A Repeating Fast Radio Burst Source in a Low-Luminosity Dwarf Galaxy

Danté M. Hewitt, Mohit Bhardwaj, Alexa C. Gordon, Aida Kirichenko, Kenzie Nimmo, Shivani Bhandari, Ismaël Cognard, Wen-fai Fong, Armando Gil de Paz, Akshatha Gopinath, Jason W. T. Hessels, Franz Kirsten, Benito Marcote, Vladislavs Bezrukovs, Richard Blaauw, Justin D. Bray, Salvatore Buttaccio, Tomas Cassanelli, Pragya Chawla, Alessandro Corongiu, William Deng, Hannah N. Didehbani, Yuxin Dong, Marcin P. Gawroński, Marcello Giroletti, Lucas Guillemot, Jeff Huang, Ronniy C. Joseph, Victoria M. Kaspi, Mattias Lazda, Michael Lindqvist, Maccaferri Giuseppe, Lluis Mas-Ribas, Kiyoshi W. Masui, Ryan Mckinven, Daniele Michilli, Anya E. Nugent, Omar S. Ould-Boukattine, Zsolt Paragi, Aaron B. Pearlman, Ue-Li Pen, Ziggy Pleunis, Ketan R. Sand, Vishwangi Shah, Kaitlyn Shin, Mark P. Snelders, Tiziana Venturi, Na Wang, David R. A. Williams-Baldwin, Jun Yang, Jianping P. Yuan

Published 2024-10-22Version 1

We present the localization and host galaxy of FRB 20190208A, a repeating source of fast radio bursts (FRBs) discovered using CHIME/FRB. As part of the PRECISE repeater localization program on the EVN, we monitored FRB 20190208A for 65.6 hours at $\sim1.4$ GHz and detected a single burst, which led to its VLBI localization with 260 mas uncertainty (2$\sigma$). Follow-up optical observations with the MMT Observatory ($i\gtrsim 25.7$ mag (AB)) found no visible host at the FRB position. Subsequent deeper observations with the GTC, however, revealed an extremely faint galaxy ($r=27.32 \pm0.16$ mag), very likely ($99.95 \%$) associated with FRB 20190208A. Given the dispersion measure of the FRB ($\sim580$ pc cm$^{-3}$), even the most conservative redshift estimate ($z_{\mathrm{max}}\sim0.83$) implies that this is the lowest-luminosity FRB host to date ($\lesssim10^8L_{\odot}$), even less luminous than the dwarf host of FRB 20121102A. We investigate how localization precision and the depth of optical imaging affect host association, and discuss the implications of such a low-luminosity dwarf galaxy. Unlike the other repeaters with low-luminosity hosts, FRB 20190208A has a modest Faraday rotation measure of a few tens of rad m$^{-2}$, and EVN plus VLA observations reveal no associated compact persistent radio source. We also monitored FRB 20190208A for 40.4 hours over 2 years as part of the \'ECLAT repeating FRB monitoring campaign on the Nan\c{c}ay Radio Telescope, and detected one burst. Our results demonstrate that, in some cases, the robust association of an FRB with a host galaxy will require both high localization precision, as well as deep optical follow-up.