An accretion disc model for quasar optical variability

We investigate the optical variability of 7658 quasars from SDSS Stripe 82. Taking advantage of a larger sample and relatively more data points for each quasar, we estimate variability amplitudes and divide the sample into small bins of redshift, rest-frame wavelength, black hole mass, Eddington ratio, and bolometric luminosity, respectively, to investigate the relationships between variability and these parameters. An anti-correlation between variability and rest-frame wavelength is found. The variability amplitude of radio-quiet quasars shows almost no cosmological evolution, but that of radio-loud ones may weakly anti-correlate with redshift. In addition, variability increases as either luminosity or Eddington ratio decreases. However, the relationship between variability and black hole mass is uncertain; it is negative when the influence of Eddington ratio is excluded, but positive when the influence of luminosity is excluded. The intrinsic distribution of variability amplitudes for radio-loud and radio-quiet quasars are different. Both radio-loud and radio-quiet quasars exhibit a bluer-when-brighter chromatism. Assuming that quasar variability is caused by variations of accretion rate, the Shakura–Sunyaev disk model can reproduce the tendencies of observed correlations between variability and rest-frame wavelength, luminosity as well as Eddington ratio, supporting that changes of accretion rate play an important role in producing the observed optical variability. However, the predicted positive correlation between variability and black hole mass seems to be inconsistent with the observed negative correlation between them in small bins of Eddington ratio, which suggests that other physical mechanisms may still need to be considered in modifying the simple accretion disk model.

Context. Quasar variability has proven to be a powerful tool to constrain the properties of their inner engine and the accretion process onto supermassive black holes. Correlations between UV/optical variability and physical properties have been long studied with a plethora of different approaches and time-domain surveys, although the detailed picture is not yet clear. Aims. We analysed archival data from the SDSS Stripe-82 region to study how the quasar power spectral density (PSD) depends on the black hole mass, bolometric luminosity, accretion rate, redshift, and rest-frame wavelength. We developed a model-independent analysis framework that could be easily applied to upcoming large surveys such as the Legacy Survey of Space and Time (LSST). Methods. We used light curves of 8042 spectroscopically confirmed quasars, observed in at least six yearly seasons in five filters ugriz. We split the sample into bins of similar physical properties containing at least 50 sources, and we measured the ensemble PSD in each of them. Results. We find that a simple power law is a good fit to the power spectra in the frequency range explored. Variability does not depend on the redshift at a fixed wavelength. Instead, both PSD amplitude and slope depend on the black hole mass, accretion rate, and rest-frame wavelength. We provide scaling relations to model the observed variability as a function of the physical properties, and discuss the possibility of a universal PSD shape for all quasars, where frequencies scale with the black hole mass, while normalization and slope(s) are fixed (at any given wavelength and accretion rate).

Aims. It is speculated that a merger of two massive stellar-origin black holes in a dense stellar environment may lead to the formation of a massive black hole in the pair-instability mass gap (∼50−135 M⊙). Such a merger-formed black hole is expected to typically have a high spin (a ∼ 0.7). If such a massive black hole acquires another black hole it may lead to another merger detectable by LIGO/Virgo in gravitational waves. Acquiring a companion may be hindered by gravitational-wave kick/recoil, which accompanies the first merger and may quickly remove the massive black hole from its parent globular or nuclear cluster. We test whether it is possible for a massive merger-formed black hole in the pair-instability gap to be retained in its parent cluster and have low spin. Such a black hole would be indistinguishable from a primordial black hole. Methods. We employed results from numerical relativity calculations of black hole mergers to explore the range of gravitational-wave recoil velocities for various combinations of merging black hole masses and spins. We compared merger-formed massive black hole speeds with typical escape velocities from globular and nuclear clusters. Results. We show that a globular cluster is highly unlikely to form and retain a ∼100 M⊙ black hole if the spin of the black hole is low (a ≲ 0.3). Massive merger-formed black holes with low spins acquire high recoil speeds (≳ 200 km s−1) from gravitational-wave kick during formation that exceed typical escape speeds from globular clusters (∼ 50 km s−1). However, a very low-spinning (a ∼ 0.1) and massive (∼100 M⊙) black hole could be formed and retained in a galactic nuclear star cluster. Even though such massive merger-formed black holes with such low spins acquire high speeds during formation (∼ 400 km s−1), they may avoid ejection since massive nuclear clusters have high escape velocities (∼ 300−500 km s−1). A future detection of a massive black hole in the pair-instability mass gap with low spin would therefore not be proof of the existence of primordial black holes, which are sometimes claimed to have low spins and arbitrarily high masses.

