We calculate the observable signature of a black hole (BH) accretion disk with a gap or a hole created by a secondary BH embedded in the disk. We find that for an interesting range of parameters of ...BH masses ({approx}10{sup 6}-10{sup 9} M{sub Sun }), orbital separation ({approx}1 AU to {approx}0.1 pc), and gap width (10-190 disk scale heights), the missing thermal emission from a gap manifests itself in an observable decrement in the spectral energy distribution (SED). We present observational diagnostics in terms of power-law forms that can be fit to line-free regions in active galactic nucleus (AGN) spectra or in fluxes from sequences of broad filters. Most interestingly, the change in slope in the broken power law is almost entirely dependent on the width of the gap in the accretion disk, which in turn is uniquely determined by the mass ratio of the BHs, such that it scales roughly as q {sup 5/12}. Thus, one can use spectral observations of the continuum of bright AGNs to infer not only the presence of a closely separated BH binary, but also the mass ratio. When the BH merger opens an entire hole (or cavity) in the inner disk, the broadband SED of the AGNs or quasar may serve as a diagnostic. Such sources should be especially luminous in optical bands but intrinsically faint in X-rays (i.e., not merely obscured). We briefly note that viable candidates may have already been identified, though extant detailed modeling of those with high-quality data have not yet revealed an inner cavity.
We present an analysis of the fundamental plane of black hole accretion, an empirical correlation of the mass of a black hole (M), its 5 GHz radio continuum luminosity ( L ), and its 2-10 keV X-ray ...power-law continuum luminosity (LX). We compile a sample of black holes with primary, direct black hole-mass measurements that also have sensitive, high-spatial-resolution radio and X-ray data. Taking into account a number of systematic sources of uncertainty and their correlations with the measurements, we use Markov chain Monte Carlo methods to fit a mass-predictor function of the form log ( M 10 8 M ) = 0 + R log ( L R 10 38 erg s − 1 ) + X log ( L X 10 40 erg s − 1 ) . Our best-fit results are 0 = 0.55 0.22, R = 1.09 0.10, and X = − 0.59 − 0.15 + 0.16 with the natural logarithm of the Gaussian intrinsic scatter in the log-mass direction ln ϵ = − 0.04 − 0.13 + 0.14 . This result is a significant improvement over our earlier mass scaling result because of the increase in active galactic nuclei sample size (from 18 to 30), improvement in our X-ray binary sample selection, better identification of Seyferts, and improvements in our analysis that takes into account systematic uncertainties and correlated uncertainties. Because of these significant improvements, we are able to consider potential influences on our sample by including all sources with compact radio and X-ray emission but ultimately conclude that the fundamental plane can empirically describe all such sources. We end with advice for how to use this as a tool for estimating black hole masses.
Tidal forces close to massive black holes can violently disrupt stars that make a close approach. These extreme events are discovered via bright X-ray and optical/ultraviolet flares in galactic ...centres. Prior studies based on modelling decaying flux trends have been able to estimate broad properties, such as the mass accretion rate. Here we report the detection of flows of hot, ionized gas in high-resolution X-ray spectra of a nearby tidal disruption event, ASASSN-14li in the galaxy PGC 043234. Variability within the absorption-dominated spectra indicates that the gas is relatively close to the black hole. Narrow linewidths indicate that the gas does not stretch over a large range of radii, giving a low volume filling factor. Modest outflow speeds of a few hundred kilometres per second are observed; these are below the escape speed from the radius set by variability. The gas flow is consistent with a rotating wind from the inner, super-Eddington region of a nascent accretion disk, or with a filament of disrupted stellar gas near to the apocentre of an elliptical orbit. Flows of this sort are predicted by fundamental analytical theory and more recent numerical simulations.
