Spherical symmetry in the kilonova AT2017gfo/GW170817
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Spherical symmetry in the kilonova AT2017gfo/GW170817. / Sneppen, Albert; Watson, Darach; Bauswein, Andreas; Just, Oliver; Kotak, Rubina; Nakar, Ehud; Poznanski, Dovi; Sim, Stuart.
I: Nature, Bind 614, Nr. 7948, 16.02.2023, s. 436-439.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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T1 - Spherical symmetry in the kilonova AT2017gfo/GW170817
AU - Sneppen, Albert
AU - Watson, Darach
AU - Bauswein, Andreas
AU - Just, Oliver
AU - Kotak, Rubina
AU - Nakar, Ehud
AU - Poznanski, Dovi
AU - Sim, Stuart
PY - 2023/2/16
Y1 - 2023/2/16
N2 - The mergers of neutron stars expel a heavy-element enriched fireball that can be observed as a kilonova(1-4). The kilonova's geometry is a key diagnostic of the merger and is dictated by the properties of ultra-dense matter and the energetics of the collapse to a black hole. Current hydrodynamical merger models typically show aspherical ejecta(5-7). Previously, Sr+ was identified in the spectrum(8) of the only well-studied kilonova(9-11) AT2017gfo(12), associated with the gravitational wave event GW170817. Here we combine the strong Sr+ P Cygni absorption-emission spectral feature and the blackbody nature of kilonova spectrum to determine that the kilonova is highly spherical at early epochs. Line shape analysis combined with the known inclination angle of the source(13) also show the same sphericity independently. We conclude that energy injection by radioactive decay is insufficient to make the ejecta spherical. A magnetar wind or jet from the black-hole disk could inject enough energy to induce a more spherical distribution in the overall ejecta; however, an additional process seems necessary to make the element distribution uniform.
AB - The mergers of neutron stars expel a heavy-element enriched fireball that can be observed as a kilonova(1-4). The kilonova's geometry is a key diagnostic of the merger and is dictated by the properties of ultra-dense matter and the energetics of the collapse to a black hole. Current hydrodynamical merger models typically show aspherical ejecta(5-7). Previously, Sr+ was identified in the spectrum(8) of the only well-studied kilonova(9-11) AT2017gfo(12), associated with the gravitational wave event GW170817. Here we combine the strong Sr+ P Cygni absorption-emission spectral feature and the blackbody nature of kilonova spectrum to determine that the kilonova is highly spherical at early epochs. Line shape analysis combined with the known inclination angle of the source(13) also show the same sphericity independently. We conclude that energy injection by radioactive decay is insufficient to make the ejecta spherical. A magnetar wind or jet from the black-hole disk could inject enough energy to induce a more spherical distribution in the overall ejecta; however, an additional process seems necessary to make the element distribution uniform.
KW - SUPERLUMINAL MOTION
KW - II SUPERNOVAE
KW - MERGER
KW - NUCLEOSYNTHESIS
KW - SPECTRA
KW - IDENTIFICATION
KW - POLARIZATION
KW - COUNTERPART
KW - ABSORPTION
KW - EVOLUTION
U2 - 10.1038/s41586-022-05616-x
DO - 10.1038/s41586-022-05616-x
M3 - Journal article
C2 - 36792736
VL - 614
SP - 436
EP - 439
JO - Nature
JF - Nature
SN - 0028-0836
IS - 7948
ER -
ID: 340940815