The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
J. I. Katz - One of the best experts on this subject based on the ideXlab platform.
-
Are fast Radio Bursts made by neutron stars
Monthly Notices of the Royal Astronomical Society: Letters, 2020Co-Authors: J. I. KatzAbstract:Popular models of repeating Fast Radio Bursts (and perhaps of all Fast Radio Bursts) involve neutron stars because of their high rotational or magnetostatic energy densities. These models take one of two forms: giant but rare pulsar-like pulses like those of Rotating Radio Transients and outBursts like those of Soft Gamma Repeaters. Here I collate the evidence, recently strengthened, against these models, including the absence of Galactic micro-FRB, and attribute the 16 day periodicity of FRB 180916.J0158+65 to the precession of a jet produced by a massive black hole's accretion disc.
-
Fast Radio Bursts Not Made By Neutron Stars
arXiv: High Energy Astrophysical Phenomena, 2019Co-Authors: J. I. KatzAbstract:Popular models of repeating Fast Radio Bursts (and perhaps of all Fast Radio Bursts) involve neutron stars because they may have high rotational or magnetostatic energy densities available to power energetic Bursts. These models take two forms: giant but rare pulsar-like pulses like those of Rotating Radio Transients and outBursts like those of Soft Gamma Repeaters. Here I collate the evidence, recently strengthened, against these models.
-
fast Radio Bursts
Progress in Particle and Nuclear Physics, 2018Co-Authors: J. I. KatzAbstract:Abstract 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 temperature 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.
-
Fast Radio Bursts
Progress in Particle and Nuclear Physics, 2018Co-Authors: J. I. KatzAbstract: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.
-
coherent emission in fast Radio Bursts
Physical Review D, 2014Co-Authors: J. I. KatzAbstract:The fast (ms) Radio Bursts reported by Thornton, {\it et al.} have extremely high brightness temperatures if at the inferred cosmological distances. This implies coherent emission by "bunches" of charges. We model the emission region as a screen of dipole radiators resonant at the frequency of observation and calculate the necessary charge bunching. From this we infer the minimum electron energy required to overcome electrostatic repulsion. The FRB, like the giant pulses of the Crab pulsar, display banded spectra that may be harmonics of plasma frequency emission by plasma turbulence. If FRB are the counterparts of comparatively frequent Galactic events, these may be detected by Radio telescopes in their far sidelobes or by small arrays of dipoles.
Zi-gao Dai - One of the best experts on this subject based on the ideXlab platform.
-
Galactic and cosmological fast Radio Bursts as scaled-up solar Radio Bursts
Monthly Notices of the Royal Astronomical Society, 2020Co-Authors: Fa-yin Wang, G. Q. Zhang, Zi-gao DaiAbstract:ABSTRACT Fast Radio Bursts (FRBs) are bright milliseconds Radio transients with large dispersion measures. Recently, FRB 200428 was detected in temporal coincidence with a hard X-ray flare from the Galactic magnetar SGR 1935+2154, which supports that at least some FRBs are from magnetar activity. Interestingly, a portion of X-ray flares from magnetar XTE J1810−197 and the Sun are also accompanied by Radio Bursts. Many features of Galactic FRB 200428 and cosmological FRBs resemble solar Radio Bursts. However, a common physical origin among FRBs, magnetar Radio pulses, and solar Radio Bursts has not yet been established. Here, we report a universal correlation between X-ray luminosity and Radio luminosity over 20 orders of magnitude among solar type III Radio Bursts, XTE J1810−197 and Galactic FRB 200428. This universal correlation reveals that the energetic electrons that produce the X-ray flares and those that cause Radio emissions have a common origin, which can give stringent limits on the generation process of Radio Bursts. Moreover, we find similar occurrence frequency distributions of energy, duration, and waiting time for solar Radio Bursts, SGR 1935+2154 and repeating FRB 121102, which also support the tight correlation and the X-ray flares temporally associated with Radio Bursts. All of these distributions can be understood by avalanche models of self-organized criticality systems. The universal correlation and statistical similarities indicate that the Galactic FRB 200428 and FRBs seen at cosmological distances can be treated as scaled-up solar Radio Bursts.
