A Possible Subclassification of Fast Radio Bursts

TL;DR

This paper proposes a new subclassification scheme for fast radio bursts (FRBs) based on their observed properties and distributions, aiming to better understand their origins and physical mechanisms.

Contribution

It introduces a novel subclassification of non-repeating and repeating FRBs using observational data from the CHIME/FRB catalog, linking subclasses to stellar populations and physical properties.

Findings

Type Ia FRBs are associated with old stellar populations.

Type Ib FRBs track star formation history, linked to young stars.

Distinct empirical correlations differentiate the subclasses.

Abstract

Although fast radio bursts (FRBs) have been an active field in astronomy and cosmology, their origin is still unknown to date. One of the interesting topics is the classification of FRBs, which is closely related to the origin of FRBs. Different physical mechanisms are required by different classes of FRBs. In the literature, they usually could be classified into non-repeating and repeating FRBs. Well motivated by the observations, here we are interested in the possible subclassification of FRBs. By using the first CHIME/FRB catalog, we propose to subclassify non-repeating (type I) FRBs into type Ia and Ib FRBs. The distribution of type Ia FRBs is delayed with respect to the cosmic star formation history (SFH), and hence they are probably associated with old stellar populations, while the distribution of type Ib FRBs tracks SFH, and hence they are probably associated with young stellar populations. Accordingly, the physical criteria for this subclassification of type I FRBs have been clearly determined. We find that there are some tight empirical correlations for type Ia FRBs but not for type Ib FRBs, and vice versa. These make them different in physical properties. Similarly, we suggest that repeating (type II) FRBs could also be subclassified into type IIa and IIb FRBs. A universal subclassification scheme is given at the end. This subclassification of FRBs might help us to reveal quite different physical mechanisms behind them, and improve their applications in astronomy and cosmology.