Disk Inclination Angle Research Articles

Detection of QPO Soft Lag during the Outburst of Swift J1727.8-1613: Estimation of Intrinsic Parameters from Spectral Study

The recently discovered bright transient black hole candidate Swift J1727.8-1613 is studied in a broad energy range (0.5–79 keV) using combined NICER and NuSTAR data taken on 2023 August 29. A prominent type C quasiperiodic oscillation (QPO) at 0.89 ± 0.01 Hz with its harmonic was observed in NICER data of 0.5–10 keV. Interestingly, the harmonic becomes weaker in the lower energy bands (0.5–1 and 1–3 keV). We also report the first detection of a soft time lag of 0.014 ± 0.001 s at the QPO frequency between harder (3–10 keV) and softer (0.5–3 keV) band photons observed with the NICER/X-ray timing instrument. This indicates that the inclination of the accretion disk in the binary system might be high. From the detailed spectral analysis with the relxill reflection model, we found the disk inclination angle of the source to be ∼85°. We discuss how the accretion flow configuration inferred from spectral analysis can help us understand the origin of QPOs and soft lag in this source.

The 2018 Outburst of MAXI J1820+070 as Seen by Insight-HXMT

We present an analysis of the whole 2018 outburst of the black hole X-ray binary MAXI J1820+070 with Insight-HXMT data. We focus our study on the temporal evolution of the parameters of the source. We employ two different models to fit the disk’s thermal spectrum: the Newtonian model diskbb and the relativistic model nkbb. These two models provide different pictures of the source in the soft state. With diskbb, we find that the inner edge of the disk is close to the innermost stable circular orbit of a fast-rotating black hole and the corona changes geometry from the hard to the soft state. With nkbb, we find that the disk is truncated in the soft state and that the coronal geometry does not change significantly during the whole outburst. However, the model with nkbb can predict an untruncated disk around a fast-rotating black hole if we assume that the disk inclination angle is around 30° (instead of ∼60°, which is the inclination angle of the jet and is usually adopted as the disk inclination angle in the literature) and we employ a high-density reflection model. In such a case, we measure a high value of the black hole spin parameter with observations in the soft state, in agreement with the high spin value found from the analysis of the reflection features and in disagreement with the low spin value found by previous continuum-fitting method measurements with the disk inclination angle set to the value of the jet inclination angle.

On the evolution of a twisted thin accretion disc in eccentric inclined supermassive binary black holes

ABSTRACT We propose a model of a twisted accretion disc around a Kerr black hole interacting with a secondary black hole of a smaller mass on an inclined eccentric orbit. We use parameters of the system, which may be appropriate for the so-called precessing massive model of OJ 287. We calculate expressions for torque exerted on the disc by the secondary and a contribution of the secondary to the apsidal precession of disc elements by a double averaging procedure over the periods of the secondary and the disc elements. These expressions are used at all scales of interest, including the ones inside the binary orbit. We calculate numerically the evolution of the disc tilt and twist assuming a flat initial configuration. We consider the disc aspect ratio h/r = 10−3, a rather large viscosity parameter α = 0.1 and several values of the primary rotational parameter, χ. We find that, after a few periods of Lense–Thirring precession of the orbit, the disc relaxes to a quasi-stationary configuration in the precessing frame with a non-trivial distribution of the disc inclination angle, β, over the radial scale. We propose an analytic model for this configuration. We show that the presence of the twisted disc leads to multiple crossings of the disc by the secondary per one orbital period, with time periods between the crossings being different from the flat disc model. Our results should be taken into account in the modelling of OJ 287. They can also be applied to similar sources.