view Abstract Citations (27) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Ultraviolet/Optical Continuum of Hercules X-1/HZ Herculis Vrtilek, S. D. ; Cheng, F. H. Abstract We present observations of the binary X-ray pulsar system Hercules X-1/HZ Herculis taken with the International Ultraviolet Explorer (lUE) and several ground-based observatories as part of a multi- wavelength campaign conducted in 1993 August. The 1993 campaign found the source in an unusual state, with substantially reduced X-ray flux, and also revealed a significant reduction in ultraviolet flux observed around eclipse ingress and egress, which implies an absence of the normally observed excess attributed to X-ray heating of the disk. Comprehensive modeling of the ultraviolet and optical continuum flux suggests that the ultraviolet and optical light curves can be reproduced by assuming variations in Mdot alone; however, changes in accretion rate are insufficient to account for the observed drop in X-ray flux. Shifts in disk inclination angle and changes in mass accretion rate can consistently explain the observed changes in X-ray, ultraviolet, and optical fluxes. Changes in mass accretion rate and disk inclination angle may be related to shifts in the 35 day precession period, with the average mass accretion rate corresponding to the average 35 day period. The rapid fluctuations in soft X-ray flux, observed several times during the campaign, may be caused by rapid variation of the mass accretion rate. Publication: The Astrophysical Journal Pub Date: July 1996 DOI: 10.1086/177475 Bibcode: 1996ApJ...465..915V Keywords: STARS: INDIVIDUAL CONSTELLATION NAME: HERCULES X-1; STARS: INDIVIDUAL CONSTELLATION NAME: HZ HERCULIS; ULTRAVIOLET: STARS full text sources ADS | data products SIMBAD (3) MAST (1) INES (1)

We report spectral analysis of the persistent black hole X-ray binary, 4U 1957+115, using AstroSat, Swift, and NuSTAR observations carried out between 2016 and 2019. Modelling with a disc emission, thermal Comptonization, and blurred reflection components revealed that the source was in the high-soft state with the disc flux ∼87 per cent of the total and high-energy photon index ∼2.6. There is an evidence that either the inner disc radius varied by ∼25 per cent or the colour hardening factor changed by ∼12 per cent. The values of the inner disc radius imply that for a non-spinning black hole, the black hole mass is < 7 M ⊙ and the source is located > 30 kpc away. On the other hand, a rapidly spinning black hole would be consistent with the more plausible black hole mass of < 10 M ⊙ and a source distance of ∼10 kpc. Fixing the distance to 10 kpc and using a relativistic accretion disc model, constrained the black hole mass to 6 M⊙ and inclination angle to 72°. A positive correlation is detected between the accretion rate and inner radii or equivalently between the accretion rate and colour factor.

view Abstract Citations (62) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Accretion disks around massive black holes: persistent emission spectra. Eardley, D. M. ; Lightman, A. P. ; Payne, D. G. ; Shapiro, S. L. Abstract Detailed model calculations of steady X-ray emission from gaseous accretion disks around massive black holes are presented. The continuous X-ray spectrum of such a disk for black-hole masses of 100, 1000, and 10,000 solar masses and a range of accretion rates is discussed using three different disk models ('standard', 'two-temperature', and 'optically thin') capable of generating a copious flux of X-rays above 1 keV. Comparison with observations of galactic X-ray sources in the energy range from 2 to 20 keV shows that the two-temperature and standard models may be ruled out for many of the sources, while the bremsstrahlung regime of the optically thin model is still possible. The standard model is found to be too soft, and the two-temperature model too hard, to explain the observations of both galactic-bulge and globular-cluster X-ray sources. It is concluded that a massive black hole with an accretion disk requires the bremsstrahlung regime of the optically thin model to explain observed bulge and globular-cluster sources. Publication: The Astrophysical Journal Pub Date: August 1978 DOI: 10.1086/156349 Bibcode: 1978ApJ...224...53E Keywords: Black Holes (Astronomy); Emission Spectra; Globular Clusters; Stellar Mass Accretion; X Ray Sources; Bremsstrahlung; Disks (Shapes); Galactic Bulge; Galactic Radiation; X Ray Spectra; Astrophysics; Accretion Disks:Black Holes; Accretion Disks:X-Ray Spectra; Globular Clusters:X-Ray Sources full text sources ADS |

