Chen-Chen Miao, Victoria Blackmon, Wei-Wei Zhu, Dong-Zi Li, Mingyu Ge, Xiao-Peng You, Maura McLaughlin, Di Li, Na Wang, Pei Wang, Jia-Rui Niu, M. Cruces, Jian-Ping Yuan, Jun-Tao Bai, D. J. Champion, Yu-Tong Chen, Ming-Min Chi, P. C. C. Freire, Yi Feng, Zhen-Ye Gan, M. Kramer, Fei-Fei Kou, Yu-Xi Li, Xue-Li Miao, Ling-Qi Meng, Chen-Hui Niu, Sheng-Nan Sun, Zhong-Yi Sun, H. M. Tedila, Shuang-Qiang Wang, Qing-Dong Wu, Jing-Bo Wang, Zhi-Gang Wen, Shen Wang, Ya-Biao Wang, Cheng-Jie Wang, Meng-Yao Xue, You-Ling Yue, Mao Yuan, Ju-Mei Yao, Wen-Ming Yan, Ru-Shuang Zhao, Lei Zhang, De Zhao
We report the radio observations of the eclipsing black widow pulsar J1720-0534, a 3.26 ms pulsar in orbit with a low mass companion of mass 0.029 to 0.034 M$_{\odot}$. We obtain the phase-connected timing ephemeris and polarization profile of this millisecond pulsar (MSP) using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST), the Green Bank Telescope (GBT), and the Parkes Telescope. For the first time from such a system, an oscillatory polarisation angle change was observed from a particular eclipse egress with partial depolarization, indicating 10-milliGauss-level reciprocating magnetic fields oscillating in a length scale of 5000 km (assuming an orbital inclination angle of 90 degrees) outside the companion's magnetosphere. The dispersion measure variation observed during the ingresses and egresses shows the rapid raising of the electron density in the shock boundary between the companion's magnetosphere and the surrounding pulsar wind. We suggest that the observed oscillatory magnetic fields originate from the pulsar wind outside the companion's magnetosphere.
Weining Weng, Yang Gu, Shuai Guo, Yuan Ma, Zhaohua Yang, Yuchen Liu, Yiqiang Chen
Electroencephalogram (EEG) is a non-invasive technique to record bioelectrical signals. Integrating supervised deep learning techniques with EEG signals has recently facilitated automatic analysis across diverse EEG-based tasks. However, the label issues of EEG signals have constrained the development of EEG-based deep models. Obtaining EEG annotations is difficult that requires domain experts to guide collection and labeling, and the variability of EEG signals among different subjects causes significant label shifts. To solve the above challenges, self-supervised learning (SSL) has been proposed to extract representations from unlabeled samples through well-designed pretext tasks. This paper concentrates on integrating SSL frameworks with temporal EEG signals to achieve efficient representation and proposes a systematic review of the SSL for EEG signals. In this paper, 1) we introduce the concept and theory of self-supervised learning and typical SSL frameworks. 2) We provide a comprehensive review of SSL for EEG analysis, including taxonomy, methodology, and technique details of the existing EEG-based SSL frameworks, and discuss the difference between these methods. 3) We investigate the adaptation of the SSL approach to various downstream tasks, including the task description and related benchmark datasets. 4) Finally, we discuss the potential directions for future SSL-EEG research.
Lingqi Meng, Weiwei Zhu, Michael Kramer, Xueli Miao, Gregory Desvignes, Lijing Shao, Huanchen Hu, Paulo C. C. Freire, Yongkun Zhang, Mengyao Xue, Ziyao Fang, David J. Champion, Mao Yuan, Chenchen Miao, Jiarui Niu, Qiuyang Fu, Jumei Yao, Yanjun Guo, Chengmin Zhang
Mar 26, 2024·astro-ph.HE·PDF We observe systematic profile changes in the visible pulsar of the compact double neutron star system PSR~J1946+2052 using observations with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The interpulse of PSR~J1946+2052 changed from single-peak to double-peak shape from 2018 to 2021. We attribute this evolution as the result of the relativistic spin precession of the pulsar. With the high sensitivity of FAST, we also measure significant polarization for the first time, allowing us to model this with the precessional rotating vector model. Assuming, to the first order, a circular hollow-cone-like emission beam pattern and taking the validity of general relativity, we derive the binary's orbital inclination angle (${63^\circ}^{+5^\circ}_{-3^\circ}$) and pulsar's spin geometry. Pulsar's spin vector and the orbital angular momentum vector are found to be only slightly misaligned (${0.21^\circ}^{+0.28^\circ}_{-0.10^\circ}$).The quoted uncertainties do not reflect the systematic uncertainties introduced by our model assumptions. By simulating future observations of profile and polarization evolution, we estimate that we could constrain the precession rate within a $43\%$ uncertainty in 9 years. Hence, we suggest that the system's profile evolution could be combined with precise pulsar timing to test general relativity in the future.