Plane polarisation in Comptonization process: A Monte Carlo study

Abstract High energies emissions observed in X-ray binaries (XRBs), active galactic nuclei (AGNs) are linearly polarised. The prominent mechanism for X-ray is the Comptonization process. We revisit the theory for polarisation in Compton scattering with unpolarised electrons and note that the ( $k \times k^{\prime}$ )-coordinate (in which, ( $k \times k^{\prime}$ ) acts as a z-axis, here k and k′ are incident and scattered photon momentum, respectively) is more convenient to describe it. Interestingly, for a fixed scattering plane the degree of polarisation PD after single scattering for randomly oriented low-energy unpolarised incident photons is $\sim$ 0.33. At the scattering angle $\theta$ = 0 or $\theta \equiv$ [0,25 $^{\circ}$ ], the modulation curve of k′ exhibits the same PD and PA (angle of polarisation) of k, and even the distribution of projection of electric vector of k′ ( $k^{\prime}_{e}$ ) on perpendicular plane to the k indicates same (so, an essential criteria for detector designing). We compute the polarisation state in Comptonization process using Monte Carlo methods with considering a simple spherical corona. We obtain the PD of emergent photons as a function of $\theta$ -angle (or alternatively, the disc inclination angle i) on a meridian plane (i.e. the laws of darkening, formulated by Chandrasekhar (1946, ApJ, 103, 351) after single scattering with unpolarised incident photons. To explore the energy dependency we consider a general spectral parameter set corresponding to hard and soft states of XRBs, we find that for average scattering no. $\langle N_{sc}\rangle$ $\sim$ 1.1 the PD is independent of energy and PA $\sim 90^{\circ}$ ( $k^{\prime}_{e}$ is parallel to the disc plane), and for $\langle N_{sc}\rangle$ $\sim$ 5 the PD value is maximum for $i=45^{\circ}$ . We also compare the results qualitatively with observation of IXPE for five sources.

The Spin Measurement of MAXI J0637-430: a Black Hole Candidate with High Disk Density

The Galactic black hole candidate MAXI J0637-430 was first discovered by MAXI/GSC on 2019 November 2. We study the spectral properties of MAXI J0637-430 by using the archived NuSTAR data and Swift/XRT data. After fitting the eight spectra by using a disk component and a powerlaw component model with absorption, we select the spectra with relatively strong reflection components for detailed X-ray reflection spectroscopy. Using the most state-of-art reflection model, relxillCp, the spectral fitting measures a black hole spin a * > 0.72 and the inclination angle of the accretion disk i = degrees, at a 90% confidence level. In addition, the fitting results show an extreme supersolar iron abundance. Combined with the fitting results of reflection model reflionx_hd, we consider that this unphysical iron abundance may be caused by a very high-density accretion disk (n e > 2.34 × 1021 cm−3) or a strong Fe Kα emission line. The soft excess is found in the soft state spectral fitting results, which may be an extra free–free heating effect caused by high density of the accretion disk. Finally, we discuss the robustness of black hole spin obtained by X-ray reflection spectroscopy. The result of relatively high spin is self-consistent with broadened Fe Kα line. Iron abundance and disk density have no effect on the spin results.

The Hard-to-soft Transition of GX 339–4 as Seen by Insight–HXMT

We present an analysis of the relativistic reflection spectra of GX 339–4 during the hard-to-soft transition of its 2021 outburst observed by Insight–HXMT. The strong relativistic reflection signatures in the data suggest a high black hole spin (a * > 0.86) and an intermediate disk inclination angle (i ≈ 35°–43°) of the system. The transition is accompanied by an increasing temperature of the disk and a softening of the corona emission, while the inner disk radius remains stable. Assuming a lamppost geometry, the corona height is also found to stay close to the black hole across the state transition. If we include the Comptonization of the reflection spectrum, the scattering fraction parameter is found to decrease during the state transition. We also perform an analysis with a reflection model designed for hot accretion disks of stellar mass black holes where the surface of the innermost accretion disk is illuminated by emission from the corona and the thermal disk below. Our results support the scenario in which the state transition is associated with variations in the corona properties.

The Spin of a Newborn Black Hole: Swift J1728.9-3613

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 (1σ 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 5σ 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.

SIMULATION-BASED INVESTIGATION OF THE EFFECTS OF MAJOR PARAMETERS ON MAGNETORHEOLOGICAL BRAKE TORQUE

In this paper, a magnetorheological brake (MRB) model that supports a van truck going downhill without interfering with the conventional braking system installed on this vehicle is designed and simulated. The simulation model demonstrates the impact of key variables on brake torque, including operation conditions, MRB tooth tilt angle, MRB rotor thickness, and MRB tooth count. As a result, the simulation results show that the maximum brake torque value is about 136.41 Nm at the 75-degree inclination angle of the tooth disk. The MRB rotor thickness does not have many effects on the brake torque. The maximum brake torque (138.7 Nm) can be achieved at 10 cm rotor thickness. The brake torque increases following an increase in the number of MRB teeth. The brake torque increases by 6% when the number of teeth increases from 1 to 3. Keywords: Magnetorheological Fluid, Magnetorheological Brake, MRB Tooth Tilt Angle, MRB Rotor Thickness, Braking Torque DOI： https://doi.org/10.35741/issn.0258-2724.58.3.21

