Relativistic Accretion Disk Model Research Articles

Testing relativistic accretion disk models with GRO J1655‐40

AbstractBlack hole X‐ray binaries are ideal environments to test the accretion phenomena in the presence of strong gravitational potentials. KERRBB held an important place in the X‐ray spectral continuum method for measuring the black hole spin modeling the emission from the innermost regions of the accretion disk. In this work, we present the results of X‐ray spectral analysis using publicly available RXTE data of GRO J1655‐40 obtained during the 2005 outburst with the two relativistic accretion disk models, KERRBB and KYNBB. Our analysis showed that both models provide identical results with black hole spin measurements, disk temperature, and disk luminosity when the inner edge of the accretion disk is set at the innermost stable circular orbit (ISCO) for the same accretion rates. We could not obtain reasonable fits for ∼89% of the observations with a fixed black hole spin value at a* = 0.7 using both models. Allowing the spin parameter to vary improved the fit statistic significantly with reduced χ2 values being reduced from ∼10 to 100 to below 2. Both models revealed black hole spin values varying between 0.52 < a* < 0.94, which can be interpreted as a variable inner edge of the disk throughout different accretion states.

Re-estimating the Spin Parameter of the Black Hole in Cygnus X-1

Abstract Cygnus X-1 is a well-studied persistent black hole X-ray binary. Recently, the three parameters needed to estimate the black hole spin of this system, namely the black hole mass M, the orbital inclination i, and the source distance D, have been updated. In this work we redetermine the spin parameter using the continuum-fitting technique for those updated parameter values. Based on the assumption that the spin axis of the black hole is aligned with the orbital plane, we fit the thermal disk component to a fully relativistic thin accretion disk model. The error in the spin estimate arising from the combined observational uncertainties is obtained via Monte Carlo simulations. We demonstrate that, without considering the counteracting torque effect, the new spin parameter is constrained to be a * > 0.9985 (3σ), which confirms that the spin of the black hole in Cygnus X-1 is extreme.

A Spectral Study of the Black Hole Candidate XTE J1752−223 in the High/Soft State with MAXI, Suzaku, and Swift

Abstract We report on an X-ray spectral analysis of the black hole candidate XTE J1752$-$223 in the 2009–2010 outburst, utilizing data obtained with the MAXI/Gas Slit Camera (GSC), the Swift/XRT, and Suzaku, which work complementarily. As already reported by Nakahira et al. (2010, PASJ, 62, L27), MAXI monitored the source continuously throughout the entire outburst for about eight months. All of the MAXI/GSC energy spectra in the high/soft state, lasting for 2 months, are well represented by a multi-color disk plus power-law model. The innermost disk temperature changed from $\sim\ $0.7 keV to $\sim\ $0.4 keV and the disk flux decreased by an order of magnitude. Nevertheless, the innermost radius is constant at $\sim\ $41 $D_{3.5}$(cos $i$)$^{-{1}/{2}}\ $km, where $D_{3.5}$ is the source distance in units of 3.5 kpc and $i$ the inclination. The multi-color disk parameters obtained with the MAXI/GSC are consistent with those with the Swift/XRT and Suzaku. The Suzaku data also suggest a possibility that the disk emission is slightly Comptonized, which could account for broad iron-K features reported previously. Assuming that the obtained innermost radius represents the innermost stable circular orbit for a non-rotating black hole, we estimate the mass of the black hole to be 5.51$\ \pm\ $0.28$\ M_{\odot}$$D_{3.5}$(cos $i$)$^{-{1}/{2}}\ $, where the correction for the stress-free inner boundary condition and color hardening factor of 1.7 are taken into account. If the inclination is less than 49$^{\circ}$, as suggested from radio monitoring of transient jets, and the soft-to-hard transition in 2010 April occurred at 1%–4% of Eddignton luminosity, the fitting of the Suzaku spectra with a relativistic accretion-disk model derives constraints on the mass and the distance to be 3.1–55$\ M_{\odot}$ and 2.3–22 kpc, respectively. This confirms that the compact object in XTE J1752$-$223 is a black hole.

