A repeating fast radio burst source localised to a nearby spiral galaxy (2001.02222v1)

Abstract: Fast radio bursts (FRBs) are brief, bright, extragalactic radio flashes. Their physical origin remains unknown, but dozens of possible models have been postulated. Some FRB sources exhibit repeat bursts. Though over a hundred FRB sources have been discovered to date, only four have been localised and associated with a host galaxy, with just one of the four known to repeat. The properties of the host galaxies, and the local environments of FRBs, provide important clues about their physical origins. However, the first known repeating FRB has been localised to a low-metallicity, irregular dwarf galaxy, and the apparently non-repeating sources to higher-metallicity, massive elliptical or star-forming galaxies, suggesting that perhaps the repeating and apparently non-repeating sources could have distinct physical origins. Here we report the precise localisation of a second repeating FRB source, FRB 180916.J0158+65, to a star-forming region in a nearby (redshift $z = 0.0337 \pm 0.0002$) massive spiral galaxy, whose properties and proximity distinguish it from all known hosts. The lack of both a comparably luminous persistent radio counterpart and a high Faraday rotation measure further distinguish the local environment of FRB 180916.J0158+65 from that of the one previously localised repeating FRB source, FRB 121102. This demonstrates that repeating FRBs have a wide range of luminosities, and originate from diverse host galaxies and local environments.

• The paper precisely localizes FRB 180916.J0158+65 to a star-forming region in a nearby spiral galaxy at approximately 149 Mpc, underscoring host diversity.
• The paper used CHIME discovery and EVN interferometry, detecting four bursts with signal-to-noise ratios from 9.5 to 46 for accurate localization.
• The paper highlights different local conditions compared to FRB 121102, with no persistent radio counterpart and a low Faraday rotation measure, implying varied progenitor models.

A Repeating Fast Radio Burst Source Localized to a Nearby Spiral Galaxy

The paper presents a significant finding in the paper of fast radio bursts (FRBs): the precise localization of a repeating FRB source, designated FRB 180916.J0158+65, to a star-forming region in a nearby spiral galaxy with redshift $z = 0.0337 \pm 0.0002$. This discovery marks only the second instance of a repeating FRB being associated with its host galaxy, providing new insights into the diversity of FRB sources and their environments.

Key Findings

1. Localization of FRB 180916.J0158+65: The paper reports the localization of the FRB to a massive spiral galaxy, notably different from the previously identified repeating FRB 121102, which was linked to a low-metallicity, irregular dwarf galaxy. The proximity ($\sim149.0 \pm 0.9$ Mpc) and the attributes of the host galaxy—such as its high stellar mass and metallicity—offer a new perspective on the potential diversity of FRB environments.
2. Observational Methodology: The CHIME/FRB Collaboration initially discovered FRB 180916.J0158+65. The localization was further refined using interferometric observations conducted by the European Very-long-baseline-interferometry Network (EVN). A total of four bursts were detected, with high signal-to-noise ratios ranging from 9.5 to 46, solidifying the precise position associated with the host galaxy.
3. Lack of Persistent Counterpart: Unlike FRB 121102, the local environment of FRB 180916.J0158+65 lacks a luminous persistent radio counterpart and shows a relatively low Faraday rotation measure. These observations suggest different local conditions and potentially distinct origins or mechanisms for the repeating phenomenon.
4. Astrophysical Implications: The investigation highlights the variability in host galaxy types for repeating FRBs and suggests that repeating and non-repeating FRBs may not have a singular origin. The paper speculates on a variety of progenitor models, including young magnetars or interactions between a neutron star and another astrophysical entity.

Theoretical and Practical Implications

• Diversity of Host Galaxies: The findings demonstrate that FRB sources can inhabit a broad spectrum of galactic environments, from the high-metallicity, massive spirals akin to the Milky Way to irregular dwarfs. This diversity challenges the notion of a uniform progenitor and supports the hypothesis that different physical mechanisms may be at play.
• Potential for Future Exploration: The paper underscores the importance of enhanced interferometric localization capabilities in advancing our understanding of FRBs. The proximity of FRB 180916.J0158+65 opens up opportunities for in-depth multi-wavelength studies, which may constrain existing models or inspire novel hypotheses regarding FRB origins.

In conclusion, the precise localization of FRB 180916.J0158+65 to a nearby spiral galaxy signifies an important step in elucidating the origins of fast radio bursts. The paper contributes to a growing body of evidence that FRB phenomena may arise from multiple astrophysical channels, with implications for both the theoretical understanding and observational strategies in radio astronomy. Future research, particularly involving more localized FRBs, will be critical for discerning the full range of environments and mechanisms responsible for these enigmatic cosmic signals.