arXiv subjects

Y. H. Zhu

Publications and source records attributed to Y. H. Zhu.

6 recordsLinked to original sources

arXiv2026

A sudden dramatic change and recovery of magneto-environment of a repeating fast radio burst

Fast radio bursts (FRBs) are millisecond-duration radio bursts with unidentified extra-galactic origin. Some FRBs exhibit mild magneto-ionic environmental variations, possibly attributed to plasma turbulence or binary configuration. We report an abrupt magneto-ionic variation of FRB 20220529, a repeating FRB from a disk galaxy at redshift $0.1839 \pm 0.0001$. Initially, the Faraday rotation measure (RM) had a median of $17~{\rm rad~m^{-2}}$ and a scatter of $101~{\rm rad~m^{-2}}$ over 17 months. In December 2023, it jumped to $1977 \pm 84~{\rm rad~m^{-2}}$, and returned to typical values within two weeks. This drastic RM variation suggests that a dense magnetized clump enters and exits the line of sight in week timescales. One plausible scenario invokes a coronal mass ejection from a companion star, while other scenarios invoking extreme turbulence or binary orbital motion are also possible.

astro-ph.HE↗

arXiv2025

Decadal evolution of a repeating fast radio burst source

The origin of fast radio bursts (FRBs), the brightest cosmic radio explosions, is still unknown. Bearing critical clues to FRBs' origin, the long-term evolution of FRBs has yet to be confirmed, since the field is still young and most FRBs were seen only once. Here we report clear evidence of decadal evolution of FRB~20121102A, the first precisely localized repeater. In conjunction with archival data, our FAST and GBT monitoring campaign since 2020 reveals a significant 7% decline of local dispersion measure (DM). The rotation measure (RM) of 30,755$\pm$16 $\mathrm{rad\,m^{-2}}$ detected in the last epoch represents a 70% decrease compared to that from December 2016. The $σ_{RM}$ parameter, which describes the complexity of the magneto-ionic environment surrounding the source, was shown to have decreased by 13%. These general trends reveal an evolving FRB environment, which could originate from an early-phase supernova associated with an enhanced pair wind from the FRB central engine.

astro-ph.HE↗

arXiv2024

Sudden polarization angle jumps of the repeating fast radio burst FRB 20201124A

We report the first detection of polarization angle (PA) orthogonal jumps, a phenomenon previously only observed from radio pulsars, from a fast radio burst (FRB) source FRB 20201124A. We find three cases of orthogonal jumps in over two thousand bursts, all resembling those observed in pulsar single pulses. We propose that the jumps are due to the superposition of two orthogonal emission modes that could only be produced in a highly magnetized plasma, and they are caused by the line of sight sweeping across a rotating magnetosphere. The shortest jump timescale is of the order of one-millisecond, which hints that the emission modes come from regions smaller than the light cylinder of most pulsars or magnetars. This discovery provides convincing evidence that FRB emission originates from the complex magnetosphere of a magnetar, suggesting an FRB emission mechanism that is analogous to radio pulsars despite a huge luminosity difference between two types of objects.

astro-ph.HE↗

arXiv2014

Thermoelectric properties of Sr0.61Ba0.39Nb2O6-δ ceramics annealed in different oxygen-reduction conditions

The thermoelectric properties of Sr0.61Ba0.39Nb2O6 ceramics, reduced in different conditions, were investigated in the temperature region from 323 K to 1073 K. The electrical transport behaviors of the samples are dominated by the thermal-activated polaron hopping, the Fermi glass behavior, and the Anderson localized behavior from low temperatures to high temperatures, respectively. The lattice thermal conductivity presents a plateau at high temperatures, indicating a glass-like thermal conduction behavior. Both the thermoelectric power factor and the thermal conductivity increase with the increasing degree of oxygen-reduction. Taking these two factors into account, the oxygen-reduction can still contribute to promoting the thermoelectric figure of merit. The highest ZT value (~0.19 at 1073 K) is obtained in the heaviest oxygen reduced sample.

cond-mat.mtrl-sci↗

arXiv2011

System-size scan of dihadron azimuthal correlations in ultra-relativistic heavy ion collisions

System-size dependence of dihadron azimuthal correlations in ultra-relativistic heavy ion collision is simulated by a multi-phase transport model. The structure of correlation functions and yields of associated particles show clear participant path-length dependences in collision systems with a partonic phase. The splitting parameter and root-mean-square width of away-side correlation functions increase with collision system size from $^{14}$N+$^{14}$N to $^{197}$Au+$^{197}$Au collisions. The double-peak structure of away-side correlation functions can only be formed in sufficient "large" collision systems under partonic phase. The contrast between the results with partonic phase and with hadron gas could suggest some hints to study onset of deconfinment.

nucl-th↗

arXiv2010

Collision system size dependence of dihadron azimuthal correlations in ultra-relativistic heavy ion collisions

The system size dependence of dihadron azimuthal correlations in ultra-relativistic heavy ion collision is simulated by a multi-phase transport model. The structure of correlation functions and yields of associated particles show clear participant path-length dependences in collision systems with a partonic phase. The splitting parameter ($D$) and Root Mean Square Width ($Δϕ_{rms}$) of away side correlation functions increase with collision system size from $^{14}$N+$^{14}$N to $^{197}$Au+$^{197}$Au collisions. The double-peak structure of away side correlation functions can only be formed in sufficient "large" collision systems. These properties provide some hints to study onset of deconfinement, which is related to the QCD phase boundary and QCD critical point, by an energy-size scan.

nucl-th↗