THE DISTANCE, INCLINATION, AND SPIN OF THE BLACK HOLE MICROQUASAR H1743-322

During its 2003 outburst, the black-hole X-ray transient H1743-322 produced two-sided radio and X-ray jets. Applying a simple and symmetric kinematic model to the trajectories of these jets, we determine the source distance, 8.5 \pm 0.8 kpc, and the inclination angle of the jets, 75 \pm 3 degrees. Using these values, we estimate the spin of the black hole by fitting its RXTE spectra, obtained during the 2003 outburst, to a standard relativistic accretion-disk model. For its spin, we find a*=0.2 \pm 0.3 (68% limits); -0.3 < a* < 0.7 at 90% confidence. We rule strongly against an extreme value of spin: a* < 0.92 at 99.7% confidence. H1743-322 is the third known microquasar (after A0620-00 and XTE J1550-564) that displays large-scale ballistic jets and has a moderate value of spin. Our result, which depends on an empirical distribution of black hole masses, takes into account all known sources of measurement error.

Long-Term Monitoring of the Black Hole Binary GX 339−4 in the High/Soft State during the 2010 Outburst with MAXI/GSC

We present the results of monitoring the galactic black hole candidate GX 339 $-$ 4 with the Monitor of All-sky X-ray Image (MAXI) / Gas Slit Camera in the high/soft state during an outburst in 2010. All of the spectra throughout the 8-month period were well reproduced with a model consisting of multi-color disk emission and its Comptonization component, whose fraction is $\leq\ $ 25% in the total flux. In spite of the flux variability over a factor of 3, the innermost disk radius is constant at $R_{\rm in}$$=$ 61 $\ \pm\ $ 2 km for an inclination angle of $i$$=$ 46 $^\circ$ and a distance of $d$$=$ 8 kpc. This $R_{\rm in}$ value is consistent with those of past measurements with Tenma in the high/soft state. Assuming that the disk extends to the innermost stable circular orbit of a non-spinning black hole, we estimate the black hole mass to be $M$$=$ 6.8 $\ \pm\ $ 0.2 $\ M_{\odot}$ for $i$$=$ 46 $^\circ$ and $d$$=$ 8 kpc, which is consistent with that estimated from the Suzaku observation of the previous low/hard state. Further combined with the mass function, we obtained a mass constraint of 4.3 $\ M_\odot$$&amp;lt;$$M$$&amp;lt;$ 13.3 $\ M_\odot$ for the allowed range of $d$$=$ 6–15 kpc and $i$$&amp;lt;$ 60 $^\circ$ . We also discuss the spin parameter of the black hole in GX 339 $-$ 4 by applying relativistic accretion disk models to the Swift/XRT data.

LINEAR POLARIZATION OF A DOUBLE PEAKED BROAD EMISSION LINE IN ACTIVE GALACTIC NUCLEI

A small number of active galactic nuclei are known to exhibit prominent double peak emission profiles that are well-fitted by a relativistic accretion disk model. We develop a Monte Carlo code to compute the linear polarization of a double peaked broad emission line arising from Thomson scattering. A Keplerian accretion disk is adopted for the double peak emission line region and the geometry is assumed to be Schwarzschild. Far from the accretion disk where flat Minkowski geometry is appropriate, we place an azimuthally symmetric scattering region in the shape of a spherical shell sliced with <TEX>${\Delta}{\mu}=0.1$</TEX>. Adopting a Monte Carlo method we generate line photons in the accretion disk in arbitrary directions in the local rest frame and follow the geodesic paths of the photons until they hit the scattering region. The profile of the polarized flux is mainly determined by the relative location of the scattering region with respect to the emission source. When the scattering region is in the polar direction, the degree of linear polarization also shows a double peak structure. Under favorable conditions we show that up to 0.6% linear polarization may be obtained. We conclude that spectropolarimetry can be a powerful probe to reveal much information regarding the accretion disk geometry of these active galactic nuclei.