Yi Feng, Di Li, Yong-Kun Zhang, Chao-Wei Tsai, Wei-Yang Wang, Yuan-Pei Yang, Yuanhong Qu, Pei Wang, Dengke Zhou, Jiarui Niu, Chenchen Miao, Mao Yuan, Jiaying Xu, Ryan S. Lynch, Will Armentrout, Brenne Gregory, Lingqi Meng, Shen Wang, Xianglei Chen, Shi Dai, Chen-Hui Niu, Mengyao Xue, Ju-Mei Yao, Bing Zhang, Junshuo Zhang, Weiwei Zhu, Yuhao Zhu
Apr 28, 2023·astro-ph.HE·PDF Fast radio bursts (FRBs) are bright radio bursts originating at cosmological distances. Only three repeating FRBs FRB 20121102A, FRB 20190520B and FRB 20201124A among $\sim$ 60 known repeating FRBs have circular polarization. We observed the FRB 20220912A with the Robert C. Byrd Green Bank Telescope (GBT) at L-band on 24 October 2022 and detected 128 bursts in 1.4 hours, corresponding to a burst rate of about 90 hr$^{-1}$, which is the highest yet for FRBs observed by the GBT. The average rotation measure (RM) was $-$0.4$\pm$0.3$\,$rad$\,$m$^{-2}$ with negligible intraday RM change, indicating a likely non-magneto-ionic environment. 61% bursts have linear polarization fraction greater than 90%. Approximately 56% of the bright bursts have circular polarization. A downward drift in frequency and polarization angle swings were found in our sample. The characterization of FRB 20220912A indicates that the circular polarization is unlikely to be caused by the magneto-ionic environment for at least some of the repeating FRB population.
Xuefeng Jiang, Yuan Ma, Pengxiang Li, Leimeng Xu, Xin Wen, Kun Zhan, Zhongpu Xia, Peng Jia, Xianpeng Lang, Sheng Sun
In recent years, diffusion models have demonstrated remarkable potential across diverse domains, from vision generation to language modeling. Transferring its generative capabilities to modern end-to-end autonomous driving systems has also emerged as a promising direction. However, existing diffusion-based trajectory generative models often exhibit mode collapse where different random noises converge to similar trajectories after the denoising process.Therefore, state-of-the-art models often rely on anchored trajectories from pre-defined trajectory vocabulary or scene priors in the training set to mitigate collapse and enrich the diversity of generated trajectories, but such inductive bias are not available in real-world deployment, which can be challenged when generalizing to unseen scenarios. In this work, we investigate the possibility of effectively tackling the mode collapse challenge without the assumption of pre-defined trajectory vocabulary or pre-computed scene priors. Specifically, we propose TransDiffuser, an encoder-decoder based generative trajectory planning model, where the encoded scene information and motion states serve as the multi-modal conditional input of the denoising decoder. Different from existing approaches, we exploit a simple yet effective multi-modal representation decorrelation optimization mechanism during the denoising process to enrich the latent representation space which better guides the downstream generation. Without any predefined trajectory anchors or pre-computed scene priors, TransDiffuser achieves the PDMS of 94.85 on the closed-loop planning-oriented benchmark NAVSIM, surpassing previous state-of-the-art methods. Qualitative evaluation further showcases TransDiffuser generates more diverse and plausible trajectories which explore more drivable area.
