external layers of the star and, once out of the star, produce detectable gamma-rays (the so-called GRB). Finally, the external layers of the star are ejected, generating a hypernova explosion, tens of times brighter than a typical supernova. Although the connection between GRBs and hypernovae has been well established over the last 20 years, the opposite is not so clear, since there have been several hypernovae that do not have associated GRBs.
"This work has allowed us to find Institute Of Astrophysics Of Andalusia On the other hand, the jet can fail to pierce the external layers of the star and never emerge into the circumstellar medium if it lacks the necessary energy. In this case we would observe a hypernova but not a GRB. The cocoon detected in this study is the link between the two subtypes of hypernovae that had been studied until now, and the chocked jets would naturally explain the observed differences.
The Story of the Event Thone, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) who participated in the discovery -. In fact, with our early observations we managed to obtain the earliest detection of a hypernova to date, less than one day after the collapse of the star". And indeed, very early on the first features of a hypernova were detected with the Gran Telescopio Canarias, on the island of La Palma. "This was only possible because the luminosity of the jet was much weaker than usual, as typically the jets outshine the hypernova during the first week - says Antonio de Ugarte Postigo, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) who participated in the paper -. What we saw, however, was a very peculiar component, which showed unprecedented expansion velocities and chemical abundances that were different to the ones seen in similar events". This peculiar chemical composition and the high expansion velocities matched the expectations for the existence of a cocoon accompanying the jet at the surface of the star. This had been predicted but had been never observed before. The cocoon observed during the first days dragged material out from the interior of the star, and its chemical composition was determined in this study. After a few days, this component faded away, and the hypernova evolved in a similar way as the ones previously observed. The total energy emitted by the cocoon during these first days was larger than that of the GRB, implying that the jet transferred a large part of its energy to the cocoon. However, it also indicates that the energy of the GRB depends to some degree on the interaction between the jet and the stellar material, and on this new component, the cocoon. This discovery also implies that the models must be revised: "While in the standard model of supernovae the collapse of the nucleus leads to quasi-spherical explosions, the evidence of such an energetic emission produced by the cocoon suggests that the jet plays an important role in core-collapse supernovae which means we will need to consider it in supernova explosion models", concludes Izzo (IAA-CSIC).
Team of telescopes finds X-ray engine inside mysterious supernova Paris (ESA) Jan 14, 2019 ESA's high-energy space telescopes Integral and XMM-Newton have helped to find a source of powerful X-rays at the centre of an unprecedentedly bright and rapidly evolving stellar explosion that suddenly appeared in the sky earlier this year. The ATLAS telescope in Hawaii first spotted the phenomenon, since then named AT2018cow, on 16 June. Soon after that, astronomers all over the world were pointing many space- and ground-based telescopes towards the newly found celestial object, located in a gal ... read more
|
|
The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us. |