THE CONSTANT INNER-DISK RADIUS OF LMC X-3: A BASIS FOR MEASURING BLACK HOLE SPIN

The black hole binary system LMC X-3 has been observed by virtually every X-ray mission since the inception of X-ray astronomy. Among the persistent sources, LMC X-3 is uniquely both habitually soft and highly variable. Using a fully relativistic accretion disk model, we analyze hundreds of spectra collected during eight X-ray missions that span 26 years. For a selected sample of 391 RXTE spectra, we find that to within ≈2% the inner radius of the accretion disk is constant over time and unaffected by source variability. Even considering an ensemble of eight X-ray missions, we find consistent values of the radius to within ≈4%–6%. Our results provide strong evidence for the existence of a fixed inner-disk radius. The only reasonable inference is that this radius is closely associated with the general relativistic innermost stable circular orbit. Our findings establish a firm foundation for the measurement of black hole spin.

Precise Measurement of the Spin Parameter of the Stellar-Mass Black Hole M33 X-7

In prior work, {\it Chandra} and Gemini-North observations of the eclipsing X-ray binary M33 X-7 have yielded measurements of the mass of its black hole primary and the system's orbital inclination angle of unprecedented accuracy. Likewise, the distance to the binary is known to a few percent. In an analysis based on these precise results, fifteen {\it Chandra} and {\it XMM-Newton} X-ray spectra, and our fully relativistic accretion disk model, we find that the dimensionless spin parameter of the black hole primary is $a_* = 0.77 \pm 0.05$. The quoted 1-$\sigma$ error includes all sources of observational uncertainty. Four {\it Chandra} spectra of the highest quality, which were obtained over a span of several years, all lead to the same estimate of spin to within statistical errors (2%), and this estimate is confirmed by 11 spectra of lower quality. There are two remaining uncertainties: (1) the validity of the relativistic model used to analyze the observations, which is being addressed in ongoing theoretical work; and (2) our assumption that the black hole spin is approximately aligned with the angular momentum vector of the binary, which can be addressed by a future X-ray polarimetry mission.

An XMM‐Newton survey of broad iron lines in AGN

AbstractWe report on the iron Kα line properties of a sample of Seyfert galaxies observed with the XMM‐Newton EPIC pn instrument. Using a systematic and uniform analysis, we find that complexity at iron‐K is extremely common in the XMM‐Newton spectra. Once appropriate soft X‐ray absorption, narrow 6.4 keV emission and associated Compton reflection are accounted for, ∼75% of the sample show an improvement when a further component is introduced. The typical properties of the broad emission are both qualitatively and quantitatively consistent with previous results from ASCA. The complexity is in general very well described by relativistic accretion disk models. In most cases the characteristic emission radius is constrained to be within ∼50R g, where strong gravitational effects become important. We find in about 1/3 of the sample the accretion disk interpretation is strongly favoured over competing models. In a few objects no broad line is apparent. We find evidence for emission within 6R g in only two cases, both of which exhibit highly complex absorption. Evidence for black hole spin based on the X‐ray spectra therefore remains tentative. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

The Spin of the Near‐Extreme Kerr Black Hole GRS 1915+105

Based on a spectral analysis of the X-ray continuum that employs a fully relativistic accretion-disk model, we conclude that the compact primary of the binary X-ray source GRS 1915+105 is a rapidly-rotating Kerr black hole. We find a lower limit on the dimensionless spin parameter of a* greater than 0.98. Our result is robust in the sense that it is independent of the details of the data analysis and insensitive to the uncertainties in the mass and distance of the black hole. Furthermore, our accretion-disk model includes an advanced treatment of spectral hardening. Our data selection relies on a rigorous and quantitative definition of the thermal state of black hole binaries, which we used to screen all of the available RXTE and ASCA data for the thermal state of GRS 1915+105. In addition, we focus on those data for which the accretion disk luminosity is less than 30% of the Eddington luminosity. We argue that these low-luminosity data are most appropriate for the thin alpha-disk model that we employ. We assume that there is zero torque at the inner edge of the disk, as is likely when the disk is thin, although we show that the presence of a significant torque does not affect our results. Our model and the model of the relativistic jets observed for this source constrain the distance and black hole mass and could thus be tested by determining a VLBA parallax distance and improving the measurement of the mass function. Finally, we comment on the significance of our results for relativistic-jet and core-collapse models, and for the detection of gravitational waves.

