arXiv subjects

Shuai Zha

Publications and source records attributed to Shuai Zha.

30 records · Page 2Linked to original sources

arXiv2023

Light Curves of Type IIP Supernovae from Neutrino-driven Explosions of Red Supergiants Obtained by a Semi-analytic Approach

Type IIP supernovae (SNe IIP) mark the explosive death of red supergiants (RSGs), evolved massive stars with an extended hydrogen envelope. They are the most common supernova type and allow for benchmarking of supernova explosion models by statistical comparison to observed population properties rather than comparing individual models and events. We construct a large synthetic set of SNe IIP light curves (LCs) using the radiation hydrodynamics code \texttt{SNEC} and explosion energies and nickel masses obtained from an efficient semi-analytic model for two different sets of stellar progenitor models. By direct comparison we demonstrate that the semi-analytic model yields very similar predictions as alternative phenomenological explosion models based on one-dimensional simulations. We find systematic differences of a factor of $\mathord{\sim}2$ in plateau luminosities between the two progenitor sets due to different stellar radii, which highlights the importance of the RSG envelope structure as a major uncertainty in interpreting LCs of SNe IIP. A comparison to a volume-limited sample of observed SNe IIP shows decent agreement in plateau luminosity, plateau duration and nickel mass for at least one of the synthetic LC sets. The models, however, do not produce sufficient events with very small nickel mass $M_\mathrm{Ni}<0.01\,M_\odot$ and predict an anticorrelation between plateau luminosity and plateau duration that is not present in the observed sample, a result that warrants further study. Our results suggest that a better understanding of RSG stellar structure is no less important for reliably explaining the light curves of SNe IIP than the explosion physics.

astro-ph.HE↗

arXiv2023

Impact of Rotation on the Multimessenger Signatures of a Hadron-quark Phase Transition in Core-collapse Supernovae

We study the impact of rotation on the multimessenger signals of core-collapse supernovae (CCSNe) with the occurrence of a first-order hadron-quark phase transition (HQPT). We simulate CCSNe with the \texttt{FLASH} code starting from a 20~$M_\odot$ progenitor with different rotation rates, and using the RDF equation of state from \textit{Bastian} 2021 that prescribes the HQPT. Rotation is found to delay the onset of the HQPT and the resulting dynamical collapse of the protocompact star (PCS) due to the centrifugal support. All models with the HQPT experience a second bounce shock which leads to a successful explosion. The oblate PCS as deformed by rotation gives rise to strong gravitational-wave (GW) emission around the second bounce with a peak amplitude larger by a factor of $\sim10$ than that around the first bounce. The breakout of the second bounce shock at the neutrinosphere produces a $\barν_e$-rich neutrino burst with a luminosity of serveral 10$^{53}$~erg~s$^{-1}$. In rapidly rotating models the PCS pulsation following the second bounce generates oscillations in the neutrino signal after the burst. In the fastest rotating model with the HQPT, a clear correlation is found between the oscillations in the GW and neutrino signals immediately after the second bounce. In addition, the HQPT-induced collapse leads to a jump in the ratio of rotational kinetic energy to gravitational energy ($β$) of the PCS, for which persistent GW emission may arise due to secular nonaxisymmetric instabilities.

astro-ph.HE↗

arXiv2022

Hydrodynamic Simulations of Electron-capture Supernovae: Progenitor and Dimension Dependence

We present neutrino-transport hydrodynamic simulations of electron-capture supernovae (ECSNe) in \texttt{FLASH} with new two-dimensional (2D) collapsing progenitor models. These progenitor models feature the 2D modelling of oxygen-flame propagation until the onset of core collapse. We perform axisymmetric simulations with 6 progenitor models that, at the time of collapse, span a range of propagating flame front radii. For comparison, we also perform a simulation with the same setup using the canonical, spherically-symmetrical progenitor model n8.8. We found that the variations in the progenitor models inherited from simulations of stellar evolution and flame propagation do not significantly alter the global properties of the neutrino-driven ECSN explosion, such as the explosion energy ($\sim1.36$-$1.48\times10^{50}$ erg) and the mass ($\sim0.017$-$0.018M_\odot$) and composition of the ejecta. Due to aspherical perturbations induced by the 2D flame, the ejecta contains a small amount ($\lesssim1.8\times10^{-3}~M_\odot$) of low-$Y_e$ ($0.35<Y_e<0.4$) component. The baryonic mass of the protoneutron star is $\sim1.34~M_\odot$ ($\sim1.357~M_\odot$) with the new (n8.8) progenitor models when simulations end at $\sim400$ ms and the discrepancy is due to updated weak-interaction rates in the progenitor evolutionary simulations. Our results reflect the nature of ECSN progenitors containing a strongly degenerate ONeMg core and suggest a standardized ECSN explosion initialized by ONeMg core collapse. Moreover, we carry out a rudimentary three-dimensional simulation and find that the explosion properties are fairly compatible with the 2D counterpart. Our paper facilitates a more thorough understanding of ECSN explosions following the ONeMg core collapse, though more three-dimensional simulations are still needed.

