- The paper presents the detection of FRB 180814.J0422+73 as a second repeating fast radio burst, confirmed by six repeat bursts with a dispersion measure twice that of expected Milky Way values.
- It details the methodology using CHIME’s variable sensitivity and exposure during the pre-commission phase, analyzing sub-pulse frequency structures and drift rates of –6.4±0.7 and –1.3±0.3 MHz ms⁻¹.
- The study implies that non-cataclysmic models may explain repeating FRBs and suggests that improved telescope sensitivity will likely reveal a larger population of such sources.
Analysis of CHIME's Second Repeating Fast Radio Burst Discovery
The paper presents significant findings related to the detection of a second repeating Fast Radio Burst (FRB), designated as FRB 180814.J0422+73, discovered by the Canadian Hydrogen Intensity Mapping Experiment (CHIME). This discovery provides critical insights into the nature and population of repeating FRB sources.
FRB 180814.J0422+73 was identified during CHIME's pre-commissioning phase—a period characterized by varying observational schedules and sensitivities. Despite these operational challenges, six repeat bursts were detected, all originating from the same celestial coordinates and having a consistent dispersion measure (DM) of 189 pc cm−3. This DM is notably twice the expected value based on the Milky Way's column density, leading to an inferred redshift of z<0.1, which is approximately half the estimated distance to FRB 121102, previously the only known repeating FRB.
The repeat bursts exhibited sub-pulse frequency structures, frequency drifting, and spectral variations akin to those observed in FRB 121102. Specifically, frequency drift rates were observed at −6.4±0.7 and −1.3±0.3 MHz ms−1 for different bursts, drawing parallels to the drift patterns noted in ultrafast radio bursts.
An extensive analysis was conducted on the exposure and sensitivity of CHIME during the detection phases, detailed in the methods section. Exposure time of approximately 23 hours was determined for the source position, with notable variations in sensitivity due to differing observational transits. This underscores CHIME's capability to detect such phenomena despite non-ideal observational conditions.
The implications of this research extend to both observational and theoretical astrophysics. The detection of a second repeating source suggests that non-cataclysmic models are relevant to a subset of the FRB population, supporting the notion of a potentially significant population of repeaters. This has implications for our understanding of magneto-ionic environments around these sources and the mechanisms behind FRB emissions. The authors speculate on the physical origins of the drifting patterns, highlighting the possibility of propagation effects or intrinsic source mechanisms akin to those proposed for type II solar radio bursts.
On the practical side, these findings emphasize the capability of current wide-field radio telescopes to identify multiple repeating sources, potentially broadening the sample size for FRB studies and aiding in demographic and environmental analyses.
In terms of future developments, the paper posits that improved telescope sensitivity and targeted observing strategies will likely uncover more repeating FRBs. The ongoing enhancements in CHIME’s data collection, including the ability to capture polarization information, are anticipated to provide further clarity on the magnetic environments influencing FRB properties and to refine source localizations.
In conclusion, the detection of FRB 180814.J0422+73 not only reinforces the existence of repeating FRB phenomena but also propels our understanding of FRB characteristics and their astrophysical environments, paving a path for future breakthroughs in the fast-evolving field of radio astronomy.