The Statistical Polarization Properties of Coherent Curvature Radiation by Bunches: Application to Fast Radio Burst Repeaters

Liu, Ze-Nan; Wang, Weiyang; Yang, Yuan-Pei; Dai, Z. G.

doi:10.3847/1538-4357/acac23

Cited by 10 publications

(13 citation statements)

References 69 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…circular polarizations will be canceled, leading to the linear polarization being dominated. A detailed analysis was also discussed in et al (2022b) and Liu et al (2023). Therefore, the linear polarization degree could be approximately given by…”

Section: A1 Deflection Angle Larger Than Radiation Beaming Anglementioning

confidence: 88%

See 1 more Smart Citation

Implications of Narrow Spectra of Fast Radio Bursts

Yang

2023

ApJ

View full text Add to dashboard Cite

Fast radio bursts (FRBs) are millisecond-duration radio transients with extremely high brightness temperatures at cosmological distances, and the physical origin and the radiation mechanism of FRBs are still unknown. The observed spectral bandwidth of some FRBs appeared narrow compared with their peak frequencies, which could be used to constrain the radiation mechanism and the astrophysical environment of FRBs. In this work, we investigate some of the possible physical origins of the narrow spectra from the perspectives of intrinsic radiation mechanisms, coherent processes, radiative transfers, and interference processes. We find that: (1) If the observed narrow spectra of FRBs are attributed to the intrinsic radiation mechanism by a single charged particle, the particle’s deflection angle should be much smaller than the radiation beaming angle. (2) Coherent process can cause narrow spectra. For the bunching mechanism, the narrow spectra might arise from the radiating bunches with a quasiperiodic distribution. For the maser mechanism, the negative absorption process can naturally cause a narrow spectrum. (3) Most absorption and scattering processes seem not to significantly change the observed spectra based on the current observation of some FRB repeaters. (4) Scintillation and plasma lensing in the FRB source environment can modulate the spectra, leading to the narrow spectra and the burst-to-burst variation of spectra. A planet-like object can generate the spectral modulation via gravitational lensing at the gigahertz band, but the observed burst-to-burst variation of the spectra does not support this scenario.

show abstract

Section: A1 Deflection Angle Larger Than Radiation Beaming Anglementioning

confidence: 88%

“…For a certain frequency w ˆ, the larger the viewing angle γθ, the lower (higher) the linear (circular) polarization degree. Thus, the high circular polarization degree should be attributed to the off-beam observation (Wang et al 2022a;Liu et al 2023;.…”

Section: A1 Deflection Angle Larger Than Radiation Beaming Anglementioning

confidence: 99%

Implications of Narrow Spectra of Fast Radio Bursts

Yang

2023

ApJ

View full text Add to dashboard Cite

show abstract

“…The polarization properties of curvature radiation have been studied within the framework of pulsars (e.g. Gil & Snakowski 1990) and FRBs (Gangadhara 2010;Wang et al 2022d,c;Tong & Wang 2022;Liu et al 2023) by various authors. Consider a bunch with charge 𝑄 = 𝑁 𝑒 |𝑒| and Lorentz factor 𝛾 moving along the local magnetic field with curvature radius 𝜌.…”

Section: Coherent Curvature Radiationmentioning

confidence: 99%

Polarization of Fast Radio Bursts: radiation mechanisms and propagation effects

Qu¹,

Zhang²

2023

Preprint

View full text Add to dashboard Cite

Observations show that fast radio bursts (FRBs) are highly polarized. Most have high linear polarization degree but a small fraction shows significant circular polarization. In this paper, we systematically investigate a variety of polarization mechanisms of FRBs within the magnetar theoretical framework considering two possible emission sites, i.e. inside and outside the magnetosphere. For each site, we discuss both intrinsic radiation mechanisms and propagation effects. Inside the magnetosphere, we investigate the polarization properties of both coherent curvature radiation and inverse Compton scattering by charged bunches and conclude that both mechanisms produce 100% linear polarization at an on-axis geometry but can produce circular polarization if the viewing angle is off axis. In order to have the majority of bursts not having high circular polarization, the bunches should have a large cross section involving a bunch of field lines. Resonant cyclotron absorption within magnetosphere can produce high circular polarization if the resonant condition is satisfied below light cylinder and if electrons and positrons have asymmetric Lorentz factor distribution. Outside the magnetosphere, we consider the synchrotron maser intrinsic emission mechanism and find that the on-beam emission is highly linear polarized. Circular polarization would show up at off-beam angles but the flux is greatly degraded and such bursts are not detectable at cosmological distances. For propagation effects, we consider synchrotron absorption, which tends to reduce circular polarization degree; cyclotron absorption, which tends to generate significant circular polarization; and Faraday conversion, which can convert one polarization mode to another. We discuss astronomical scenarios to allow these processes to happen and conclude that the first two absorption processes require stringent physical conditions. Faraday conversion requires field reversal, which may realize in binary systems or when the FRB engine is surrounded by a supernova remnant.

show abstract

“…FRB 20201124A has been observed to show frequency-dependent polarization (Hilmarsson et al 2021;Feng et al 2022;Kumar et al 2022). Significant circular bursts were reported by Xu et al (2022), which are considered to be generated by a specific radiation mechanism (Wang et al 2022b;Liu et al 2023;Qu & Zhang 2023). We then excluded those highly circular polarized bursts from our filtered data set.…”

Section: Spectra Fittingmentioning

confidence: 99%

Temporal Evolution of Depolarization and Magnetic Field of Fast Radio Burst 20201124A

Lu,

Zhao,

Wang

et al. 2023

ApJL

View full text Add to dashboard Cite

Fast radio bursts (FRBs) are energetic millisecond phenomena in the radio band. Polarimetric studies of repeating FRBs indicate that many of these sources occupy extreme and complex magnetoionized environments. Recently, a frequency-dependent depolarization has been discovered in several repeating FRBs. However, the temporal evolution of polarization properties is limited by the burst rate and observational cadence of telescopes. In this Letter, the temporal evolution of depolarization in repeating FRB 20201124A is explored. Using the simultaneous variation of rotation measure and dispersion measure, we also measure the strength of a magnetic field parallel to the line of sight. The strength ranges from a few μG to 103 μG. In addition, we find that the evolution of depolarization and magnetic field traces the evolution of rotation measure. Our result supports that the variation of depolarization, rotation measure, and the magnetic field are determined by the same complex magnetoionized screen surrounding the FRB source. The derived properties of the screen are consistent with the wind and the decretion disk of a massive star.

show abstract

The Statistical Polarization Properties of Coherent Curvature Radiation by Bunches: Application to Fast Radio Burst Repeaters

Cited by 10 publications

References 69 publications

Implications of Narrow Spectra of Fast Radio Bursts

Implications of Narrow Spectra of Fast Radio Bursts

Polarization of Fast Radio Bursts: radiation mechanisms and propagation effects

Temporal Evolution of Depolarization and Magnetic Field of Fast Radio Burst 20201124A

Contact Info

Product

Resources

About