Origin Of Fast Radio Bursts Research Articles

Damping of Strong GHz Waves near Magnetars and the Origin of Fast Radio Bursts

We investigate how a fast radio burst (FRB) emitted near a magnetar would propagate through its surrounding dipole magnetosphere at radii r = 107–109 cm. First, we show that a GHz burst emitted in the O-mode with luminosity L ≫ 1040 erg s−1 is immediately damped for all propagation directions except a narrow cone along the magnetic axis. Then, we examine bursts in the X-mode. GHz waves propagating near the magnetic equator behave as magnetohydrodynamic (MHD) waves if they have L ≫ 1040 erg s−1. The waves develop plasma shocks in each oscillation and dissipate at r∼3×108L42−1/4 cm. Waves with lower L or propagation directions closer to the magnetic axis do not obey MHD. Instead, they interact with individual particles and require a kinetic description. The kinetic interaction quickly accelerates particles to Lorentz factors 104–105 at the expense of the wave energy, which again results in strong damping of the wave. In either propagation regime, MHD or kinetic, the dipole magnetosphere surrounding the FRB source acts as a pillow absorbing the radio burst and reradiating the absorbed energy in X-rays. These results constrain the origin of observed FRBs. We argue that the observed FRBs avoid damping because they are emitted by relativistic outflows from magnetospheric explosions, so that the GHz waves do not need to propagate through the outer equilibrium magnetosphere surrounding the magnetar.

Fast Radio Burst Energy Function in the Presence of DMhost Variation

Fast radio bursts (FRBs) have been found in great numbers, but the physical mechanism of these sources is still a mystery. The redshift evolutions of the FRB energy distribution function and the volumetric rate shed light on the origin of FRBs. However, such estimations rely on the dispersion measurement (DM)–redshift (z) relationship. A few FRBs that have been detected recently show large excess DMs beyond the expectation from the cosmological and Milky Way contributions, which indicates large spread of DMs from their host galaxies. In this work, we adopt two lognormal-distributed DMhost models and estimate the energy function using the non-repeating FRBs selected from the Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB Catalog 1. By comparing the lognormal-distributed DMhost models to a constant DMhost model, the FRB energy function results are consistent within the measurement uncertainty. We also estimate the volumetric rate of the non-repeating FRBs in three different redshift bins. The volumetric rate shows that the trend is consistent with the stellar-mass density redshift evolution. Since the lognormal-distributed DMhost model increases the measurement errors, the inference of FRBs tracking the stellar-mass density is nonetheless undermined.

Searching for Associations between Short Gamma-Ray Bursts and Fast Radio Bursts

The physical origin of fast radio bursts (FRBs) is still unclear. However, young magnetars associated with short-duration gamma-ray bursts (SGRBs) have been thought to be possible central engines for some FRBs. In this paper, we perform a systematic search for SGRBs that are associated with FRBs in a sample including 623 FRBs (601 one-off bursts and 22 repeaters) and 168 SGRBs with precise localizations. We find that FRB 190309A is spatially associated with GRB 060502B, with a chance probability of 0.05 when temporal and redshift information is taken into account. Considering the high chance probability (the statistical significance is <3σ), we examine other observational properties such as the host galaxy, the dispersion measure, and the energy budget of the central engine to check the possibility of their association. Although the available observational information is insufficient to determine whether they are physically associated, it does not rule out such a possibility. As the only pair of FRB and GRB that are spatially associated, it remains an interesting case worthy of further attention.

