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A sudden dramatic change and recovery of magneto-environment of a repeating fast radio burst

Y. Li, S. B. Zhang, Y. P. Yang, C. W. Tsai, X. Yang, C. J. Law, R. Anna-Thomas, X. L. Chen, K. J. Lee, Z. F. Tang, D. Xiao, H. Xu, X. L. Yang, G. Chen, Y. Feng, D. Z. Li, R. Mckinven, J. R. Niu, K. Shin, B. J. Wang, C. F. Zhang, Y. K. Zhang, D. J. Zhou, Y. H. Zhu, Z. G. Dai, C. M. Chang, J. J. Geng, J. L. Han, L. Hu, D. Li, R. Luo, C. H. Niu, D. D. Shi, T. R. Sun, X. F. Wu, W. W. Zhu, P. Jiang, B. Zhang

TL;DR

The study reports an unprecedented RM flare in FRB 20220529, where RM rose from a baseline of about $17\,rad\,m^{-2}$ to $\sim2000\,rad\,m^{-2}$ over ~weeks and returned to baseline shortly after, indicating a transient, dense magnetized clump along the line of sight. A comprehensive, multi-telescope campaign combining FAST, Parkes, and VLA, together with optical host identification (DESI/GTC) and host-galaxy analysis, establishes the FRB environment in a disk galaxy at $z\approx0.184$, with RM/DM/polarization providing diagnostics of the local magneto-ionic medium. Among several physical scenarios, a coronal mass ejection (CME) from a companion star in a binary system best explains the RM flare, yielding DM variations compatible with the data and predicting infrequent, stochastic RM events in repeating FRBs. The results demonstrate that FRB magneto-ionic environments can undergo rapid, dramatic changes on week timescales, driven by localized plasma structures, and offer a novel probe of binary stellar environments and stellar activity in FRB hosts.

Abstract

Fast radio bursts (FRBs) are millisecond-duration radio bursts with unidentified extra-galactic origin. Some FRBs exhibit mild magneto-ionic environmental variations, possibly attributed to plasma turbulence or binary configuration. We report an abrupt magneto-ionic variation of FRB 20220529, a repeating FRB from a disk galaxy at redshift $0.1839 \pm 0.0001$. Initially, the Faraday rotation measure (RM) had a median of $17~{\rm rad~m^{-2}}$ and a scatter of $101~{\rm rad~m^{-2}}$ over 17 months. In December 2023, it jumped to $1977 \pm 84~{\rm rad~m^{-2}}$, and returned to typical values within two weeks. This drastic RM variation suggests that a dense magnetized clump enters and exits the line of sight in week timescales. One plausible scenario invokes a coronal mass ejection from a companion star, while other scenarios invoking extreme turbulence or binary orbital motion are also possible.

A sudden dramatic change and recovery of magneto-environment of a repeating fast radio burst

TL;DR

The study reports an unprecedented RM flare in FRB 20220529, where RM rose from a baseline of about to over ~weeks and returned to baseline shortly after, indicating a transient, dense magnetized clump along the line of sight. A comprehensive, multi-telescope campaign combining FAST, Parkes, and VLA, together with optical host identification (DESI/GTC) and host-galaxy analysis, establishes the FRB environment in a disk galaxy at , with RM/DM/polarization providing diagnostics of the local magneto-ionic medium. Among several physical scenarios, a coronal mass ejection (CME) from a companion star in a binary system best explains the RM flare, yielding DM variations compatible with the data and predicting infrequent, stochastic RM events in repeating FRBs. The results demonstrate that FRB magneto-ionic environments can undergo rapid, dramatic changes on week timescales, driven by localized plasma structures, and offer a novel probe of binary stellar environments and stellar activity in FRB hosts.

Abstract

Fast radio bursts (FRBs) are millisecond-duration radio bursts with unidentified extra-galactic origin. Some FRBs exhibit mild magneto-ionic environmental variations, possibly attributed to plasma turbulence or binary configuration. We report an abrupt magneto-ionic variation of FRB 20220529, a repeating FRB from a disk galaxy at redshift . Initially, the Faraday rotation measure (RM) had a median of and a scatter of over 17 months. In December 2023, it jumped to , and returned to typical values within two weeks. This drastic RM variation suggests that a dense magnetized clump enters and exits the line of sight in week timescales. One plausible scenario invokes a coronal mass ejection from a companion star, while other scenarios invoking extreme turbulence or binary orbital motion are also possible.

Paper Structure

This paper contains 20 sections, 39 equations, 14 figures, 6 tables.

Table of Contents

  1. Materials and Methods
  2. FAST & Parkes observations
  3. FAST observations
  4. Parkes observations
  5. Burst detection
  6. Polarization properties
  7. RM Variation
  8. Linear Polarization Degree Variation
  9. DM Variation
  10. VLA observation and localization
  11. Optical image and host galaxy identification
  12. GTC spectrum observation
  13. Host Galaxy Properties
  14. Supplementary text
  15. Possible astrophysical origins of the "RM flare"
  16. ...and 5 more sections

Figures (14)

  • Figure 1: Temporal variations of various quantities of FRB 20220529.(A) Daily observing time. (B) Daily number of bursts detected. (C) Daily burst rate of FRBs. Vertical grey dotted lines indicate the days with observations, including those with non-detection. (D) Dispersion measure of bursts. Blue dots present bursts detected with FAST and cyan dots are those detected with Parkes. The orange line shows the average DMs for each day.(E) Linear Polarization fraction of bursts. Orange triangles indicate the upper limits, and the orange line shows the average $f_\mathrm{L}$ for each day.(F) Rotation measure of bursts. The horizontal dotted line indicates the estimated contribution of the Milky Way. The filled blue region covers the minimum to maximum range of the low RM state. A distinct RM flare is clearly visible.
  • Figure 2: Host-galaxy properties of FRB 20220529.(A) DESI $r$-band image of the host galaxy of FRB 20220529. The FRB position from the VLA observation is overplotted as a red circle, and the center of the host galaxy is marked as a blue cross. (B) GTC spectrum of the FRB 20220529 host galaxy (blue). Emission lines from the $z = 0.1839$ host galaxy are labeled with gray dashed lines.
  • Figure 3: Best-fitting results of different models as well as the first and second derivatives. (A) The best fits for different models. CME Case I model with assumed $t_0=-20, -27, -50$ and $-100$ days before the first detection of the "RM flare" is presented as orange, red, pink and magenta lines. The daily averaged observed data are overplotted for comparison. The best-fitting parameters are provided in Table \ref{['table: model_nobkg']}. (B) The first derivatives of different best-fitting models. (C) The second derivatives of different best-fitting models.
  • Figure S1: RM Variability for bursts of FRB 20220529. The normalized linear polarized flux is shown as a function of RM for seven bursts on different days (sorted by MJD). The RM of each burst is determined by its maximum linear polarization value.
  • Figure S2: Polarization profiles of eight bursts on different days from FRB 20220529, ordered by MJD. In each subplot, the upper panel displays the position angle of linear polarization at the center frequency. The middle panel shows the polarization pulse profile, where black, red, and blue curves denote total intensity, linear polarization, and circular polarization, respectively. The lower panel presents the dynamic spectra for the total intensity of all pulses, with a frequency resolution of $0.97\,{\rm MHz/channel}$ and a time resolution of 393 or $786\,{\rm \mu s/bin}$. Note that the burst at 60300.3530282 was detected with one of the highest S/N ratios during the "RM flare", although no RM measurement was obtained.
  • ...and 9 more figures