2018/08/31 by Meng-Ru Wu, Jennifer Barnes, J. E. Barnes +3 · 1 citation
Physics and Astronomy · #Astrophysics #Ejecta #Gamma-ray burst #Gamma-ray bursts and supernovae #Isotope #Kilonova #Nuclear physics #Nuclear physics research studies #Nucleosynthesis #Physics #Pulsars and Gravitational Waves Research #Radioactive decay #Supernova #astro-ph.HE #nucl-th #r-process
paper · pdf · doi:10.1103/physrevlett.122.062701
published as Phys. Rev. Lett. 122, 062701 (2019) · 11 pages, 8 figures including supplemental material, accepted by PRL
arxiv created 2019/01/06 · openalex publication_date 2019/02/12 · arxiv updated 2019/02/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
The kilonova emission observed following the binary neutron star merger event GW170817 provided the first direct evidence for the synthesis of heavy nuclei through the rapid neutron capture process (r process). The late-time transition in the spectral energy distribution to near-infrared wavelengths was interpreted as indicating the production of lanthanide nuclei, with atomic mass number A≳140. However, compelling evidence for the presence of even heavier third-peak (A≈195) r-process elements (e.g., gold, platinum) or translead nuclei remains elusive. At early times (∼days) most of the r-process heating arises from a large statistical ensemble of β decays, which thermalize efficiently while the ejecta is still dense, generating a heating rate that is reasonably approximated by a single power law. However, at later times of weeks to months, the decay energy input can also possibly be dominated by a discrete number of α decays, 223Ra (half-life t1/2=11.43 d), 225Ac (t1/2=10.0 d, following the β decay of 225Ra with t1/2=14.9 d), and the fissioning isotope 254Cf (t1/2=60.5 d), which liberate more energy per decay and thermalize with greater efficiency than β-decay products. Late-time nebular observations of kilonovae which constrain the radioactive power provide the potential to identify signatures of these individual isotopes, thus confirming the production of heavy nuclei. In order to constrain the bolometric light to the required accuracy, multiepoch and wideband observations are required with sensitive instruments like the James Webb Space Telescope. In addition, by comparing the nuclear heating rate obtained with an abundance distribution that follows the solar r abundance pattern, to the bolometric lightcurve of AT2017gfo, we find that the yet-uncertain r abundance of 72Ge plays a decisive role in powering the lightcurve, if one assumes that GW170817 has produced a full range of the solar r abundances down to mass number A∼70.