We present a general relativistic accretion disc model and its application to the soft-state X-ray spectra of black hole binaries. The model assumes a flat, optically thick disc around a rotating Kerr black hole. The disc locally radiates away the dissipated energy as a blackbody. Special and general relativistic effects influencing photons emitted by the disc are taken into account. The emerging spectrum, as seen by a distant observer, is parametrized by the black hole mass and spin, the accretion rate, the disc inclination angle and the inner disc radius. We fit the ASCA soft state X-ray spectra of LMC X-1 and GRO J1655-40 by this model. We find that having additional limits on the black hole mass and inclination angle from optical/UV observations, we can constrain the black hole spin from X- ray data. In LMC X-1 the constrain is weak, we can only rule out the maximally rotating black hole. In GRO J1655-40 we can limit the spin much better, and we find 0.68 � a � 0.88. Accretion discs in both sources are radiation pressure dominated. We don't find Compton reflection features in the spectra of any of these objects.

Americanae nace como un proyecto conjunto que surge dentro de la Red Europea de Información y Documentación sobre América Latina (REDIAL), y que ha afrontado la Biblioteca de la Agencia Española de Cooperación Internacional para el Desarrollo (AECID). Esta nueva biblioteca virtual hace más accesibles los libros digitales de tema americanista a los investigadores y usuarios interesados de cualquier parte del mundo.

Recent work has suggested that black holes (BHs) could be cosmologically coupled to the accelerated expansion of the Universe, potentially becoming a candidate for origin of dark energy. This would imply that BH mass growth follows cosmological expansion, with the masses of individual BHs growing as MBH ∝ (1 + z)3. In this Letter, we discuss the binary systems Gaia BH1 and Gaia BH2, which contain ∼9 M⊙ BHs orbited by ∼1 M⊙ stars in widely separated orbits. The ages of both systems can be constrained by the properties of the luminous stars. If BH masses are indeed growing as (1 + z)3, the masses of both BHs at formation would have been significantly smaller than today. We find a 77% probability that the mass of the BH in Gaia BH2 would have been below 2.2 M⊙ at formation. This is below the classical Tolman–Oppenheimer–Volkov limit, though it is not yet clear whether or not BHs subject to cosmological coupling should obey this limit. For Gaia BH1, the same probability is 70%. This analysis is consistent with results from two BHs in the globular cluster NGC 3201, but unlike the NGC 3201 BHs, the Gaia BHs have well-constrained inclinations and therefore firm upper mass limits. The discovery of more BHs in binary systems with Gaia astrometry in the coming years will allow us to test the cosmological coupling hypothesis decisively.

We study the orbital evolution and accretion history of massive black hole (MBH) pairs in rotationally supported circumnuclear discs up to the point where MBHs form binary systems. Our simulations have high resolution in mass and space which, for the first time, makes it feasible to follow the orbital decay of a MBH either counter- or co-rotating with respect to the circumnuclear disc. We show that a moving MBH on an initially counter-rotating orbit experiences an "orbital angular momentum flip" due to the gas-dynamical friction, i.e., it starts to corotate with the disc before a MBH binary forms. We stress that this effect can only be captured in very high resolution simulations. Given the extremely large number of gas particles used, the dynamical range is sufficiently large to resolve the Bondi-Hoyle-Lyttleton radii of individual MBHs. As a consequence, we are able to link the accretion processes to the orbital evolution of the MBH pairs. We predict that the accretion rate is significantly suppressed and extremely variable when the MBH is moving on a retrograde orbit. It is only after the orbital angular momentum flip has taken place that the secondary rapidly "lights up" at which point both MBHs can accrete near the Eddington rate for a few Myr. The separation of the double nucleus is expected to be around ~10 pc at this stage. We show that the accretion rate can be highly variable also when the MBH is co-rotating with the disc (albeit to a lesser extent) provided that its orbit is eccentric. Our results have significant consequences for the expected number of observable double AGNs at separations of <100 pc.