Pei Wang, Jian Li, Long Ji, Xian Hou, Erbil Gugercinoglu, Di Li, Diego F. Torres, Yutong Chen, Jiarui Niu, Weiwei Zhu, Bing Zhang, En-wei Liang, Li Zhang, Mingyu Ge, Zigao Dai, Lin Lin, Jinlin Han, Yi Feng, Chenhui Niu, Yongkun Zhang, Dengjiang Zhou, Heng Xu, Chunfeng Zhang, Jinchen Jiang, Chenchen Miao, Mao Yuan, Weiyang Wang, Youling Yue, Yunsheng Wu, Yabiao Wang, Chengjie Wang, Zhenye Gan, Yuxi Li, Zhongyi Sun, Mingmin Chi
Aug 17, 2023·astro-ph.HE·PDF Magnetars are neutron stars with extremely strong magnetic fields, frequently powering high-energy activity in X-rays. Pulsed radio emission following some X-ray outbursts have been detected (\citealt{Camilo2006,camilo2007a}), albeit its physical origin is unclear. It has long been speculated that the origin of magnetars' radio signals is different from those from canonical pulsars, although convincing evidence is still lacking. Five months after magnetar SGR 1935+2154's X-ray outburst and its associated Fast Radio Burst (FRB) 20200428, a radio pulsar phase was discovered. Here we report the discovery of X-ray spectral hardening associated with the emergence of periodic radio pulsations from SGR 1935+2154 and a detailed analysis of the properties of the radio pulses. The observations suggest that radio emission originates from the outer magnetosphere of the magnetar, and the surface heating due to the bombardment of inward-going particles from the radio emission region is responsible for the observed X-ray spectral hardening.
Zhi Jun Wang, Di Gao, Kai Kai Zhang, Yuan Yuan Ma, Yan Jun Sun
Hadronic electromagnetic form factors and radiative decay properties offer a crucial window into the nonperturbative dynamics of Quantum chromodynamics (QCD). In this work, we employ the light-cone sum rules (LCSR) method to systematically investigate the M1 radiative decay of vector mesons. Our study covers processes including $K^{*-}\rightarrow K^-γ$, $D^*\rightarrow Dγ$, $B^*\rightarrow Bγ$, $D^{*+}_s\rightarrow D^+_sγ$, and $B_s^*\rightarrow B_sγ$, and further extends to the excited charmonium state $ψ(2S)$. Our calculations yield decay widths for $K^*$ and $ψ(2S)$ that are in excellent agreement with experimental data. For the charm and bottom meson decays, where precise measurements are lacking, we provide theoretical predictions and compare them with other theoretical approaches. Most notably, our analysis reveals a universal linear dependence of the decay width on a function A(x) in the logarithmic coordinate system, which originates from the two-body decay dynamics and the ratio of the initial and final state decay constants. This relationship holds for the ground state $V \rightarrow P γ$ processes here and suggests a broader applicability to radiative decays of ground-state vector mesons.
Yan-Wei Xie, Jing-Bo Wang, George Hobbs, Di Li, Jie Zhang, Shi Dai, Andrew Cameron, Jane Kaczmarek, Lei Zhang, Chenchen Miao, Mao Yuan, Shen Wang, Songbo Zhang, Renxin Xu
Flux density measurements provide fundamental observational parameters that describe a pulsar. In the current pulsar catalogue, 27% of radio pulsars have no flux density measurement in the 20 cm observing band. Here, we present the first measurements of the flux densities in this band for 32 pulsars observed using the Parkes radio telescope and provide updated pulse profiles for these pulsars. We have used both archival and new observations to make these measurements. Various schemes exist for measuring flux densities. We show how the flux densities measured vary between these methods and how the presence of radio-frequency-interference will bias flux density measurements
Lei Zhang, George Hobbs, Richard N. Manchester, Di Li, Pei Wang, Shi Dai, Jingbo Wang, Jane F. Kaczmarek, Andrew D. Cameron, Lawrence Toomey, Weiwei Zhu, Qijun Zhi, Chenchen Miao, Mao Yuan, Songbo Zhang, Zhenzhao Tao
Oct 26, 2019·astro-ph.HE·PDF We report the first wideband observations of pulsars C, D and J in the globular cluster 47Tucanae (NGC 104) using the Ultra-Wideband Low (UWL) receiver system recently installed on the Parkes 64 m radio telescope. The wide frequency range of the UWL receiver (704-4032 MHz), along with the well-calibrated system, allowed us to obtain flux density measurements and polarization pulse profiles. The mean pulse profiles have significant linear and circular polarization, allowing for determination of the Faraday rotation measure for each pulsar. Precise measurements of the dispersion measures show a significant deviation in the value for pulsar D compared to earlier results. Searches for new pulsars in the cluster are on-going and we have determined optimal bands for such searches using the Parkes UWL receiver system.
