Comparison of burst properties between FRB 20190520B and FRB 20121102A

Abstract

ABSTRACT A comparative analysis of the individual bursts between FRB 20190520B and FRB 20121102A is presented by compiling a sample of bursts in multiple wavelengths. It is found that the peak frequency (νp) distribution of the bursts of FRB 20190520B illustrates four discrete peaks in ∼1–6 GHz and their spectral width distribution can be fitted with a lognormal function peaking at 0.35 GHz. The discrete νp distribution and the narrow-banded spectral feature are analogous to FRB 20121102A. The burst duration of FRB 20190520B in the rest frame averages to 10.72 ms, longer than that of FRB 20121102A by a factor 3. The specific energy $\left(E_{\rm\mu_{\rm c}}\right)$ at 1.25 GHz of FRB 20190520B observed with the Five-hundred-meter Aperture Spherical Radio Telescope narrowly ranges in [0.4, 1] × 1038 erg, different from the bimodal $E_{\rm \mu _{\rm c}}$ distribution of FRB 20121102A. Assuming a Gaussian spectral profile of the bursts, our Monte Carlo simulation analysis suggests that a power law (PL) or a cut-off power-law (CPL) energy function can comparably reproduce the $E_{\rm \mu _{\rm c}}$ distribution of FRB 20190520B. The derived energy function index of the PL model is 4.46 ± 0.17, much steeper than that of FRB 20121102A ($1.82^{+0.10}_{-0.30}$ ). For the CPL model, we obtain an index of 0.47 and a cut-off energy of 7.4 × 1037 erg. Regarding the predicted νp distribution in 1–2 GHz, the CPL model is more preferred than the PL model. These results indicate that FRB 20190520B and FRB 20121102A share similar spectral properties, but their energy functions are intrinsically different.