-
Galactic and cosmological fast Radio Bursts as scaled-up solar Radio Bursts
arXiv: High Energy Astrophysical Phenomena, 2019Co-Authors: Fa-yin Wang, G. Q. Zhang, Zi-gao DaiAbstract:Fast Radio Bursts (FRBs) are bright milliseconds Radio transients with large dispersion measures. Recently, FRB 200428 was detected in temporal coincidence with a hard X-ray flare from the Galactic magnetar SGR 1935+2154, which supports that at least some FRBs are from magnetar activity. Interestingly, a portion of X-ray flares from magnetar XTE J1810-197 and the Sun are also accompanied by Radio Bursts. Many features of Galactic FRB 200428 and cosmological FRBs resemble solar Radio Bursts. However, a common physical origin among FRBs, magnetar Radio pulses and solar Radio Bursts has not yet been established. Here we report a universal correlation between X-ray luminosity and Radio luminosity over twenty orders of magnitude among solar type III Radio Bursts, XTE J1810-197 and Galactic FRB 200428. This universal correlation reveals that the energetic electrons which produce the X-ray flares and those which cause Radio emissions have a common origin, which can give stringent limits on the generation process of Radio Bursts. Moreover, we find similar occurrence frequency distributions of energy, duration and waiting time for solar Radio Bursts, SGR 1935+2154 and repeating FRB 121102, which also support the tight correlation and the X-ray flares temporally associated with Radio Bursts. All of these distributions can be understood by avalanche models of self-organized criticality systems. The universal correlation and statistical similarities indicate that the Galactic FRB 200428 and FRBs seen at cosmological distances can be treated as scaled-up solar Radio Bursts.
-
Constraints on the Photon Mass with Fast Radio Bursts
The Astrophysical Journal, 2016Co-Authors: Songbo Zhang, Zi-gao Dai, Bing Zhang, He Gao, Junjie Wei, Yuanchuan Zou, Weihua Lei, P MeszarosAbstract:Fast Radio Bursts (FRBs) are Radio Bursts characterized by millisecond durations, high Galactic latitude positions, and high dispersion measures. Very recently, the cosmological origin of FRB 150418 has been confirmed by \cite{kea16}, and FRBs are now strong competitors as cosmological probes. The simple sharp feature of the FRB signal is ideal for them to probe some of the fundamental laws of physics. Here we show that by analyzing the delay time between different frequencies, the FRB data can place stringent upper limits on the rest mass of the photon. For FRB 150418 at $z=0.492$, one can potentially reach $m_{\gamma} \leq 5.2 \times 10^{-47}$ g, which is $10^{20}$ times smaller than the rest mass of electron, and is about $10^3$ times smaller than that obtained using other astrophysical sources with the same method.
-
constraints on the photon mass with fast Radio Bursts
The Astrophysical Journal, 2016Co-Authors: Songbo Zhang, Zi-gao Dai, Bing Zhang, He Gao, Junjie Wei, Yuanchuan Zou, Weihua Lei, P MeszarosAbstract:Fast Radio Bursts (FRBs) are Radio Bursts characterized by millisecond durations, high Galactic latitude positions, and high dispersion measures. Very recently, the cosmological origin of FRB 150418 has been confirmed by Keane et al., and FRBs are now strong competitors as cosmological probes. The simple sharp feature of the FRB signal is ideal to probe some of the fundamental laws of physics. Here we show that by analyzing the delay time between different frequencies, the FRB data can place stringent upper limits on the rest mass of the photon. For FRB 150418 at z = 0.492, one can potentially reach m(gamma) <= 5.2 10(-47) g, which is 10(20) times smaller than the rest mass of electron and is about 10(3) times smaller than that obtained using other astrophysical sources with the same method.
Nat Gopalswamy - One of the best experts on this subject based on the ideXlab platform.