Broadband Spectral Properties of MAXI J1348–630 using AstroSat Observations

We present broadband X-ray spectral analysis of the black hole X-ray binary MAXI J1348–630, performed using five AstroSat observations. The source was in the soft spectral state for the first three observations and in the hard state for the last two. The three soft state spectra were modeled using a relativistic thin accretion disk with reflection features and thermal Comptonization. Joint fitting of the soft state spectra constrained the spin parameter of the black hole a * > 0.97 and the disk inclination angle i = degrees. The bright and faint hard states had bolometric flux a factor of ∼6 and ∼10 less than that of the soft state respectively. Their spectra were fitted using the same model except that the inner disk radius was not assumed to be at the last stable orbit. However, the estimated values do not indicate large truncation radii and the inferred accretion rate in the disk was an order of magnitude lower than that of the soft state. Along with earlier reported temporal analysis, AstroSat data provide a comprehensive picture of the evolution of the source.

The Velocity Map Asymmetry of Ionized Gas in MaNGA. I. The Catalog and General Properties

The SDSS-IV MaNGA survey has measured two-dimensional maps of emission-line velocities for a statistically powerful sample of nearby galaxies. The asymmetric features of these kinematics maps reflect the nonrotational component of a galaxy’s internal motion of ionized gas. In this study, we present a catalog of kinematic asymmetry measurements of the Hα velocity map of a sample of 5353 MaNGA galaxies. Based on this catalog, we find that “special” galaxies (e.g., merging galaxies, barred galaxies, and active galactic nucleus host galaxies) contain more galaxies with highly asymmetric velocity maps. However, we notice that more than half of galaxies with high kinematic asymmetry in our sample are quite “regular.” For those “regular” galaxies, kinematic asymmetry shows a significant anticorrelation with stellar mass at , while such a trend becomes very weak at . Moreover, at a given stellar mass, the kinematic asymmetry shows weak correlations with photometric morphology, star formation rate, and environment, while it is independent of H i gas content. We also have quantified the observational effects in the kinematic asymmetry measurement. We find that both the signal-to-noise ratio of Hα flux and disk inclination angle contribute to the measures of kinematic asymmetry, while the physical spatial resolution is an irrelevant factor inside the MaNGA redshift coverage.

Circumnuclear dense gas disk fuelling the active galactic nucleus in the nearby radio galaxy NGC 4261

The cold molecular gas in the circumnuclear disk (CND) of radio galaxies provides critical information for understanding the mass accretion onto active galactic nuclei. We present the first detection and maps of HCNJ= 1–0 and HCO+J= 1–0 emission lines from the circumnuclear region of a nearby radio galaxy, NGC 4261, using the Northern Extended Millimeter Array. Both molecular lines are detected at a radial velocity of ±700 km s−1relative to the systemic velocity of the galaxy, and they arise from a CND with an outer radius of 100 pc. The velocity fields of HCN and HCO+are fitted with a Keplerian disk rotation. The enclosed mass is (1.6 ± 0.1) × 109 M⊙, assuming a disk inclination angle of 64°. The continuum image at 80 GHz reveals a weak two-sided jet structure extending over 5 kpc along the east–west direction and a bright core at the centre. The continuum spectrum between 80 and 230 GHz shows a spectral index of −0.34 ± 0.02, which suggests optically thin synchrotron radiation. The dense gas mass associated with the CND is calculated to be 6.03 × 107 M⊙. It supports a positive correlation between the dense gas mass in the CND and the accretion rate onto the supermassive black hole, though there are uncertainties in the parameters of the correlation.

