In less than a decade, fast radio bursts have gone from a single debated curiosity to a diverse extragalactic population with established host galaxies and energy scales. While a wide range of models remain viable, the central engines of FRBs are likely to involve energetic young magnetars, as confirmed by the recent discovery of a Galactic analog to these extragalactic bursts. Here we provide a brief introductory review of fast radio bursts, focusing on the rapid recent progress in observations of these enigmatic events, our understanding of their central engines, and their use as probes of the intergalactic medium. We caution against a rush to judgement on the mechanisms and classification of all FRBs: at this point, it remains plausible that there could be one dominant central engine, as well as the possibility that radio bursts are a generic feature produced by many different mechanisms. We also emphasize the importance of improved modeling of our Galaxy and Galactic halo, which otherwise impose systematic errors on every FRB line of sight. The future of science with fast radio bursts appears bright.
More than a decade after their discovery, astronomical Fast Radio Bursts remain enigmatic. They are known to occur at "cosmological" distances, implying large energy and radiated power, extraordinarily high brightness and coherent emission. Yet their source objects, the means by which energy is released and their radiation processes remain unknown. This review is organized around these unanswered questions.
We briefly review main observational properties of fast radio bursts (FRBs) and discuss two most popular hypothesis for the explanation of these enigmatic intense millisecond radio flashes. FRBs most probably originate on extragalactic distances, and their rate on the sky is about a few thousand per day with fluences above $\sim$~1~Jy~ms (or with fluxes larger than few tenths of Jy). Two leading scenarios describing these events include strong flares of magnetars and supergiant pulses of young radio pulsars with large rotational energy losses, correspondingly. At the moment, it is impossible t…
The recent development of sensitive, high time resolution instruments at radio telescopes has enabled the discovery of millisecond duration fast radio bursts (FRBs). The FRB class encompasses a number of single pulses, many unique in their own way, so far hindering the development of a consensus for their origin. The key to demystifying FRBs lies in discovering many of them in realtime in order to localise them and identity commonalities. Despite rigorous follow-up, only one FRB has been seen to repeat suggesting the possibility of there being two independent classes of FRBs and thus two class…
It is now more than 40 years since the discovery of gamma-ray bursts (GRBs) and in the last two decades there has been major progress in the observations of bursts, the afterglows and their host galaxies. This recent progress has been fueled by the ability of gamma-ray telescopes to quickly localise GRBs and the rapid follow-up observations with multi-wavelength instruments in space and on the ground. A total of 674 GRBs have been localised to date using the coded aperture masks of the four gamma-ray missions, BeppoSAX, HETE II, INTEGRAL and Swift. As a result there are now high quality observ…
The nature of fast radio bursts (FRBs) remains enigmatic. Highly energetic radio pulses of millisecond duration, FRBs are observed with dispersion measures consistent with an extragalactic source. A variety of models have been proposed to explain their origin. One popular class of theorized FRB progenitor is the coalescence of compact binaries composed of neutron stars and/or black holes. Such coalescence events are strong gravitational-wave emitters. We demonstrate that measurements made by the LIGO and Virgo gravitational-wave observatories can be leveraged to severely constrain the validity…
A Brief Review on the Statistical Properties of Fast Radio Bursts
Center for Gravitation and Cosmology, College of Physical Science and Technology, Yangzhou University（扬州大学物理科学与技术学院引力与宇宙学中心）；Department of Physics, Chongqing University（重庆大学物理系）
Currently, FRB 121102 is the only fast radio burst source that was observed to give out bursts repeatedly. It shows a high repeating rate, with more than one hundred bursts being spotted, but with no obvious periodicity in the activities. Thanks to its repetition, the source was well localized with a subarcsecond accuracy, leading to a redshift measurement of about 0.2. FRB 121102 is a unique source that can help us understand the enigmatic nature of fast radio bursts. In this study, we analyze the characteristics of the waiting times between bursts from FRB 121102. It is found that there is a…