Associating fast radio bursts with compact binary mergers via gravitational lensing

ABSTRACT The origin of fast radio bursts (FRBs) is currently an open question with several proposed sources and corresponding mechanisms for their production. Among them are compact binary coalescences (CBCs) that also generate gravitational waves (GWs). Spatial and temporal coincidences between GWs and FRBs have so far been used to search for potential FRB counterparts to GWs from CBCs. However, such methods suffer from relatively poor sky-localization of the GW sources, and similarly poor luminosity distance estimates of both GW and FRB sources. The expected time-delay between the GW and radio emission is also poorly understood. In this work, we propose an astrophysical scenario that could potentially provide an unambiguous association between CBCs and FRBs, if one exists, or unambiguously rule out FRB counterparts to a given CBC GW event. We demonstrate that if a CBC that emitted both GWs and FRBs is gravitationally lensed, we can make a &amp;gt;5σ association using time-delay estimates of the lensed GW and FRB images (in strong lensing), which are expected to be measured with millisecond (for GW) and nano-second (FRB) precisions. We also demonstrate that the CBC–FRB association can be made in the microlensing regime as well where wave-optics effects modulate the GW waveform. We further investigate the rate of such detected associations in future observing scenarios of both GW and radio detectors.

Change of Rotation Measure during the Eclipse of a Black Widow PSR J2051−0827

Black widows are millisecond pulsars ablating their companions. The material blown from the companion blocks the radio emission, resulting in radio eclipses. The properties of the eclipse medium are poorly understood. Here, we present direct evidence of the existence of magnetic fields in the eclipse medium of the black widow PSR J2051−0827 using observations made with the Five-hundred-meter Aperture Spherical radio Telescope. We detect a regular decrease in rotation measure (RM) in the egress of the eclipse, changing from 60 to −28.7 rad m−2. The RM gradually changes back to normal when the line of sight moves away from the eclipse. The estimated line-of-sight magnetic field strength in the eclipse medium is ∼0.1 G. The RM reversal could be caused by a change in the magnetic field strength along the line of sight due to binary orbital motion. The RM reversal phenomenon has also been observed in some repeating fast radio bursts (FRBs), and the study of spider pulsars may provide additional information about the origin of FRBs.

Reanalysis of the X-Ray-burst-associated FRB 200428 with Insight-HXMT Observations

A double-peak X-ray burst from the Galactic magnetar SGR J1935+2154 was discovered to be associated with the two radio pulses of FRB 200428 separated by 28.97 ± 0.02 ms. Precise measurements of the timing and spectral properties of the X-ray bursts are helpful for understanding the physical origin of fast radio bursts. In this paper, we have reconstructed some information about the hard X-ray events, which were lost because the High Energy X-ray Telescope (HE) on board the Insight-HXMT mission was saturated by this extremely bright burst, and used the information to improve the temporal and spectral analyses of the X-ray burst. The arrival times of the two X-ray peaks by fitting the new Insight-HXMT/HE lightcurve with multi-Gaussian profiles are 2.77 ± 0.45 ms and 34.30 ± 0.56 ms after the first peak of FRB 200428, respectively, while these two parameters are 2.57 ± 0.52 ms and 32.5 ± 1.4 ms if the fitting profile is a fast-rise and exponential decay function. The spectrum of the two X-ray peaks could be described by a cutoff power law with cutoff energy ∼60 keV and photon index ∼1.4; the latter is softer than the result obtained in Li et al. when the two X-ray peaks appeared.

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.