Testing Accretion Disk Theory in Black Hole X‐Ray Binaries

We present results from spectral modeling of three black hole X-ray binaries: LMC X-3, GRO J1655-40, and XTE J1550-564. Using a sample of disk dominated observations, we fit the data with a range of spectral models that includes a simple multitemperature blackbody (DISKBB), a relativistic accretion disk model based on color-corrected blackbodies (KERRBB), and a relativistic model based on non-LTE atmosphere models within an alpha prescription (BHSPEC). BHSPEC provides the best fit for a BeppoSAX observation of LMC X-3, which has the broadest energy coverage of our sample. It also provides the best fit for multiple epochs of Rossi X-ray Timing Explorer (RXTE) data in this source, except at the very highest luminosity (L/L_{Edd} >~ 0.7), where additional physics must be coming into play. BHSPEC is also the best-fit model for multi-epoch RXTE observations of GRO J1655-40 and XTE J1550-564, although the best-fit inclination of the inner disk differs from the binary inclination. All our fits prefer alpha=0.01 to alpha=0.1, in apparent disagreement with the large stresses inferred from the rapid rise times observed in outbursts of these two sources. In all three sources our fits imply moderate black hole spins (a/M ~ 0.1 - 0.8), but this is sensitive to the reliability of independent measurements of these system parameters and to the physical assumptions which underly our spectral models.

Relativistic Accretion Disk Models of High‐State Black Hole X‐Ray Binary Spectra

We present calculations of non-LTE, relativistic accretion disk models applicable to the high/soft state of black hole X-ray binaries. We include the effects of thermal Comptonization and bound-free and free-free opacities of all abundant ion species. We present spectra calculated for a variety of accretion rates, black hole spin parameters, disk inclinations, and stress prescriptions. We also consider nonzero inner torques on the disk, and explore different vertical dissipation profiles, including some which are motivated by recent radiation MHD simulations of magnetorotational turbulence. Bound-free metal opacity generally produces significantly less spectral hardening than previous models which only considered Compton scattering and free-free opacity. It also tends to keep the effective photosphere near the surface, resulting in spectra which are remarkably independent of the stress prescription and vertical dissipation profile, provided little dissipation occurs above the effective photosphere. We provide detailed comparisons between our models and the widely used multicolor disk model. Frequency dependent discrepancies exist that may affect the parameters of other spectral components when this simpler disk model is used to fit modern X-ray data. For a given source, our models predict that the luminosity in the high/soft state should approximately scale with the fourth power of the empirically inferred maximum temperature, but with a slight hardening at high luminosities. This is in good agreement with observations. (abridged)

ASCA observation of the X-ray transient GRS 1009-45

We report on the result of the X-ray observation of X-ray Nova Velorum 1993 (GRS 1009-45), made with ASCA on November 10–11, 1993. The energy spectrum was extremely soft and accompanied by a hard tail, characteristics of the Galactic black-hole binaries in the soft state. It is well represented by a two component model consisting of a multicolor disk model or a general relativistic accretion disk model, both describing emission from an optically-thick accretion disk, and a power-law component with a photon index of ∼ 2.5. Spectral analysis of the soft component allows estimation of the mass of the central object. For the optically-estimated distance (> 1 kpc) and inclination (> 37°), the mass is estimated to be > 3.1 M ⊙. These results strongly support that the compact object is a black hole.

