Nine New Repeating Fast Radio Burst Sources from CHIME/FRB (2001.03595v2)

Abstract: We report on the discovery and analysis of bursts from nine new repeating fast radio burst (FRB) sources found using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. These sources span a dispersion measure (DM) range of 195 to 1380 pc cm$^{-3}$. We detect two bursts from three of the new sources, three bursts from four of the new sources, four bursts from one new source, and five bursts from one new source. We determine sky coordinates of all sources with uncertainties of $\sim$10$^\prime$. We detect Faraday rotation measures for two sources, with values $-20(1)$ and $-499.8(7)$ rad m$^{-2}$, that are substantially lower than the RM derived from bursts emitted by FRB 121102. We find that the DM distribution of our events, combined with the nine other repeaters discovered by CHIME/FRB, is indistinguishable from that of thus far non-repeating CHIME/FRB events. However, as previously reported, the burst widths appear statistically significantly larger than the thus far non-repeating CHIME/FRB events, further supporting the notion of inherently different emission mechanisms and/or local environments. These results are consistent with previous work, though are now derived from 18 repeating sources discovered by CHIME/FRB during its first year of operation. We identify candidate galaxies that may contain FRB 190303.J1353+48 (DM = 222.4 pc cm$^{-3}$).

Nine New Repeating Fast Radio Burst Sources from CHIME/FRB: An Overview

The discovery and characterization of nine new repeating Fast Radio Burst (FRB) sources detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is presented in this paper. The FRBs exhibit a dispersion measure (DM) range spanning 195 to 1380 pc cm$^{-3}$, adding to the growing catalog of known repeating FRBs and providing a unique opportunity for understanding the bursts' inherent characteristics and locational environments.

Key Findings

• Repeater Frequency and Dispersion: The paper reports multiple burst detections per repeater, ranging from a minimum of two to a maximum of five bursts. These results span significant DM ranges and are detected with uncertainties in sky coordinates of approximately 10 arcminutes.
• Faraday Rotation Measures: Two sources among the nine exhibit Faraday rotation measures (RM) of $-20(1)$ and $-499.8(7)$~rad~m$^{-2}$. These values starkly contrast with the high RM values previously recorded for FRB 121102, suggesting diversity in the magneto-ionic environments of repeating FRBs.
• Morphological Analysis: The paper observes statistically significant broader pulse widths for repeating sources as compared to non-repeating ones, bolstering hypotheses of differing emission mechanisms or distinct local environments.
• Localization and Candidate Host Galaxies: The CHIME/FRB beam model allows for localizing bursts to a precision of $\sim$10 arcminutes, facilitating the potential identification of host galaxies. One potential candidate is identified for the repeating FRB 190303.J1353+48.

Implications

The findings provide further evidence that seemingly similar FRB phenomena could have varied underlying causes or source conditions. The detection of smaller RMs than those observed in FRB 121102 suggests the presence of less extreme magneto-ionic environments and potential stratification in the conditions that give rise to FRBs. Such diversity has implications for the modeling of FRB progenitors and requires multifaceted approaches to accurately constrain the conditions and processes at play.

Practically, the discovery enhances the case for pursuing localization efforts using interferometric methods and multi-wavelength observations to better infer FRB environments. The contrasts drawn in RM profiles between previously known FRBs and the newly detected instances caution against generalized environmental assumptions and highlight the importance of context-specific investigations.

Future Directions

The discoveries underscore the necessity for a layered investigation into FRBs, incorporating both high-resolution spatial data and a broadened temporal paper of burst sequences. Furthermore, statistical studies incorporating increasingly comprehensive datasets of both repeating and one-off FRB events will prove invaluable in delineating the population's characteristics.

As more data accumulates, the opportunity to piece together the FRB puzzle across different observational techniques will enhance the grasp of these enigmatic astronomical phenomena. Fundamental questions regarding their origins, potential periodicity, and overall contribution to the cosmic landscape remain exciting fronts for future research.

Conclusion

This work by the CHIME/FRB collaboration is pivotal in the cataloging and examination of repeating FRBs. It provides a touchstone for future investigations and inquiries into the nature of these astrophysical events. The implications of this research extend beyond the immediate context, enriching the broader astrophysical discourse surrounding transient radio sources and their cosmic implications.