Fast neutrino flavor conversion, ejecta properties, and nucleosynthesis in newly-formed hypermassive remnants of neutron-star mergers

George, Manu; Wu, Meng-Ru; Tamborra, Irene; Ardevol-Pulpillo, R.; Janka, Hans-Thomas

doi:10.1103/physrevd.102.103015

Cited by 99 publications

(53 citation statements)

References 68 publications

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“…Secondly, the quantitati ve ef fects of weak reactions may depend on the details of the merger dynamics and the shock heating strength during the merging, and therefore on the adopted EoS (Sekiguchi et al 2015 ) and possibly, to some extent, on numerics. In addition, fla v our conversions of the neutrino species can also affect the neutron richness, hence the nucleosynthesis in the merger ejecta (Wu & Tamborra 2017 ;George et al 2020 ).…”

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confidence: 99%

Dynamical ejecta of neutron star mergers with nucleonic weak processes I: nucleosynthesis

Kullmann

Goriely

Just

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present a coherent study of the impact of neutrino interactions on the r-process element nucleosynthesis and the heating rate produced by the radioactive elements synthesised in the dynamical ejecta of neutron star-neutron star (NS-NS) mergers. We have studied the material ejected from four NS-NS merger systems based on hydrodynamical simulations which handle neutrino effects in an elaborate way by including neutrino equilibration with matter in optically thick regions and re-absorption in optically thin regions. We find that the neutron richness of the dynamical ejecta is significantly affected by the neutrinos emitted by the post-merger remnant, in particular when compared to a case neglecting all neutrino interactions. Our nucleosynthesis results show that a solar-like distribution of r-process elements with mass numbers $A \gtrsim 90$ is produced, including a significant enrichment in Sr and a reduced production of actinides compared to simulations without inclusion of the nucleonic weak processes. The composition of the dynamically ejected matter as well as the corresponding rate of radioactive decay heating are found to be rather independent of the system mass asymmetry and the adopted equation of state. This approximate degeneracy in abundance pattern and heating rates can be favourable for extracting the ejecta properties from kilonova observations, at least if the dynamical component dominates the overall ejecta. Part II of this work will study the light curve produced by the dynamical ejecta of our four NS merger models.

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confidence: 99%

Dynamical ejecta of neutron star mergers with nucleonic weak processes I: nucleosynthesis

Kullmann

Goriely

Just

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…We note that recent BNSM simulations that include the effect of weak interactions generally predict less neutron-rich conditions in the early-time ejecta, particularly for the component that originates from the collisional interface of the two NSs(Wanajo et al 2014;Radice et al 2016;Bovard et al 2017;Vincent et al 2020;George et al 2020; Kullmann et al 2021). However, the exact electron fraction (Ye) distribution of this component still vary substantially in different works and require further improved treatment of weak interactions in simulations.…”

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confidence: 74%

Constraints on $R$-process Nucleosynthesis from $^{129}$I and $^{247}$Cm in the Early Solar System

Banerjee,

Wu,

2021

Preprint

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GW170817 has confirmed binary neutron star mergers as one of the sites for rapid neutron capture (r) process. However, there are large theoretical and experimental uncertainties associated with the resulting nucleosynthesis calculations and additional sites may be needed to explain all the existing observations. In this regard, abundances of short-lived radioactive isotopes (SLRIs) in the early solar system (ESS), that are synthesized exclusively by rprocess, can provide independent clues regarding the nature of r-process events. In this work, we study the evolution of r-process SLRIs 129 I and 247 Cm as well as the corresponding reference isotopes 127 I and 235 U at the Solar location. We consider up to three different sources that have distinct 129 I/ 247 Cm production ratios corresponding to the varied r-process conditions in different astrophysical scenarios. In contrast to the results found by Côté et al. ( 2021), we find that 129 I and 247 Cm in the ESS do not come entirely from a single major event but get contributions from at least two more minor contributors. This has a dramatic effect on the evolution of the 129 I/ 247 Cm ratio, such that the measured ESS value in meteorites may not correspond to that of the "last" major r-process event. Interestingly, however, we find that the 129 I/ 247 Cm ratio, in combination with the observed 129 I/ 127 I and 247 Cm/ 235 U ratio in the ESS, can still provide important constraints on the properties of proposed r-process sources operating in the Milky Way.

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“…Moreover, neutrino oscillations could change the nucleosynthesis signature of the ejecta and reduce their lanthanide content (e.g. Zhu et al 2016;George et al 2020). Apart from the dynamical ejecta and subsequent neutrino-driven winds from the surface of the hyper-massive NS, additional fast and lanthanide-poor material could be ejected in connection to magnetic-field effects (e.g.…”

Section: Discussionmentioning

confidence: 99%

Dynamical ejecta of neutron star mergers with nucleonic weak processes II: Kilonova emission

Just,

Kullmann,

Goriely

et al. 2021

Preprint

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The majority of existing results for the kilonova (or macronova) emission from material ejected during a neutron-star (NS) merger is based on (quasi-)one-zone models or manually constructed toy-model ejecta configurations. In this study we present a kilonova analysis of the material ejected during the first ∼ 10 ms of a NS merger, called dynamical ejecta, using directly the outflow trajectories from general relativistic smoothed-particle hydrodynamics simulations including a sophisticated neutrino treatment and the corresponding nucleosynthesis results, which have been presented in Part I of this study. We employ a multi-dimensional two-moment radiation transport scheme with approximate M1 closure to evolve the photon field and use a heuristic prescription for the opacities found by calibration with atomic-physics based reference results. We find that the photosphere is generically ellipsoidal but augmented with small-scale structure and produces emission that is about 1.5-3 times stronger towards the pole than the equator. The kilonova typically peaks after 0.7 − 1.5 days in the near-infrared frequency regime with luminosities between 3 − 7 × 10 40 erg s −1 and at photospheric temperatures of 2.2 − 2.8 × 10 3 K. A softer equation of state or higher binary-mass asymmetry leads to a longer and brighter signal. Significant variations of the light curve are also obtained for models with artificially modified electron fractions, emphasizing the importance of a reliable neutrino-transport modeling. None of the models investigated here, which only consider dynamical ejecta, produces a transient as bright as AT2017gfo. The near-infrared peak of our models is incompatible with the early blue component of AT2017gfo.

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Fast neutrino flavor conversion, ejecta properties, and nucleosynthesis in newly-formed hypermassive remnants of neutron-star mergers

Cited by 99 publications

References 68 publications

Dynamical ejecta of neutron star mergers with nucleonic weak processes I: nucleosynthesis

Dynamical ejecta of neutron star mergers with nucleonic weak processes I: nucleosynthesis

Constraints on $R$-process Nucleosynthesis from $^{129}$I and $^{247}$Cm in the Early Solar System

Dynamical ejecta of neutron star mergers with nucleonic weak processes II: Kilonova emission

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