CHIME/FRB Detection of Eight New Repeating Fast Radio Burst Sources (1908.03507v3)

Abstract: We report on the discovery of eight 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 103.5 to 1281 pc cm$^{-3}$. They display varying degrees of activity: six sources were detected twice, another three times, and one ten times. These eight repeating FRBs likely represent the bright and/or high-rate end of a distribution of infrequently repeating sources. For all sources, we determine sky coordinates with uncertainties of $\sim$10$^\prime$. FRB 180916.J0158+65 has a burst-averaged DM = $349.2 \pm 0.3$ pc cm$^{-3}$ and a low DM excess over the modelled Galactic maximum (as low as $\sim$20 pc cm$^{-3}$); this source also has a Faraday rotation measure (RM) of $-114.6 \pm 0.6$ rad m$^{-2}$, much lower than the RM measured for FRB 121102. FRB 181030.J1054+73 has the lowest DM for a repeater, $103.5 \pm 0.3$ pc cm$^{-3}$, with a DM excess of $\sim$ 70 pc cm$^{-3}$. Both sources are interesting targets for multi-wavelength follow-up due to their apparent proximity. The DM distribution of our repeater sample is statistically indistinguishable from that of the first 12 CHIME/FRB sources that have not repeated. We find, with 4$\sigma$ significance, that repeater bursts are generally wider than those of CHIME/FRB bursts that have not repeated, suggesting different emission mechanisms. Our repeater events show complex morphologies that are reminiscent of the first two discovered repeating FRBs. The repetitive behavior of these sources will enable interferometric localizations and subsequent host galaxy identifications.

• The paper reports the discovery of eight new repeating FRB sources using CHIME’s wide-field detections and detailed dispersion measure analysis.
• The study finds that repeater bursts are generally broader than non-repeaters, indicating possible differences in emission mechanisms.
• Precise localizations open avenues for future multi-wavelength follow-ups to better understand FRB host environments and origins.

CHIME/FRB Discovery of Eight New Repeating Fast Radio Burst Sources

The paper conducted by the CHIME/FRB Collaboration presents the discovery of eight new repeating Fast Radio Burst (FRB) sources using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. These findings significantly contribute to the expanding research on FRBs, a transient astrophysical phenomenon characterized by millisecond-duration radio wave bursts, whose dispersion measures (DMs) suggest a cosmological origin.

Key Findings and Observations

The CHIME telescope's detections span a DM range from 103.5 to 1281 pc cm$^{-3}$, demonstrating varying levels of activity: six sources were detected twice, one three times, and another source was observed bursting ten times. The paper asserts that these newly identified repeating FRBs likely exemplify the brighter or more frequently repeating end of an extensive spectrum of FRB sources. The precise sky coordinates for all identified sources were resolved with a margin of uncertainty of approximately 10 arcminutes.

A particular point of interest highlighted in the research is the distinct properties of two sources:

1. FRB 180916.J0158+65 maintains a burst-averaged DM of 349.2 pc cm$^{-3}$ with a minimal DM excess over the modeled Galactic maximum, suggesting potential proximity. Its Faraday rotation measure (RM) is -114.6 rad m$^{-2}$, notably less than that recorded for FRB 121102.
2. FRB 181030.J1054+73 holds the lowest DM for a repeater at 103.5 pc cm$^{-3}$, again with a minor DM excess, indicating its location might be relatively nearby and beneficial for follow-up across multiple wavelengths.

The DM distribution from the repeater sample does not statistically distinguish itself from CHIME/FRB sources that have not repeated, suggesting commonalities in fundamental properties may exist between repeater and so-far non-repeating bursts.

Analysis and Implications

The paper finds, with a 4σ significance level, that repeater bursts are generally broader than non-repeater bursts detected by CHIME/FRB, which might imply variances in their emission mechanisms. The complex morphologies of these bursts closely resemble the initial repeaters identified, such as FRB 121102, and showcase the value of continued observation for the localizations and identification of host galaxies.

Among the broader implications:

• Theoretical Implications: This research prompts speculation about the existence of diverse populations of FRBs and challenges the prevailing theories of their origins. The nature of the RM and its variability across different sources could lead to insights on local environments or emission processes.
• Practical Implications: The discovery underlines the importance of technologies like CHIME for high-rate FRB detection, highlighting the utility of wide-bandwidth capabilities and high temporal resolution for the paper of these enigmatic astronomical events.
• Future Directions: As the research indicates, gaining the ability to localize these FRBs to specific host galaxies will significantly further our understanding of FRB sources' local environments and origins. It raises questions about the relationship between observed DM excess and host galaxy characteristics, potentially informing larger cosmic models.

In summary, this paper marks a notable advancement in FRB research, demonstrating the diversity among repeaters and presenting new opportunities for targeted follow-up measures. Such discoveries are pivotal to unraveling the complexities surrounding fast radio bursts and their place in the cosmic landscape.