Long and Short Fast Radio Bursts Are Different from Repeating and Nonrepeating Transients
X. J. Li, Xiaofei Dong, Zhi-Bin Zhang, Di Li
Abstract
Abstract We collect 133 fast radio bursts (FRBs), including 110 nonrepeating and 23 repeating ones, and systematically investigate their observational properties. To check the frequency dependence of FRB classifications, we define our samples with a central frequency below/above 1 GHz as subsample I/II. First, we find that there is a clear bimodal distribution of pulse width for subsample I. If we classify FRBs into short FRBs ( s FRBs; <100 ms) and long FRBs ( l FRBs; >100 ms) as done for short and long gamma-ray bursts (GRBs), the s FRBs at higher central frequency are commonly shorter than those at lower central frequency not only for nonrepeating but also repeating s FRBs. Second, we find that fluence and peak flux density are correlated with a power-law relation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>F</mml:mi> <mml:mo>∝</mml:mo> <mml:msubsup> <mml:mrow> <mml:mi>S</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>p</mml:mi> <mml:mo>,</mml:mo> <mml:mi>obs</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> for both s FRBs and l FRBs whose distributions are obviously different. Third, the l FRBs with isotropic energies ranging from 10 42 to 10 44 erg are more energetic than the s FRBs in the F – DM EX plane, indicating that they are two representative types. Finally, it is interesting to note that the peak flux density behaves independently on the redshift when the distance of the FRBs becomes far enough, which is similar to the scenario of the peak flux evolving with redshift in the field of GRBs. We predict that fainter FRBs at a higher redshift of z > 2 can be successfully detected by FAST and the Square Kilometre Array in the near future.