A radio pulsar phase from SGR J1935+2154 provides clues to the magnetar FRB mechanism

Abstract

The megajansky radio burst, FRB 20200428, and other bright radio bursts detected from the Galactic source SGR J1935+2154 suggest that magnetars can make fast radio bursts (FRBs), but the emission site and mechanism of FRB-like bursts are still unidentified. Here, we report the emergence of a radio pulsar phase of the magnetar 5 months after FRB 20200428. Pulses were detected in 16.5 hours over 13 days using the Five-hundred-meter Aperture Spherical radio Telescope, with luminosities of about eight decades fainter than FRB 20200428. The pulses were emitted in a narrow phase window anti-aligned with the x-ray pulsation profile observed using the x-ray telescopes. The bursts, conversely, appear in random phases. This dichotomy suggests that radio pulses originate from a fixed region within the magnetosphere, but bursts occur in random locations and are possibly associated with explosive events in a dynamically evolving magnetosphere. This picture reconciles the lack of periodicity in cosmological repeating FRBs within the magnetar engine model.

A bright radio burst from FRB 20200120E in a globular cluster of the nearby galaxy M81

“…Consequently, the repeating FRB 20200120E would be classified as a nearby apparent one-off FRB if it were placed at a distance of 10s of Mpc. The same could be said for SGR 1935+2154 3,4,16,19,20 .…”

“…The datasets of radio pulses in this research are follows: (1) other bursts from FRB 20200120E, observed by CHIME 5 , DSS-63 17 , and Effelsberg telescopes 6, 10 ; (2) three well-studied localized repeating FRBs: FRB 20121102A 7 , FRB 20201124A 8 and FRB 20180916B 18,36,37 ; (3) radio bursts or pulses from the Galactic magnetar SGR 1935+2154 3,4,16,19,20 using a distance of 6.6 kpc; (4) a sample of super-giant pulses from the Crab pulsar 26 ; (5) single pulses of RRATs (RRATalog), and (6) pulsars at 1400 MHz 38 . For pulsars and RRATs, we presented the average properties of pulses from these sources.…”

“…Three well-studied localized repeating FRBs with known distances are also plotted: FRB 20121102A 7 in violet crosses, FRB 20201124A 8 in thistle crosses, and FRB 20180916B18,36,37 in blue crosses. Radio bursts or pulses from the Galactic magnetar SGR 1935+21543,4,16,19,20 are denoted by black squares, while super-giant pulses from the Crab pulsar26 are shown in tan. The pulsar38 and rotating radio transient (RRAT) population (RRATalog) are marked in thistle and slateblue, respectively.…”

Upper Limits on the Radio Pulses from Magnetars and a Central Compact Object with FAST

“…Recently, the first Galactic fast radio burst FRB 20200428 was detected from the magnetar SGR 1935 + 2154 (Bochenek et al 2020;CHIME/FRB Collaboration et al 2020), establishing that magnetars are one channel to produce FRBs. Radio pulses with a large range of strengths were found from this magnetar, FRBs being just the high fluency outliers (Pleunis & CHIME/FRB Collaboration 2020; Kirsten et al 2021;Zhu et al 2023). It is conceivable that other magnetars may also emit FRBs.…”

Solving the Mystery of Fast Radio Bursts: A Detective’s Approach

“…The pulses are found to be confined in a narrow phase window. FRB bursts, on the other hand, appear in random rotation phases, suggesting that the bursts and pulses likely originate from different locations and probably have somewhat different mechanisms (albeit sharing similar physics) [18]. • Cosmological FRBs are observed to have two apparent types: repeaters and nonrepeaters.…”