Periodicity in fast radio bursts due to forced precession by a fallback disk

Recently,a 16-day periodicity in a fast radio burst was reported.We propose that this 16-day periodicity may be due to forced precession of the neutron star by a fallback disk.When the rotation axis is misaligned with respect to the normal direction of the disk plane,the neutron star will precess.The eccentricity of the neutron star may be due to rotation or strong magnetic field,or similar reasons.We found that the 16-day period may be understood using typical masses of the fallback disk.Polarization observations and information about the neutron star rotation period may help to discriminate different models.The possible precession observations in pulsars,magnetars and fast radio bursts may be understood together considering forced precession by a fallback disk.

A quark nova in the wake of a core-collapse supernova:a unifying model for long duration gamma-ray bursts and fast radio bursts

By appealing to a quark nova(QN;the explosive transition of a neutron star to a quark star) in the wake of a core-collapse supernova(CCSN) explosion of a massive star,we develop a unified model for long duration gamma-ray bursts(LGRBs) and fast radio bursts(FRBs).The time delay(years to decades)between the SN and the QN,and the fragmented nature(i.e.,millions of chunks) of the relativistic QN ejecta are key to yielding a robust LGRB engine.In our model,an LGRB light curve exhibits the interaction of the fragmented QN ejecta with turbulent(i.e.,filamentary and magnetically saturated) SN ejecta which is shaped by its interaction with an underlying pulsar wind nebula(PWN).The afterglow is due to the interaction of the QN chunks,exiting the SN ejecta,with the surrounding medium.Our model can fit BAT/XRT prompt and afterglow light curves simultaneously with their spectra,thus yielding the observed properties of LGRBs(e.g.,the Band function and the X-ray flares).We find that the peak luminositypeak photon energy relationship(i.e.,the Yonetoku law),and the isotropic energy-peak photon energy relationship(i.e.,the Amati law) are not fundamental but phenomenological.FRB-like emission in our model results from coherent synchrotron emission(CSE) when the QN chunks interact with non-turbulent weakly magnetized PWN-SN ejecta,where conditions are prone to the Weibel instability.Magnetic field amplification induced by the Weibel instability in the shocked chunk frame sets the bunching length for electrons and pairs to radiate coherently.The resulting emission frequency,luminosity and duration in our model are consistent with FRB data.We find a natural unification of high-energy burst phenomena from FRBs(i.e.,those connected to CCSNe) to LGRBs including X-ray flashes(XRFs) and X-ray rich GRBs(XRR-GRBs) as well as superluminous SNe(SLSNe).We find a possible connection between ultra-high energy cosmic rays and FRBs and propose that a QN following a binary neutron star merger can yield a short duration GRB(SGRB) with fits to BAT/XRT light curves.

Statistical properties of fast radio bursts elucidate their origins:magnetars are favored over gamma-ray bursts

Fast radio bursts(FRBs) are extremely strong radio flares lasting several milliseconds,most of which come from unidentified objects at a cosmological distance.They can be apparently repeating or not.In this paper,we analyzed 18 repeaters and 12 non-repeating FRBs observed in the frequency bands of 400–800 MHz from Canadian Hydrogen Intensity Mapping Experiment(CHIME).We investigated the distributions of FRB isotropic-equivalent radio luminosity,considering the K correction.Statistically,the luminosity distribution can be better fitted by Gaussian form than by power-law.Based on the above results,together with the observed FRB event rate,pulse duration,and radio luminosity,FRB origin models are evaluated and constrained such that the gamma-ray bursts(GRBs) may be excluded for the non-repeaters while magnetars or neutron stars(NSs) emitting the supergiant pulses are preferred for the repeaters.We also found the necessity of a small FRB emission beaming solid angle(about 0.1 sr) from magnetars that should be considered,and/or the FRB association with soft gamma-ray repeaters(SGRs) may lie at a low probability of about 10%.Finally,we discussed the uncertainty of FRB luminosity caused by the estimation of the distance that is inferred by the simple relation between the redshift and dispersion measure(DM).