Xiaofei Li, Yu Wang, Xin Liu, Yuan Ma, Yangjian Cai, Sergey A. Ponomarenko, Xianlong Liu
Having shown early promise, free-space optical communications (FSO) face formidable challenges in the age of information explosion. The ever-growing demand for greater channel communication capacity is one of the challenges. The inter-channel crosstalk, which severely degrades the quality of transmitted information, creates another roadblock in the way of efficient FSO implementation. Here we advance theoretically and realize experimentally a potentially high-capacity FSO protocol that enables high-fidelity transfer of an image, or set of images through a complex environment. In our protocol, we complement random light structuring at the transmitter with a deep learning image classification platform at the receiver. Multiplexing novel, independent, mutually orthogonal degrees of freedom available to structured random light can potentially significantly boost the channel communication capacity of our protocol without introducing any deleterious crosstalk. Specifically, we show how one can multiplex the degrees of freedom associated with the source coherence radius and a spatial position of a beamlet within an array of structured random beams to greatly enhance the capacity of our communication link. The superb resilience of structured random light to environmental noise, as well as extreme efficiency of deep learning networks at classifying images guarantees high-fidelity image transfer within the framework of our protocol.
Tao Yang, Yuan Ma, Peng Zhang
Small-scale flickering buoyant diffusion flames in externally swirling flows were computationally investigated with a particular interest in identifying and characterizing various distinct dynamical behaviors of the flame oscillators under different swirling flow conditions. By varying the external swirl, six distinct flame dynamical modes, such as the flickering flame, the oscillating flame, the steady flame, the lifted flame, the spiral flame, and the flame with a vortex bubble, were computationally identified in both physical and phase spaces and analyzed from the perspective of vortex dynamics. Specifically, the frequency of buoyancy-induced flame flicker nonlinearly increases with the swirling intensity in the weak swirl regime. Further increasing the swirling intensity causes the vortex shedding to occur either around the flame tip or downstream of the flame, and the flame stops flickering but oscillates with small amplitude or stays in a steady state. A sufficiently high swirling intensity locally extinguishes the flame at its base, leading to a lifted flame. In addition, the spiral mode and the vortex-bubble mode were found for the flame at large swirl angles. Through establishing the phase portrait for featuring the flow in flames, the dynamical behaviors are presented and compared in phase space.
Yi Feng, Di Li, Yuan-Pei Yang, Yongkun Zhang, Weiwei Zhu, Bing Zhang, Wenbin Lu, Pei Wang, Shi Dai, Ryan S. Lynch, Jumei Yao, Jinchen Jiang, Jiarui Niu, Dejiang Zhou, Heng Xu, Chenchen Miao, Chenhui Niu, Lingqi Meng, Lei Qian, Chao-Wei Tsai, Bojun Wang, Mengyao Xue, Youling Yue, Mao Yuan, Songbo Zhang, Lei Zhang
Feb 19, 2022·astro-ph.HE·PDF The polarization of fast radio bursts (FRBs), bright astronomical transients, contains crucial information about their environments. We report polarization measurements of five repeating FRBs, the abundant signals of which enable wide-band observations with two telescopes. A clear trend of lower polarization at lower frequencies was found, which can be well characterized by a single parameter rotation-measure-scatter (σRM) and modeled by multi-path scatter. Sources with higher σRM have higher RM magnitude and scattering timescales. The two sources with the most substantial σRM, FRB 20121102A and FRB 20190520B, are associated with a compact persistent radio source. These properties indicate a complex environment near the repeating FRBs, such as a supernova remnant or a pulsar wind nebula, consistent with their arising from young populations.
