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A peculiar hard X-ray counterpart of a Galactic fast radio burst

Nature Astronomy volume 5, pages 372–377 (2021)Cite this article

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Abstract

Fast radio bursts (FRBs) are bright, millisecond-scale radio flashes of unknown physical origin1. Young, highly magnetized, isolated neutron stars—magnetars—have been suggested as the most promising candidates for FRB progenitors owing to their energetics and high X-ray flaring activity2,3. Here we report the detection with Konus-Wind of a hard X-ray event of 28 April 2020 temporally coincident with a bright, two-peak radio burst4,5 in the direction of Galactic magnetar SGR 1935+2154, with properties remarkably similar to those of FRBs. We show that the two peaks of the double-peaked X-ray burst coincide in time with the radio peaks and infer a common source and the association of these phenomena. An unusual hardness of the X-ray spectrum strongly distinguishes the 28 April event among multiple ‘ordinary’ flares from SGR 1935+2154. A recent non-detection5,6,7 of radio emission from about 100 typical soft bursts from SGR 1935+2154 favours the idea that bright, FRB-like magnetar signals are associated with rare, hard-spectrum X-ray bursts. The implied rate of these hard X-ray bursts (~0.04 yr−1 magnetar−1) appears consistent with the rate estimate4 of SGR 1935+2154-like radio bursts (0.007–0.04 yr−1 magnetar−1).

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Fig. 1: Hard X-ray burst from SGR 1935+2154 of 28 April 2020.
Fig. 2: Radio to X-ray spectral energy distribution.
Fig. 3: Properties of the April 28 event and other SGR 1935+2154 X-ray bursts.

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Data availability

The data that support the plots within this paper and other findings of this study are available from http://www.ioffe.ru/LEA/papers/RidnaiaNatAstr2020/data or from the corresponding author upon reasonable request. Links to the Wind predicted ephemeris and clock accuracy data are provided in the Methods (https://spdf.gsfc.nasa.gov/pub/data/wind/orbit/pre_or and ftps://pwgdata.sci.gsfc.nasa.gov/pub/wind_clock/wind_20-119-13-21-00.cc_rpt). Source data are provided with this paper.

Code availability

XSPEC is freely available online (https://heasarc.gsfc.nasa.gov/xanadu/xspec/). Python scripts used in the plot preparation are available from http://www.ioffe.ru/LEA/papers/RidnaiaNatAstr2020/data.

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Acknowledgements

S.P. acknowledges support from the Program of Development of the M. V. Lomonosov Moscow State University (Leading Scientific School ‘Physics of stars, relativistic objects, and galaxies’). The calculations were partially done on computers of the RAS JSCC and St Petersburg department of the RAS JSCC and at the Tornado subsystem of the St. Petersburg Polytechnic University supercomputing centre. The Konus-Wind experiment is supported by the Russian State Space Agency ROSCOSMOS.

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Authors and Affiliations

  1. Ioffe Institute, St Petersburg, Russia

    A. Ridnaia, D. Svinkin, D. Frederiks, A. Bykov, R. Aptekar, S. Golenetskii, A. Lysenko, A. Tsvetkova & M. Ulanov

  2. Sternberg Astronomical Institute, Lomonosov Moscow State University, Moscow, Russia

    S. Popov

  3. Department of Physics, National Research University ‘Higher School of Economics’, Moscow, Russia

    S. Popov

  4. NASA Goddard Space Flight Center, Greenbelt, MD, USA

    T. L. Cline

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Contributions

A.R., D.S. and D.F. performed the KW data analysis. A.R., D.S., D.F., A.B. and S.P. contributed to the discussion of the results in the context of KW magnetar observations, magnetar emission models and FRB–magnetar connections. A.L. contributed to the KW spectral analysis. S.G., A.T. and M.U. contributed to the KW data reduction. R.A., S.G. and D.F. contributed to the KW design and calibrations. R.A. was the principal investigator of the KW experiment and T.L.C. was the co-PI from the American side. A.R., D.S. and D.F. wrote the manuscript with contributions from A.B. and S.P. All co-authors provided comments on the final version of the manuscript.

Corresponding author

Correspondence to A. Ridnaia.

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Extended data

Extended Data Fig. 1 Temporal parameters.

the burst start time relative to T0 (2nd column), the burst end time relative to T0 (3rd column), the total burst duration (4th column), T50 and T90 durations (5th and 6th columns, respective-ly) along with their 68% confidence intervals are given for specif-ic energy band (1st column).

Extended Data Fig. 2 Spectral fit results with thermal models (BB and 2BB) for two spectra.

time-averaged spectrum (0.0 - 0.256 s) and the peak spectrum (0.0 - 0.064 s), measured near the peak count rate. The times are given relative to T0. The errors are given at 90% CL. Model normalizations are proportional to the surface area \({R}_{km}^{2}/{d}_{10}^{2}\), where Rkm is the source radius in km and d10 is the distance to the source in units of 10 kpc.

Extended Data Fig. 3 Spectral fit results with non-thermal models (PL and CPL) for two spectra.

time-averaged spectrum (0.0 - 0.256 s) and the peak spectrum (0.0 - 0.064 s), measured near the peak count rate. The times are given relative to T0. The errors are given at 90% CL.

Extended Data Fig. 4 Spectral parameters (CPL model) and energetics of 22 SGR 1935+2154 bursts detected by KW.

The errors are given at 68% CL. The fluences and the peak fluxes are estimated in the 20 - 500 keV band. a The FRB burst.

Source data

Extended Data Fig. 5 Peak energies Ep (CPL model) and energy fluences of hard magnetar bursts detected by KW.

The errors are given at 68% CL. The fluences are estimated in the 20 - 500 keV band. a Two hard bursts from SGR 1900+14 were also reported by BATSE78. b The parameters were estimated using optically thin thermal bremsstrahlung (OTTB) spectrum (f(E) ∝ E−1exp(− E/kTOTTB)) c The 2009-01-25 burst from SGR 1550-5418 was also reported by INTEGRAL79,80 [cite ATel1908,Mereghetti2009]. d The 2009-01-29 burst from SGR 1550-5418 was also detected by Fermi-GBM (https://gammaray.nsstc.nasa.gov/gbm/science/magnetars.html). e The FRB burst (this work).

Extended Data Fig. 6 Peak energies Ep vs. total energy fluences of 250 bright magnetar bursts detected by Konus-Wind since November 1994.

Six bursts marked by stars have unusually high Ep values (Extend-ed Data Figure 5): two bursts from SGR 1900+14 (orange), one from SGR 1627-41 (blue), two from SGR 1550-5418 (green), and the April 28 event (red). The error bars are given at the 68% confidence level. For extremely bright bursts from SGR 1627-41 and SGR 1550-5418 (shown by stars) the error bars represent systematic uncer-tainties due to the high count rate, which exceed statistical er-rors.

Supplementary information

Supplementary Information

Supplementary Figs. 1 and 2.

Source data

Source Data Extended Data Fig. 4

Spectral parameters (CPL model) and energetics of 22 SGR 1935+2154 bursts detected by KW.

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Ridnaia, A., Svinkin, D., Frederiks, D. et al. A peculiar hard X-ray counterpart of a Galactic fast radio burst. Nat Astron 5, 372–377 (2021). https://doi.org/10.1038/s41550-020-01265-0

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