The Three Spectral Regimes Found in the Stellar Black Hole XTE J1550–564 in Its High/Soft State

By Aya Kubota, K. Makishima. 2003

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The present paper describes the analysis of multiple RXTE PCA data of the black hole binary with superluminal jet, XTE J1550-564, acquired during its 1998-1999 outburst. The X-ray spectra show features typical of the high/soft spectral state and can approximately be described by an optically thick disk spectrum plus a power-law tail. Three distinct spectral regimes, which we call the "standard regime," the "anomalous regime," and the "apparently standard regime," have been found from the entire set of the observed spectra. When the X-ray luminosity is well below ~6 × 1038 ergs s-1 (assuming a distance of 5 kpc), XTE J1550-564 resides in the standard regime, in which the soft spectral component dominates the power-law component and the observed disk inner radius is kept constant. When the luminosity exceeds the critical luminosity, the apparently standard regime is realized, in which the luminosity of the optically thick disk rises less steeply with the temperature, and the spectral shape is moderately distorted from that of the standard accretion disk. In this regime, the radial temperature gradient of the disk has been found to be flatter than that of the standard accretion disk. The results of the apparently standard regime suggest a slim disk, which is a solution predicted for a high mass accretion rate. In the intermediate anomalous regime (or very high state in the literature), the spectrum becomes much harder, and the disk inner radius derived using a simple disk model spectrum apparently varies significantly with time. These properties can be explained as a result of significant thermal inverse Comptonization of the disk photons, as was found from GRO J1655-40 in its anomalous regime by Kubota and coworkers.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/7e30fcfeb905f899fd3ac785d17f2f0e6015c58b

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In Astronomy and Astrophysics

1. Ramesh Narayan
2. J. E. McClintock
3. J. Steiner
4. Ronald A. Remillard
5. S. Davis
6. Lijun Gou
7. C. Done
8. J. Orosz

Citations in the corpus

• Modelling the behaviour of accretion flows in X-ray binaries (2007, background): “When the number of photons in the Comptonized spectrum is not negligible compared to those in the disc then the intrinsic disc spectrum is brighter than observed (Kubota & Makishima 2004; Kubota & Done 2004).”
• Measuring the spins of accreting black holes (2011, background): “…state has been presented for a number of sources via plots showing that the bolometric luminosity of the thermal component is approximately proportional to T 4in (e.g., Kubota et al 2001, Kubota and Makishima 2004, Gierliński and Done 2004, Abe et al 2005, McClintock et al 2009, Dunn et al 2010).”
• A Simple Comptonization Model (2008, methodology): “Kubota & Makishima (2004) similarly identified a constant normalization for the black hole binary XTE J1550–564 between the TD and SPL states in an analysis using the model DISKBB þ THCOMP.”
• X-Ray Properties of Black-Hole Binaries (2006, methodology): “Observationally, the thermal-state spectra of BHBs are well fitted using the classical model for a multitemperature accretion disk (Mitsuda et al. 1984; Makishima et al. 1986; Kubota & Makishima 2004; Kubota et al. 2005).”
• Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets (2013, background): “…states of black hole binaries has been demonstrated for many sources by showing that the bolometric luminosity of the thermal component is approximately proportional to T 4in (Kubota et al. 2001; Kubota & Makishima 2004; Gierli´nski & Done 2004; Abe et al. 2005; McClintock et al. 2009).”
• WATCHDOG: A COMPREHENSIVE ALL-SKY DATABASE OF GALACTIC BLACK HOLE X-RAY BINARIES (2015, background): “…MAXI coverage); and (ii) complicated non-trivial behavior exhibited during outburst such as double (or multiple) peak features (e.g., XTE J1550−564; Kubota & Makishima 2004), extended flare-like activity (e.g., 4U 1630−472; Tomsick et al. 2005), and prolonged outburst periods (e.g., GX 339−4;…”
• Testing Accretion Disk Theory in Black Hole X-Ray Binaries (2006, background): “A potential explanation for this hardening is that advection may be becoming increasingly important as these sources approach the Eddington limit (Kubota & Makishima 2004).”