AT2020hur: A Possible Optical Counterpart of FRB 180916B

Abstract

The physical origin of fast radio bursts (FRBs) remains unclear. Finding multiwavelength counterparts of FRBs can provide a breakthrough for understanding their nature. In this work, we perform a systematic search for astronomical transients whose positions are consistent with FRBs. We find an unclassified optical transient AT2020hur (α = 01h58m00.ˢ750 ± 1″, δ = 65 ° 43 ′ 00 .″ 30 ± 1 ″ ) that is spatially coincident with the repeating FRB 180916B (α = 01h58m00.ˢ7502 ± 2.3 mas, δ = 65 ° 43 ′ 00 .″ 3152 ± 2.3 mas; Marcote et al. 2020). The chance possibility of the AT2020hur–FRB 180916B association is about 0.04%, which corresponds to a significance of 3.5σ. We develop a giant flare (GF) afterglow model to fit AT2020hur. Although the GF afterglow model can interpret the observations of AT2020hur, the derived kinetic energy of such a GF is at least three orders of magnitude larger than that of a typical GF, and a lot of fine-tuning and coincidences are required for this model. Another possible explanation is that AT2020hur might consist of two or more optical flares originating from the FRB source, e.g., fast optical bursts produced by the inverse Compton scattering of FRB emission. Besides, AT2020hur is located in one of the activity windows of FRB 180916B, which provides independent support for the association. This coincidence may be due to the optical counterparts being subject to the same periodic modulation as FRB 180916B, as implied by the prompt FRB counterparts. Future simultaneous observations of FRBs and their optical counterparts may help to reveal their physical origin.

Searching for Associations between Short Gamma-Ray Bursts and Fast Radio Bursts

“…The dispersion measures (DMs) of FRBs exceed the Milky Way's contribution and some of them have been reliably determined to be located in extragalactic systems (Chatterjee et al 2017;Bannister et al 2019;Ravi et al 2019;Marcote et al 2020). Up to now, except for the X-ray burst from the Galactic soft gamma repeater (SGR) SGR 1935+2154 coincident with the fast radio burst FRB 200428 (Bochenek et al 2020;CHIME/FRB Collaboration et al 2020), no other multiwavelength/multimessenger transients associated with FRBs have been definitely observed (DeLaunay et al 2016;Yamasaki et al 2016;Hardy et al 2017;Xi et al 2017;Zhang & Zhang 2017;Cunningham et al 2019;James et al 2019;Mereghetti et al 2020;Tavani et al 2020;Li et al 2021;Xin et al 2021;Abbott et al 2023;Wang & Nitz 2022), though there have been some works claiming tentative associations of FRBs with multiwavelength transient counterparts (Li et al 2022;Wang et al 2020b). Current FRB models can be divided into two categories: catastrophic models (e.g., Kashiyama et al 2013;Totani 2013;Falcke & Rezzolla 2014;Zhang 2014;Liu et al 2016;Wang et al 2016;Zhang 2016) and non-catastrophic models (e.g., Dai et al 2016;Murase et al 2016;Metzger et al 2017;Margalit & Metzger 2018;Ioka & Zhang 2020;Wang et al 2020a;Zhang 2020;…”

A Generic Model for a Persistent Radio Source around Fast Radio Bursts

“…It has been proposed that the large DM and scattering of FRB 190520B are dominated by the host galaxy, making the bursts a probe into the circumstances, e.g., the plasma and turbulence (Ocker et al 2022(Ocker et al , 2023. Since counterparts like PRSs can unveil insights into the FRB itself, a search for other counterparts in different wave bands (e.g., optical) was raised (Chibueze et al 2022;Li et al 2022;Vohl et al 2023aVohl et al , 2023b), yet no optical counterpart of FRB 190520B was confirmed (Niino et al 2022). With the discovery of an FRB in a clean environment (Feng et al 2023) and the suggestion that there is no obvious evidence for repeaters or nonrepeaters to be preferentially associated with PRSs (Law et al 2022), this may indicate that FRBs and PRSs are two aspects of the central engine rather than the same origin, as pointed out that the polarization of PRSs differs from that of FRBs in Bhandari et al (2023).…”

Multi-wavelength afterglow emission from bursts associated with magnetar flares and fast radio bursts

“…For example, Yi et al (2014) studied multi-wavelength afterglows from GRB-like outflows, and Lin & Totani (2020) studied the detectability of afterglows in light of the binary neutron star merger model for FRBs. Li et al (2022) discussed a possible connection between FRB 180916B and a possible optical counterpart AT2020hur of FRB assuming a collimated outflow.…”