The Remnant of Neutron Star-White Dwarf Merger and the Repeating Fast Radio Bursts

Fast radio bursts (FRBs) at cosmological distances still hold concealed physical origins. Previously Liu (2018) proposes a scenario that the collision between a neutron star (NS) and a white dwarf (WD) can be one of the progenitors of non-repeating FRBs and notices that the repeating FRBs can also be explained if a magnetar formed after such NS-WD merger. In this paper, we investigate this channel of magnetar formation in more detail. We propose that the NS-WD post-merger, after cooling and angular momentum redistribution, may collapse to either a black hole or a new NS or even remains as a hybrid WDNS, depending on the total mass of the NS and WD. In particular, the newly formed NS can be a magnetar if the core of the WD collapsed into the NS while large quantities of degenerate electrons of the WD compressed to the outer layers of the new NS. A strong magnetic field can be formed by the electrons and positive charges with different angular velocities induced by the differential rotation of the newborn magnetar. Such a magnetar can power the repeating FRBs by the magnetic reconnections due to the crustal movements or starquakes.

Burst Astrophysics

This article proposes an explanation for Fast Radio Bursts (FRBs) and Gamma Ray Bursts (GRBs) through the frames of Hypersphere World-Universe Model (WUM). WUM predicts that the concentration of protons and electrons in Intergalactic Plasma decreases inversely proportional to time and in present epoch equals to . The energy density of Intergalactic Plasma relative to the critical energy density equals to . Time delay of FRBs is calculated through these characteristics. A number of experimental results, including the redshift for FRB 150418, remarkable brightness for FRB 150807, and transient gamma-ray counterpart for FRB 131104 are explained. The distance to FRB 150807 object is predicted to be ~800 Mpc. WUM holds that all macroobjects (galaxies, stars, and planets) contain a core composed of Dark Matter Particles. GRBs are explained as a sum of contributions of multicomponent dark matter annihilation. The spectra of such bursts depend on the composition of the Cores.

周期性重复快速射电暴双星模型再研究

在椭圆轨道的致密双星模型作为周期性重复快速射电暴(Fast Radio Bursts,FRBs)起源的基础上,考虑引力辐射对快速射电暴周期性行为的影响。这个双星系统包含一个具有强偶极磁场的中子星和一个磁化的白矮星。当白矮星充满它的洛希瓣时,物质将通过内拉格朗日点转移到中子星表面。由于角动量守恒,白矮星可能在一次爆发之后被踢开,接着在演化过程中由于引力辐射再次充满洛希瓣,实现再次爆发。这种情况下,快速射电暴的周期对应于双星轨道周期P_(orb),而它与两次质量转移时间间隔Δt之间的关系是能否显现周期性行为的关键因素。很明显,Δt≈P_(orb)或者Δt<P_(orb)是周期性行为显现的必要条件。反之,如果Δt>>P_(orb),周期性将很难观测到。结果表明,只有相对较长周期的快速射电暴才能显示周期性行为,这表明目前仅有的两个周期性快速射电暴都对应于较长的周期是合理的。

快速射电暴光学对应体在中国未来大视场望远镜中的可探测性分析

快速射电暴是近年来发展最快的天文学科之一。理论上,快速射电暴可能存在毫秒到小时时标的光学对应体.快速射电暴光学对应体有可能在中国未来大视场望远镜中探测到,例如:中国空间站工程巡天望远镜(China Space Station Telescope,CSST)、中国科学技术大学和紫金山天文台合作的2.5m大视场巡天望远镜(WideField Survey Telescope,WFST)和地球2.0(Earth 2.0,ET)等。快速射电暴光学对应体通常分为毫秒时标光学对应体、小时时标光学对应体和光学余辉。前两者可产生于快速射电暴的高能外延或是快速射电暴的射电辐射与高能电子的逆康普顿散射,探测率与光学-射电流量比η_(v)关系密切.对于毫秒时标光学对应体,最理想情况下WFST、CSST和ET的探测率可以达到每年上百个.当η_(v)~10^(-3)时,WFST、CSST的年探测率仅为1个的量级,ET的年探测率为19.5个.对于小时时标光学对应体,最理想情况下超新星遗迹的年龄为5年且η_(v)约为10^(-6)时,年探测率可到100以上.FRB200428的X射线对应体表明,快速射电暴可能产生相对论性外流并且与星际介质相互作用产生光学余辉.结合快速射电暴的能量、在宇宙中的分布以及标准余辉模型,可以对快速射电暴余辉的可探测性进行研究.当总能量-射电能量比与FRB200428类似(ζ=10^(5))时,CSST、WFST和ET的年探测率分别为1.3、1.0和67个。

The physics of fast radio bursts

In 2007, a very bright radio pulse was identified in the archival data of the Parkes Telescope in Australia, marking the beginning of a new research branch in astrophysics. In 2013, this kind of millisecond bursts with extremely high brightness temperature takes a unified name, fast radio burst(FRB). Over the first few years, FRBs seemed very mysterious because the sample of known events was limited. With the improvement of instruments over the last five years, hundreds of new FRBs have been discovered.The field is now undergoing a revolution and understanding of FRB has rapidly increased as new observational data increasingly accumulate. In this review, we will summarize the basic physics of FRBs and discuss the current research progress in this area.We have tried to cover a wide range of FRB topics, including the observational property, propagation effect, population study,radiation mechanism, source model, and application in cosmology. A framework based on the latest observational facts is now under construction. In the near future, this exciting field is expected to make significant breakthroughs.

