arXiv subjects

Yu-Jia Wei

Publications and source records attributed to Yu-Jia Wei.

11 recordsLinked to original sources

arXiv2025

Unveiling Multimessenger Emission from Hidden Cores of Microquasars

Microquasars are radio-emitting X-ray binaries accompanied by relativistic jets. They are established sources of 100~TeV gamma rays and are considered promising candidates for cosmic-ray acceleration. Motivated by recent detections of $\sim 100~$TeV photons from Cygnus~X-1 and $\sim~$PeV photons from Cygnus~X-3 by the Large High Altitude Air Shower Observatory (LHAASO), we employ the Astrophysical Multimessenger Emission Simulator (AMES) to model their multimessenger emission considering compact outflow regions as cosmic-ray accelerators, spanning from radio to ultra-high-energy gamma rays. Our results show that the observed $>$TeV gamma rays can originate from either $pγ$ or $pp$ interactions, depending on the location and physical conditions of the emission region, while also reproducing the lower-energy spectra. The different configurations yield unique, observationally testable predictions. In the $0.1-10$~TeV energy range, where current observations provide only upper limits, they predict either a deep dip, a mild suppression, or a power-law spectrum. Additionally, models involving AU-scale blob regions predict strong variability, while those invoking more extended and static external zones show more stable behavior. We also provide a possible qualitative explanation for the distinct modulation patterns across different energy bands, which relies primarily on changes in the Doppler factor and external $γγ$ absorption. Finally, our neutrino predictions, which properly account for muon and pion cooling effects, reveal a significantly suppressed flux, indicating that detecting these sources may be more challenging than previously anticipated.

astro-ph.HE↗

arXiv2025

Probable evidence for a transient mega-electron volt emission line in the GRB 221023A

Detection of spectral line in gamma-ray bursts (GRBs) is importance for studying GRB physics, as it provides insights into the composition and physical conditions of the GRB environment. However, progress in detecting X-ray or gamma-ray emission and absorption lines in GRB spectra has been relatively slow, only the narrow emission line feature of about 10 MeV found in GRB 221009A has exhibited a significance exceeding $5 σ$. Here, we report the probable evidence of a narrow emission feature at about 2.1 mega-electron volts (MeV) in the spectrum of GRB 221023A. The highest statistical significance of this feature is observed in the time interval between 8 and 30 seconds after Fermi Gamma-Ray Burst Monitor trigger, with the chance probability value $<2.56 \times 10^{-5}$ (after accounting for the look-elsewhere effect), corresponding to a Gaussian-equivalent significance $> 4.20 σ$. We interpret this feature as being generated through the de-excitation of excited electrons in the relativistic hydrogen-like high-atomic-number ions entrained in the GRB jet.

astro-ph.HE↗

arXiv2024

Multiwavelength Radiation from the Interaction between Magnetar Bursts and Companion Star in a Binary System

Magnetars are young, highly magnetized neutron stars that are associated with magnetar short bursts (MSBs), magnetar giant flares (MGFs), and at least some fast radio bursts (FRBs). In this work, we consider a magnetar and a main sequence star in a binary system and analyze the properties of the electromagnetic signals generated by the interaction between the magnetar bursts and the companion star. During the preburst period, persistent radiation could be generated by the interaction between the $e^+e^-$-pair wind from the magnetar and the companion or its stellar wind. We find that for a newborn magnetar, the persistent preburst radiation from the strong magnetar wind can be dominant, and it is mainly at the optical and ultraviolet (UV) bands. For relatively old magnetars, the re-emission from a burst interacting with the companion is larger than the persistent preburst radiation and the luminosity of the companion itself. The transient re-emission produced by the heating process has a duration of $0.1 - 10^5 {\rm~s}$ at the optical, UV, and X-ray bands. Additionally, we find that if these phenomena occur in nearby galaxies within a few hundred kiloparsecs, they could be detected by current or future optical telescopes.

