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

Weiwei Zhu^{1

2}, Heng Xu^{1

3

4}, Dejiang Zhou^{1

5}, Lin Lin^{2

6}, Bojun Wang^{1

3}, Pei Wang^{1

2}, Chunfeng Zhang^{1

3}, Jiarui Niu^{1

5}, Yutong Chen^{1

5}, Chengkui Li⁷, Lingqi Meng^{1

5}, Kejia Lee^{1

3

4}, Bing Zhang^{8

9}, Yi Feng¹⁰, Mingyu Ge⁷, Ersin Göğüş¹¹, Xing Guan¹, Jinlin Han¹, Jinchen Jiang^{1

3}, Peng Jiang^{1

12}, Chryssa Kouveliotou¹³, Di Li^{1

11}, Chenchen Miao^{1

5}, Xueli Miao¹, Yunpeng Men¹⁴, Chenghui Niu¹, Weiyang Wang^{3

5}, Zhengli Wang¹⁴, Jiangwei Xu^{1

3}, Renxin Xu², Mengyao Xue¹, Yuanpei Yang¹⁵, Wenfei Yu¹⁶, Mao Yuan^{1

5}, Youling Yue¹, Shuangnan Zhang⁷, Yongkun Zhang^{1

5}

Affiliations

¹ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China.
² Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, China.
³ Department of Astronomy, Peking University, Beijing 100871, China.
⁴ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China.
⁵ University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100049, China.
⁶ Department of Astronomy, Beijing Normal University, Beijing 100875, China.
⁷ Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
⁸ Nevada Center for Astrophysics, University of Nevada, Las Vegas, NV 89154, USA.
⁹ Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154, USA.
¹⁰ Zhejiang Lab, Hangzhou, Zhejiang 311121, China.
¹¹ Faculty of Engineering and Natural Sciences, Sabancı University, 34956 İstanbul, Turkey.
¹² Department of Physics, The George Washington University, 725 21st St. NW, Washington, DC 20052, USA.
¹³ Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany.
¹⁴ GuangXi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, GuangXi University, Naning 530004, China.
¹⁵ South-Western Institute for Astronomy Research, Yunnan University, Kunming 650500, Yunnan, China.
¹⁶ Shanghai Astronomical Observatory, Chinese Academy of Science, Shanghai 200030, China.

PMID: 37506211
PMCID: PMC12488042
DOI: 10.1126/sciadv.adf6198

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

Weiwei Zhu et al. Sci Adv. 2023.

. 2023 Jul 28;9(30):eadf6198.

doi: 10.1126/sciadv.adf6198. Epub 2023 Jul 28.

Authors

Affiliations

¹ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China.
² Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, China.
³ Department of Astronomy, Peking University, Beijing 100871, China.
⁴ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China.
⁵ University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100049, China.
⁶ Department of Astronomy, Beijing Normal University, Beijing 100875, China.
⁷ Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
⁸ Nevada Center for Astrophysics, University of Nevada, Las Vegas, NV 89154, USA.
⁹ Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154, USA.
¹⁰ Zhejiang Lab, Hangzhou, Zhejiang 311121, China.
¹¹ Faculty of Engineering and Natural Sciences, Sabancı University, 34956 İstanbul, Turkey.
¹² Department of Physics, The George Washington University, 725 21st St. NW, Washington, DC 20052, USA.
¹³ Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany.
¹⁴ GuangXi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, GuangXi University, Naning 530004, China.
¹⁵ South-Western Institute for Astronomy Research, Yunnan University, Kunming 650500, Yunnan, China.
¹⁶ Shanghai Astronomical Observatory, Chinese Academy of Science, Shanghai 200030, China.

PMID: 37506211
PMCID: PMC12488042
DOI: 10.1126/sciadv.adf6198

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.

PubMed Disclaimer

Figures

**Fig. 1.. A plot of spin phases of the radio pulses detected by FAST in October 2020.**
The size of the marker represents the signal-to-noise ratio (S/N) of the pulse. The phases of the pulses are computed on the basis of our best-fit timing solution (Table 1). We separate the emission into three phases (marked by blue, orange, and green), of which the pulse phase distribution is different.

**Fig. 2.. The radio and x-ray campaign and the bursts’ rotational phases.**
(A) The timeline of our FAST observational campaign of SGR J1935+2154 in cyan and NICER observations in black, with important events labeled with colored vertical dash lines. T_obs is the FAST or NICER on-source observation time, N_bursts is the number of bursts detected by FAST, and r is the FAST event rate in the unit of 1/hour. (B) Black curves represent the persistent pulse profile detected by NICER or XMM-Newton. We aligned the x-ray profiles across different panels by fitting them with sinusoidal curves except for the profile from 28 to 30 April 2020. The NICER profile of 28 to 30 April 2020 differs in shape from the rest of the x-ray profiles, so we manually moved it by +0.2 to better align its peak with the other x-ray profiles. The vertical lines label the phases of the FRB20200428 bursts (red), the FAST #1 (cyan), the Westerbork bursts (magenta), the CHIME 8 October bursts (red), and the FAST pulsar radiation taken on 18 October (cyan curve). We also present the FAST integrated profile from 18 October in cyan in the bottom plot of (B).

