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Register a new userA unified accretion-ejection paradigm for black hole X-ray binaries. IV. Replication of the 2010--2011 activity cycle of GX 339-4
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Transients XrB exhibit different spectral shapes during their evolution. In luminosity-color diagrams, their X-ray behavior forms unexplained q-shaped cycles. We proposed a framework where the innermost regions of the accretion disk evolve as a response to variations imposed in the outer regions. These variations lead not only to modifications of the inner disk accretion rate $dot m_{in}$ but also to the evolution of the transition radius $r_J$ between two regions. The outermost region is a standard accretion disk (SAD), whereas the innermost region is a jet-emitting disk (JED) where all the disk angular momentum is carried away vertically by two self-confined jets. In the previous papers of this series, it has been shown that such a configuration reproduces the typical spectral properties of the five canonical XrB states. The aim of this paper is now to replicate all X-ray spectra and radio emission observed during GX 339-4 2010-2011 outburst. We use the 2T plasma code presented in papers II and III, and design an automatic fitting procedure that gives the parameters $(dot m_{in},r_J)$ that best fit each X-ray spectrum. We use RXTE/PCA X-ray data spread over 438 days, together with radio observations at 9 GHz (ATCA). We obtain the time distributions of $dot m_{in}$ and $r_J$ that uniquely reproduce the X-ray luminosity and the spectral shape of the whole cycle. Using the classical self-absorbed jet synchrotron emission model, the JED-SAD configuration reproduces also very satisfactorily the radio properties, in particular the switch-off and -on events and the radio-X-ray correlation. Within the JED-SAD framework, radio emission can be used to constrain the underlying disk configuration. If this result is confirmed using other outbursts from GX 339-4 or other X-ray binaries, then radio could be indeed used as another means to indirectly probe disk physics.
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We proposed that the spectral evolution of transient X-ray binaries (XrB) is due to an interplay between two flows: a standard accretion disk (SAD) in the outer parts and a jet-emitting disk (JED) in the inner parts. We showed in previous papers that the spectral evolution in X-ray and radio during the 2010-2011 outburst of GX339-4 can be recovered. We now investigate the presence of low frequency quasi-periodic oscillations (LFQPOs) during an X-ray outburst, and address the possible correlation between the frequencies of these LFQPOs and the transition radius between the two flows, rJ. We select X-ray and radio data form 3 outbursts of GX339-4. We use the method detailed in paper IV to obtain $r_J(t)$ and $dot{m}_{in}(t)$ for each outburst to reproduce the correlated evolution of the X-ray spectra and the radio emission for 3 different activity cycles of GX339-4. We also independently search and report the detection of 7 new LFQPOs in addition to the literature. We show that the frequency of Type C QPOs can be linked to the dynamical JED-SAD transition radius rJ, rather than the radius of optically thin-thick transition. The scaling factor q such that $ u_{QPO} simeq u_K (r_J) / q$ is $q simeq 70-140$, consistent during the 4 cycles and similar to previous studies. The JED-SAD hybrid disk configuration not only provides a successful paradigm allowing us to describe XrB cycles, but also matches the QPO frequencies evolution. QPOs provide an indirect way to probe the JED-SAD transition radius, where an undetermined process produces secular variability. The demonstrated relation between the transition radius links Type C QPOs to the transition between the two flows, tying it to the inner magnetized structure of the jets. This direct connection between the jets structure and the process responsible for Type C QPOs could naturally explain their puzzling multi-wavelength behavior.
We elaborate on the paradigm proposed in Ferreira et al. (2006), where the increase and decrease in the disk accretion rate is accompanied by a modification of the disk magnetization $mu propto B_z^2/dot{m}_{in}$, which in turn determines the dominant torque allowing accretion. For $mu>0.1$, the accretion flow produces jets that vertically, carry away the disk angular momentum (jet-emitting disk or JED). The goal of this paper is to investigate the spectral signatures of the JED configurations. We have developed a two-temperature plasma code that computes the disk local thermal equilibria, taking into account the advection of energy in an iterative way. Our code addresses optically thin-to-thick transitions, both radiation and gas supported regimes and computes in a consistent way the emitted spectrum from a steady-state disk. The optically thin emission is obtained using the BELM code, which provides accurate spectra for bremsstrahlung and synchrotron emission processes as well as for their local Comptonization. For a range in radius and accretion rates, JEDs exhibit three thermal equilibria, one thermally unstable and two stables. Due to the existence of two thermally stable solutions, a hysteresis cycle is naturally obtained. However, standard outbursting X-ray binary cycles cannot be reproduced. Another striking feature of JEDs is their ability to reproduce luminous hard states. Showing that when the loss of angular momentum and power in jets is consistently taken into account, accretion disks have spectral signatures that are consistent with hard states, even up to high luminosities. The reproduction of soft states being well performed by standard accretion disks (SAD), this study argues for the existence of hybrid disk configuration: JED and SAD. A study of such hybrid configuration will be presented in a forthcoming paper III.