Fast Radio Bursts (FRBs) are bright enigmatic radio pulses of roughly millisecond duration that come from extragalactic distances. As part of the MeerTRAP project, we use the MeerKAT telescope array in South Africa to search for and localise those bursts to high precision in real-time. We aim to pinpoint FRBs to their host galaxies and, thereby, to understand how they are created. However, the transient nature of FRBs presents various challenges, e.g. in system design, raw compute power and real-time communication, where the real-time requirements are reasonably strict (a few tens of seconds).…
The discovery of a fast radio burst (FRB) in our galaxy associated with a magnetar (neutron star with strong magnetic field) has provided a critical piece of information to help us finally understand these enigmatic transients. We show that the volumetric rate of Galactic-FRB like events is consistent with the faint end of the cosmological FRB rate, and hence they most likely belong to the same class of transients. The Galactic FRB had an accompanying X-ray burst but many X-ray bursts from the same object had no radio counterpart. Their relative rates suggest that for every FRB there are rough…
Fast radio bursts (FRB) are enigmatic powerful single radio pulses with durations of several milliseconds and high brightness temperatures suggesting coherent emission mechanism. For the time being a number of extragalactic FRBs have been detected in the high-frequency radio band including repeating ones. The most plausible explanation for these phenomena is magnetar hyperflares. The first observational evidence of this scenario was obtained in April 2020 when an FRB was detected from the direction of the Galactic magnetar and soft gamma repeater SGR1935+2154. The FRB was preceded with a numbe…
The highest brightness temperature ever observed are from "nanoshots" from the Crab pulsar which we argue could be the signature of bursts of vacuum $e^{\pm}$ pair production. If so this would be the first time the astronomical Schwinger effect has been observed. These "Schwinger sparks" would be an intermittent but extremely powerful, $\sim 10^3 L_{\astrosun}$, 10 PeV $e^{\pm}$ accelerator in the heart of the Crab. These nanosecond duration sparks are generated in a volume less than $1 m^3$ and the existence of such sparks has implications for the small scale structure of the magnetic field o…
Fast radio bursts (FRBs) are an emerging class of short and bright radio transients whose sources remain enigmatic. Within the galactic center, the non-detection of pulsars within the inner $\sim \!10\,{\rm pc}$ has created a missing pulsar problem that has intensified with time. With all reserve, we advance the notion that the two problems could be linked by a common solution: the collapse of neutron stars (NS) due to capture and sedimentation of dark matter (DM) within their cores. Bramante \& Linden (2014), Phys.\ Rev.\ Lett.~19, 191301 showed that certain DM properties allow for rapid NS c…
Recent polarization measurements of fast radio bursts (FRBs) provide new insights on these enigmatic sources. We show that the nearly 100% linear polarization and small variation of the polarization position angles (PAs) of multiple bursts from the same source suggest that the radiation is produced near the surface of a strongly magnetized neutron star. As the emitted radiation travels through the magnetosphere, the electric vector of the X-mode wave adiabatically rotates and stays perpendicular to the local magnetic field direction. The PA freezes at a radius where the plasma density becomes …
The millisecond-duration radio flashes known as Fast Radio Bursts (FRBs) represent an enigmatic astrophysical phenomenon. Recently, the sub-arcsecond localization (~ 100mas precision) of FRB121102 using the VLA has led to its unambiguous association with persistent radio and optical counterparts, and to the identification of its host galaxy. However, an even more precise localization is needed in order to probe the direct physical relationship between the millisecond bursts themselves and the associated persistent emission. Here we report very-long-baseline radio interferometric observations u…
Indian Institute of Science Education and Research Thiruvananthapuram（印度科学教育研究所特里凡得琅分校）；Department of Physics and Astronomy, University of California, Riverside（加州大学河滨分校物理与天文系）；Department of Astronomy, University of California Berkeley（加州大学伯克利分校天文系）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Physik-Institut, University of Zurich（苏黎世大学物理学院）
Fast radio bursts (FRBs) are an enigmatic class of extragalactic transients emitting Jy-level radio bursts in the GHz band, lasting for only a few ms. So far, some objects are known to repeat while several others are not, likely indicating multiple origins. There are many theoretical models, some predict prompt VHE or optical emission correlated with FRBs while others imply VHE afterglows hours after the FRB. To test these predictions and unravel the nature of FRB progenitors, the stereoscopic Imaging Atmospheric Cherenkov Telescopes (IACTs) system MAGIC has been participating in FRB observati…
Cosmological evolution of fast radio bursts and its rapid decline relative to star formation rate