**Fig. 3.. Comparison of various SGR J1935+2154 radio emissions with emission from other sources.**
The y axis is the radio luminosity, and the x axis is the product of observing the frequency and the width of radio emission (bursts or pulses). The thick red crosses denote the single pulses of SGR J1935+2154 reported in this work. The blue line indicates the position of the detection threshold for the FAST observations. The radio bursts from SGR J1935+2154 are shown in purple pluses, from top to bottom are the FRB-like burst detected by CHIME (1) and STARE2 (2), intermediate bursts detected by Westerbork (22) and CHIME (25), and pulse #1 detected by FAST (21). Emissions from other active FRB sources—FRB 20201124A (30), FRB 121102 (31), FRB 20180916B (32, 33), FRB 20200120E (34), and FRBs from CHIME catalog 1 (35)—are plotted in different colors. The emission from pulsars and RRATs are shown in gray crosses and pluses, respectively, with cyan pluses representing Crab nanoshots (–38).

**Fig. 4.. A gallery of emission properties of SGR J1935+2154’s pulses.**
The x axis T is time in units of seconds. We present in each panel the polarization position angle (PA) at 1250 MHz in units of degree, the pulse intensity profile with its off-pulse variance normalized to unity, and the grayscale image displays the power as a function of both time T and frequency ν (also called the “waterfall” plot) after dedispersion of radio signals with DM = 332.703 cm⁻³ pc. (A to C) Pulses with multiple components. (D to F) Pulses with narrow bandwidth and frequency drift features.

**Fig. 5.. Folded pulse profiles on 10, 18, and 29 October 2020 and the evolution of the folded profiles and single pulses.**
(A) Polarization PAs measured at 1250 MHz. (B) Polarization integrated pulse profile, with total intensity, linear polarization, and circular polarization in black, red, and blue, respectively. (C) Folded pulse profiles (colored curves). The horizontal box error bars show the center and the 90% flux width of the best-fit Gaussian. (D) Phases of the single pulses.

**Fig. 6.. Polarization PA–pulse phase distribution of bright single pulses (S/N > 20).**
We compare the polarization PAs of the Westerbork bursts (red bars) and that of the FAST pulses (blue bars) after derotating them to infinite frequency. Note that the Westerbork bursts (Wb #1 and Wb #2) and the FAST #1 burst are placed in arbitrary phases for convenience of comparison. We cannot extend our timing solutions to compute the phases of those bursts accurately. For the FAST pulses, we assumed a fixed RM of 111 rad m⁻². The size of each FAST data point is proportional to the S/N of the pulse, and the reference marker of S/N = 20 is plotted. The solid contour labeled with 1σ is the 68% contour of the cumulative distribution of FAST PAs derived from a Gaussian kernel density estimation (43).

**Fig. 7.. Pulse bandwidth and center frequency distribution of SGR J1935+1054.**
(A) A downsampled snapshot of a single pulse that is smoothed using a Gaussian filter of a two-pixel radius. The resulting smoothed image is fitted with a 2D vertical Gaussian profile (the yellow contour in the inlet marks the 1σ radius ellipse, and the red marks the 2σ radius). We take the center of the resulting vertical Gaussian profile as the central frequency of the pulse and two times the best-fit Gaussian width (encompassing 95% of the pulse energy) as the characteristic bandwidth for the single pulse. (B) The distribution of the central frequency and bandwidth for the pulses. Some pulses’ emission comes mainly from one side of the observing band; their central frequency could be outside the observable range, and their bandwidth could be larger than the observable bandwidth (450 MHz). In these cases, we plotted them using gray points. In (C), we show two histograms; the step histogram shows the distribution of center frequencies for all pulses, and the filled histogram shows the pulses with center frequency inside of our observable range and bandwidth smaller than our observable bandwidth. Similarly, (D) shows the distribution of best-fit bandwidths of all the pulses and pulses with reasonable fit parameters.

**Fig. 8.. The waiting time and energy distribution of SGR J1935+2154.**
(A) The waiting time distribution. The vertical dashed line marks the period of the pulsar. We fit the millisecond-scale waiting times (red dashed curve) with a normal distribution in the logarithmic scale and find a peak at 5(1) ms with a σ of 0.6(1) dex. (B) Energy distributions of the single pulses in the October 2020 episode–filled histogram: the detected energy distribution of the SGR J1935+2154’s single pulses. Red error bars, the estimated energy distribution after correcting for the sample completeness. Solid curve, the best-fit log-normal distribution curve.