Hunting for gamma-ray emission from fast radio bursts

Context. Fast radio bursts (FRBs) are a recently discovered class of GHz-band, ms-duration, Jansky-level-flux astrophysical transients. Although hundreds of models have been proposed so far for FRB progenitors (the most popular ones involve magnetars), their physical origin and emission mechanism are still a mystery, making them one of the most compelling problems in astrophysics. Aims. FRBs are caused by astrophysical processes that are not yet understood. Exploring their high-energy counterpart is crucial for constraining their origin and emission mechanism. Methods. Thanks to more than 13 years of gamma-ray data collected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, and to more than 1000 FRB events (from 561 non-repeating and 22 repeating sources), one of the largest samples created thus far, we performed the largest and deepest search for high-energy emission from FRB sources to date (between 100 MeV and 1 TeV). In addition to the analysis involving individual FRB events on different timescales (from a few seconds up to several years), we performed, for the first time, a stacking analysis on the full sample of FRB events as well as a search for triplet photons in coincidence with the radio event. Results. We do not detect significant emission, reporting the most stringent constraints, on short timescales, for the FRB-like emission from SGR 1935+2154 with Eγ &lt; 1041 erg, corresponding to a factor η &lt; 107 with respect to the emitted radio energy. Similarly, for the stacked signal of steady emission from all repeaters, the obtained upper limit (UL) on the FRBs luminosity (Lγ &lt; 1.6 × 1043 erg s−1) is more than two orders of magnitude lower than those derived from the individual sources. Finally, no individual or triplet photons have been significantly associated with FRB events. We derived the LAT ms-sensitivity to be ∼0.3 ph cm−2 s−1 and constrained the gamma-ray energy Eγ,δT = 1 ms ≲ 1047(DL/150 Mpc)2 erg, ruling out a gamma-ray-to-radio energy ratio greater than 109 on ms timescales. Conclusions. The results reported here represent the most stringent UL reported so far on the high-energy emission from FRBs on short and long time scales, as well as on cumulative emission and individual photon searches. While the origin of FRBs is still unclear, our work provides important constraints for FRB modelling, which might shed light on their emission mechanism.

FAST helps push the study of fast radio bursts into statistical regimes

<p indent="0mm">The 2007 discovery of fast radio bursts (FRBs), bright and millisecond-duration astronomical radio pulses, presented to the astronomical community a tantalizing opportunity into the transient Universe. Understanding the origins, mechanisms and applications of FRBs is currently one of the most rapidly evolving sub-fields of astrophysics. Most FRBs originate from far outside the Milky Way and are many orders of magnitude more luminous than other known bursting radio sources, particularly pulsars (neutron stars). The total FRB population now stands at approximately 600 published sources, 24 repeaters, and 19 with localized host galaxies. Most FRBs appear to be one-off, only about four percent of the FRBs are now known to repeat. While the volume of observations grows at a breakneck pace, the overarching question of the field remains: “Where do FRBs come from?” Interestingly, FRBs can be hosted in a variety of galaxy types and environments. FRB 20121102 was successfully located in a low-mass and low-metallicity dwarf galaxy, coincident with a persistent radio source. VLBI observations have demonstrated that this source is compact. With the Five-hundred-meter Aperture Spherical radio Telescope (FAST), FRB 20121102 has been extensively observed, resulting in the discovery of 1652 independent bursts with a peak burst rate of 122 per hour and over three orders of magnitude variation in energy. For the first time, the burst energy distribution can be fully recovered and is found to be bimodal, suggesting that there may be more than one emission mechanisms or emission sites or beam shapes. In contrast to the single power-law energy distribution commonly found for FRBs, a characteristic peak in the burst rate energy distribution is found at <sc>4.8×10³⁷ erg.</sc> The estimated total isotropic energy, <sc>6.4×10⁴⁶ erg,</sc> released during the 47-day observational campaign, corresponds to approximately 38% of the available magnetar spin energy. Despite the high burst rate, no periodicity has been found. Higher time-resolution data, sustained monitoring, and better localization from the last <sc>2–3 years</sc> have provided a wealth of information and significant discoveries regarding the origin of FRBs. A supremely bright FRB-like burst (FRB 20200428) has been detected from a Galactic magnetar SGR 1935+2154 by STARE2 and CHIME/FRB. It provides strong evidence linking magnetars to sources of FRBs. The explosively growing number of FRBs and studies of individual FRBs start to reveal the source and radiation mechanisms of FRBs. Significant breakthroughs rely on the emergence of new observational facilities as well as a growing breadth of expertise joining the field. With ever-growing capabilities of observing facilities and processing power, the FRB sample in the next <sc>5 years</sc> will supersede that of radio pulsars from the past half century. We are witnessing the unveiling of a dynamic Universe.