School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；School of Physics and Physical Engineering, Qufu Normal University（曲阜师范大学物理工程学院）；Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, China（教育部现代天文学与天体物理重点实验室（南京大学））
Fast radio bursts (FRBs) are short (millisecond) radio pulses originating from enigmatic sources at extragalactic distances so far lacking a detection in other energy bands. Magnetized neutron stars (magnetars) have been considered as the sources powering the FRBs, but the connection is controversial because of differing energetics and the lack of radio and X-ray detections with similar characteristics in the two classes. We report here the detection by the AGILE satellite on April 28, 2020 of an X-ray burst in coincidence with the very bright radio burst from the Galactic magnetar SGR 1935+21…
Fast radio bursts (FRBs) are enigmatic transients with very short radio emission. Their nature is still widely debated. I provide the first analysis of atomic gas properties of a small sample of FRB hosts to constrain their nature. HI observations exist for NGC 3252, the host of FRB 181030A, M81, the host of FRB 200120E, and the Milky Way, the host of FRB 200428. I report three observables: i) all three FRB hosts are interacting galaxies; ii) the Hi spectra of both FRB hosts with such data available are highly asymmetric, several standard deviations above the general population of galaxies; ii…
GECAM discovery of a peculiar magnetar X-ray burst (MXB 221120) from SGR J1935+2154 associated with a fast radio burst
State Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所粒子天体物理国家重点实验室）；University of Chinese Academy of Sciences, Chinese Academy of Sciences（中国科学院大学）；College of Physics and Hebei Key Laboratory of Photophysics Research and Application, Hebei Normal University（河北师范大学物理学院河北省光物理研究与应用重点实验室）；College of Electronic and Information Engineering, Tongji University（同济大学电子与信息工程学院）；Department of Nuclear Science and Technology, School of Energy and Power Engineering, Xi’an Jiaotong University（西安交通大学能源与动力工程学院核科学与技术系）；Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）；Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences（中国科学院天体结构与演化重点实验室）；Department of Astronomy, Peking University（北京大学天文学系）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Beijing Laser Acceleration Innovation Center, Huairou, Beijing（北京激光加速创新中心）；School of Physical Science and Technology, Southwest Jiaotong University（西南交通大学物理科学与技术学院）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；School of Physics and Electronic Science, Guizhou Normal University（贵州师范大学物理与电子科学学院）；Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing, Guizhou Normal University（贵州师范大学贵州省射电天文与数据处理重点实验室）；Institute of Astrophysics, Central China Normal University（华中师范大学天体物理研究所）
Fast Radio Bursts (FRBs) are intense, millisecond-duration broadband radio transients, the emission mechanisms of which are not understood. Masui et al. recently presented Green Bank Telescope observations of FRB 110523, which displayed temporal variation of the linear polarisation position angle (PA). This effect is commonly seen in radio pulsars and is attributed to a changing projected magnetic field orientation in the emission region as the star rotates. If a neutron star is the progenitor of this FRB, and the emission mechanism is pulsar-like, we show that the progenitor is either rapidly…
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…
The field of Fast Radio Burst (FRB) science is currently thriving and growing rapidly. The lines of active investigation include theoretical and observational aspects of these enigmatic millisecond radio signals. These pursuits are for the most part intertwined so that each keeps the other in check, characteristic of the healthy state of the field. The immediate future for FRB science is full of promise --- we will in the next few years see two orders of magnitude more FRBs discovered by the now diverse group of instruments spread across the globe involved in these efforts. This increased crop…
Despite their different nature and physics, blazars and gamma-ray bursts have in common very powerful relativistic jets, which make them the most luminous sources in the Universe. The energy extraction from the central compact object, the jet collimation, the role and geometry of the magnetic fields, the structure of the jet itself represent still big enough questions, that a complete paradigm cannot yet be drawn. This article is concerned with the main observational facts about blazars and gamma-ray burst jets, based on multi-wavelength campaigns, and on the clues one can glean from these on …
The recent progress in the understanding the physical nature of neutron star equilibrium configurations and the first observational evidence of a genuinely short gamma-ray burst, GRB 090227B, allows to give an estimate of the gravitational waves versus the X and Gamma-ray emission in a short gamma-ray burst.