Abstract Iron K α (Fe K α ) emission is observed ubiquitously in active galactic nuclei (AGN), and it is a powerful probe of their circumnuclear environment. Examinations of the emission line play a ...pivotal role in understanding the disk geometry surrounding black holes. It has been suggested that the torus and the broad-line region (BLR) are the origins of emission. However, there is no universal location for the emitting region relative to the BLR. Here, we present an analysis of the narrow component of the Fe K α line in the Seyfert AGN MCG-5-23-16, one of the brightest AGN in X-rays and in Fe K α emission, to localize the emitting region. Spectra derived from Chandra/HETGS observations show asymmetry in the narrow Fe K α line, which has only been confirmed before in the AGN NGC 4151. Models including relativistic Doppler broadening and gravitational redshifts are preferred over simple Gaussians and measure radii consistent with R ≃ 200–650 r g . These results are consistent with those of NGC 4151 and indicate that the narrow Fe K α line in MCG-5-23-16 is primarily excited in the innermost part of the optical BLR, or X-ray BLR. Characterizing the properties of the narrow Fe K α line is essential for studying the disk geometries of the AGN population and mapping their innermost regions.
The Spin of a Newborn Black Hole: Swift J1728.9-3613 Draghis, Paul A.; Balakrishnan, Mayura; Miller, Jon M. ...
Astrophysical journal/The Astrophysical journal,
04/2023, Volume:
947, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract
The origin and distribution of stellar-mass black hole spins are a rare window into the progenitor stars and supernova events that create them. Swift J1728.9-3613 is an X-ray binary, likely ...associated with the supernova remnant (SNR) G351.9-0.9. An NuSTAR X-ray spectrum of this source during its 2019 outburst reveals reflection from an accretion disk extending to the innermost stable circular orbit. Modeling of the relativistic Doppler shifts and gravitational redshifts imprinted on the spectrum measures a dimensionless spin parameter of
a
= 0.86 ± 0.02 (1
σ
confidence), a small inclination angle of the inner accretion disk
θ
< 10°, and a subsolar iron abundance in the disk
A
Fe
< 0.84. This high spin value rules out a neutron star primary at the 5
σ
level of confidence. If the black hole is located in a still visible SNR, it must be young. Therefore, we place a lower limit on the natal black hole spin of
a
> 0.82, concluding that the black hole must have formed with a high spin. This demonstrates that black hole formation channels that leave an SNR, and those that do not (e.g., Cyg X-1), can both lead to high natal spin with no requirement for subsequent accretion within the binary system. Emerging disparities between the population of high-spin black holes in X-ray binaries and the low-spin black holes that merge in gravitational wave events may therefore be explained in terms of different stellar conditions prior to collapse, rather than different environmental factors after formation.
Here we study a 1-200 keV energy spectrum of the black hole binary Cygnus X-1 taken with NuSTAR and Suzaku. This is the first report of a NuSTAR observation of Cyg X-1 in the intermediate state, and ...the observation was taken during the part of the binary orbit where absorption due to the companion's stellar wind is minimal. The spectrum includes a multi-temperature thermal disk component, a cutoff power-law component, and relativistic and nonrelativistic reflection components. Our initial fits with publicly available constant density reflection models (relxill and reflionx) lead to extremely high iron abundances (>9.96 and times solar, respectively). Although supersolar iron abundances have been reported previously for Cyg X-1, our measurements are much higher and such variability is almost certainly unphysical. Using a new version of reflionx that we modified to make the electron density a free parameter, we obtain better fits to the spectrum even with solar iron abundances. We report on how the higher density ( cm−3) impacts other parameters such as the inner radius and inclination of the disk.
A Systematic View of Ten New Black Hole Spins Draghis, Paul A.; Miller, Jon M.; Zoghbi, Abderahmen ...