Repeating fast radio bursts: Coherent circular polarization by bunches

Fast radio bursts(FRBs) are millisecond-duration signals that are highly dispersed at distant galaxies. However, the physical origin of FRBs is still unknown. Coherent curvature emission by bunches, e.g., powered by starquakes, has already been proposed for repeating FRBs. It has the nature of understanding narrowband radiation exhibiting time-frequency drifting. Recently, a highly active FRB source, i.e., FRB 20201124A, was reported to enter a newly active episode and emit at least some highly circular-polarized bursts. In this study, we revisit the polarized FRB emission, particularly investigating the production mechanisms of a highly circular polarization(CP) by deriving the intrinsic mechanism and propagative effect. The intrinsic mechanisms of invoking charged bunches are approached with radiative coherence. Consequently, a highly CP could naturally be explained by the coherent summation of outcome waves, generated or scattered by bunches, with different phases and electric vectors. Different kinds of evolutionary trajectories are found on the Poincaré sphere for the bunch-coherent polarization, and this behavior could be tested through future observations. Cyclotron resonance can result in the absorption of R-mode photons at a low altitude region of the magnetosphere, and an FRB should then be emitted from a high-altitude region if the waves have strong linear polarization. Circularly polarized components could be produced from Faraday conversion exhibiting a λ-oscillation, but the average CP fraction depends only on the income wave, indicating a possibility of a highly circular-polarized income wave. The analysis could be welcome if extremely high(e.g., almost 100%) CP from repeating FRBs is detected in the future. Finally, the production of a bulk of energetic bunches in the pulsar-like magnetosphere is discussed, which is relevant to the nature of the FRB central engine.

Scintillation Arc from FRB 20220912A

We present the interstellar scintillation analysis of fast radio burst(FRB)20220912A during its extremely active episode in 2022using data from the Five-hundred-meter Aperture Spherical Radio Telescope(FAST).We detect a scintillation arc in the FRB’s secondary spectrum,which describes the power in terms of the scattered FRB signals’time delay and Doppler shift.The arc indicates that the scintillation is caused by a highly localized region.Our analysis favors a Milky Way origin of the ionized interstellar medium(IISM)for the localized scattering medium but cannot rule out a host galaxy origin.We present our method for detecting the scintillation arc,which can be applied generally to sources with irregularly spaced bursts or pulses.These methods could help shed light on the complex interstellar environment surrounding the FRBs and in our Galaxy.

快速射电暴的观测及理论研究进展

快速射电暴是近几年观测到的一种在射电波段短暂出现的高能天体物理爆发现象。它们的光变曲线通常表现为单个脉冲轮廓,持续时间一般为若干毫秒,大部分峰值流量密度可达到央斯基量级。对快速射电暴研究概况进行了评述,系统描述了快速射电暴的观测进展,介绍了已提出的快速射电暴前身星物理模型及快速射电暴在天体物理领域中的应用等,也对快速射电暴的未来研究进行了展望。

较差转动中子星放大磁场的数值计算与分析

存在较大较差转动角速度的中子星会由于磁冻结效应扭曲内部的径向磁场线,放大出一个超过1013T的环向磁场.这个环向磁场的磁浮力大于与其耦合的粒子的重力,能够携带物质冲出中子星外壳,形成喷发.基于此效应提出了较差转动中子星作为伽马射线暴(GRB)和伽马射线暴早期余辉中X射线耀发能源的两个模型,在不同的初始条件下做了数值计算和分析.根据计算得到的环向磁场的放大速度以及初始条件,指出了这两个模型存在的缺陷,最后提出较差转动中子星可作为快速射电暴(FRB)的能量来源.

快速射电暴脉冲研究进入高统计性时代

快速射电暴(fast radio burst,FRB)是在宇宙空间中发生的持续时标为毫秒量级的射电脉冲信号,瞬时辐射流量峰值可达数十央斯基(Jy),爆发的总能量相当于太阳几天甚至几个月内辐射的总能量.快速射电暴于2007年被Lorimer等人[1]首次发现并报道之后,经历了初期的真实性质疑.