astro-ph.HE↗

arXiv2021

Supernova Preshock Neutronization Burst as a Probe of Non-Standard Neutrino Interactions

Core-collapse supernova (CCSN) provides a unique astrophysical site for studying neutrino-matter interactions. Prior to the shock-breakout neutrino burst during the collapse of the iron core, a preshock $ν_e$ burst arises from the electron capture of nuclei and it is sensitive to the low-energy coherent elastic neutrino-nucleus scattering (CE$ν$NS) which dominates the neutrino opacity. Since the CE$ν$NS depends strongly on the non-standard neutrino interactions (NSI) which are completely beyond the standard model and yet to be determined, the detection of the preshock burst thus provides a clean way to extract the NSI information. Within the spherically symmetric general-relativistic hydrodynamic simulation for the CCSN, we investigate the NSI effects on the preshock burst. We find that the NSI can maximally enhance the peak luminosity of the preshock burst almost by a factor of three, reaching a value comparable with that of the shock-breakout burst. Future detection of the preshock burst will have critical implications on astrophysics, neutrino physics and physics beyond the standard model.

astro-ph.HE↗

arXiv2021

Gravitational-wave Signature of a First-order Quantum Chromodynamics Phase Transition in Core-Collapse Supernovae

A first-order quantum chromodynamics (QCD) phase transition (PT) may take place in the protocompact star (PCS) produced by a core-collapse supernova (CCSN). In this work, we study the consequences of such a PT in a non-rotating CCSN with axisymmetric hydrodynamic simulations. We find that the PT leads to the collapse of the PCS and results in a loud burst of gravitational waves (GWs). The amplitude of this GW burst is $\sim30$ times larger than the post-bounce GW signal normally found for non-rotating CCSN. It shows a broad peak at high frequencies ($\sim2500-4000$ Hz) in the spectrum, has a duration of $\lesssim5 {\rm ms}$, and carries $\sim3$ orders of magnitude more energy than the other episodes. Also, the peak frequency of the PCS oscillation increases dramatically after the PT-induced collapse. In addition to a second neutrino burst, the GW signal, if detected by the ground-based GW detectors, is decisive evidence of the first-order QCD PT inside CCSNe and provides key information about the structure and dynamics of the PCS.

astro-ph.HE↗

arXiv2021

Quantum Enhanced Interferometer for Kilohertz Gravitational Wave Detection

The gravitational wave detector of higher sensitivity and greater bandwidth in kilohertz window is required for future gravitational wave astronomy and cosmology. Here we present a new type broadband high frequency laser interferometer gravitational wave detector utilizing polarization of light as signal carrier. Except for Fabry-Perot cavity arms we introduce dual power recycling to further amplify the gravitational wave signals. A novel method of weak measurement amplification is used to amplify signals for detection and to guarantee the long-term run of detector. Equipped with squeezed light, the proposed detector is shown sensitive enough within the window from 300Hz to several kHz, making it suitable for the study of high frequency gravitational wave sources. With the proposed detector added in the current detection network, we show that the ability of exploring binary neutron stars merger physics be significantly improved. The detector presented here is expected to provide an alternative way of exploring the possible ground-based gravitational wave detector for the need of future research.

