Эрдэмтэд удаан үргэлжилдэг гамма туяаны тэсрэлтүүд нь нейтрон оддын мөргөлдөөнөөс бус, харин оддын сүйрлээр хар нүх үүсэх үйл явцаас үүдэлтэй болохыг тогтоожээ.
АНУ-ын Лос-Аламос үндэсний лабораторийн эрдэмтэд 2021 болон 2023 онд NASA-гийн Fermi багажаар илрүүлсэн GRB 211211A болон GRB 20307A гэх хоёр удаан үргэлжилдэг гамма туяаны тэсрэлтийг судалжээ. Уг үзэгдлийг өмнө нь нейтрон оддын нэгдэл буюу килонова гэж таамаглаж байсан ч шинэ судалгаагаар энэ нь “коллапсар” буюу нейтрон од хар нүх болон нурж унах үйл явц болохыг баталсан байна.
Судлаачид HPE Cray EX “Chicoma” суперкомпьютер ашиглан тэсрэлтүүдийн загварчлалыг гаргажээ. Ингэхдээ тэд гамма туяаны тэсрэлтүүд нь төмрөөс хүнд элементүүдийг (алт, хар тугалга, уран гэх мэт) нейтрон хураах замаар үүсгэдэг гэсэн механизмаа ашигласан байна. Загварчлалын үр дүн нь ажиглагдсан өгөгдөлтэй бараг ижил байсан нь уг үйл явцыг тайлбарлах шинэ өнцөг болж байна.
Тус судалгааны багийн ахлагч Марко Ристич болон онолын физикч Мэттью Мампоуэр нарын тайлбарласнаар, килоновагийн үйл явц нь өмнө нь төсөөлж байснаас илүү олон янз бөгөөд нарийн төвөгтэй байж болох юм. Энэхүү судалгаа нь гамма туяаны тэсрэлтийн загварчлалыг дахин үнэлэхэд хүргэж байгаа бөгөөд ирээдүйд таталцлын долгионыг ажигласнаар сансар огторгуйн эдгээр эрс тэс үзэгдлүүдийн гарал үүслийг илүү тодорхой ойлгох боломжтой болно.
https://heasarc.gsfc.nasa.gov/docs/cgro/epo/vu/overview/bursts/bursts.html
https://www.lanl.gov/media/news/0617-gamma-ray-bursts
https://iopscience.iop.org/article/10.3847/2041-8213/ae5e53
https://www.hpcwire.com/off-the-wire/los-alamos-national-laboratory-deploys-hpe-cray-ex-chicoma-supercomputer/
Дэлгэрэнгүйг эх сурвалжаас харах
Эх сурвалжийг нээх ↓
Gamma-ray bursts (GRBs) are some of the most energetic events in the Universe, releasing more energy in a few seconds than most stars release in their entire lifetime. These mysterious events were first detected in 1967 by NASA’s Vela satellites, which were developed at the Los Alamos National Laboratory (LANL) to detect clandestine nuclear testing. In a recent study, scientists at Los Alamos analyzed two long-duration GRBs and determined they were caused by neutron stars collapsing to form black holes (a collapsar event).
As they explain in their study, which appeared in The Astrophysical Journal Letters, these collapsar events released tremendous bursts of gamma rays in the process. Before their analysis, scientists speculated that the two events were caused by the merger of two neutron stars, known as a kilonova event (a burst of energy associated with the formation of heavy elements). Their findings confirm an earlier interpretation of the events and are causing astronomers to reevaluate how they model these exotic, energetic events.
As Marko Ristić, a Los Alamos postdoctoral fellow and the lead author on the study, explained in a LANL press release:
Gamma-ray bursts are products of some of the most intense, exotic situations in the universe, with really high densities and temperatures, relativistic effects, and different time scales coming together. With our modeling and simulation of a new perspective on these two peculiar long-duration gamma-ray bursts, we’re gaining a new view on these complicated and fascinating extreme events.
The collision of two neutron stars can create rare elements like gold. Credit: Dana Berry/SkyWorks Digital, Inc.
The events are designated GRB 211211A and GRB 20307A, which were detected by NASA’s Fermi Gamma-ray Burst Monitor in 2021 and 2023, respectively. Using the NASA datasets, the team modeled the events on the Laboratory’s HPE Cray EX “Chicoma” supercomputer to better understand the creation of kilonovae and the resulting formation of heavy elements through nucleosynthesis. In a previous study, the team proposed a new mechanism for this process in which collapsars create elements heavier than iron (gold, lead, uranium, etc.) via rapid neutron capture.
Their results predicted an element composition without the very heavy elements, which was nearly identical to the GRB observations. This is consistent with one of the leading interpretations of GRBs: that they occur in one of two ways: short-duration bursts (less than 2 seconds) and long-duration bursts (longer than 2 seconds). Whereas the former are thought to result from neutron star mergers, the latter appear to originate from collapsars. Said Los Alamos theoretical physicist and study co-author Matthew Mumpower:
What we’ve learned is that, contrary to contemporary interpretations, the type of kilonova represented with these long-duration gamma-ray bursts does not inherently imply the synthesis of gold, despite the signal showing a red component typically associated with lanthanide production. A simple explanation arises from this work, requiring only a single-component model, which suggests kilonovae are even more varied and difficult to interpret than we thought in the past.
Future observations that include gravitational-wave (GW) detections will enable astrophysicists to better understand the cosmic origins of kilonovae and their associated GRBs.
Further Reading: Los Alamos National Laboratory, The Astrophysical Journal Letters