We present the first interferometric detections of Fast Radio Bursts (FRBs), an enigmatic new class of astrophysical transient. In a 180-day survey of the Southern sky we discovered 3 FRBs at 843 MHz with the UTMOST array, as part of commissioning science during a major ongoing upgrade. The wide field of view of UTMOST ($\approx 9$ deg$^{2}$) is well suited to FRB searches. The primary beam is covered by 352 partially overlapping fan-beams, each of which is searched for FRBs in real time with pulse widths in the range 0.655 to 42 ms, and dispersion measures $\leq$2000 pc cm$^{-3}$. Detections …
The various stages of baryonic gamma-ray burst afterglow blast waves are reviewed. These are responsible for the afterglow emission from which much of our understanding of gamma-ray bursts derives. Initially, the blast waves are confined to the dense medium surrounding the burster (stellar envelope or dense wind), giving rise to a jet-cocoon structure. A massive ejecta is released and potentially fed by ongoing energy release from the burster and a forward-reverse shock system is set up between ejecta and ambient density. Ultimately the blast wave spreads sideways and slows down, and the domin…
At the time of defining the science objectives of the INTernational Gamma-Ray Astrophysics Laboratory (INTEGRAL), such a rapid and spectacular development of multi-messenger astronomy could not have been predicted, with new impulsive phenomena becoming accessible through different channels. Neutrino telescopes have routinely detected energetic neutrino events coming from unknown cosmic sources since 2013. Gravitational wave detectors opened a novel window on the sky in 2015 with the detection of the merging of two black holes and in 2017 with the merging of two neutron stars, followed by signa…
A second-scale periodicity in an active repeating fast radio burst source
School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education（现代天体学与天体物理学教育部重点实验室（南京大学））；Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；School of Physics and Astromoy, Anqing Normal University（安庆师范大学物理与天文学院）；Institute of Astronomy and Astrophysics, Anqing Normal University（安庆师范大学天体物理研究所）；Guizhou Provincial Laboratory of Big Data, College of Big Data and Information Engineering, Guizhou University（贵州大学大数据与信息工程学院贵州省大数据重点实验室）；Xinjiang Astronomical Observatory, Chinese Academy of Sciences（中国科学院新疆天文台）；State Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences（中国科学院射电天文与技术国家重点实验室）；Xinjiang Key Laboratory of Radio Astrophysics（新疆射电天文重点实验室）；College of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）
The dispersion measure (DM)--redshift relation of fast radio bursts (FRBs) has been proposed as a potential new tool for probing intergalactic medium (IGM) and for studying cosmology. However, the poor knowledge of the baryon fraction in the IGM ($f_{\mathrm{IGM}}$) and its degeneracy with cosmological parameters impose restrictions on the cosmological applications of FRBs. Furthermore, DMs contributed by the IGM ($\mathrm{DM_{IGM}}$) and host galaxy ($\mathrm{DM_{host}}$), important cosmological quantities, cannot be exactly extracted from observations, which would bring uncontrolled systemat…
Due to differing gravitational potentials and path lengths, gravitational lensing induces time delays between multiple images of a source which, for solar mass objects, is of order $\sim10^{-5}$ seconds. If an astrophysically compact source, such as a Fast Radio Burst (FRB), is observed through a region with a high optical depth of such microlensing masses, this gravitational lensing time delay can be imprinted on short timescale transient signals. In this paper, we consider the impact of the parity of the macroimage on the resultant microlensing time delays. It is found that this parity is di…
Boasting supreme magnetic strengths, magnetars are among the prime candidates to generate fast radio bursts. Several theories have been proposed for the formation mechanism of magnetars, but have not yet been fully tested. As different magnetar formation theories expect distinct magnetar space velocity distributions, high-precision astrometry of Galactic magnetars can serve as a probe for the formation theories. In addition, magnetar astrometry can refine the understanding of the distribution of Galactic magnetars. This distribution can be compared against fast radio bursts (FRBs) localized in…
Fast Luminous Extragalactic Transients in the VLA Sky Survey: Implications for the rates of Accretion-Induced Collapse Events, Fast Blue Optical Transients and Gamma Ray Burst Afterglows