astro-ph.IM↗

arXiv2021

Equation of State Dependence of Gravitational Waves in Core-Collapse Supernovae

Gravitational waves (GWs) provide unobscured insight into the birthplace of neutron stars (NSs) and black holes in core-collapse supernovae (CCSNe). The nuclear equation of state (EOS) describing these dense environments is yet uncertain, and variations in its prescription affect the proto-neutron star (PNS) and the post-bounce dynamics in CCSNe simulations, subsequently impacting the GW emission. We perform axisymmetric simulations of CCSNe with Skyrme-type EOSs to study how the GW signal and PNS convection zone are impacted by two experimentally accessible EOS parameters, (1) the effective mass of nucleons, $m^\star$, which is crucial in setting the thermal dependence of the EOS, and (2) the isoscalar incompressibility modulus, $K_{\rm{sat}}$. While $K_{\rm{sat}}$ shows little impact, the peak frequency of the GWs has a strong effective mass dependence due to faster contraction of the PNS for higher values of $m^\star$ owing to a decreased thermal pressure. These more compact PNSs also exhibit more neutrino heating which drives earlier explosions and correlates with the GW amplitude via accretion plumes striking the PNS, exciting the oscillations. We investigate the spatial origin of the GWs and show the agreement between a frequency-radial distribution of the GW emission and a perturbation analysis. We do not rule out overshoot from below via PNS convection as another moderately strong excitation mechanism in our simulations. We also study the combined effect of effective mass and rotation. In all our simulations we find evidence for a power gap near $\sim$1250 Hz, we investigate its origin and report its EOS dependence.

astro-ph.HE↗

arXiv2021

Progenitor Dependence of Hadron-quark Phase Transition in Failing Core-collapse Supernovae

We study the consequences of a hadron-quark phase transition (PT) in failing core-collapse supernovae (CCSNe) which give birth to stellar-mass black holes (BH). We perform a suite of neutrino-transport general-relativistic hydrodynamic simulations in spherical symmetry with 21 progenitor models and a hybrid equation of state (EoS) including hadrons and quarks. We find that the effect of the PT on the CCSN postbounce dynamics is a function of the bounce compactness parameter $ξ_{2.2}$. For $ξ_{2.2}\gtrsim0.24$, the PT leads to a second dynamical collapse of the protocompact star (PCS). While BH formation starts immediately after this second collapse for models with $ξ_{2.2}\gtrsim0.51$, the PCS experiences a second bounce and oscillations for models with $0.24\lesssimξ_{2.2}\lesssim0.51$. These models emit potent oscillatory neutrino signals with a period of $\sim$ms for tens of ms after the second bounce, which can be a strong indicator of the PT in failing CCSNe if detected in the future. However, no shock revival occurs and BH formation inevitably takes place in our spherically-symmetric simulations. Furthermore, via a diagram of mass-specific entropy evolution of the PCS, the progenitor dependence can be understood through the appearance of third-family of compact stars emerging at large entropy induced by the PT.

astro-ph.HE↗

arXiv2019

Accretion-Induced Collapse of Dark Matter Admixed White Dwarfs -- I: Formation of Low-mass Neutron Stars

Recently observed pulsars with masses $\sim 1.1 ~M_{\odot}$ challenge the conventional neutron star (NS) formation path by core-collapse supernova (CCSN). Using spherically symmetric hydrodynamics simulations, we follow the collapse of a massive white dwarf (WD) core triggered by electron capture, until the formation of a proto-NS (PNS). For initial WD models with the same central density, we study the effects of a static, compact dark matter (DM) admixed core on the collapse and bounce dynamics and mass of the PNS, with DM mass $\sim 0.01 ~M_{\odot}$. We show that increasing the admixed DM mass generally leads to slower collapse and smaller PNS mass, down to about 1.0 $M_{\odot}$. Our results suggest that the accretion-induced collapse of dark matter admixed white dwarfs can produce low-mass neutron stars, such as the observed low-mass pulsar J0453+1559, which cannot be obtained by conventional NS formation path by CCSN.

astro-ph.HE↗

arXiv2019

Evolution of ONeMg Core in Super-AGB Stars towards Electron-Capture Supernovae: Effects of Updated Electron-Capture Rate

