太阳射电分米波尖峰辐射和米波射电爆发

本文分析了云南天文台四波段快速采样射电望远镜在1990年1月至1991年3月间记录到的毫秒级尖峰辐射事件。结合此期间S.G.D.公布的米波射电大爆发资料,给出了毫秒级尖峰辐射的各种特征,总结出毫秒级尖峰辐射同Ⅲ型、Ⅱ型和Ⅳ型太阳射电爆发的关系,最后做出了相应的解释和讨论。     

1998年4月15日微波爆发观测

北京天文台１ ．０２ ．０ＧＨｚ 太阳射电频谱仪从１９９４ 年开始观测至１９９８ 年９ 月记录到太阳射电爆发１７１ 个,２ ．６３ ．８ＧＨｚ 太阳射电频谱仪１９９６ 年９ 月投入观测至１９９８ 年９ 月,记录到１４６ 个太阳射电爆发。１９９８ 年４ 月１５ 日太阳射电爆发同时在这两台频谱仪上记录到。这个事件在时间和频率上显示了丰富的幅度和结构的变化。发现了微波Ⅲ型爆发对群,并存在着丰富的快速活动现象。取得了高时间分辨率、高质量的动态谱资料,为研究耀斑各种尺度的时间及空间演化过程提供了丰富的信息。     

FAST漂移扫描观测:快速射电暴信号模拟与模拟样本

快速射电暴(fast radio burst, FRB)是一种发生在毫秒时标的射电爆发现象。观测发现,它们很可能来自银河系外,对研究致密天体并合、星际介质、宇宙大尺度结构等有着重要意义。中国新近建成的500 m口径球面射电望远镜(Five-hundred-meter Aperture Spherical Telescope, FAST)是世界上最大的单天线射电望远镜,其多波束漂移扫描观测有望在快速射电暴观测方面作出贡献。针对FAST的漂移扫描观测模式,开展了多种参数和分布下的快速射电暴模拟,构建了下述快速射电暴的样本:一个是对快速射电暴在射电观测参数空间进行模拟获得的样本;一个是根据快速射电暴本身距离(红移)与色散之间可能存在的关系,进行物理参数空间模拟获得的样本。每个样本均有50 000个模拟的快速射电暴信号,它们不仅可用来检验应用于FAST巡天扫描观测的快速射电暴搜寻算法的探测效率,还可以用来研究FAST漂移扫描观测和各类快速射电暴搜寻算法的选择效应,从而有可能从实际快速射电暴探测结果反推快速射电暴的内禀物理性质和分布。获得的快速射电暴样本对重复快速射电暴观测和数据分析具有借鉴意义。     

快速射电暴的数据统计

快速射电暴于2007年首次在脉冲星巡天的历史数据中被发现,是一种在射电波段观测到的具有色散量的单个强脉冲,其特征为持续时间仅为若干毫秒,峰值流量密度可达到央斯基量级。类似于射电脉冲星的单个脉冲,但其色散显著超过同一视线方向上银河系内星际介质的预期最大值。对截止2018年6月帕克斯望远镜、绿岸望远镜、阿雷西博射电望远镜、UTMOST望远镜和ASKAP望远镜已探测到的52例快速射电暴进行了观测量统计分析,根据模型扣除银河系星际介质导致的色散量后,快速射电暴平均色散量为584.5 pc·cm^-3,暗示着快速射电暴来自河外。通过最佳拟合估算红移幂律分布谱dN/dF_obs=4.14±1.30×F■sky^-1·day^-1。根据分析结果预计,FAST望远镜使用19波束接收机后,其多科学目标同时巡天在经过一年时间内能发现大约10个快速射电暴,将有效地扩大样本数量,为快速射电暴研究提供重要信息。     

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。     

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\lk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\lk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(Wide Field 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$\eta_\nu$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$\eta_\nu$~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$\eta_\nu$约为10^-6时, 年探测率可到100以上. FRB 200428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FRB 200428类似(ζ = 10⁵)时, CSST、WFST和ET的 年探测率分别为1.3、1.0和67个.     