The era of fast radio bursts (FRBs) was open in 2007, when a very bright radio pulse of unknown origin was discovered occasionally in the archival data of Parkes Telescope. Over the past fifteen years, this mysterious phenomenon have caught substantial attention among the scientific community and become one of the hottest topic in high-energy astrophysics. The total number of events has a dramatic increase to a few hundred recently, benefiting from new dedicated surveys and improved observational techniques. Our understanding of these bursts has been undergoing a revolutionary growth with obse…
This review focuses on the physics of Gamma Ray Bursts probed through their radio afterglow emission. Even though radio band is the least explored of the afterglow spectrum, it has played an important role in the progress of GRB physics, specifically in confirming the hypothesized relativistic effects. Currently radio astronomy is in the beginning of a revolution. The high sensitive Square Kilometer Array (SKA) is being planned, its precursors and pathfinders are about to be operational, and several existing instruments are undergoing upgradation. Thus, the afterglow detection statistics and r…
Neutrino-dominated accretion flows (NDAFs) around rotating stellar-mass black holes (BHs) are plausible candidates for the central engines of gamma-ray bursts (GRBs). NDAFs are hyperaccretion disks with accretion rates in the range of around 0.001-10 $M_\odot ~\rm s^{-1}$, which have high density and temperature and therefore are extremely optically thick and geometrically slim or even thick. We review the theoretical progresses in studying the properties of NDAFs as well as their applications to the GRB phenomenology. The topics include: the steady radial and vertical structure of NDAFs and t…
We investigate the expected radio emission from short GRBs, guided by the observed distributions of their afterglow parameters. Our motivation is to explore the radio signatures of the forward and reverse shock in a sGRB jet, as well as the off-axis jet component and radio emission from the dynamical ejecta. We estimate the fraction of GRBs detectable in the radio that may be coincident with a GW signal from a neutron star (NS) merger. At the distance to which aLIGO at design specification is sensitive to GWs from NS mergers, we may detect up to 20 % of off-axis jet radio components of these e…
Fast radio bursts (FRBs) represent one of the most exciting astrophysical discoveries of the recent past. The study of their low-frequency emission, which was only effectively picked up about ten years after their discovery, has helped shape the field thanks to some of the most important detections to date. Observations between 400 and 800 MHz, carried out by the CHIME/FRB telescope, in particular, have led to the detection of ~500 FRBs in little more than 1 year and, among them, ~20 repeating sources. Detections at low frequencies have uncovered a nearby population that we can study in detail…
Recently, in a few case studies we demonstrated that gyrosynchrotron microwave emission can be detected directly from the acceleration region when the trapped electron component is insignificant. For the statistical study reported here, we have identified events with steep (narrowband) microwave spectra that do not show a significant trapped component and at the same time show evidence of source uniformity, which simplifies the data analysis greatly. Initially, we identified a subset of more than 20 radio bursts with such narrow spectra, having low- and high-frequency spectral indices larger t…
We motivate how the most recent progress in the understanding the nature of the GeV radiation in most energetic gamma-ray bursts (GRBs), the binary-driven hypernovae (BdHNe), has led to the solution of a forty years unsolved problem in relativistic astrophysics: how to extract the rotational energy from a Kerr black hole for powering synchrotron emission and ultra high-energy cosmic rays. The "inner engine" is identified in the proper use of a classical solution introduced by Wald in 1974 duly extended to the most extreme conditions found around the newborn black hole in a BdHN. The energy ext…
Five fast radio bursts (FRBs), including three apparently non-repeating ones FRB 180924, FRB 181112, and FRB 190523, and two repeaters, FRB 121102 and FRB 180916.J0158+65, have already been localized so far. We apply a method developed recently by us (Li et al. 2019) to these five localized FRBs to give a cosmology-insensitive estimate of the fraction of baryon mass in the IGM, $f_{\rm IGM}$. Using the measured dispersion measure (DM) and luminosity distance $d_{\rm L}$ data (inferred from the FRB redshifts and $d_{\rm L}$ of type Ia supernovae at the same redshifts) of the five FRBs, we const…
