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The odyssey of the black hole low mass X-ray binary GX339-4: Five years of dense multi-wavelength monitoring

E. Tremou, S. Corbel, R. Fender, P. Woudt, J. C. A Miller-Jones, I. Heywood, F. Carotenuto, S. Motta, A. Tzioumis, P. J. Groot, D. M. Russell, J. Crook-Mansour, P. Saikia, W. Yu, J. van den Eijnden, A. J. van der Horst, D. R. A. Williams-Baldwin, X. Zhang

TL;DR

This study presents the densest five-year, weekly, quasi-simultaneous multi-wavelength campaign of GX 339−4, spanning MeerKAT, ATCA, Swift-XRT, MAXI, and MeerLICHT data to trace jet–accretion dynamics across multiple outbursts. It captures two hard-only and two full outbursts, including a major radio flare and a resolved transient jet with measurable proper motion, offering insights into jet production and large-scale ejecta. The results show persistent compact jets during hard states, jet quenching during soft transitions, and a maintained radio–X-ray correlation across rise and decay phases, while underscoring the need for high angular resolution to separate core and ejecta contributions. A public legacy dataset of 252 MeerKAT L-band maps is released to enable ongoing community studies of jet physics in BH-LMXBs.

Abstract

We present the longest and the densest quasi-simultaneous radio, X-ray and optical campaign of the black hole low mass X-ray binary GX339-4, covering five years of weekly GX339-4 monitoring with MeerKAT, Swift-XRT and MeerLICHT, respectively. Complementary high frequency radio data with the Australia Telescope Compact Array are presented to track in more detail the evolution of GX339-4 and its transient ejecta. During the five years, GX339-4 has been through two "hard-only" outbursts and two "full" outbursts, allowing us to densely sample the rise, quenching and re-activation of the compact jets. Strong radio flares were also observed close to the transition between the hard and the soft states. Following the radio flare, a transient optically thin ejection was spatially resolved during the 2020 outburst, and was observed for a month. We also discuss the radio/X-ray correlation of GX339-4 during this five year period, which covers several states in detail from the rising phase to the quiescent state. This campaign allowed us to follow ejection events and provide information on the jet proper motion and its intrinsic velocity. With this work we publicly release the weekly MeerKAT L-band radio maps from data taken between September 2018 and October 2023.

The odyssey of the black hole low mass X-ray binary GX339-4: Five years of dense multi-wavelength monitoring

TL;DR

This study presents the densest five-year, weekly, quasi-simultaneous multi-wavelength campaign of GX 339−4, spanning MeerKAT, ATCA, Swift-XRT, MAXI, and MeerLICHT data to trace jet–accretion dynamics across multiple outbursts. It captures two hard-only and two full outbursts, including a major radio flare and a resolved transient jet with measurable proper motion, offering insights into jet production and large-scale ejecta. The results show persistent compact jets during hard states, jet quenching during soft transitions, and a maintained radio–X-ray correlation across rise and decay phases, while underscoring the need for high angular resolution to separate core and ejecta contributions. A public legacy dataset of 252 MeerKAT L-band maps is released to enable ongoing community studies of jet physics in BH-LMXBs.

Abstract

We present the longest and the densest quasi-simultaneous radio, X-ray and optical campaign of the black hole low mass X-ray binary GX339-4, covering five years of weekly GX339-4 monitoring with MeerKAT, Swift-XRT and MeerLICHT, respectively. Complementary high frequency radio data with the Australia Telescope Compact Array are presented to track in more detail the evolution of GX339-4 and its transient ejecta. During the five years, GX339-4 has been through two "hard-only" outbursts and two "full" outbursts, allowing us to densely sample the rise, quenching and re-activation of the compact jets. Strong radio flares were also observed close to the transition between the hard and the soft states. Following the radio flare, a transient optically thin ejection was spatially resolved during the 2020 outburst, and was observed for a month. We also discuss the radio/X-ray correlation of GX339-4 during this five year period, which covers several states in detail from the rising phase to the quiescent state. This campaign allowed us to follow ejection events and provide information on the jet proper motion and its intrinsic velocity. With this work we publicly release the weekly MeerKAT L-band radio maps from data taken between September 2018 and October 2023.
Paper Structure (19 sections, 1 equation, 13 figures, 2 tables)

This paper contains 19 sections, 1 equation, 13 figures, 2 tables.

Table of Contents

  1. Introduction
  2. The black hole low mass X-ray binary, GX 339--4
  3. Observations
  4. MeerKAT radio observations
  5. ATCA radio observations
  6. Swift XRT X-ray observations
  7. MAXI GSC observations
  8. MeerLICHT observations
  9. Results
  10. The 2018-2019 (MJD 58446 -- 58649) outburst. A "hard-only" outburst or a long lived hard state?
  11. The 2019--2020 (MJD 58650 --59180) outburst phase
  12. The major radio flare and the subsequent transient jet
  13. First detection of moving GX 339-4 core with MeerKAT
  14. The 2021 (MJD 59188 -- 59607) outburst
  15. The 2022 (MJD 59797 -- 59965) outburst. A "hard-only" outburst
  16. ...and 4 more sections

Figures (13)

  • Figure 1: Example of a single-epoch L-band MeerKAT radio map showing 1.5$\times$1.5 degrees of the field centered on GX 339--4 (red cross mark). The rms noise is 32.6 $\mu$Jy beam$^{-1}$ enabling the detection of weak sources down to 100 $\mu$Jy. It was taken on June 19, 2021 (MJD 59384), with an integration time of 10 minutes on source. The circular synthesized beam size is 5$\arcsec$.
  • Figure 2: The X-ray, radio and optical light-curves of GX 339--4 over the five years of our monitoring campaign. The bottom panel shows the MeerLICHT optical magnitudes (filters $q,u,i$), while the radio flux densities measured by MeerKAT (red:upper limits and blue:detections, dashed line: quiescent level) and ATCA (pink and orange data points) are shown in the third panel. The second panel shows the scaled 2--6 keV (yellow) and 15--50 keV (cyan) X-ray flux from MAXI and Swift/BAT, respectively. The top panel shows in purple the Swift/XRT 3-9 keV X-ray fluxes that were obtained quasi-simultaneously with the radio observations. The grey shaded background indicates the times that source was in soft X-ray state based on the spectral fitting of Swift/XRT 3-9 keV data.
  • Figure 3: Evolution of the photon index $\Gamma$ during the 2018--2019 outburst using Swift/XRT data.
  • Figure 4: Spectral index following the flare during the 2019--2020 outburst.Noting here that the spatial resolution from ATCA is higher than the one from MeerKAT. The grey shaded background indicates the time that source was in soft X-ray state.The spectral index from ATCA data turns to positive at the soft to hard transition.
  • Figure 5: Lightcurve of GX 339--4 with 1 minute intervals during the time of the major flare on 2019-2020 outburst where it reached its peak flux density. Top: 28 December 2019, MJD 58845 (major flare). Middle: 03 January 2020, MJD 58851. Bottom: 10 January 2020, MJD 58868. The flux is decreasing by $\sim$ 4 mJy within 5 minutes.
  • ...and 8 more figures