AT2020hur: A Possible Optical Counterpart of FRB 180916B

The physical origin of fast radio bursts (FRBs) remains unclear. Finding multiwavelength counterparts of FRBs can provide a breakthrough for understanding their nature. In this work, we perform a systematic search for astronomical transients whose positions are consistent with FRBs. We find an unclassified optical transient AT2020hur (α = 01h58m00.ˢ750 ± 1″, ) that is spatially coincident with the repeating FRB 180916B (α = 01h58m00.ˢ7502 ± 2.3 mas, mas; Marcote et al. 2020). The chance possibility of the AT2020hur–FRB 180916B association is about 0.04%, which corresponds to a significance of 3.5σ. We develop a giant flare (GF) afterglow model to fit AT2020hur. Although the GF afterglow model can interpret the observations of AT2020hur, the derived kinetic energy of such a GF is at least three orders of magnitude larger than that of a typical GF, and a lot of fine-tuning and coincidences are required for this model. Another possible explanation is that AT2020hur might consist of two or more optical flares originating from the FRB source, e.g., fast optical bursts produced by the inverse Compton scattering of FRB emission. Besides, AT2020hur is located in one of the activity windows of FRB 180916B, which provides independent support for the association. This coincidence may be due to the optical counterparts being subject to the same periodic modulation as FRB 180916B, as implied by the prompt FRB counterparts. Future simultaneous observations of FRBs and their optical counterparts may help to reveal their physical origin.

Depolarized waves point to the origin of fast radio bursts

Depolarized waves point to the origin of fast radio bursts

The periodic origin of fast radio bursts

Fast radio bursts (FRBs) are pulsed radio signals with a duration of milliseconds and a large dispersion measure. Recent observations indicate that FRB 180916 and FRB 121102 show periodic activities. Some theoretical models have been proposed to explain periodic FRBs, and here we test these using corresponding X-ray and γ-ray observations. We find that the orbital periodic model, the free precession model, the radiation-driven precession model, the fall-back disk precession model where eccentricity is due to the internal magnetic field, and the rotation periodic model are not consistent with observations. The geodetic precession model is the most likely periodic model for FRB 180916. We also propose methods to test the periodic models with yet-to-be-obtained observational data in the future.

Fast radio burst distributions consistent with the first CHIME/FRB catalog

Currently, fast radio bursts (FRBs) have become a very active field in astronomy and cosmology. However, the origin of FRBs is still unknown to date. The studies on the intrinsic FRB distributions might help us to reveal the possible origins of FRBs, and improve the simulations for FRB cosmology. Recently, the first CHIME/FRB catalog of 536 events was released. Such a large uniform sample of FRBs detected by a single telescope is very valuable to test the FRB distributions. Later, it has been claimed that the FRB distribution model tracking the cosmic star formation history (SFH) was rejected by the first CHIME/FRB catalog. In the present work, we consider some empirical FRB distribution models, and find that many of them can be fully consistent with the CHIME/FRB observational data for some suitable model parameters. Notice that a suppressed evolution with respect to SFH is commonly found for FRBs. In particular, we independently confirm that the FRB distribution model tracking SFH can be rejected at very high confidence. On the other hand, all the "successful" models effectively require a certain degree of "delay" with respect to SFH. These results might shed light on the origin of FRBs and FRB cosmology.

Constraints on Optical Emission of FAST-detected FRB 20181130B with GWAC Synchronized Observations

Abstract Multiwavelength simultaneous observations are essential to the constraints on the origin of fast radio bursts (FRBs). However, it is a significant observational challenge due to the nature of FRBs as transients with a radio millisecond duration, which occur randomly in the sky regardless of time and position. Here, we report the search for short-time fast optical bursts in the Ground-based Wide Angle Camera (GWAC) archived data associated with FRB 20181130B, which were detected by the Five-hundred-meter Aperture Spherical radio Telescope and recently reported. No new credible sources were detected in all single GWAC images with an exposure time of 10 s, including images with coverage of the expected arrival time in optical wavelength by taking the high dispersion measurements into account. Our results provide a limiting magnitude of 15.43 ± 0.04 mag in the R band, corresponding to a flux density of 1.66 Jy or 8.35 mag in AB system by assuming that the duration of the optical band is similar to that of the radio band of about 10 ms. This limiting magnitude makes the spectral index of α &lt; 0.367 from optical to radio wavelength. The possible existence of longer-duration optical emission was also investigated with upper limits of 0.33 Jy (10.10 mag), 1.74 mJy (15.80 mag), and 0.16 mJy (18.39 mag) for the durations of 50 ms, 10 s, and 6060 s, respectively. This undetected scenario could be partially attributed to the shallow detection capability, as well as the high inferred distance of FRB 20181130B and the low fluence in radio wavelength. The future detectability of optical flashes associated with nearby and bright FRBs are also discussed in this paper.