Stars with $\sim 8-10~{M}_{\odot}$ evolve to form a strongly degenerate ONeMg core. When the core mass becomes close to the Chandrasekhar mass, the core undergoes electron captures on $^{24}$Mg and $^{20}$Ne, which induce the electron-capture supernova (ECSN). In order to clarify whether the ECSN leads to a collapse or thermonuclear explosion, we calculate the evolution of an $8.4~M_\odot$ star from the main sequence until the oxygen ignition in the ONeMg core. We apply the latest electron-capture rate on $^{20}$Ne including the second forbidden transition, and investigate how the location of the oxygen ignition (center or off-center) and the $Y_e$ distribution depend on the input physics and the treatment of the semiconvection and convection. The central density when the oxygen deflagration is initiated, $ρ_{\rm c,def}$, can be significantly higher than that of the oxygen ignition thanks to the convection, and we estimate $\log_{10}(ρ_{\rm c,def}/\mathrm{g~cm^{-3}})>10.10$. We perform two-dimensional simulations of the flame propagation to examine how the final fate of the ONeMg core depends on the $Y_e$ distribution and $ρ_{\rm c,def}$. We find that the deflagration starting from $\log_{10}(ρ_{\rm c,def}/\mathrm{g~cm^{-3}})>10.01 (< 10.01)$ leads to a collapse (thermonuclear explosion). Since our estimate of $ρ_{\rm c,def}$ exceeds this critical value, the ONeMg core is likely to collapse, although further studies of the convection and semiconvection before the deflagration are important.

astro-ph.HE↗

arXiv2019

Electron-capture Rates in $^{20}$Ne for a Forbidden Transition to the Ground State of $^{20}$F Relevant to Final Evolution of High-density O-Ne-Mg Cores

Electron capture on $^{20}$Ne is critically important for the final stage of evolution of stars with the initial masses of 8 - 10 $M_{\odot}$. In the present paper, we evaluate electron capture rates for a forbidden transition $^{20}$Ne (0$_{g.s.}^{+}$) $\rightarrow$ $^{20}$F (2$_{g.s.}^{+}$) in stellar environments by the multipole expansion method with the use of shell-model Hamiltonians. These rates have not been accurately determined in theory as well as in experiments. Our newly evaluated rates are compared with those obtained by a prescription that treats the transition as an allowed Gamow-Teller (GT) transition with the strength determined from a recent $β$-decay experiment for $^{20}$F (2$_{g.s.}^{+}$) $\rightarrow$ $^{20}$Ne (0$_{g.s.}^{+}$) \citep{Kirsebom}. We find that different electron energy dependence of the transition strengths between the two methods leads to sizable differences in the weak rates of the two methods. We also find that the Coulomb effects, that is, the effects of screening on ions and electrons are non-negligible. We apply our e-capture rates on $^{20}$Ne to the calculation of the evolution of high-density O-Ne-Mg cores of 8 - 10 $M_{\odot}$ stars. We find that our new rates affect the abundance distribution and the central density at the final stage of evolution.

astro-ph.SR↗

arXiv2019

Accretion-Induced Collapse of Dark Matter Admixed White Dwarfs -- II: Rotation and Gravitational-wave Signals

We present axisymmetric hydrodynamical simulations of accretion-induced collapse (AIC) of dark matter (DM) admixed rotating white dwarfs (WD) and their burst gravitational-wave (GW) signals. For initial WD models with the same central baryon density, the admixed DM is found to delay the plunge and bounce phases of AIC, and decrease the central density and mass of the proto-neutron star (PNS) produced. The bounce time, central density and PNS mass generally depend on two parameters, the admixed DM mass $M_\mathrm{DM}$ and the ratio between the rotational kinetic and gravitational energies of the inner core at bounce $β_\mathrm{ic,b}$. The emitted GWs have generic waveform shapes and the variation of their amplitudes $h_+$ show a degeneracy on $β_\mathrm{ic,b}$ and $M_\mathrm{DM}$. We found that the ratios between the GW amplitude peaks around bounce allow breaking the degeneracy and extraction of both $β_\mathrm{ic,b}$ and $M_\mathrm{DM}$. Even within the uncertainties of nuclear matter equation of state, a DM core can be inferred if its mass is greater than 0.03 $M_{\odot}$. We also discuss possible DM effects on the GW signals emitted by PNS g-mode oscillations. GW may boost the possibility for the detection of AIC, as well as open a new window in the indirect detection of DM.

astro-ph.HE↗