-
Low-frequency Radio Bursts and space weather
2016 URSI Asia-Pacific Radio Science Conference (URSI AP-RASC), 2016Co-Authors: Nat GopalswamyAbstract:Low-frequency Radio phenomena are due to the presence of nonthermal electrons in the interplanetary (IP) medium. Understanding these phenomena is important in characterizing the space environment near Earth and other destinations in the solar system. Substantial progress has been made in the past two decades, because of the continuous and uniform data sets available from space-based Radio and white-light instrumentation. This paper highlights some recent results obtained on IP Radio phenomena. In particular, the source of type IV Radio Bursts, the behavior of type III storms, shock propagation in the IP medium, and the solar-cycle variation of type II Radio Bursts are considered. All these phenomena are closely related to solar eruptions and active region evolution. The results presented were obtained by combining data from the Wind and SOHO missions.
-
Low-frequency solar Radio Bursts and their space weather implications
2015 1st URSI Atlantic Radio Science Conference (URSI AT-RASC), 2015Co-Authors: Nat Gopalswamy, Pertti Makela, Hong Xie, Seiji YashiroAbstract:The Sun is a Radio emitter in the millimeter to kilometer wavelength range (100s of GHz to a few kHz). The low frequency solar Radio Bursts are of particular importance, because they are associated with large-scale solar eruptions and the associated interplanetary disturbances such as coronal mass ejections (CMEs) and shocks. The Radio Bursts are produced by energetic electrons (>1 keV) by nonthermal processes. The Radio Bursts provide important information not only on the solar disturbances but also on the ambient medium.
-
Solar Radio Bursts and Space Weather
2012Co-Authors: Nat GopalswamyAbstract:Radio Bursts from the Sun are produced by electron accelerated to relativistic energies by physical processes on the Sun such as solar flares and coronal mass ejections (CMEs). The Radio Bursts are thus good indicators of solar eruptions. Three types of nonthermal Radio Bursts are generally associated with CMEs. Type III Bursts due to accelerated electrons propagating along open magnetic field lines. The electrons are thought to be accelerated at the reconnection region beneath the erupting CME, although there is another view that the electrons may be accelerated at the CME-driven shock. Type II Bursts are due to electrons accelerated at the shock front. Type II Bursts are also excellent indicators of solar energetic particle (SEP) events because the same shock is supposed accelerate electrons and ions. There is a hierarchical relationship between the wavelength range of type /I Bursts and the CME kinetic energy. Finally, Type IV Bursts are due to electrons trapped in moving or stationary structures. The low frequency stationary type IV Bursts are observed occasionally in association with very fast CMEs. These Bursts originate from flare loops behind the erupting CME and hence indicate tall loops. This paper presents a summary of Radio Bursts and their relation to CMEs and how they can be useful for space weather predictions.
-
CME-Associated Radio Bursts from Satellite Observations
2012Co-Authors: Nat GopalswamyAbstract:Coronal mass ejections (CMEs) are closely associated with various types of Radio Bursts from the Sun. All Radio Bursts are due to nonthermal electrons, which are accelerated during the eruption of CMEs. Radio Bursts at frequencies below about 15 MHz are of particular interest because they are associated with energetic CMEs that contribute to severe space weather. The low-frequency Bursts need to be observed primarily from space because of the ionospheric cutoff. The main CME-related Radio Bursts are associated are: type III Bursts due to accelerated electrons propagating along open magnetic field lines, type II Bursts due to electrons accelerated in shocks, and type IV Bursts due to electrons trapped in post-eruption arcades behind CMEs. This paper presents a summary of results obtained during solar cycle 23 primarily using the white-light coronagraphic observations from the Solar Heliospheric Observatory (SOHO) and the WAVES experiment on board Wind. Particular emphasis will be placed on what we can learn about particle acceleration in the coronal and interplanetary medium by analyzing the CMEs and the associated Radio Bursts.
-
Interplanetary Radio Bursts
Solar and Space Weather Radiophysics, 2004Co-Authors: Nat GopalswamyAbstract:Nonthermal Radio Bursts in the interplanetary medium indicate the far-reaching effect of solar eruptions that inject energetic particles, plasmas and shock waves into the inner heliosphere. More than half a century of ground-based observations and subsequent space-based observations exist on this phenomena. In this paper, I summarize the understanding we have gained on the type III and type II Radio Bursts, which are indicative of electron beams and shocks, respectively. Observations in the new Radio window (1–14 MHz) from Wind/WAVES have not only confirmed previous results, but also led to a number of new discoveries. Availability of simultaneous white light (SOHO) and Radio (Wind) observations from the same spatial domain in the near-Sun IP medium is largely responsible for these discoveries on the IP propagation of CMEs, so this paper discusses Radio Bursts in the context of white light observations. After exploring the origin of normal, complex and storm type III Bursts, I discuss the type II Bursts and their relation to coronal mass ejections. Finally I discuss some of the recent developments on IP Radio emission.