Yi Feng, George Hobbs, Di Li, Shi Dai, Weiwei Zhu, Youling Yue, Pei Wang, Songbo Zhang, Lei Qian, Lei Zhang, Shuangqiang Wang, Chenchen Miao, Mao Yuan, Yongkun Zhang
Dec 12, 2020·astro-ph.HE·PDF Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we have recorded 10^5 single pulses from PSR J1022+1001. We studied the polarization properties, their energy distribution and their times of arrival. This is only possible with the high sensitivity available using FAST. There is no indication that PSR~J1022+1001 exhibits giant pulse, nulling or traditional mode changing phenomena. The energy in the leading and trailing components of the integrated profile is shown to be correlated. The degree of both linear and circular polarization increases with the pulse flux density for individual pulses. Our data indicates that pulse jitter leads to an excess noise in the timing residuals of 67 ns when scaled to one hour, which is consistent with Liu et al. (2015). We have unsuccessfully trialled various methods to improve timing precision through the selection of specific single pulses. Our work demonstrates that FAST can detect individual pulses from pulsars that are observed in order to detect and study gravitational waves. This capability enables detailed studies, and parameterisation, of the noise processes that affect the sensitivity of a pulsar timing array.
Xuezhi Ma, Yuan Ma, Preston Cunha, Qiushi Liu, Kaushik Kudtarkar, Da Xu, Jiafei Wang, Ming Liu, M. Cynthia Hipwell, Shoufeng Lan
Resonance is instrumental in modern optics and photonics for novel phenomena such as cavity quantum electrodynamics and electric-field-induced transparency. While one can use numerical simulations to sweep geometric and material parameters of optical structures, these simulations usually require considerably long calculation time (spanning from several hours to several weeks) and substantial computational resources. Such requirements significantly limit their applicability in understanding and inverse designing structures with desired resonance performances. Recently, the introduction of artificial intelligence allows for faster predictions of resonance with less demanding computational requirements. However, current end-to-end deep learning approaches generally fail to predict resonances with high quality-factors (Q-factor). Here, we introduce a universal deep learning strategy that can predict ultra-high Q-factor resonances by decomposing spectra with an adaptive data acquisition (ADA) method while incorporating resonance information. We exploit bound states in the continuum (BICs) with an infinite Q-factor to testify this resonance-informed deep learning (RIDL) strategy. The trained RIDL strategy achieves high-accuracy prediction of reflection spectra and photonic band structures while using a considerably small training dataset. We further develop an inverse design algorithm based on the RIDL strategy for a symmetry-protected BIC on a suspended silicon nitride photonic crystal (PhC) slab. The predicted and measured angle-resolved band structures show minimum differences. We expect the RIDL strategy to apply to many other physical phenomena which exhibit Gaussian, Lorentzian, and Fano resonances.
Rui Kang, Yixiong Liang, Chunyan Lian, Yuan Mao
The urine sediment analysis of particles in microscopic images can assist physicians in evaluating patients with renal and urinary tract diseases. Manual urine sediment examination is labor-intensive, subjective and time-consuming, and the traditional automatic algorithms often extract the hand-crafted features for recognition. Instead of using the hand-crafted features, in this paper, we exploit CNN to learn features in an end-to-end manner to recognize the urine particles. We treat the urine particles recognition as object detection and exploit two state-of-the-art CNN-based object detection methods, Faster R-CNN and SSD, as well as their variants for urine particles recognition. We further investigate different factors involving these CNN-based object detection methods for urine particles recognition. We comprehensively evaluate these methods on a dataset consisting of 5,376 annotated images corresponding to 7 categories of urine particles, i.e., erythrocyte, leukocyte, epithelial cell, crystal, cast, mycete, epithelial nuclei, and obtain a best mAP (mean average precision) of 84.1% while taking only 72 ms per image on a NVIDIA Titan X GPU.