We compile black hole (BH) masses for ~60,000 quasars in the redshift range 0.1 z 4.5 included in the Fifth Data Release of the Sloan Digital Sky Survey, using virial BH mass estimators based on the Hβ, Mg II, and C IV emission lines. Within our sample, the widths of the three lines follow lognormal distributions, with means and dispersions that do not depend strongly on luminosity or redshift. The Mg II- and Hβ-estimated BH masses are consistent with one another, but there is a positive bias between the C IV- and Mg II-estimated BH masses correlated with the C IV-Mg II blueshift, suggesting that the C IV estimator is more severely affected by a disk wind. If the underlying BH mass distribution decreases with mass and the Eddington ratio distribution at fixed true BH mass has nonzero width, we show that the measured virial BH mass and Eddington ratio distributions within finite luminosity bins are subject to Malmquist bias. We present a model that reproduces the observed virial mass distribution, quasar luminosity function, and line width distribution of our sample; it has an underlying BH mass distribution dN/dlog M ∝ M−2.6 and a lognormal true Eddington ratio distribution at fixed true mass with dispersion 0.4 dex and mean dependent on BH mass. In this model, the observed virial mass (Eddington ratio) distribution for the SDSS sample is biased high (low) by ~0.6 dex within finite luminosity bins. Finally, we compare virial BH masses of radio and broad absorption line quasars with ordinary quasars matched in redshift and luminosity.

Most massive galaxies have supermassive black holes at their centres, and the masses of the black holes are believed to correlate with properties of the host-galaxy bulge component. Several explanations have been proposed for the existence of these locally established empirical relationships, including the non-causal, statistical process of galaxy-galaxy merging, direct feedback between the black hole and its host galaxy, and galaxy-galaxy merging and the subsequent violent relaxation and dissipation. The empirical scaling relations are therefore important for distinguishing between various theoretical models of galaxy evolution, and they furthermore form the basis for all black-hole mass measurements at large distances. Observations have shown that the mass of the black hole is typically 0.1 per cent of the mass of the stellar bulge of the galaxy. Until now, the galaxy with the largest known fraction of its mass in its central black hole (11 per cent) was the small galaxy NGC 4486B. Here we report observations of the stellar kinematics of NGC 1277, which is a compact, lenticular galaxy with a mass of 1.2 × 10(11) solar masses. From the data, we determine that the mass of the central black hole is 1.7 × 10(10) solar masses, or 59 per cent of its bulge mass. We also show observations of five other compact galaxies that have properties similar to NGC 1277 and therefore may also contain over-massive black holes. It is not yet known if these galaxies represent a tail of a distribution, or if disk-dominated galaxies fail to follow the usual black-hole mass scaling relations.

We present results on the evolution of the intrinsic scatter of black hole masses considering different implementations of a model in which black holes only grow via mergers. We demonstrate how merger driven growth affects the correlations between black hole mass and host bulge mass. The simple case of an initially lognormal distributed scatter in black hole and bulge masses combined with random merging within the galaxy population results in a decreasing scatter with merging generation/number as predicted by the central-limit theorem. In general we find that the decrease in scatter σ is well approximated by σ&lt;inf&gt;merg&lt;/inf&gt;(&lt;it&gt;m&lt;/it&gt;) ∼σ&lt;inf&gt;ini&lt;/inf&gt;× (&lt;it&gt;m&lt;/it&gt;+ 1)−&lt;it&gt;a&lt;/it&gt;/2 with &lt;it&gt;a&lt;/it&gt;= 0.42 for a range of mean number of mergers &lt;it&gt;m&lt;/it&gt; &lt; 50. For a large mean number of mergers (&lt;it&gt;m&lt;/it&gt; &gt; 100) we find a convergence to &lt;it&gt;a&lt;/it&gt;= 0.61. This is valid for a wide range of different initial distributions, refill-scenarios or merger mass ratios. Growth scenarios based on halo merger trees of a (100 Mpc)3ΛCDM-simulation show a similar behaviour with a scatter decrease of &lt;it&gt;a&lt;/it&gt;= 0.30 with typical number of mergers &lt;it&gt;m&lt;/it&gt; &lt; 50 consistent with random merging (best matching model: &lt;it&gt;a&lt;/it&gt;= 0.34). Assuming a present-day scatter of 0.3 dex in black hole mass and a mean number of mergers not exceeding &lt;it&gt;m&lt;/it&gt;= 50 our results imply a scatter of 0.6 dex at &lt;it&gt;z&lt;/it&gt;= 3 and thus a possible scenario in which overmassive (and undermassive) black holes at high redshift are a consequence of a larger intrinsic scatter in black hole mass. A simple toy model connecting the growth of black holes to the growth of ΛCDM haloes via mergers, neglecting any contribution from accretion, yields a consistent &lt;it&gt;M&lt;/it&gt;&lt;inf&gt;•&lt;/inf&gt;–&lt;it&gt;M&lt;/it&gt;&lt;inf&gt;Bulge&lt;/inf&gt; relation at &lt;it&gt;z&lt;/it&gt;= 0– if we assume the correct initial relation.