It has been suggested that the cycles of activity of X-ray Binaries (XrB) are triggered by a switch in the dominant disk torque responsible for accretion (paper I). As the disk accretion rate increases, the disk innermost regions would change from a jet-emitting disk (JED) to a standard accretion disk (SAD). While JEDs have been proven to successfully reproduce hard states (paper II), the existence of an outer cold SAD introduces an extra non local cooling term. We investigate the thermal structure and associated spectra of such a hybrid disk configuration. We use the 2T plasma code elaborated in paper II, allowing to compute outside-in the disk local thermal equilibrium with self-consistent advection and optically thin-to-thick transitions, in both radiation and gas supported regimes. The non-local inverse Compton cooling introduced by the external soft photons is computed by the BELM code. This additional term has a profound influence on JED solutions, allowing a smooth temperature transition from the outer SAD to the inner JED. We explore the full parameter space in disk accretion rate and transition radius, and show that the whole domain in X-ray fluxes and hardness ratios covered by standard XrB cycles is well reproduced by such hybrid configurations. Precisely, a reasonable combination of these parameters allows to reproduce the 3-200 keV spectra of five canonical XrB states. Along with X-ray signatures, JED-SAD configurations also naturally account for the radio emission whenever it is observed. By varying only the transition radius and the accretion rate, hybrid disk configurations combining an inner JED and an outer SAD are able to reproduce simultaneously the X-ray spectral states and radio emission of X-ray binaries during their outburst. Adjusting these two parameters, it is then possible to reproduce a full cycle. This will be shown in a forthcoming paper (paper IV).
We investigate variability of optical and near-infrared light curves of the X-ray binary GX 339-4 on a timescale of days. We use the data in four filters from six intervals corresponding to the soft state and from four intervals corresponding to the quiescent state. In the soft state, we find prominent oscillations with the average period P = 1.772 $pm$ 0.003 d, which is offset from the measured orbital period of the system by 0.7 per cent. We suggest that the measured periodicity originates from the superhumps. In line with this interpretation we find no periodicity in the quiescent state. The obtained period excess $epsilon$ is below typical values found for cataclysmic variables for the same mass ratio of the binary. We discuss implications of this finding in the context of the superhump theory.
Black hole X-ray binaries show signs of non-thermal emission in the optical/near-infrared range. We analyze the optical/near-infrared SMARTS data on GX339$-$4 over the 2002--2011 period. Using the soft state data, we estimate the interstellar extinction towards the source and characteristic color temperatures of the accretion disk. We show that various spectral states of regular outbursts occupy similar regions on the color-magnitude diagrams, and that transitions between the states proceed along the same tracks despite substantial differences in the observed light curves morphology. We determine the typical duration of the hard-to-soft and soft-to-hard state transitions and the hard state at the decaying stage of the outburst to be one, two and four weeks, respectively. We find that the failed outbursts cannot be easily distinguished from the regular ones at their early stages, but if the source reaches 16 mag in $V$-band, it will transit to the soft state. By subtracting the contribution of the accretion disk, we obtain the spectra of the non-thermal component, which have constant, nearly flat shape during the transitions between the hard and soft states. In contrast to the slowly evolving non-thermal component seen at optical and near-infrared wavelengths, the mid-infrared spectrum is strongly variable on short timescales and sometimes shows a prominent excess with a cutoff below $10^{14}$ Hz. We show that the radio to optical spectrum can be modeled using three components corresponding to the jet, hot flow and irradiated accretion disk.
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