The Northern Cross Fast Radio Burst project. III. The FRB-magnetar connection in a sample of nearby galaxies
Abstract
Context. Fast radio bursts (FRBs) are millisecond radio transients observed at cosmological distances. The nature of their progenitors is still a matter of debate, although magnetars are invoked by most models. The proposed FRB-magnetar connection was strengthened by the discovery of an FRB-like event from the Galactic magnetar SGR J1935+2154.
Aims: In this work we aim to investigate how prevalent magnetars such as SGR J1935+2154 are within FRB progenitors.
Methods: To this end, we carried out an FRB search in a sample of seven nearby (< 12 Mpc) galaxies with the Northern Cross Radio Telescope for a total of 692 h.
Results: We detected one 1.8 ms burst in the direction of M 101 with a fluence of 58 ± 5 Jy ms. Its dispersion measure of 303 pc cm−3 places it most likely beyond M 101. Considering that no significant detection comes indisputably from the selected galaxies, we place a 38 yr−1 upper limit on the total burst rate (i.e. including the whole sample) at the 95% confidence level. This upper limit constrains the event rate per magnetar to λmag < 0.42 magnetar−1 yr−1 or, if combined with literature observations of a similar sample of nearby galaxies, it yields a joint constraint of λmag < 0.25 magnetar−1 yr−1. We also provide the first constraints on the expected rate of FRBs hypothetically originating from ultra-luminous X-ray (ULX) sources, since some of the galaxies observed during our observational campaign host confirmed ULXs. We obtain < 13 yr−1 per ULX for the total sample of galaxies observed.
Conclusions: Our results indicate that bursts with energies E > 1034 erg from magnetars such as SGR J1935+2154 appear more rarely compared to previous observations and further disfavour them as unique progenitors for the cosmological FRB population. This provides support to the idea that there is a greater contribution from a population of more exotic magnetars not born via core-collapsed supernovae.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- June 2023
- DOI:
- 10.1051/0004-6361/202346307
- arXiv:
- arXiv:2304.11179
- Bibcode:
- 2023A&A...674A.223P
- Keywords:
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- Local Group;
- methods: observational;
- stars: magnetars;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 9 pages, 4 figures, published in A&