Disk Wind Models Research Articles

Spectroscopic observations of V455 Andromedae superoutburst in 2007: The most exotic spectral features in dwarf nova outbursts

Abstract We present our spectroscopic observations of V455 Andromedae during the 2007 superoutburst. Our observations cover this superoutburst from around the optical peak of the outburst to the post-superoutburst stage. During the early superhump phase, the emission lines of the Balmer series, He i, He ii, Bowen blend, and C iv/N iv blend were detected. The He ii 4686 line exhibited a double-peaked emission profile, where Balmer emission lines were single-peaked, which is unexpected from its high inclination. In the ordinary superhump phase, the Balmer series transitioned to double-peaked emission profiles, and high-ionization lines were significantly weakened. These transitions of the line profiles should be related to the structural transformation of the accretion disk, as expected between the early and ordinary superhump transition in the thermal–tidal instability model. The Doppler map of Hα during the early superhump phase exhibits a compact blob centered at the primary white dwarf. In analogy to SW Sex-type cataclysmic variables, this feature could emerge from the disk wind and/or the mass accretion column on to the magnetized white dwarf. The Doppler map of He ii 4686 Å is dominated by the ring-like structure and imposed two flaring regions with the velocity of ∼300 km s−1, which is too slow for a Keplerian accretion disk. The phase of the flaring regions was coincident with the inner spiral arm structure identified during the early superhump phase. Our disk wind model with the enhanced emission from the wind component launched from the inner arm structure successfully reproduced the observed properties of He ii 4686 Å. Therefore, V455 And is the first case in dwarf nova outbursts where the presence of the disk wind is inferred from an optical spectrum.

Probing Protoplanetary Disk Winds with C ii Absorption

Abstract We present an analysis of wind absorption in the C ii λ1335 doublet toward 40 classical T Tauri stars with archival far-ultraviolet (FUV) spectra obtained by the Hubble Space Telescope. Absorption features produced by fast or slow winds are commonly detected (36 out of 40 targets) in our sample. The wind velocity of the fast wind decreases with disk inclination, which is consistent with expectations for a collimated jet. Slow wind absorption is mostly detected in disks with intermediate or high inclination, without a significant dependence of wind velocity on disk inclination. Both the fast and slow wind absorption are preferentially detected in FUV lines of neutral or singly ionized atoms. The Mg ii λ λ2796, 2804 lines show wind absorption consistent with the absorption in the C ii lines. We develop simplified semi-analytical disk/wind models to interpret the observational disk wind absorption. Both fast and slow winds are consistent with expectations from a thermal-magnetized disk wind model and are generally inconsistent with a purely thermal wind. Both the models and the observational analysis indicate that wind absorption occurs preferentially from the inner disk, which offers a wind diagnostic in complement to optical forbidden line emission that traces the wind in larger volumes.

The first interferometric survey of massive YSOs in the K-band

Context. Circumstellar discs are essential for the formation of high mass stars, while multiplicity, and in particular binarity, appears to be an inevitable outcome, as the vast majority of massive stars (>8 M⊙) are found in binaries (up to 100%). Our understanding of the innermost regions of accretion discs around massive stars and the binarity of high-mass young stars is sparse because of the high spatial resolution and sensitivity required to trace these rare and distant objects. Aims. We aim to spatially resolve and constrain the sizes of the dust and ionised gas emission from the innermost regions of a sample of massive young stellar objects (MYSOs) for the first time, and to provide high-mass binary statistics for young stars at 2–300 au scales using direct interferometric measurements. Methods. We observed six MYSOs using long-baseline near-infrared K-band interferometry on the VLTI (GRAVITY, AMBER) in order to resolve and characterise the 2.2 μm hot dust emission originating from the inner rim of circumstellar discs around MYSOs, and the associated Brγ emission from ionised gas. We fitted simple geometrical models to the interferometric observables, and determined the inner radius of the dust emission. We placed MYSOs with K-band measurements in a size–luminosity diagram for the first time, and compared our findings to their low- and intermediate-mass counterparts (T Tauris and Herbig AeBes). We also compared the observed K-band sizes (i.e. inner rim radius) to the sublimation radius predicted by three different disc scenarios: a classical thick flattened structure with oblique heating in action, and direct heating from the protostar via an optically thin cavity with and without backwarming effects. Lastly, we applied binary geometries to trace close binarity among MYSOs. Results. The characteristic size of the 2.2 μm continuum emission towards this sample of MYSOs shows a large scatter at the given luminosity range. When the inner sizes of MYSOs are compared to those of lower mass Herbig AeBe and T Tauri stars, they appear to follow a universal trend in that the sizes scale with the square-root of the stellar luminosity. The Brγ emission originates from a similar or somewhat smaller and co-planar area compared to the 2.2 μm continuum emission. We discuss this new finding with respect to a disc-wind or jet origin. Finally, we report an MYSO binary fraction of 17–25% at milli-arcsecond separations (2–300 au). Conclusions. The size–luminosity diagram indicates that the inner regions of discs around young stars scale with luminosity independently of the stellar mass. The observed fraction of MYSO binaries in K-band is almost ‘flat’ for a wide range of separations (2–10 000 au). At the targeted scales (2–300 au), the MYSO binary fraction is lower than what was previously reported for the more evolved main sequence massive stars, which, if further confirmed, could implicate predictions from massive binary formation theories. Lastly, with this study, we can finally spatially resolve the crucial star–disc interface in a sample of MYSOs, showing that au-scale discs are prominent in high-mass star formation and are similar to their low-mass equivalents, while the ionised gas can be linked to disc wind and disc accretion models similar to Herbig AeBes.