Yin Kang, Weiyi Yin, Xianzhe Li, Yixuan Liu, Yue Wang, Yuan Ma, Kaiqing Zhang, Chao Feng
High-power multi-color terahertz (THz) radiation exhibits extraordinary scientific application prospects at various scientific frontiers, for its capacity to deliver THz excitation at multiple frequencies simultaneously. However, the generation of high-power multi-color THz radiation with tunable frequencies remains a challenge for existing techniques. Here, a technique by combining the multi-laser pulses frequency beating and coherent undulator amplification is proposed for generating high-power multi-color THz radiation with tunable frequency. Numerical simulations indicate that the proposed technique can produce multi-color THz radiation with three to six distinguished colors and a peak power up to hundreds of MW, and the temporally separated two-color pulses can also be produced by employing undulators with different resonance. Due to the intrinsic properties of the proposed technique, the THz frequencies, the color number and the frequency interval can be effectively controlled by simply adjusting the beating laser. This method paves the way for advanced application of THz pump-THz probe experiments for selective excitation of atomic multi-level systems and molecular fingerprint recognition.
Jin-Tao Xie, Yi Feng, Di Li, Yong-Kun Zhang, Dengke Zhou, Yuanhong Qu, Xianghan Cui, Jianhua Fang, Jiaying Xu, Chenchen Miao, Mao Yuan, Chao-Wei Tsai, Pei Wang, Chen-Hui Niu, Xiang-Lei Chen, Mengyao Xue, Jun-Shuo Zhang
Oct 14, 2024·astro-ph.HE·PDF Fast radio bursts (FRBs) are transient radio bursts of extragalactic origin characterized by millisecond durations and high luminosities. We report on observations of FRB 20240114A conducted with the Robert C. Byrd Green Bank Telescope (GBT) at frequencies ranging from 720 to 920 MHz. A total of 437 bursts were detected, with a single observation recording 365 bursts over 1.38 hours, corresponding to a burst rate of 264 bursts per hour. The average rotation measures (RMs) were $347.0 \pm 1.0$ rad m$^{-2}$ on February 23, 2024, and $353.7 \pm 0.6$ rad m$^{-2}$ on March 1, 2024. Of the 301 bursts with detected RMs, 81% have a linear polarization fraction greater than 90%, and 14% exhibit circular polarization with a signal-to-noise ratio $> 5$. Our sample also displayed polarization angle swings. We compared the linear polarization fraction of FRB~20240114A with those of the repeating sources FRB~20201124A and FRB~20220912A. Our analysis reveals that all three exhibit similar distributions in both linear and circular polarization fractions. These results indicate that the three sources share the same radiation mechanism. We analyze the fluence and waiting-time distributions of FRB~20240114A, revealing a right-skewed fluence distribution and a bimodal waiting-time structure, suggesting intrinsic emission timescales and potential multiple burst populations. Additionally, We present a novel method to determine the frequency range of bursts based on their spectral characteristics. This algorithm is independent of spectral models and remains unaffected by the removal of interference-affected channels in the data, ensuring robust performance.
Hao Jiang, Zhi-Ming Lu, Yuan Ma, Kai Leong Chong
The modulation of drag through dispersed phases in wall turbulence has been a longstanding focus. This study examines the effects of particle Stokes number ($St$) and Froude number ($Fr$) on drag modulation in turbulent Taylor-Couette (TC) flow, using a two-way coupled Eulerian-Lagrangian approach with Reynolds number $Re_i = r_i ω_i d/ν$ fixed at 3500. For light particles (small $St$), drag reduction is observed in the TC system, exhibiting a non-monotonic dependence on $Fr$. In specific, drag reduction initially increases and then decreases with stronger influence of gravitational settling (characterized by inverse of $Fr$), indicating the presence of an optimal $Fr$ for maximum drag reduction. For heavy particles, similar non-monotonic trend can also be observed, but significant drag enhancement is resulted at large $Fr^{-1}$. We further elucidate the role of settling particles in modulating the flow structure in TC by decomposing the advective flux into contributions from coherent Taylor vortices and background turbulent fluctuations. At moderate effects of particle inertia and gravitational settling, particles suppress the coherence of Taylor vortices which remarkably reduces angular velocity transport and thus leads to drag reduction. However, with increasing influence of particle inertia and gravitational settling, the flow undergoes abrupt change. Rapidly settling particles disrupt the Taylor vortices, shifting the bulk flow from a vortex-dominated regime to one characterized by particle-induced turbulence. With the dominance by particle-induced turbulence, velocity plumes -- initially transported by small-scale G{ö}rtler vortices near the cylinder wall and large-scale Taylor vortices in bulk region -- are instead carried into the bulk by turbulent fluctuations driven by the settling particles.