Gennady Pavlovich Chernov - One of the best experts on this subject based on the ideXlab platform.
-
termination shock as a source of unusual solar Radio Bursts
arXiv: Solar and Stellar Astrophysics, 2020Co-Authors: V V Fomichev, Gennady Pavlovich ChernovAbstract:Using centimeter wave and decimeter wave solar Radio spectral observations of the flares of November 18, 2003 and September 12, 2004, we have discussed two type II like Bursts at the meter waves. The Radio Bursts show that the ordinary frequency drift from high to low frequencies slows down and stops, and a frequency drift from low to high frequencies appears. An analysis of all data on the corresponding flares provides evidence of formation of quasi standing fast mode shocks (termination shocks, TS). TS are able to generate energetic electrons, responsible for the appearance of new sources of hard X ray radiation and generation of fast Radio Bursts (spikes), fibers and zebra structures. The sources of the Radio emission bands with the unusual frequency drift are situated above the top of the post flare loops (lower TS) or are connected with the erupting prominence or coronal mass ejection (CME, upper TS). Estimations of the critical Mach numbers for the ordinary plasma parameters in the solar flares give the values 1.3 easily realized in the flare events. The conditions necessary for generation of unusual Radio Bursts are likely to occur in the helmet shaped magnetic structures in the solar corona.
-
Solar Radio Bursts Associated with Standing Shock Waves
Geomagnetism and Aeronomy, 2020Co-Authors: V V Fomichev, Gennady Pavlovich ChernovAbstract:A number of phenomena with Radio Bursts in the decimeter and centimeter wavelength ranges similar to type-II Bursts in the meter range have been considered. In all phenomena, the Radio Bursts are characterized by the cessation of frequency drift and its reversal. Analysis of all of the available data on relevant Bursts provides evidence of termination shocks with particle accelerations in their fronts. This is confirmed by the generation of new sources of hard X-ray radiation and the Radio emission of fast Bursts (spikes), fibers, and zebra structures. The sources of drift stripes with a drift turn are located either between the burst loop and the lower shock wave or between the lower and upper shock waves. Estimates of the critical Mach number for common parameters of the burst plasma indicated that the values (M_cr = 1.1–1.3) can easily be observed in the given phenomena and that the radiation can be associated with the Buneman instability. The conditions necessary for the generation of observed electromagnetic radiation Bursts can be provided in helmet-shaped magnetic structures in the solar corona.
-
Fine Structure of Solar Radio Bursts
2011Co-Authors: Gennady Pavlovich ChernovAbstract:Preface.- Acknowledgments.- 1 Introduction.- 2 Pulsations.- 3 Spike Bursts.- 4 Zebra pattern and fiber Bursts.- 5 Recent results of zebra patterns in solar Radio Bursts.- References.- Subject Index.
-
Fine Structure of Solar Radio Bursts
Astrophysics and Space Science Library, 2011Co-Authors: Gennady Pavlovich ChernovAbstract:The study of the fine structure of solar Radio emissions is key to understanding plasma processes in the solar corona. It remains a reliable means for both diagnosing the corona and verifying the results of laboratory plasma experiments on wave-wave and wave-particle interactions. This monograph provides a comprehensive review of the fine structure of solar Radio Bursts. Based on the diversity of experimental data resulting from the progress made in observational techniques, the validity of various theoretical models is reexamined. The book serves as an up-to-date reference work for all researchers in this field
Bing Zhang - One of the best experts on this subject based on the ideXlab platform.