astro-ph.HE↗

arXiv2024

A Novel Model for the MeV Emission Line in GRB 221009A

Gamma-ray bursts (GRBs) have long been considered potential sources of ultra-high-energy cosmic rays (UHECRs; with energy $\gtrsim 10^{18} {\rm~eV}$). In this work, we propose a novel model generating MeV emission lines in GRB, which can constrain the properties of heavy nuclei that potentially exist in GRB jets. Specifically, we find that relativistic hydrogen-like high-atomic-number ions originating from the $β$ decay of unstable nuclei and/or the recombination entrained in the GRB jet can generate narrow MeV emission lines through the de-excitation of excited-electrons. This model can successfully explain the MeV emission line observed in the most luminous GRB ever recorded, GRB~221009A, with suitable parameters including a Lorentz factor $γ\sim 820-1700$ and a total mass of heavy nuclei $M_{\rm tot} \sim 10^{23} - 10^{26}$~g. Especially, the emission line broadening can be reasonably attributed to both the expansion of the jet shell and the thermal motion of nuclei, naturally resulting in a narrow width ($σ_{\rm line} / E_{\rm line} \lesssim 0.2$) consistent with the observation. Furthermore, we predict that different GRBs can exhibit lines in different bands with various evolving behaviors, which might be confirmed with further observations. Finally, our model provides indirect evidence that GRBs may be one of the sources of UHECRs.

astro-ph.HE↗

arXiv2024

The physical origin of the periodic activity for FRB 20180916B

Fast radio bursts (FRBs) are transient radio signals with millisecond-duration, large dispersion measure (DM) and extremely high brightness temperature. Among them, FRB 20180916B has been found to have a 16-day periodically modulated activity. However, the physical origin of the periodicity is still a mystery. Here, we utilize the comprehensive observational data to diagnose the periodic models. We find that the ultra-long rotation model is the most probable one for the periodic activity. However, this model cannot reproduce the observed rotation measure (RM) variations. We propose a self-consistent model, i.e., a massive star binary containing a slowly rotational neutron star and a massive star with large mass loss, which can naturally accommodate the wealth of observational features for FRB 20180916B. In this model, the RM variation is periodic, which can be tested by future observations.

astro-ph.HE↗

arXiv2024

GRB 231115A: a nearby Magnetar Giant Flare or a cosmic Short Gamma-Ray Burst?

There are two classes of gamma-ray transients with a duration shorter than 2 seconds. One consists of cosmic short Gamma-Ray Bursts (GRBs) taking place in the deep universe via the neutron star mergers, and the other is the magnetar giant flares (GFs) with energies of $\sim 10^{44}-10^{46}$ erg from ``nearby" galaxies. Though the magnetar GFs and the short GRBs have rather similar temporal and spectral properties, their energies ($E_{\rm γ,iso}$) are different by quite a few orders of magnitude and hence can be distinguished supposing the host galaxies have been robustly identified. The newly observed GRB 231115A has been widely discussed as a new GF event for its high probability of being associated with M82. Here we conduct a detailed analysis of its prompt emission observed by Fermi-GBM, and compare the parameters with existing observations. The prompt gamma-ray radiation properties of GRB 231115A, if associated with M82, nicely follow the $E_{\rm p,z}-E_{γ,\rm iso}$ relation of the GFs, where $E_{\rm p,z}$ is the peak energy of the gamma-ray spectrum after the redshift ($z$) correction. To be a short GRB, the reshift needs to be $\sim 1$. Though such a chance is low, the available X-ray/GeV observation upper limits are not stringent enough to further rule out this possibility. We have also discussed the prospect of convincingly establishing the magnetar origin of GRB 231115A-like events in the future.

astro-ph.HE↗

arXiv2017

Quantum State Transfer from a Single Photon to a Distant Quantum-Dot Electron Spin