1997年昆明日偏食射电快速过程的观测

介绍了１９９７年３月９日昆明日偏食过程中云南天文台四波段射电高时间分辨率同步观测结果,通过掩食和露放黑子前后射电快速起伏率的变化现象,推测日冕缓变源存在电子加速过程,它可能对射电快速起伏率的增强有贡献。     

太阳分米波射电快速精细结构的观测分析

通过分析云南天文台(YNO)0.7～1.5GHz太阳射电频谱仪2000年9月至2001年9月取得的158个射电爆发,发现其中约有65%存在4类不同类型的快速精细结构(FFS):毫秒尖峰辐射、Ⅲ型爆发、准周期脉动、慢漂移结构。给出了其中6个典型精细结构的介绍和相关的初步解释。     

1997年昆明日偏食射电快速过程的观测

介绍了１９９７年３月９日昆明日食偏过程中云南天文台四波段射电高时间分辨率同步观测结果,通过掩食和露放黑子前后射电快速起伏率的变化现象,推测日冕缓变源存在电子加速过程,它可能对射电快速起伏率的增强有贡献。     

太阳分米波射电快速精细结构的观测分析

通过分析云南天文台（YNO）0.7～1.5GHz太阳射电频谱仪2000年9月至2001年9月取得的158个射电爆发、发现其中约有65%存在4类不同类型的快速精细结构（FFS）；毫秒类峰辐射、Ⅲ型爆发、准周期脉动，慢漂移结构。给出了其中6个典型精细结构的介绍和相关的初步解释。     

Observational Characteristics of Radio Emission Related to Multi-polar Magnetic Configuration

We present a, large complex radio burst and its associated fast tune structures observed on 2001 April 10 in the frequency range of 0.65-7.6 GHz. The NoRH radio image observation shows very complex radio source structures which include preexisting, newly emerging, submerging/cancelling polarities and a bipolar, a tripolar (a 'bipolar + remote unipolar'), and a quadrupolar structure. This suggests that the radio burst is generated from a very complicated loop structure. According to the spectral and image observations, we assume that the beginning of this flare was caused by a single bipolar loop configuration with a 'Y-type' re-connection structure. A composite of radio continuum and fast time structures is contained in this flare. The various fast radio emission phenomena include normal and reverse drifting type III bursts, and slowly drifting and no-drift structures. The tripolar configurations may form a double-loop with a 'three-legged' structure, which is an important source of the various types of fast time structures. The two-loop reconnection model can lead simultaneously to electron acceleration and corona heating. We have also analyzed the behaviors of coronal magnetic polarities and the emission processes of different types radio emission qualitatively. Interactions of a bipolar or multi-polar loop are consistent with our observational results. Our observations favor the magnetic reconnection configurations of the 'inverted Y-type' (bipolar) and the 'three-legged' structures (tripolar or quadrupolar).     

Fast solar electrons,interplanetary plasma and km-wave type-III radio bursts observed from the IMP-6 spacecraft

IMP-6 spacecraft observations of low frequency radio emission, fast electrons, and solar wind plasma are used to examine the dynamics of the fast electron streams which generate solar type-III radio bursts. Of twenty solar electron events observed between April, 1971 and August, 1972, four were found to be amenable to detailed analysis. Observations of the direction of arrival of the radio emission at different frequencies were combined with the solar wind density and velocity measurements at 1 AU to define an Archimedean spiral trajectory for the radio burst exciter. The propagation characteristics of the exciter and of the fast electrons observed at 1 AU were then conpared. We find that: (1) the fast electrons excite the radio emission at the second harmonic; (2) the total distance travelled by the electrons was between 30 and 70% longer than the length of the smooth spiral defined by the radio observations; (3) this additional distance travelled is the result of scattering of the electrons in the interplanetary medium; (4) the observations are consistent with negligible true energy loss by the fast electrons.     

太阳射电快速精细结构的日面分布

对云南天文台“四波段太阳射电高时间分辨率同步观测系统”自１９８９年１２月—１９９４年１月期间观测到的１００个射电爆发和与其共生的２９个快速精细结构在日球和日面的经度分布做了统计,并做了初步的分析和讨论。     

关于太阳射电快速活动真伪信号识别问题

本文列举了云南天文台四波段太阳射电实测中得到的几种干扰实例及确认的太阳快速信号，在认识到太阳射电和干扰信号十分相似的基础上，探讨如何识别真伪信号问题。     

Radio observations of the planetary nebula around the OH/IR star OH 354.88-0.54 (V1018 Sco)

We present radio observations of the unique, recently formed, planetary nebula (PN) associated with a very long-period OH/IR variable star V1018 Sco that is unequivocally still in its asymptotic giant branch phase. Two regions within the optical nebula are clearly detected in non-thermal radio continuum emission, with radio spectral indices comparable to those seen in colliding-wind Wolf–Rayet binaries. We suggest that these represent shocked interactions between the hot, fast stellar wind and the cold nebular shell that represents the PN's slow wind moving away from the central star. This same interface produces both synchrotron radio continuum and the optical PN emission. The fast wind is neither spherical in geometry nor aligned with any obvious optical or radio axis. We also report the detection of transient H₂O maser emission in this nebula.     