Lingqi Meng, Paulo C. C. Freire, Kevin Stovall, Norbert Wex, Xueli Miao, Weiwei Zhu, Michael Kramer, James M. Cordes, Huanchen Hu, Jinchen Jiang, Emilie Parent, Lijing Shao, Ingrid H. Stairs, Mengyao Xue, Adam Brazier, Fernando Camilo, David J. Champion, Shami Chatterjee, Fronefield Crawford, Ziyao Fang, Qiuyang Fu, Yanjun Guo, Jason W. T. Hessels, Maura MacLaughlin, Chenchen Miao, Jiarui Niu, Ziwei Wu, Jumei Yao, Mao Yuan, Youlin Yue, Chengmin Zhang
Oct 14, 2025·astro-ph.HE·PDF We conducted high-precision timing of PSR J1946+2052 to determine the masses of the two neutron stars in the system, test general relativity (GR) and assessed the system's potential for future measurement of the moment of inertia of the pulsar. We analysed seven years of timing data from the Arecibo 305-m radio telescope, the Green Bank Telescope (GBT), and the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The data processing accounted for dispersion measure variations and relativistic spin precession-induced profile evolution. We employed both DDFWHE and DDGR binary models to measure the spin parameters, kinematic parameters and orbital parameters. The timing campaign has resulted in the precise measurement of five post-Keplerian parameters, which yield very precise masses for the system and three tests of general relativity. One of these is the second most precise test of the radiative properties of gravity to date: the intrinsic orbital decay, $\dot{P}_{\rm b,int}=-1.8288(16)\times10^{-12}\rm\,s\,s^{-1}$, represents $1.00005(91)$ of the GR prediction, indicating that the theory has passed this stringent test. The other two tests, of the Shapiro delay parameters, have precisions of 6\% and 5\% respectively; this is caused by the moderate orbital inclination of the system, $\sim 74^{\circ}$; the measurements of the Shapiro delay parameters also agree with the GR predictions. Additionally, we analysed the higher-order contributions of $\dotω$, including the Lense-Thirring contribution. Both the second post-Newtonian and the Lense-Thirring contributions are larger than the current uncertainty of $\dotω$ ($δ\dotω=4\times10^{-4}\,\rm deg\,yr^{-1}$), leading to the higher-order correction for the total mass.
Weiwei Zhu, Heng Xu, Dejiang Zhou, Lin Lin, Bojun Wang, Pei Wang, Chunfeng Zhang, Jiarui Niu, Yutong Chen, Chengkui Li, Lingqi Meng, Kejia Lee, Bing Zhang, Yi Feng, Mingyu Ge, Ersin Göğüş, Xing Guan, Jinlin Han, Jinchen Jiang, Peng Jiang, Chryssa Kouveliotou, Di Li, Chenchen Miao, Xueli Miao, Yunpeng Men, Chenghui Niu, Weiyang Wang, Zhengli Wang, Jiangwei Xu, Renxin Xu, Mengyao Xue, Yuanpei Yang, Wenfei Yu, Mao Yuan, Youling Yue, Shuangnan Zhang, Yongkun Zhang
Jul 30, 2023·astro-ph.HE·PDF The megajansky radio burst, FRB 20200428, and other bright radio bursts detected from the Galactic source SGR J1935+2154 suggest that magnetars can make fast radio bursts (FRBs), but the emission site and mechanism of FRB-like bursts are still unidentified. Here we report the emergence of a radio pulsar phase of the magnetar five months after FRB 20200428. 795 pulses were detected in 16.5 hours over 13 days by the Five-hundred-meter Aperture Spherical Radio telescope, with luminosities about eight decades fainter than FRB 20200428. The pulses were emitted in a narrow phase window anti-aligned with the X-ray pulsation profile observed by the X-ray telescopes. The bursts, conversely, appear in random phases. This dichotomy suggests that radio pulses originate from a fixed region within the magnetosphere, but bursts occur in random locations and are possibly associated with explosive events in a dynamically evolving magnetosphere. This picture reconciles the lack of periodicity in cosmological repeating FRBs within the magnetar engine model.