Quantum state transfer from flying photons to stationary matter qubits is an important element in the realization of quantum networks. Self-assembled semiconductor quantum dots provide a promising solid-state platform hosting both single photon and spin, with an inherent light-matter interface. Here, we develop a method to coherently and actively control the single-photon frequency bins in superposition using electro-optic modulators, and measure the spin-photon entanglement with a fidelity of $0.796\pm0.020$. Further, by Greenberger-Horne-Zeilinger-type state projection on the frequency, path and polarization degrees of freedom of a single photon, we demonstrate quantum state transfer from a single photon to a single electron spin confined in an InGaAs quantum dot, separated by 5 meters. The quantum state mapping from the photon's polarization to the electron's spin is demonstrated along three different axis on the Bloch sphere, with an average fidelity of $78.5\%$.

quant-ph↗

arXiv2017

Optical positioning of single quantum dots in micropillar with >65% extraction efficiency for on-demand quantum light sources

We report optical positioning single quantum dots (QDs) in planar cavity with an average position uncertainty $<$20 nm using an optimized two-color photoluminescence imaging technique. We create single-photon sources based on these QDs in determined micropillar cavities. The brightness of the QD fluorescence is greatly enhanced on resonance with the fundamental mode of the cavity, leading to an high extraction efficiency of 68%$\pm$6% into a lens with numerical aperture of 0.65, and simultaneously exhibiting low multi-photon probability ($g^{2}(0)$=0.144$\pm$0.012) at this collection efficiency.

quant-ph↗

arXiv2014

Temperature-dependent Mollow triplet spectra from a single quantum dot: Rabi frequency renormalisation and sideband linewidth insensitivity

We investigate temperature-dependent resonance fluorescence spectra obtained from a single self-assembled quantum dot. A decrease of the Mollow triplet sideband splitting is observed with increasing temperature, an effect we attribute to a phonon-induced renormalisation of the driven dot Rabi frequency. We also present first evidence for a non-perturbative regime of phonon coupling, in which the expected linear increase in sideband linewidth as a function of temperature is cancelled by the corresponding reduction in Rabi frequency. These results indicate that dephasing in semiconductor quantum dots may be less sensitive to changes in temperature than expected from a standard weak-coupling analysis of phonon effects.

cond-mat.mes-hall↗

arXiv2014

Deterministic and Robust Generation of Single Photons On a Chip with 99.5% Indistinguishability Using Rapid Adiabatic Passage

We demonstrate deterministic and robust generation of pulsed resonance fluorescence single photons from a single InGaAs quantum dot using the method of rapid adiabatic passage. Comparative study is performed with transform-limited, negatively chirped and positively chirped pulses, identifying the last one to be the most robust against fluctuation of driving strength. The generated single photons are background free, have a vanishing two-photon emission probability of 0.3% and a raw (corrected) two-photon Hong-Ou-Mandel interference visibility of 97.9% (99.5%), reaching a precision that places single photons at the threshold for fault-tolerant surface-code quantum computing. The single-photon source can be readily scaled up to multi-photon entanglement and used for quantum metrology, boson sampling and linear optical quantum computing.

quant-ph↗

arXiv2013

On-demand semiconductor single-photon source with near-unity indistinguishability

Single photon sources based on semiconductor quantum dots offer distinct advantages for quantum information, including a scalable solid-state platform, ultrabrightness, and interconnectivity with matter qubits. A key prerequisite for their use in optical quantum computing and solid-state networks is a high level of efficiency and indistinguishability. Pulsed resonance fluorescence (RF) has been anticipated as the optimum condition for the deterministic generation of high-quality photons with vanishing effects of dephasing. Here, we generate pulsed RF single photons on demand from a single, microcavity-embedded quantum dot under s-shell excitation with 3-ps laser pulses. The pi-pulse excited RF photons have less than 0.3% background contributions and a vanishing two-photon emission probability. Non-postselective Hong-Ou-Mandel interference between two successively emitted photons is observed with a visibility of 0.97(2), comparable to trapped atoms and ions. Two single photons are further used to implement a high-fidelity quantum controlled-NOT gate.

quant-ph↗