About Yong-Lin Zhu 朱勇霖
Yonglin Zhu grew up in Xuzhou, China, where he completed his Bachelor Degree in Science with major in Optical Information Science and Technology, at CUMT. After that, he moved from the east coast of China to the same part of the U.S. and pursue his Ph.D. at North Carolina State University.
He worked on computational Condensed Matter Physics and then found more interests in Nuclear-astrophysics. He is working with Gail C. McLaughlin on Neutrino oscillation and Nucleosynthesis in Compact Object Mergers. His research interests including neutrino oscillation in the dense environment, fission in r-process elements, electromagnetic transients observables from heavy nuclei radioactive energy transport.
Kilonova Observations and Nuclear Physics
We examined different combinations of nuclear inputs of nuclear mass, spontaneous fission rate, fission yields in modeling kilonova light curves. Such nuclear physics uncertainties typically generate at least one order of magnitude uncertainty in key quantities such as the nuclear heating (one and a half orders of magnitude at one day post-merger), the bolometric luminosity (one order of magnitude at five days post-merger), and the inferred mass of material from the bolometric luminosity
(factor of eight when considering the eight to ten days region). [Zhu et al 2020, Barnes et al 2020]
r-process Nucleosynthesis in Neutron Star Mergers
I performed dynamical nucleosynthesis calculations and identified a single isotope, 254Cf, which has a particularly high impact on the brightness of electromagnetic transients associated with mergers on the order of 15 to 250 days [Zhu et al 2018a].
Neutrinos in Compact Objects Mergers
We confirmed that Matter-neutrino Resonance transitions occur for both hierarchies close to the merger core, which may potentially change the physics of nucleosynthesis and neutron star merger [Zhu et al 2016]. Then confirmed that Matter-neutrino Resonance transitions occur with elastic scattering in general relativistic ray tracing for neutrinos [Deaton et al 2018].
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Neutrinos in Compact Object Mergers
Matter-neutrino resonance transitions above a neutron star merger remnant
Neutrinos are a necessary component of the physics of several phenomena associated with neutron star merger remnants, examples include nucleosynthesis and jet production in gamma-ray bursts. Many essential neutrino interactions are dependent on neutrino flavor so that an understanding of the flavor content of the neutrinos is critical for providing an accurate picture of merger phenomena.
Once neutrinos are emitted from hot, dense astrophysical objects, they can change their flavor through neutrino oscillations. In the last few years, it has become apparent that many interesting oscillation effects occur in environments with large numbers of neutrinos. In particular, neutrinos may experience collective neutrino oscillations in supernovae [1], and possibly in compact binary mergers. In merger remnant environments, it has been suggested that neutrinos can undergo not only the same type of flavor transformations as in supernova scenarios but also a novel type of transition called matter-neutrino resonance (MNR) transitions [2].
A collaboration led by NC State graduate student Yong-Lin Zhu along with TU Darmstadt researcher Albino Perego and JINA-CEE member Gail McLaughlin performed a study of MNR transitions using the results of a dynamically evolved detailed three-dimensional, Newtonian simulation of the aftermath of a binary neutron star merger under the influence of neutrino cooling and heating. This is the first calculation that has used self-consistent neutrino and matter distributions from the same dynamical simulation.
They found that neutrinos typically pass through a resonance location at the edge of the low-density funnel above the massive neutron star where the neutrino and matter potentials have the approximately the same magnitude. Thus many neutrinos emitted from the massive neutron star have the opportunity to encounter an MNR. The type of MNR transition varies between neutrino trajectories, but in most cases, at the end of the MNR transition(s), the electron neutrinos have completely converted to mu or tau-type neutrinos, whereas the electron antineutrinos experience an oscillation but then return to their original configuration.
Future studies of MNR transitions in binary neutron star merger remnants are needed to elucidate the consequences of these transitions, as well as to further probe the efficacy of the MNR transition itself. These results have implications for various nucleosynthesis scenarios as from collisionally heated material as well as neutrino-driven winds. Additionally, if a merger were to occur within the range of current or future neutrino detectors, the flavor dependent neutrino signal will provide a wealth of information about these objects.
Researchers: Yong-Lin Zhu (NC State), Albino Perego (TU Darmstadt), Gail C. McLaughlin (NC State)
Further reading:
[1]Duan, H., Fuller, G.M. and Qian, Y.Z., 2006. Physical Review D, 74(12), p.123004.
[2]Malkus, A., Kneller, J.P., McLaughlin, G.C. and Surman, R., 2012. Physical Review D, 86(8), p.085015.
This work was published (highlighted as editor’s suggestion) as:
Zhu, Y.L., Perego, A. and McLaughlin, G.C., 2016. Physical Review D, 94(10), p.105006.
Californium-254 and Kilonova Light Curves
Primary fission fragment yield of Cf-254(SF) calculated in the hybrid approach (see text).
The two-dimensional fragment yield of Cf-254(SF), with our charge distribution systematics. Stable nuclei are shaded black with the extent of FRDM2012 outlined in light gray.
The collaboration led by FIRE(Fission in R-process Elements) members from LANL(Los Almos National Lab)/NC State/Notre Dame has explored several issues concerning the nuclear physics of Cf-254 production in NSM’s observation for the first time. They model r-process nucleosynthesis using PRISM(Version 2.0, by LANL/Notre Dame) with all relevant nuclear reaction channels and reheating of the ejecta handled self-consistently. Fission from neutron-induced, β-delayed and spontaneous(SF) channels are also included.
The fission fragment yields of Cf-254 are constructed with a hybrid method that combines both theoretical and experimental data, see figures above. Due to the anomalously long half-life of this isotope and the efficiency of fission thermalization compared to other nuclear channels, it is identified that this single isotope, Cf-254, which has a particularly high impact on the brightness of electromagnetic transients associated with mergers on the order of 15 to 250 days, see left figure.
The production of Cf-254 implies the nucleosynthesis of at least some actinide material. Thus, a combined approach of improving experimental knowledge in this region along with the coupling of late-time light curves with nucleosynthetic simulations have the potential to play a major role in cementing the origin of the heaviest r-process elements. This work has been accepted for publication by APJL.
Further Reading: arXiv:1806.09724
This work was published as:
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