Disc-jet coupling changes as a possible indicator for outbursts from GX 339-4 remaining within the X-ray hard state
Abstract
We present quasi-simultaneous radio, (sub-)millimetre, and X-ray observations of the Galactic black hole X-ray binary GX 339-4, taken during its 2017-2018 outburst, where the source remained in the hard X-ray spectral state. During this outburst, GX 339-4 showed no atypical X-ray behaviour that may act as an indicator for an outburst remaining within the hard state. However, quasi-simultaneous radio and X-ray observations showed a flatter than expected coupling between the radio and X-ray luminosities (with a best-fitting relation of $L_{\rm radio} \propto L_{\rm X}^{0.39 \pm 0.06}$), when compared to successful outbursts from this system ($L_{\rm radio} \propto L_{\rm X}^{0.62 \pm 0.02}$). While our 2017-2018 outburst data only span a limited radio and X-ray luminosity range (~1 order of magnitude in both, where more than 2 orders of magnitude in LX is desired), including data from other hard-only outbursts from GX 339-4 extends the luminosity range to ~1.2 and ~2.8 orders of magnitude, respectively, and also results in a flatter correlation (where $L_{\rm radio} \propto L_{\rm X}^{0.46 \pm 0.04}$). This result is suggestive that for GX 339-4 a flatter radio-X-ray correlation, implying a more inefficient coupling between the jet and accretion flow, could act as an indicator for a hard-only outburst. However, further monitoring of both successful and hard-only outbursts over larger luminosity ranges with strictly simultaneous radio and X-ray observations is required from different single sources to explore if this applies generally to the population of black hole X-ray binaries, or even GX 339-4 at higher hard-state luminosities.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 2021
- DOI:
- 10.1093/mnras/staa3853
- arXiv:
- arXiv:2012.05206
- Bibcode:
- 2021MNRAS.502..521D
- Keywords:
-
- accretion;
- accretion discs;
- black hole physics;
- stars: individual: GX 339-4;
- outflows;
- X-rays: binaries;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 14 pages, 9 figures, 4 tables. All data is provided in the appendices, accepted for publication in MNRAS