Multifrequency observations of SGR J1935+2154

ABSTRACT Magnetars are a promising candidate for the origin of fast radio bursts (FRBs). The detection of an extremely luminous radio burst from the Galactic magnetar SGR J1935+2154 on 2020 April 28 added credence to this hypothesis. We report on simultaneous and non-simultaneous observing campaigns using the Arecibo, Effelsberg, LOFAR, MeerKAT, MK2, and Northern Cross radio telescopes and the MeerLICHT optical telescope in the days and months after the April 28 event. We did not detect any significant single radio pulses down to fluence limits between 25 mJy ms and 18 Jy ms. Some observing epochs overlapped with times when X-ray bursts were detected. Radio images made on 4 d using the MeerKAT telescope revealed no point-like persistent or transient emission at the location of the magnetar. No transient or persistent optical emission was detected over seven days. Using the multicolour MeerLICHT images combined with relations between DM, NH, and reddening, we constrain the distance to SGR J1935+2154, to be between 1.5 and 6.5 kpc. The upper limit is consistent with some other distance indicators and suggests that the April 28 burst is closer to two orders of magnitude less energetic than the least energetic FRBs. The lack of single-pulse radio detections shows that the single pulses detected over a range of fluences are either rare, or highly clustered, or both. It may also indicate that the magnetar lies somewhere between being radio-quiet and radio-loud in terms of its ability to produce radio emission efficiently.

A targeted search for repeating fast radio bursts associated with gamma-ray bursts

ABSTRACT The origin of fast radio bursts (FRBs) still remains a mystery, even with the increased number of discoveries in the last 3 yr. Growing evidence suggests that some FRBs may originate from magnetars. Large, single-dish telescopes such as Arecibo Observatory (AO) and Green Bank Telescope (GBT) have the sensitivity to detect FRB 121102-like bursts at gigaparsec distances. Here, we present searches using AO and GBT that aimed to find potential radio bursts at 11 sites of past gamma-ray bursts that show evidence for the birth of a magnetar. We also performed a search towards GW170817, which has a merger remnant whose nature remains uncertain. We place $10\sigma$ fluence upper limits of ≈0.036 Jy ms at 1.4 GHz and ≈0.063 Jy ms at 4.5 GHz for the AO data and fluence upper limits of ≈0.085 Jy ms at 1.4 GHz and ≈0.098 Jy ms at 1.9 GHz for the GBT data, for a maximum pulse width of ≈42 ms. The AO observations had sufficient sensitivity to detect any FRB of similar luminosity to the one recently detected from the Galactic magnetar SGR 1935+2154. Assuming a Schechter function for the luminosity function of FRBs, we find that our non-detections favour a steep power-law index (α ≲ −1.1) and a large cut-off luminosity (L0 ≳ 1041 erg s−1).