Analysis of spike emission data at 2545/2645 MHz in the peak year of the 22nd solar cycle

We briefly discuss the observed features including the high flux density, short duration, narrow emission band, fast frequency drift, quasi-periodic oscillation and fast variation of polarized components, of 51 spike emission events observed at 2545/2645 MHz in the solar activity peak year, 1991 January–December, and carry out correlation analysis between these events and optical flares, magnetic field intensity and configuration of flare regions, and sunspot evolution types of active regions. In view of the fact that the observed and statistical characteristics of the spike emissions are very different from those of known types of solar radio burst and known solar radio components, we think that the spike emission in the peak years is probably a new type of radio burst excited by electron cyclotron maser instability under wave-particle resonance, or a new solar radio component.     

Interpretation of a special fine structure in type-IV solar radio bursts

A special fine structure (slowly drifting chains of narrowband fiber bursts), firstly observed during the solar type-IV radio burst on April 24, 1985, is interpreted as the radio signature of whistler waves periodically excited by a switch-on/switch-off process of a loss-cone instability in a localized wave packet of the fast magnetoacoustic mode.     

Effects of the distribution function of non-thermal electrons and of cyclotron resonant absorption on millisecond radio spikes

A theoretical analysis of electron-cyclotron maser instabilities indicates that the distribution function of non-thermal electrons influences millisecond radio spikes in solar flares, and that a hollow beam distribution is more likely than a loss-cone distribution. The restrictions of classical theories of cyclotron resonant absorption are discussed and a formula is derived for the absorption coefficient near the resonant frequency. Finally, the computations show that for typical coronal parameters, the growth rates of the fundamental of fast extraordinary modes are much faster than those of their second harmonics; and because the directional angle of the fundamental is smaller, its resonant absorption may be neglected. Moreover, the band-width of the fundamental is consistent with observation of radio spikes; therefore, we claim that the millisecond radio spikes in the decimetric range are composed mainly of fundamentals of the fast extraordinary modes. The second harmonics of fast extraordinary modes may be generated for directions near to the vertical to the magnetic field, but it is impossible to observe both fundamental and second harmonics in the same direction.     

Fast Radio Bursts

We summarize our current state of knowledge of fast radio bursts (FRBs) which were first discovered a decade ago. Following an introduction to radio transients in general, including pulsars and rotating radio transients, we discuss the discovery of FRBs. We then discuss FRB follow-up observations in the context of repeat bursts before moving on to review propagation effects on FRB signals, FRB progenitor models and an outlook on FRBs as potential cosmological tools.     

Modeling fast radio burst heating a main-sequence companion star in a close binary using MESA

The exact origin of fast radio bursts (FRBs) remains a mystery. The repeating fast radio burst source, FRB20200120E, was discovered in a globular cluster containing old stellar populations. Yang (2021) suggested that this FRB might be in close binaries with low-mass main-sequence (MS) stars. They analytically investigated the observational consequences caused by the heating of FRB radio radiation onto the low-mass MS companion star in a close binary, suggesting that the radio radiation emitted by FRB could make the MS companion star more luminous and detectable in future multi-wavelength follow-up observations for a Galactic FRB. We revisited the study of Yang (2021) by numerically modeling the detailed process of FRB heating onto an MS companion with 1D stellar evolution code Modules for Experiments in Stellar Astrophysics (MESA). Our results are consistent with the trends derived from the analytical model of Yang (2021), except that the typical re-emission luminosities of our main sequence (MS) models, caused by the heating from FRBs, are generally dimmer by about two orders of magnitude compared to his findings, and our models have a longer re-emission timescale. This may indicate that the searches of the optical transients caused by the radio radiation heating companion star are more likely to be successful within a distance of 0.3 Mpc.