{"id":228567,"date":"2021-04-16T17:45:49","date_gmt":"2021-04-16T14:45:49","guid":{"rendered":"https:\/\/en.buradabiliyorum.com\/study-sheds-light-on-stellar-origin-of-iron-nuclide\/"},"modified":"2021-04-16T17:45:49","modified_gmt":"2021-04-16T14:45:49","slug":"study-sheds-light-on-stellar-origin-of-iron-nuclide","status":"publish","type":"post","link":"https:\/\/buradabiliyorum.com\/en\/study-sheds-light-on-stellar-origin-of-iron-nuclide\/","title":{"rendered":"#Study sheds light on stellar origin of iron nuclide"},"content":{"rendered":"

“#Study sheds light on stellar origin of iron nuclide<\/strong>”<\/p>\n

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60<\/sup>Fe nucleosynthesis in massive stars. Credit: LI Yutian
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Researchers from the Institute of Modern Physics (IMP) of the Chinese Academy of Science<\/a>s and their collaborators have recently made great progress in the study of the stellar beta-decay rate of 59<\/sup>Fe, which constitutes an important step towards understanding 60<\/sup>Fe nucleosynthesis in massive stars. The results were published in Physical Review Letters <\/i>on April 12.<\/p>\n


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Radioactive nuclide 60<\/sup>Fe plays an essential role in nuclear astrophysical studies. It is synthesized in massive stars by successive neutron captures on a stable nucleus of 58<\/sup>Fe and, during the late stages of stellar evolution, ejected into space via a core-collapse supernova.<\/p>\n

The characteristic gamma lines associated with the decay of 60<\/sup>Fe have been detected by space gamma-ray detectors. By comparing the 60<\/sup>Fe gamma-ray flux to that from 26<\/sup>Al, which shares a similar origin as 60<\/sup>Fe, researchers should be able to obtain important information on nucleosynthesis and stellar models. However, the observed gamma-ray flux ratio 26<\/sup>Al\/60<\/sup>Fe does not match theoretical predictions due to uncertainties in both stellar models and nuclear data inputs.<\/p>\n

The stellar beta-decay rate of 59<\/sup>Fe is among the greatest uncertainties in nuclear data inputs. During the nucleosynthesis of 60<\/sup>Fe in massive stars, 59<\/sup>Fe can either capture a neutron to produce 60<\/sup>Fe or beta decay to 59<\/sup>Co. Therefore, the stellar beta-decay rate of 59<\/sup>Fe is critical to the yield of 60<\/sup>Fe.<\/p>\n

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60<\/sup>Fe yield in 18 solar mass star. Blue lines (LMP) are calculations based on previous decay rate, red lines (present work) are those based on the new measurement. Credit: Physical Review Letters<\/i>
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Although the decay rate of 59<\/sup>Fe has been accurately measured in laboratories, its decay rate may be significantly enhanced in stellar environments due to contributions from its excited states. However, direct measurement of the beta-decay rate from excited states is very challenging since one has to create a high-temperature environment as in stars to keep the 59<\/sup>Fe nuclei in their excited states.<\/p>\n

To address this problem, researchers at IMP proposed a new method for measuring the stellar beta-decay rate of 59<\/sup>Fe. “The nuclear charge-exchange reaction is an indirect measurement alternative, which provides key nuclear structure information that can determine those decay rates.” said Gao Bingshui, a researcher at IMP.<\/p>\n

The researchers carried out their experiment at the Coupled Cyclotron Facility at Michigan State University. In the experiment, a secondary triton beam produced by the cyclotrons was used to bombard a 59<\/sup>Co target. Then the reaction products, 3<\/sup>He particles and gamma rays, were detected by the S800 spectrometer and GRETINA gamma-ray detection array. Using this information, the beta-decay rates from the 59<\/sup>Fe excited states were determined. This measurement thus eliminated one of the major nuclear uncertainties in predicting the yield of 60<\/sup>Fe.<\/p>\n

By comparing stellar model calculations using the new decay rate data with previous calculations, the researchers found that, for an 18 solar mass star, the yield of 60<\/sup>Fe is 40% less when using the new data. The result points to a reduced tension in the discrepancy in 26<\/sup>Al\/60<\/sup>Fe ratios between theoretical predictions and observations.<\/p>\n

“It is an important step towards understanding 60<\/sup>Fe nucleosynthesis in massive stars and it will provide a more solid basis for future astrophysical simulations,” said Li Kuoang, the collaborator of Gao.<\/p>\n\n

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Microscopic ‘clocks’ time distance to source of galactic cosmic rays\n <\/p><\/div>\n

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\n More information:<\/strong>
\n B. Gao et al, New Fe59 Stellar Decay Rate with Implications for the Fe60 Radioactivity in Massive Stars, Physical Review Letters<\/i> (2021). DOI: 10.1103\/PhysRevLett.126.152701<\/a><\/p><\/div>\n
\n Provided by
\n Chinese Academy of Sciences
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Citation<\/strong>:
\n Study sheds light on stellar origin of iron nuclide (2021, April 16)
\n retrieved 16 April 2021
\n from https:\/\/phys.org\/news<\/a>\/2021-04-stellar-iron-nuclide.html<\/p>\n

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
\n part may be reproduced without the written permission. The content is provided for information purposes only.<\/p><\/div>\n<\/p><\/div>\n