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Register a new userEvidence for Returning Disk Radiation in the Black Hole X-ray Binary XTE J1550-564
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We explore the accretion properties of the black hole X-ray binary j1550 during its outbursts in 1998/99 and 2000. We model the disk, corona, and reflection components of X-ray spectra taken with the {it Rossi X-ray Timing Explorer} (rxte), using the {tt relxill} suite of reflection models. The key result of our modeling is that the reflection spectrum in the very soft state is best explained by disk self-irradiation, i.e., photons from the inner disk are bent by the strong gravity of the black hole, and reflected off the disk surface. This is the first known detection of thermal disk radiation reflecting off the inner disk. There is also an apparent absorption line at $sim6.9$ keV which may be evidence of an ionized disk wind. The coronal electron temperature ($kT_{rm e}$) is, as expected, lower in the brighter outburst of 1998/99, explained qualitatively by more efficient coronal cooling due to irradiating disk photons. The disk inner radius is consistent with being within a few times the innermost stable circular orbit (ISCO) throughout the bright-hard-to-soft states (10s of $r_{rm g}$ in gravitational units). The disk inclination is low during the hard state, disagreeing with the binary inclination value, and very close to $90^{circ}$ in the soft state, recovering to a lower value when adopting a blackbody spectrum as the irradiating continuum.
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[abridged] The black hole X-ray binary XTE J1550-564 was monitored extensively at X-ray, optical and infrared wavelengths throughout its outburst in 2000. We show that it is possible to separate the optical/near-infrared (OIR) jet emission from the OIR disc emission. Focussing on the jet component, we find that as the source fades in the X-ray hard state, the OIR jet emission has a spectral index consistent with optically thin synchrotron emission (alpha ~ -0.6 to -0.7, where F_nu propto nu^alpha). This jet emission is tightly and linearly correlated with the X-ray flux; L_OIR,jet propto L_X^(0.98 +- 0.08) suggesting a common origin. This is supported by the OIR, X-ray and OIR to X-ray spectral indices being consistent with a single power law (alpha = -0.73). Ostensibly the compact, synchrotron jet could therefore account for ~ 100 % of the X-ray flux at low luminosities in the hard state. At the same time, (i) an excess is seen over the power law decay of the X-ray flux at the point in which the jet would start to dominate, (ii) the X-ray spectrum slightly softens, which seems to be due to a high energy cut-off or break shifting to a lower energy, and (iii) the X-ray rms variability increases. This may be the strongest evidence to date of synchrotron emission from the compact, steady jet dominating the X-ray flux of an X-ray binary. For XTE J1550-564, this is likely to occur within the luminosity range ~ (2 e-4 - 2 e-3) L_Edd on the hard state decline of this outburst. However, on the hard state rise of the outburst and initially on the hard state decline, the synchrotron jet can only provide a small fraction (~ a few per cent) of the X-ray flux. Both thermal Comptonization and the synchrotron jet can therefore produce the hard X-ray power law in accreting black holes.
We report the identification of the optical counterpart of the X-ray transient XTE J1550-564 described in two companion papers by Sobczak et al (1999) and Remillard et al (1999). We find that the optical source brightened by approximately 4 magnitudes over the quiescent counterpart seen at B~22 on a SERC survey plate, and then decayed by approximately 1.5 magnitudes over the 7 week long observation period. There was an optical response to the large X-ray flare described by Sobczak et al (1999), but it was much smaller and delayed by roughly 1 day.
We report multifrequency radio observations of XTE J1550-564 obtained with the Molonglo Observatory Synthesis Telescope and the Australia Telescope Compact Array at the time of its discovery and subsequent hard and soft X-ray outburst in 1998 September. A large radio flare was observed, peaking about 1.8 days after the X-ray flare. In addition, we present Australian Long Baseline Array images obtained shortly after the maximum of the radio flare which show evolving structure. The apparent separation velocity of the two outermost components is v>2c.
We present the analysis of X-ray observations of the black hole binary 4U~1630$-$47 using relativistic reflection spectroscopy. We use archival data from the RXTE, Swift, and NuSTAR observatories, taken during different outbursts of the source between $1998$ and $2015$. Our modeling includes two relatively new advances in modern reflection codes: high-density disks, and returning thermal disk radiation. Accretion disks around stellar-mass black holes are expected to have densities well above the standard value assumed in traditional reflection models (i.e., $n_{rm e}sim10^{15}~{rm cm^{-3}}$). New high-density reflection models have important implications in the determination of disk truncation (i.e., the disk inner radius). This is because one must retain self-consistency in the irradiating flux and corresponding disk ionization state, which is a function of disk density and system geometry. We find the disk density is $n_{rm e}ge10^{20}~{rm cm^{-3}}$ across all spectral states. This density, combined with our constraints on the ionization state of the material, implies an irradiating flux impinging on the disk that is consistent with the expected theoretical estimates. Returning thermal disk radiation -- the fraction of disk photons which bend back to the disk producing additional reflection components -- is expected predominantly in the soft state. We show that returning radiation models indeed provide a better fit to the soft state data, reinforcing previous results which show that in the soft state the irradiating continuum may be blackbody emission from the disk itself.
We use the Relativistic Precession Model (RPM) (Stella et al. 1999a) and quasi-periodic oscillation (QPO) observations from the Rossi X-ray Timing Explorer to derive constraints on the properties of the black holes that power these sources and to test General Relativity (GR) in the strong field regime. We extend the techniques outlined by Motta et al. (2014a,b) to use pairs of simultaneously measured QPOs, rather than triplets, and extend the underlying spacetime metric to constrain potential deviations from the predictions of GR for astrophysical black holes. To do this, we modify the RPM model to a Kerr-Newman-deSitter spacetime and model changes in the radial, ecliptic, and vertical frequencies. We compare our models with X-ray data of XTE J1550-564 and GRO J1655-40 using robust statistical techniques to constrain the parameters of the black holes and the deviations from GR. For both sources we constrain particular deviations from GR to be less than one part per thousand.
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