Electromagnetic Fireworks: Fast Radio Bursts from Rapid Reconnection in the Compressed Magnetar Wind

Abstract

One scenario for the generation of fast radio bursts (FRBs) is magnetic reconnection in a current sheet of the magnetar wind. Compressed by a strong magnetic pulse induced by a magnetar flare, the current sheet fragments into a self-similar chain of magnetic islands. Time-dependent plasma currents at their interfaces produce coherent radiation during their hierarchical coalescence. We investigate this scenario using 2D radiative relativistic particle-in-cell simulations to compute the efficiency of the coherent emission and to obtain frequency scalings. Consistent with expectations, a fraction of the reconnected magnetic field energy, f ∼ 0.002, is converted to packets of high-frequency fast magnetosonic waves, which can escape from the magnetar wind as radio emission. In agreement with analytical estimates, we find that magnetic pulses of 1047 erg s−1 can trigger relatively narrowband GHz emission with luminosities of approximately 1042 erg s−1, sufficient to explain bright extragalactic FRBs. The mechanism provides a natural explanation for a downward frequency drift of burst signals, as well as the ∼100 ns substructure recently detected in FRB 20200120E .

Three-dimensional Dynamics of Strongly Twisted Magnetar Magnetospheres: Kinking Flux Tubes and Global Eruptions

“…Similar to the "pancake" structures modeled by Yuan et al (2020Yuan et al ( , 2022 in the regime of fast shearing and by Sharma et al (2023) for slowly sheared magnetospheres, they propagate outward as nonlinear structures. Outgoing electromagnetic pulses of luminosities in this range can power coherent GHz emission in the outer magnetosphere, e.g., via synchrotron maser radiation (Lyubarsky 2014;Ghisellini 2016;Beloborodov 2017Beloborodov , 2020Metzger et al 2019;Plotnikov & Sironi 2019;Margalit et al 2020;Sironi et al 2021) or mode conversion (Thompson 2022) at relativistic magnetized shocks in the magnetar wind, or via forced magnetic reconnection in the compressed current sheet of the magnetosphere (Lyubarsky 2020;Mahlmann et al 2022a). Our globally erupting configurations are thus capable of powering both the X-ray bursts and FRB-like transients.…”

Radio Nebulae from Hyperaccreting X-Ray Binaries as Common-envelope Precursors and Persistent Counterparts of Fast Radio Bursts

“…Explaining observed FRB luminosities L FRB ∼ 10 40 -10 44 erg s −1 (top-left panel of Figure 2) via an accretion-powered jet requires a minimum accretion rate onto the NS/BH. As discussed in Sridhar et al (2021), accounting for mass loss in disk winds (which reduces the accreted mass reaching the inner disk by a factor of f w ∼ 10 −2 relative to the mass-transfer rate; Blandford & Begelman 1999) and the low predicted radio efficiencies of FRB emission models ( f ξ ∼ 10 −3 ; e.g., Plotnikov & Sironi 2019;Sironi et al 2021;Mahlmann et al 2022), this condition requires a binary mass-transfer rate Here, f b is the beaming factor, which is constrained in repeating FRB sources by the duty cycle of the burst activity (e.g., Katz 2017;Sridhar et al 2021). Despite large uncertainties, Equations (3) and (4) show that the observed FRB population is consistent with accreting systems characterized by a range of stable and unstable mass-transfer timescales, t active ∼ 10-10 6 yr.…”

“…Based in part on the similarities between these timescales and ULX superorbital periods, Sridhar et al (2021) proposed ULX-like binaries as a source of repeating (periodic) FRBs. In this scenario, FRBs are generated via magnetized shocks (Lyubarsky 2014;Beloborodov 2017;Metzger et al 2019) or magnetic reconnection (Lyubarsky 2020;Mahlmann et al 2022) in transient relativistic outflows 6 within the evacuated jet funnel of the accretion disk; periodicity in the burst activity window is imprinted by the precession of the binary jet axis-along which the FRB is relativistically beamed-in and out of the observer's line of sight (see also Katz 2017).…”

Effective resistivity in relativistic collisionless plasmoid-mediated reconnection

“…In magnetospheres, jets, accretion disks, and accretion disk coronae of black holes and neutron stars, relativistic magnetic reconnection is widely conjectured as the mechanism powering many spectacular high-energy phenomena such as flares from black hole magnetospheres (Nathanail et al 2020;Ripperda et al 2020;Chashkina et al 2021;Nathanail et al 2022;Ripperda et al 2022), high-energy emission from black hole accretion disk coronae (Sironi & Beloborodov 2020;Sridhar et al 2021Sridhar et al , 2022, neutron star binary merger precursors (Most & Philippov 2020), neutron star-black hole post-merger emission (Lyutikov & McKinney 2011;Bransgrove et al 2021), fast radio bursts (Lyubarsky 2020;Lyutikov & Popov 2020;Mahlmann et al 2022;Most & Philippov 2022), coherent radio and gammaray pulsar magnetospheric emission (Lyubarsky 2018;Philippov & Spitkovsky 2018;Philippov et al 2019;Hu & Beloborodov 2021), giant magnetar flares (Parfrey et al 2012), gamma-ray flares from pulsar wind nebulae (Cerutti et al 2012;Lyubarsky 2012) and flares from blazar jets (Giannios 2013;Petropoulou et al 2016).…”