-
"Slow" Radio Bursts from Galactic Magnetars?.
arXiv: High Energy Astrophysical Phenomena, 2020Co-Authors: Bing ZhangAbstract:Recently, one fast Radio burst, FRB 200428, was detected from the Galactic magnetar SGR J1935+2154 during one X-ray burst. This suggests that magnetars can make FRBs. On the other hand, the majority of X-ray Bursts from SGR J1935+2154 are not associated with FRBs. One possible reason of such rarity of FRB-SGR-burst associations is that the FRB emission is much more narrowly beamed than SGR burst emission. If such an interpretation is true, one would expect to detect Radio Bursts with viewing angle somewhat outside the narrow emission beam. These "slow" Radio Bursts (SRBs) would have broader widths and lower flux densities due to the smaller Doppler factor involved. The $2.2$-s long, 111 MHz Radio burst detected from SGR J1935+2154 by the BSA LPI Radio telescope may be such an SRB if the spectral slope is positive. If the FRB beam is narrow, there should be many more SRBs than FRBs from Galactic magnetars. Non-detection of these SRBs would disfavor the assumption that all SGR Bursts are associated with narrow-beam FRBs.
-
The Physical Mechanisms of Fast Radio Bursts.
Nature, 2020Co-Authors: Bing ZhangAbstract:Fast Radio Bursts are mysterious millisecond-duration transients prevalent in the Radio sky. Rapid accumulation of data in recent years has facilitated an understanding of the underlying physical mechanisms of these events. Knowledge gained from the neighboring fields of gamma-ray Bursts and Radio pulsars also offered insight. Here I review developments in this fast-moving field.Two generic categories of radiation model invoking either magnetospheres of compact objects (neutron stars or black holes) or relativistic shocks launched from such objects have been much debated. The recent detection of a Galactic fast Radio burst in association with a soft gamma-ray repeater suggests that magnetar engines can produce at least some, and probably all, fast Radio Bursts. Other engines that could produce fast Radio Bursts are not required, but are also not impossible.
-
Unexpected emission pattern adds to the enigma of fast Radio Bursts
Nature, 2020Co-Authors: Bing ZhangAbstract:A source of fast Radio Bursts with a 16-day period. Observations of millisecond-long Radio Bursts from beyond the Milky Way have revealed a repeat pattern with a roughly 16-day period — a finding that adds to the enigma of the origin of these Bursts.
-
Constraints on the Photon Mass with Fast Radio Bursts
The Astrophysical Journal, 2016Co-Authors: Songbo Zhang, Zi-gao Dai, Bing Zhang, He Gao, Junjie Wei, Yuanchuan Zou, Weihua Lei, P MeszarosAbstract:Fast Radio Bursts (FRBs) are Radio Bursts characterized by millisecond durations, high Galactic latitude positions, and high dispersion measures. Very recently, the cosmological origin of FRB 150418 has been confirmed by \cite{kea16}, and FRBs are now strong competitors as cosmological probes. The simple sharp feature of the FRB signal is ideal for them to probe some of the fundamental laws of physics. Here we show that by analyzing the delay time between different frequencies, the FRB data can place stringent upper limits on the rest mass of the photon. For FRB 150418 at $z=0.492$, one can potentially reach $m_{\gamma} \leq 5.2 \times 10^{-47}$ g, which is $10^{20}$ times smaller than the rest mass of electron, and is about $10^3$ times smaller than that obtained using other astrophysical sources with the same method.
-
constraints on the photon mass with fast Radio Bursts
The Astrophysical Journal, 2016Co-Authors: Songbo Zhang, Zi-gao Dai, Bing Zhang, He Gao, Junjie Wei, Yuanchuan Zou, Weihua Lei, P MeszarosAbstract:Fast Radio Bursts (FRBs) are Radio Bursts characterized by millisecond durations, high Galactic latitude positions, and high dispersion measures. Very recently, the cosmological origin of FRB 150418 has been confirmed by Keane et al., and FRBs are now strong competitors as cosmological probes. The simple sharp feature of the FRB signal is ideal to probe some of the fundamental laws of physics. Here we show that by analyzing the delay time between different frequencies, the FRB data can place stringent upper limits on the rest mass of the photon. For FRB 150418 at z = 0.492, one can potentially reach m(gamma) <= 5.2 10(-47) g, which is 10(20) times smaller than the rest mass of electron and is about 10(3) times smaller than that obtained using other astrophysical sources with the same method.