A Library of Synthetic X-Ray Spectra for Fitting Tidal Disruption Events

We present a tabulated version of our slim-disk model for fitting tidal disruption events (TDEs). We create a synthetic X-ray spectral library by ray-tracing stationary general relativistic slim disks and including gravitational redshift, Doppler, and lensing effects self-consistently. We introduce the library to reduce computational expense and increase access for fitting future events. Fitting requires interpolation between the library spectra; the interpolation error in the synthetic flux is generally <10% (it can rise to 40% when the disk is nearly edge-on). We fit the X-ray spectra of the TDEs ASASSN-14li and ASASSN-15oi, successfully reproducing our earlier constraints on black hole mass M • and spin a • from full on-the-fly ray-tracing. We use the library to fit mock observational data to explore the degeneracies among parameters, finding that (1) spectra from a hotter thermal disk and edge-on inclination angle offer tighter constraints on M • and a •; (2) the constraining power of spectra on M • and a • increases as a power law with the number of X-ray counts, and the index of the power law is higher for hotter thermal disk spectra; (3) multiepoch X-ray spectra partially break the degeneracy between M • and a •; (4) the time-dependent level of X-ray absorption can be constrained from spectral fitting. The tabulated model and slim-disk model are available at https://doi.org/10.25739/hfhz-xn60.

XMM–Newton observations of the narrow-line Seyfert 1 galaxy IRAS 13224−3809: X-ray spectral analysis II

ABSTRACT Previously, we modelled the X-ray spectra of the narrow-line Seyfert 1 galaxy IRAS 13224−3809 using a disc reflection model with a fixed electron density of 1015 cm−3. An additional blackbody component was required to fit the soft X-ray excess below 2 keV. In this work, we analyse simultaneously five flux-resolved XMM–Newton spectra of this source comprising data collected over 2 Ms. A disc reflection model with an electron density of ne ≈ 1020 cm−3 and an iron abundance of $Z_{\rm Fe}=3.2\pm 0.5\, \mathrm{Z}_{\odot }$ is used to fit the broad-band spectra of this source. No additional component is required to fit the soft excess. Our best-fitting model provides consistent measurements of black hole spin and disc inclination angle as previous models where a low disc density was assumed. In the end, we calculate the average illumination distance between the corona and the reflection region in the disc of IRAS 13224−3809 based on best-fitting density and ionization parameters, which changes from 0.43$\sqrt{f_{\rm AD}/f_{\rm INF}}$ rg in the lowest flux state to 1.71$\sqrt{f_{\rm AD}/f_{\rm INF}}$ rg in the highest flux state assuming a black hole mass of $2\times 10^{6}\, \mathrm{M}_{\odot }$. fAD/fINF is the ratio between the flux of the coronal emission that reaches the accretion disc and infinity. This ratio depends on the geometry of the coronal region in IRAS 13224−3809. So we only discuss its value based on the simple ‘lamppost’ model, although detailed modelling of the disc emissivity profile of IRAS 13224−3809 is required in future to reveal the exact geometry of the corona.

Spectral analysis of new black hole candidate AT2019wey observed by NuSTAR

AT2019wey is a new galactic X-ray binary that was first discovered as an optical transient by the Australia Telescope Large Area Survey (ATLAS) on December 7, 2019. AT2019wey consists of a black hole candidate as well as a low-mass companion star ($M_{\text {star }} \lesssim 0.8 M_{\odot}$) and is likely to have a short orbital period ($P_{\text {orb }} \lesssim 8$ h). Although AT2019wey began activation in the X-ray band during almost the entire outburst on March 8, 2020, it did not enter the soft state during the entire outburst. In this study, we present a detailed spectral analysis of AT2019wey in the low/hard state during its X-ray outburst on the basis of Nuclear Spectroscopic Telescope Array \emph observations. We obtain tight constraints on several of its important physical parameters by applying the State-of-art \texttt{relxill} relativistic reflection model family. In particular, we determine that the measured inner radius of the accretion disk is most likely to have extended to the innermost stable circular orbit (ISCO) radius, i.e., $R_{\text{in}}=1.38^{+0.23}_{-0.16}~R_{\text{ISCO}}$. Hence, assuming $R_{\text{in}}$=$R_{\text{ISCO}}$, we find the spin of AT2019wey to be $a_{*}\sim$ $0.97$, which is close to the extreme and an inner disk inclination angle of ~$i\sim$ $22 ^{\circ}$. Additionally, according to our adopted models, AT2019wey tends to have a relatively high iron abundance of $A_{\mathrm{Fe}}\sim$ 5 $A_{\mathrm{Fe}, \odot}$ and a high disk ionization state of $\log \xi\sim$ 3.4.