We use a large sample of Fermi flat-spectrum radio quasars (FSRQs), BL Lacertae objects (BL Lacs) and flat-spectrum radio-loud narrow-line Seyfert 1 galaxies (F-RLNLS1s) to study the relationship between them. Our main results are as follows: (i) Compared with FSRQs, the F-RLNLS1s have lower redshift, black hole mass and jet kinetic power. However, the F-RLNLS1s have higher redshift, broad-line region luminosity, accretion rate and jet kinetic power than BL Lacs on the average. When we use the median black hole mass to normalize the jet kinetic and radiation power, we find a small difference between FSRQs and F-RLNLS1s in normalized jet kinetic power. (ii) According to the BZ theory, we find that both of FSRQs and most of F-RLNLS1s may have a strong accretion disk which dominated by the radiation-pressure. (iii) Most of these F-RLNLS1s and FSRQs have accretion disk luminosity ( $L_{\text{Disk}}$ ) larger than jet radiation power ( $P_{\text{rad}}$ ), $\log L_{\text{Disk}} > \log P_{\text{rad}}$ , which suggests that FSRQs and F-RLNLS1s may have a strong accretion disk. We use a linear regression to analyze the relationship between jet power and accretion disk luminosity. It is interesting to note that the slopes of FSRQs are similar to that of F-RLNLS1s in jet power vs. accretion disk luminosity panel. These results above may suggest that the formation mechanism of jets in F-RLNLS1s is similar to that of FSRQs. (iv) By using the multiple linear regression analysis, we find that the accretion and black hole mass may have a different contribution to jet kinetic power for F-RLNLS1s. What’s more, the contribution of black hole mass is larger than that of accretion rate. These results imply that the jet kinetic power of F-RLNLS1s less than FSRQs may due to the low black hole mass of F-RLNLS1s.

We study the relation between the metallicity of quasar broad line region (BLR) and black hole (BH) mass ($10^{7.5}M_{\odot} \sim 10^{10}M_{\odot}$) and quasar bolometric luminosity ($10^{44.6}erg/s \sim 10^{48} erg/s$) using a sample of $\sim$130,000 quasars at $2.25\leq z\leq 5.25$ from Sloan Digital Sky Survey (SDSS) Data Release 12 (DR12). We generate composite spectra by stacking individual spectra in the same BH mass (bolometric luminosity) and redshift bins and then estimate the metallicity of quasar BLR using metallicity-sensitive broad emission-line flux ratios based on the photoionization models. We find a significant correlation between quasar BLR metallicity and BH mass (bolometric luminosity) but no correlation between quasar BLR metallicity and redshift. We also compare the metallicity of quasar BLR and that of host galaxies inferred from the mass-metallicity relation of star-forming galaxy at $z\sim2.3$ and $z\sim3.5$. We find quasar BLR metallicity is 0.3 $\sim$ 1.0 dex higher than their host galaxies. This discrepancy cannot be interpreted by the uncertainty due to different metallicity diagnostic methods, mass-metallicity relation of galaxy, metallicity gradient in quasar host galaxies, BH mass estimation, the effect of different spectral energy distribution (SED) models, and a few other potential sources of uncertainties. We propose a possibility that the high metallicity in quasar BLR might be caused by metal enrichment from massive star formation in the nucleus region of quasars or even the accretion disk.