Evidence for a Black Hole in the X-Ray Transient GRS 1009–45

We report on the result of an X-ray observation of the X-ray Nova Velorum 1993 (GRS 1009–45), made with ASCA on 1993 November 10-11. The energy spectrum was extremely soft and accompanied by a hard tail, characteristics of the Galactic black-hole binaries in the soft state. It is well represented by a two-component model consisting of a multicolor disk model or a general relativistic accretion disk model, both describing emission from an optically thick accretion disk, and a power-law component with a photon index of ∼ 2.5. A spectral analysis of the soft component allows an estimation of the mass of the central object. For the optically-estimated distance (&amp;gt; 1 kpc) and inclination (&amp;gt; 37°), the mass is estimated to be $\gt 3.1 M_\odot$. These results strongly support that the compact object is a black hole.

Spectropolarimetry of Double Peaked Broad Hα Lines in Radio Galaxies

AbstractSpectropolarimetric observations of 3 broad line radio galaxies exhibiting double peaked broad Hα lines, show that two of the sources (Arpl02B and 3C390.3) have single peaked line profiles in polarized flux with a position angle aligned with the jet axis. The third source (3C382) exhibits no polarized line emission at all. The consequences of these observations for the relativistic accretion disk and other BLR models are discussed.

Modeling an accretion disk in NGC 985

view Abstract Citations (7) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Modeling an Accretion Disk in NGC 985 Stanga, R. M. ; Rodriguez Espinosa, J. M. R. ; Mannucci, F. Abstract An optically thick relativistic Keplerian accretion disk model is used to fit the broad component of the Hα, Hβ and He I λ5876 emission line profiles of the active nucleus of NGC 985. A set of values of the relevant parameters is derived from the independent fits of the three lines. Those values are consistent for the lines examined and consistent with the observations, and are within the ranges expected for accretion disks on the basis of current models. Publication: The Astrophysical Journal Pub Date: October 1991 DOI: 10.1086/170531 Bibcode: 1991ApJ...379..592S Keywords: Accretion Disks; Active Galactic Nuclei; Astronomical Models; Emission Spectra; Astronomical Spectroscopy; H Lines; Seyfert Galaxies; Star Formation; Astrophysics; ACCRETION; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 985; GALAXIES: NUCLEI; GALAXIES: SEYFERT full text sources ADS | data products SIMBAD (1) NED (1)

Application of a general relativistic accretion disk model to LMC X-1, LMC X-3, X1608 - 522, and X1636 - 536

view Abstract Citations (95) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Application of a General Relativistic Accretion Disk Model to LMC X-1, LMC X-3, X1608-522, and X1636-536 Ebisawa, Ken ; Mitsuda, Kazuhisa ; Hanawa, Tomoyuki Abstract We compare the persistent X-ray spectra of black hole candidates and X-ray bursters with a model spectrum of an accretion disk around either a black hole or a neutron star. The model takes account of general relativity and assumes that the accretion disk is geometrically thin and in a steady state. First we compare this general relativistic model with other conventional model spectra that have been used to fit observations so far. It is shown that the general relativistic model, in shape, is quite similar to the multicolor disk model and the Sunyaev-Titarchuk Comptonization model. Through the medium of these conventional models, we perform spectral fitting analysis on the black hole candidates LMC X-I and LMC X-3 and on the X-ray bursters X1608-522 and X1636-536 using the general relativistic model. As a result, we obtain the lower limit of the masses of LMC X-1 and LMC X-3 and the probable masses of X1608-522 and X1636-533. The former masses are larger than the theoretical upper limit of the neutron star mass, 2.5 M_sun_and the latter masses are consistent with the canonical neutron star mass, 1.4 M_sun_. Publication: The Astrophysical Journal Pub Date: January 1991 DOI: 10.1086/169620 Bibcode: 1991ApJ...367..213E Keywords: Accretion Disks; Black Holes (Astronomy); Neutron Stars; Relativistic Theory; Stellar Models; X Ray Binaries; Doppler Effect; Stellar Mass; X Ray Sources; Astrophysics; BLACK HOLES; RELATIVITY; STARS: ACCRETION; STARS: NEUTRON; X-RAYS: BINARIES full text sources ADS | data products SIMBAD (4) NED (1)