Astrophysical journal/The Astrophysical journal,
03/2023, Volume:
946, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract
The launch of NuSTAR and the increasing number of binary black hole (BBH) mergers detected through gravitational wave observations have exponentially advanced our understanding of BHs. ...Despite the simplicity owed to being fully described by their mass and angular momentum, BHs have remained mysterious laboratories that probe the most extreme environments in the universe. While significant progress has been made in the recent decade, the distribution of spin in BHs has not yet been understood. In this work, we provide a systematic analysis of all known BHs in X-ray binary systems (XBs) that have previously been observed by NuSTAR, but have not yet had a spin measurement made using the “relativistic reflection” method obtained from those data. By looking at all the available archival NuSTAR data of these sources, we measure 10 new BH spins: IGR J17454-2919 −
a
=
0.97
−
0.17
+
0.03
;
GRS 1758-258 −
a
=
0.991
−
0.019
+
0.007
;
MAXI J1727-203 −
a
=
0.986
−
0.159
+
0.012
;
MAXI J0637-430 −
a
= 0.97 ± 0.02; Swift J1753.5-0127 −
a
=
0.997
−
0.003
+
0.001
;
V4641 Sgr −
a
=
0.86
−
0.06
+
0.04
;
4U 1543-47 −
a
=
0.98
−
0.02
+
0.01
;
4U 1957+11 −
a
=
0.95
−
0.04
+
0.02
;
H 1743-322 −
a
=
0.98
−
0.02
+
0.01
;
and MAXI J1820+070 −
a
=
0.988
−
0.028
+
0.006
(all uncertainties are at the 1
σ
confidence level). We discuss the implications of our measurements on the entire distribution of stellar-mass BH spins in XBs, and we compare them with the spin distribution in BBHs, finding that the two distributions are clearly in disagreement. Additionally, we discuss the implications of this work on our understanding of how the “relativistic reflection” spin measurement technique works, and discuss possible sources of systematic uncertainty that can bias our measurements.
A number of neutron star low-mass X-ray binaries (LMXBs) have recently been discovered to show broad, asymmetric Fe K emission lines in their X-ray spectra. These lines are generally thought to be ...the most prominent part of a reflection spectrum, originating in the inner part of the accretion disk where strong relativistic effects can broaden emission lines. We present a comprehensive, systematic analysis of Suzaku and XMM-Newton spectra of 10 neutron star LMXBs, all of which display broad Fe K emission lines. Of the 10 sources, 4 are Z sources, 4 are atolls, and 2 are accreting millisecond X-ray pulsars (also atolls). The Fe K lines are fit well by a relativistic line model for a Schwarzschild metric, and imply a narrow range of inner disk radii (6-15 GM/c {sup 2}) in most cases. This implies that the accretion disk extends close to the neutron star surface over a range of luminosities. Continuum modeling shows that for the majority of observations, a blackbody component (plausibly associated with the boundary layer) dominates the X-ray emission from 8 to 20 keV. Thus it appears likely that this spectral component produces the majority of the ionizing flux that illuminates the accretion disk. Therefore, we also fit the spectra with a blurred reflection model, wherein a blackbody component illuminates the disk. This model fits well in most cases, supporting the idea that the boundary layer illuminates a geometrically thin disk.
NGC 4051 is one of the most variable and X-ray bright Seyfert galaxies. During 2009, NGC 4051 was caught at its lowest state ever observed by XMM-Newton. The low source continuum emission allows a ...clear measurement of the He-like emission lines of and O+6. The exceptionally high intercombination line flux is a direct measurement of either a high density or a UV irradiated photoionized plasma. Either way, this provides an unambiguous distance diagnostic. We find that the line emitting region has a density of ∼3 × 1010 cm−3 and a distance of a few 1015 cm from the continuum source, placing it within the UV-optical broad line region of NGC 4051. Both N+5 and O+6 independently result in similar measurements for density and distance. In addition, we find the kinematics of the broad O+7 Ly match those of the He+1 λ4686 line, which is associated with the NGC 4051 broad line region. This is the first direct X-ray measurement of a Seyfert broad line region.
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