ALMA observations of the Extended Green Object G19.01−0.03 – I. A Keplerian disc in a massive protostellar system

ABSTRACT Using the Atacama Large Millimetre/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array (VLA), we observed the Extended Green Object (EGO) G19.01−0.03 with sub-arcsec resolution from 1.05 mm to 5.01 cm wavelengths. Our ∼0.4 arcsec ∼ 1600 au angular resolution ALMA observations reveal a velocity gradient across the millimetre core MM1, oriented perpendicular to the previously known bipolar molecular outflow, which is consistently traced by 20 lines of 8 molecular species with a range of excitation temperatures, including complex organic molecules (COMs). Kinematic modelling shows the data are well described by models that include a disc in Keplerian rotation and infall, with an enclosed mass of 40–70 M⊙ (within a 2000 au outer radius) for a disc inclination angle of i = 40○, of which 5.4–7.2 M⊙ is attributed to the disc. Our new VLA observations show that the 6.7 GHz Class II methanol masers associated with MM1 form a partial ellipse, consistent with an inclined ring, with a velocity gradient consistent with that of the thermal gas. The disc-to-star mass ratio suggests the disc is likely to be unstable and may be fragmenting into as-yet-undetected low-mass stellar companions. Modelling the centimetre–millimetre spectral energy distribution of MM1 shows the ALMA 1.05 mm continuum emission is dominated by dust, whilst a free–free component, interpreted as a hypercompact H ii region, is required to explain the VLA ∼5 cm emission. The high enclosed mass derived for a source with a moderate bolometric luminosity (∼104 L⊙) suggests that the MM1 disc may feed an unresolved high-mass binary system.

The Hα line emission of the Be star β Psc: the last 40 yr

ABSTRACT A study on the photosphere and disc of the Be star β Psc is presented. We recover almost 40 yr of high-resolution spectroscopic observations and additional data gathered from the BeSS data base. We evaluate the photospheric parameters from the spectral energy distribution (SED) and fittings of state-of-the-art non-LTE model atmospheres to observed helium, carbon, silicon, and magnesium line profiles. Our models include the stellar geometric deformation as well as the co-latitude dependence of temperature and gravity, aiming to derive the effects of rotation on the stellar parameters. We estimate the circumstellar disc parameters from the fitting of models assuming different disc properties, namely its radius and gas density profile. The disc inclination angle i is constrained from the fittings of He i 4471 Å, Mg ii 4481 Å, C ii 4267 Å, and Si ii 4128, 4132 Å lines with gravity darkened models. Our findings, based on model fittings, suggest that during the last 40 yr, the disc radius changed within the interval 5.5 ≤ Rd ≤ 7.8 $R/R_{*}\,$, the disc base gas density within 5 × 10−13 ≤ ρ ≤ 1 × 10−12 g cm−3, while the radial power-law density index m assumed values between 2.0 and 2.3. These results are in agreement with recent works dealing with spectroscopic and interferometric measurements of this object.

Double-peaked Balmer Emission Indicating Prompt Accretion Disk Formation in an X-Ray Faint Tidal Disruption Event

Abstract We present the multiwavelength analysis of the tidal disruption event (TDE) AT 2018hyz (ASASSN-18zj). From follow-up optical spectroscopy, we detect the first unambiguous case of resolved double-peaked Balmer emission in a TDE. The distinct line profile can be well-modeled by a low eccentricity (e ≈ 0.1) accretion disk extending out to ∼100 R p and a Gaussian component originating from non-disk clouds, though a bipolar outflow origin cannot be completely ruled out. Our analysis indicates that in AT 2018hyz, disk formation took place promptly after the most-bound debris returned to pericenter, which we estimate to be roughly tens of days before the first detection. Redistribution of angular momentum and mass transport, possibly through shocks, must occur on the observed timescale of about a month to create the large Hα-emitting disk that comprises ≲5% of the initial stellar mass. With these new insights from AT 2018hyz, we infer that circularization is efficient in at least some, if not all optically bright, X-ray faint TDEs. In these efficiently circularized TDEs, the detection of double-peaked emission depends on the disk inclination angle and the relative strength of the disk contribution to the non-disk component, possibly explaining the diversity seen in the current sample.

