Evidence for an expanding corona based on spectral-timing modelling of multiple black hole X-ray binaries

Abstract

Galactic black hole X-ray binaries (BHXBs) provide excellent laboratories to study accretion, as their relatively quick evolution allows us to monitor large changes in the in-flowing and/or out-flowing material over human timescales. However, the details of how the inflow-outflow coupling evolves during a BHXB outburst remain an area of active debate. In this work we attempt to probe the physical changes underlying the system evolution, by performing a systematic analysis of the multi-wavelength data of three BHXB sources: XTE J1752-223, MAXI J1659-152, and XTE J1650-500, during hard and hard-intermediate states. Using the power spectral hue which characterises the X-ray variability properties, we identify several clusters of BHXB epochs and perform the joint multi-wavelength spectral modelling to test their commonality with a physical jet model. Under the assumption that the corona is related to the base of the jet, we find that the power spectral hue traces the variation of the coronal radius (from ∼10Rg − ∼ 40Rg) in multiple BHXBs at hard and hard-intermediate states, and that the data are consistent with moderately truncated accretion discs (<25Rg) during hard-intermediate states. We also find that all epochs of low disc reflection have high hue located near the hard-intermediate to soft-intermediate state transition, indicating that in these states the vertical extent of the corona and/or its bulk speed are increasing. Our results link the geometrical similarity in the corona among multiple BHXB sources to their timing characteristics, and probe the corona responding to the disc-jet interactions at hard and intermediate states during outbursts.

The NICER “Reverberation Machine”: A Systematic Study of Time Lags in Black Hole X-Ray Binaries

“…With NICER's soft X-ray bandpass and large effective area, we are now able to find prolonged soft reverberation lags in state transitions, which provide more direct evidence of the expanding corona since the mechanism that produces hard lags is not well understood. In addition to longer lags, recent broadband spectral modeling for several BHLMXBs finds that the radius of the corona which is assumed to be the base of the jet increases from ∼10 to ∼40 R g through the hard state and the HIMS; and the reflection fraction occasionally becomes very low in the HIMS when approaching the SIMS, suggesting an increase in also the vertical extent of the corona and/or its bulk velocity (Lucchini et al 2021;Cao et al 2022, but see Steiner et al 2017.…”

“…Instead, above 2% L Edd , the increase and then decrease of soft lag amplitude is more likely to be driven by changes in the coronal geometry, which would be consistent with an evolving base of the compact jet. Recent GRMHD simulations (Liska et al 2019) show that, as the inner disk is more radiatively efficient and thus thinner, the inflowing material exerts less pressure on the jet boundary, which becomes less collimated, resulting in the base of the jet being more extended compared to lower luminosities (Lucchini et al 2021;Cao et al 2022). The decreasing soft lag amplitude above 4% L Edd could then be caused by a contracting X-ray corona before the quenching of the compact radio jet (see the schematic referred to as bright hard state in Figure 10).…”

Exploring the role of composition and mass-loading on the properties of hadronic jets

“…There is evidence of baryonloaded jets though, even in the case of a low-mass companion, such as the black hole candidate 4U 1630-47, based on iron emission lines (Díaz Trigo et al 2013). The cases of MAXI J1820+070 (Tetarenko et al 2021;Zdziarski et al 2022a), MAXI J1836-194 (Lucchini et al 2021), XTE J1752-223, MAXI J1659-152, and XTE J1650-500 (Cao et al 2021) on the other hand, favour a jet composition of the order of a few to a few tens of pairs per proton based on energetic arguments.…”

A NICER look at the jet-like corona of MAXI J1535-571 through type-B quasi-periodic oscillation

“…Using data of GRS 1915+105, Méndez et al (2022) proposed that (part of) the spread in the radio-X-ray correlation (Gallo et al 2012) could be due to changes of the corona temperature. Studies of the spectral energy distribution (SED) from the radio to the X-ray band shows that the corona emission can originate from a shock acceleration region of tens of gravitational radii (𝑅 𝑔 ) as the jet base (Markoff et al 2001;Connors et al 2019;Cao et al 2022). The spectral analysis of the reflection component in MAXI J1820+070 suggests that the corona outflows with a higher relativistic velocity as it is closer to the black hole (You et al 2021).…”