**Fig. 9.. The illustration of a possible picture for SGR J1935+2154’s radio and x-ray emission geometry.**
The x-ray hot spot (orange region) lies on the opposite side of the pulsar emission zone (red star), leading to a ≃180° phase difference between the x-ray peak and the radio pulses. We also illustrate in purple an emission geometry for FRB20200428 deduced from the illustrated pulsar emission geometry assuming a dipolar magnetic field. Note that this illustration is not to scale because that dipolar magnetic field line only starts to bend over at an altitude ≳10⁴ R_ns for such a slowly rotating magnetar.

See this image and copyright information in PMC

References

1. CHIME/FRB Collaboration , A bright millisecond-duration radio burst from a Galactic magnetar. Nature 587, 54–58 (2020). - PubMed
1. Bochenek C. D., Ravi V., Belov K. V., Hallinan G., Kocz J., Kulkarni S. R., McKenna D. L., A fast radio burst associated with a Galactic magnetar. Nature 587, 59–62 (2020). - PubMed
1. Li C. K., Lin L., Xiong S. L., Ge M. Y., Li X. B., Li T. P., Lu F. J., Zhang S. N., Tuo Y. L., Nang Y., Zhang B., Xiao S., Chen Y., Song L. M., Xu Y. P., Liu C. Z., Jia S. M., Cao X. L., Qu J. L., Zhang S., Gu Y. D., Liao J. Y., Zhao X. F., Tan Y., Nie J. Y., Zhao H. S., Zheng S. J., Zheng Y. G., Luo Q., Cai C., Li B., Xue W. C., Bu Q. C., Chang Z., Chen G., Chen L., Chen T. X., Chen Y. B., Chen Y. P., Cui W., Cui W. W., Deng J. K., Dong Y. W., du Y. Y., Fu M. X., Gao G. H., Gao H., Gao M., Gu Y. D., Guan J., Guo C. C., Han D. W., Huang Y., Huo J., Jiang L. H., Jiang W. C., Jin J., Jin Y. J., Kong L. D., Li G., Li M. S., Li W., Li X., Li X. F., Li Y. G., Li Z. W., Liang X. H., Liu B. S., Liu G. Q., Liu H. W., Liu X. J., Liu Y. N., Lu B., Lu X. F., Luo T., Ma X., Meng B., Ou G., Sai N., Shang R. C., Song X. Y., Sun L., Tao L., Wang C., Wang G. F., Wang J., Wang W. S., Wang Y. S., Wen X. Y., Wu B. B., Wu B. Y., Wu M., Xiao G. C., Xu H., Yang J. W., Yang S., Yang Y. J., Yang Y. J., Yi Q. B., Yin Q. Q., You Y., Zhang A. M., Zhang C. M., Zhang F., Zhang H. M., Zhang J., Zhang T., Zhang W., Zhang W. C., Zhang W. Z., Zhang Y., Zhang Y., Zhang Y. F., Zhang Y. J., Zhang Z., Zhang Z., Zhang Z. L., Zhou D. K., Zhou J. F., Zhu Y., Zhu Y. X., Zhuang R. L., HXMT identification of a non-thermal X-ray burst from SGR J1935+2154 and with FRB 200428. Nat. Astron. 5, 378–384 (2021).
1. Ridnaia A., Svinkin D., Frederiks D., Bykov A., Popov S., Aptekar R., Golenetskii S., Lysenko A., Tsvetkova A., Ulanov M., Cline T. L., A peculiar hard x-ray counterpart of a Galactic fast radio burst. Nat. Astron. 5, 372–377 (2021).
1. Tavani M., Casentini C., Ursi A., Verrecchia F., Addis A., Antonelli L. A., Argan A., Barbiellini G., Baroncelli L., Bernardi G., Bianchi G., Bulgarelli A., Caraveo P., Cardillo M., Cattaneo P. W., Chen A. W., Costa E., Del Monte E., Di Cocco G., Di Persio G., Donnarumma I., Evangelista Y., Feroci M., Ferrari A., Fioretti V., Fuschino F., Galli M., Gianotti F., Giuliani A., Labanti C., Lazzarotto F., Lipari P., Longo F., Lucarelli F., Magro A., Marisaldi M., Mereghetti S., Morelli E., Morselli A., Naldi G., Pacciani L., Parmiggiani N., Paoletti F., Pellizzoni A., Perri M., Perotti F., Piano G., Picozza P., Pilia M., Pittori C., Puccetti S., Pupillo G., Rapisarda M., Rappoldi A., Rubini A., Setti G., Soffitta P., Trifoglio M., Trois A., Vercellone S., Vittorini V., Giommi P., D’Amico F., An x-ray burst from a magnetar enlightening the mechanism of fast radio bursts. Nat. Astron. 5, 401–407 (2021).

LinkOut - more resources

Full Text Sources

Save citation to file

Email citation

Add to Collections

Add to My Bibliography

Your saved search

Create a file for external citation management software

Your RSS Feed

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

Affiliations

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

Authors

Affiliations

Abstract

Figures

References

LinkOut - more resources

Full Text Sources