Probing the magnetospheric accretion region of the young pre-transitional disk system DoAr 44 using VLTI/GRAVITY

Context. Young stellar objects are thought to accrete material from their circumstellar disks through their strong stellar magnetospheres. Aims. We aim to directly probe the magnetospheric accretion region on a scale of a few 0.01 au in a young stellar system using long-baseline optical interferometry. Methods. We observed the pre-transitional disk system DoAr 44 with VLTI/GRAVITY on two consecutive nights in the K-band. We computed interferometric visibilities and phases in the continuum and in the Brγ line in order to constrain the extent and geometry of the emitting regions. Results. We resolve the continuum emission of the inner dusty disk and measure a half-flux radius of 0.14 au. We derive the inclination and position angle of the inner disk, which provides direct evidence that the inner and outer disks are misaligned in this pre-transitional system. This may account for the shadows previously detected in the outer disk. We show that Brγ emission arises from an even more compact region than the inner disk, with an upper limit of 0.047 au (~5 R⋆). Differential phase measurements between the Brγ line and the continuum allow us to measure the astrometric displacement of the Brγ line-emitting region relative to the continuum on a scale of a few tens of microarcsec, corresponding to a fraction of the stellar radius. Conclusions. Our results can be accounted for by a simple geometric model where the Brγ line emission arises from a compact region interior to the inner disk edge, on a scale of a few stellar radii, fully consistent with the concept of magnetospheric accretion process in low-mass young stellar systems.

Fragmentation, rotation, and outflows in the high-mass star-forming region IRAS 23033+5951

Context. The formation process of high-mass stars (&gt;8 M⊙) is poorly constrained, particularly the effects of clump fragmentation creating multiple systems and the mechanism of mass accretion onto the cores. Aims. We study the fragmentation of dense gas clumps, and trace the circumstellar rotation and outflows by analyzing observations of the high-mass (~500 M⊙) star-forming region IRAS 23033+5951. Methods. Using the Northern Extended Millimeter Array (NOEMA) in three configurations and the IRAM 30 m single-dish telescope at 220 GHz, we probe the gas and dust emission at an angular resolution of ~0.45′′, corresponding to 1900 au. Results. In the millimeter (mm) continuum emission, we identify a protostellar cluster with at least four mm-sources, where three of them show a significantly higher peak intensity well above a signal-to-noise ratio of 100. Hierarchical fragmentation from large to small spatial scales is discussed. Two fragments are embedded in rotating structures and drive molecular outflows, traced by 13CO (2–1) emission. The velocity profiles across two of the cores are similar to Keplerian but are missing the highest-velocity components close to the center of rotation, which is a common phenomena from observations like these, and other rotation scenarios are not excluded entirely. Position–velocity diagrams suggest protostellar masses of ~6 and 19 M⊙. Rotational temperatures from fitting CH3CN (12K− 11K) spectra are used for estimating the gas temperature and thereby also the disk stability against gravitational fragmentation, utilizing Toomre’s Q parameter. Assuming that the candidate disk is in Keplerian rotation about the central stellar object and considering different disk inclination angles, we identify only one candidate disk as being unstable against gravitational instability caused by axisymmetric perturbations. Conclusions. The dominant sources cover different evolutionary stages within the same maternal gas clump. The appearance of rotation and outflows of the cores are similar to those found in low-mass star-forming regions.

High Density Reflection Spectroscopy – II. The density of the inner black hole accretion disc in AGN

ABSTRACT We present a high density disc reflection spectral analysis of a sample of 17 Seyfert 1 galaxies to study the inner disc densities at different black hole mass scales and accretion rates. All the available XMM–Newton observations in the archive are used. OM observations in the optical/UV band are used to estimate their accretion rates. We find that 65 per cent of sources in our sample show a disc density significantly higher than ne = 1015 cm−3, which was assumed in previous reflection-based spectral analyses. The best-fitting disc densities show an anticorrelation with black hole mass and mass accretion rate. High density disc reflection model can successfully explain the soft excess emission and significantly reduce inferred iron abundances. We also compare our black hole spin and disc inclination angle measurements with previous analyses.