Characterizing fast radio bursts through statistical cross-correlations

Understanding the origin of fast radio bursts (FRB's) is a central unsolved problem in astrophysics that is severely hampered by their poorly determined distance scale. Determining the redshift distribution of FRB's appears to require arcsecond angular resolution, in order to associate FRB's with host galaxies. In this paper, we forecast prospects for determining the redshift distribution without host galaxy associations, by cross-correlating FRB's with a galaxy catalog such as the SDSS photometric sample. The forecasts are extremely promising: a survey such as CHIME/FRB that measures catalogs of $\sim 10^3$ FRB's with few-arcminute angular resolution can place strong constraints on the FRB redshift distribution, by measuring the cross-correlation as a function of galaxy redshift $z$ and FRB dispersion measure $D$. In addition, propagation effects from free electron inhomogeneities modulate the observed FRB number density, either by shifting FRB's between dispersion measure (DM) bins or through DM-dependent selection effects. We show that these propagation effects, coupled with the spatial clustering between galaxies and free electrons, can produce FRB-galaxy correlations which are comparable to the intrinsic clustering signal. Such effects can be disentangled based on their angular and $(z, D)$ dependence, providing an opportunity to study not only FRB's but the clustering of free electrons.

Is GRB 110715A the Progenitor of FRB 171209?

Abstract The physical origin of fast radio bursts (FRBs) is unknown. Young magnetars born from gamma-ray bursts (GRBs) have been suggested as a possible central engine of FRBs. We test such a hypothesis by systematically searching for GRB–FRB spatial associations from 110 FRBs and 1440 GRBs. We find that one FRB event discovered by the Parkes telescope, FRB 171209, is spatially coincident with a historical long-duration GRB 110715A at z = 0.82. The afterglow of GRB 110715A is consistent with being powered by a millisecond magnetar. The extragalactic dispersion measure of FRB 171209 is in excess of that contributed by the intergalactic medium, which can be interpreted as being contributed by a young supernova remnant associated with the GRB. Overall, the significance of the association is (2.28–2.55)σ. If the association is indeed physical, our result suggests that the magnetars associated with long GRBs can be the progenitors of at least some FRBs.

Are Persistent Emission Luminosity and Rotation Measure of Fast Radio Bursts Related?

Abstract The physical origin of fast radio bursts (FRBs) is still unknown. Multiwavelength and polarization observations of an FRB source would be helpful to diagnose its progenitor and environment. So far only the first repeating source FRB 121102 appears to be spatially coincident with a persistent radio emission. Its bursts also have very large values of the Faraday rotation measure (RM), i.e., . We show that theoretically there should be a simple relation between RM and the luminosity of the persistent source of an FRB source if the observed RM mostly arises from the persistent emission region. FRB 121102 follows this relation given that the magnetic field in the persistent emission region is highly ordered and that the number of relativistic electrons powering the persistent emission is comparable to that of nonrelativistic electrons that contribute to RM. The nondetections of persistent emission sources from all other localized FRB sources are consistent with their relatively small RMs ( ) according to this relation. Based on this picture, the majority of FRBs without a large RM are not supposed to be associated with bright persistent sources.

Testing the Hypothesis of a Compact-binary-coalescence Origin of Fast Radio Bursts Using a Multimessenger Approach

Abstract In the literature, compact binary coalescences (CBCs) have been proposed as one of the main scenarios to explain the origin of some non-repeating fast radio bursts (FRBs). The large discrepancy between the FRB and CBC event rate densities suggests that their associations, if any, should only apply at most for a small fraction of FRBs. Through a Bayesian estimation method, we show how a statistical analysis of the coincident associations of FRBs with CBC gravitational wave (GW) events may test the hypothesis of these associations. We show that during the operation period of the advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO), the detection of ∼100 (∼1000) GW-less FRBs with dispersion measure (DM) values smaller than 500 pc cm−3 could reach the constraint that less than 10% (or 1%) FRBs are related to binary black hole (BBH) mergers. The same number of FRBs with DM values smaller than 100 pc cm−3 is required to reach the same constraint for binary neutron star (BNS) mergers. With the upgrade of GW detectors, the same constraints for BBH and BNS mergers can be reached with fewer FRBs or looser requirements for the DM values. It is also possible to pose constraints on the fraction of each type of CBCs that are able to produce observable FRBs based on the event density of FRBs and CBCs. This would further constrain the dimensionless charge of black holes (BHs) in binary BH systems.