A bright millisecond-duration radio burst from a Galactic magnetar (2005.10324v2)

Abstract: Magnetars are highly magnetized young neutron stars that occasionally produce enormous bursts and flares of X-rays and gamma-rays. Of the approximately thirty magnetars currently known in our Galaxy and Magellanic Clouds, five have exhibited transient radio pulsations. Fast radio bursts (FRBs) are millisecond-duration bursts of radio waves arriving from cosmological distances. Some have been seen to repeat. A leading model for repeating FRBs is that they are extragalactic magnetars, powered by their intense magnetic fields. However, a challenge to this model has been that FRBs must have radio luminosities many orders of magnitude larger than those seen from known Galactic magnetars. Here we report the detection of an extremely intense radio burst from the Galactic magnetar SGR 1935+2154 using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) FRB project. The fluence of this two-component bright radio burst and the estimated distance to SGR 1935+2154 together imply a 400-800 MHz burst energy of $\sim 3 \times 10^{34}$ erg, which is three orders of magnitude brighter than those of any radio-emitting magnetar detected thus far. Such a burst coming from a nearby galaxy would be indistinguishable from a typical FRB. This event thus bridges a large fraction of the radio energy gap between the population of Galactic magnetars and FRBs, strongly supporting the notion that magnetars are the origin of at least some FRBs.

• The paper demonstrates that an intense millisecond-duration burst from SGR 1935+2154 supports the model linking magnetars to Fast Radio Bursts.
• The study used CHIME’s real-time array and interferometric techniques to estimate the burst’s energy at about 3 x 10^34 erg.
• Simultaneous radio and X-ray emissions observed during the burst reinforce the multi-wavelength connection and the potential of magnetars as FRB sources.

A Bright Millisecond-Duration Radio Burst from a Galactic Magnetar

The paper published by the CHIME/FRB Collaboration presents a detailed paper of an intense radio burst detected from the Galactic magnetar SGR 1935+2154. This event, as observed by the Canadian Hydrogen Intensity Mapping Experiment (CHIME), provides critical evidence supporting the hypothesis that magnetars could be progenitors of Fast Radio Bursts (FRBs).

Key Findings

The research team detected a significant radio burst from SGR 1935+2154, noted for its extreme fluence. The burst, characterized by two bright components, was detected at 400-800 MHz frequencies and had an estimated energy of approximately $3 \times 10^{34}$ erg. The energy of this burst is significantly higher—by three orders of magnitude—than any previously detected radio burst from known Galactic magnetars.

The event was recorded on April 28, 2020, during an episode of pronounced X-ray activity from the magnetar, reinforcing the multi-wavelength emission characteristic of these phenomena. The burst was detected 0.3 degrees from the known position of SGR 1935+2154, validating its association with the magnetar.

Methodology

To detect and analyze this radio burst, CHIME utilized its array of equispaced antennas and powerful correlator in real-time analysis. The telescope's design allows for a vast field of view that facilitates the detection of transient phenomena like FRBs. The signal was processed to account for temporal and spectral variations related to the magnetar's emission, aiding the precise determination of the burst's properties.

The position and energy estimates of the burst were refined using a combination of interferometric data from both the CHIME and Algonquin Radio Observatory systems. This combined approach allowed the researchers to narrow down the localization and confirm the burst's Galactic origin, particularly relating to the dispersion measure consistent with known Galactic models.

Implications

The detection of such a luminous event from a Galactic magnetar narrows the observational gap between traditional magnetar bursts and the more energetic extragalactic FRBs. The event aligns with predictions that certain FRBs could originate from magnetars, albeit under more extreme circumstances.

This discovery also posits that the radio energy output of magnetars may be higher than previously estimated, suggesting that similar nearby magnetar bursts could be mistaken for FRBs if positioned within sufficiently proximate galaxies. Moreover, the simultaneous X-ray and radio emissions observed align well with proposals linking magnetar activities to high-energy phenomena, thereby bolstering the association between magnetars and repeating FRBs.

Future Directions

The paper discusses several avenues for future research, particularly focusing on improved localization techniques and the correlation between magnetar emissions and their potential as FRB sources. The paper proposes enhancements in the sensitivity and calibration of detection systems to better capture and analyze faint or distant magnetar emissions. Additionally, investigating the temporal synchronization of radio and X-ray bursts could further refine our understanding of the underlying emission mechanisms at play.

In conclusion, this CHIME/FRB detection is a pivotal step in understanding the connection between magnetars and FRBs. It enriches our comprehension of these astronomical phenomena, indicating that certain FRBs may indeed be high-energy counterparts to magnetar activity. Continued observations and technological advancements will be paramount in developing a comprehensive theory explaining the origins of FRBs, particularly in relation to magnetars.