Testing Photoevaporation and MHD Disk Wind Models through Future High-angular Resolution Radio Observations: The Case of TW Hydrae

Abstract We present theoretical predictions for the free–free emission at centimeter wavelengths obtained from photoevaporation and magnetohydrodynamic (MHD) wind disk models adjusted to the case of the TW Hydrae young stellar object. For this system, disk photoevaporation with heating due to the high-energy photons from the star has been proposed as a possible mechanism to open the gap observed in the dust emission with the Atacama Large Millimeter/submillimeter Array. We show that the photoevaporation disk model predicts a radial profile for the free–free emission that is made of two main spatial components, one originated from the bound disk atmosphere at 0.5–1 au from the star, and another more extended component from the photoevaporative wind at larger disk radii. We also show that the stellar X-ray luminosity has a significant impact on both these components. The predicted radio emission from the MHD wind model has a smoother radial distribution which extends to closer distances to the star than the photoevaporation case. We also show that a future radio telescope such as the Next Generation Very Large Array would have enough sensitivity and angular resolution to spatially resolve the main structures predicted by these models.

Launching the asymmetric bipolar jet of DO Tau

Context. The role of bipolar jets in the formation of stars, and in particular how they are launched, is still not well understood. Aims. We probe the protostellar jet launching mechanism using high-resolution observations of the near-infrared (IR) [Fe II]λ1.53,1.64 μm emission lines. Methods. We consider the case of the bipolar jet from Classical T Tauri star, DO Tau, and investigate the jet morphology and kinematics close to the star (within 140 au) using AO-assisted IFU observations from GEMINI/NIFS. Results. We find that the brighter, blueshifted jet is collimated very quickly after it is launched. This early collimation requires the presence of magnetic fields. We confirm velocity asymmetries between the two lobes of the bipolar jet, and also confirm no time variability in the asymmetry over a 20-year interval. This sustained asymmetry is in accordance with recent simulations of magnetised disc winds. We examine the data for signatures of jet rotation. We report an upper limit on differences in radial velocity of 6.3 and 8.7 km s−1 for the blue- and redshifted jets, respectively. Interpreting this as an upper limit on jet rotation implies that any steady, axisymmetric magneto-centrifugal model of jet launching is constrained to a launch radius in the disc plane of r0 < 0.5 and 0.3 au for the blue- and redshifted jets, respectively. This supports an X-wind or narrow disc-wind model. However, the result pertains only to the observed high-velocity [Fe II] emission, and does not rule out a wider flow launched from a wider radius. We report the detection of small-amplitude jet axis wiggling in both lobes. We rule out orbital motion of the jet source as the cause. Precession can better account for the observations but requires double the precession angle, and a different phase for the counter-jet. Such non-solid body precession could arise from an inclined massive Jupiter companion, or a warping instability induced by launching a magnetic disc wind. Conclusions. Overall, our observations are consistent with an origin of the DO Tau jets from the inner regions of the disc.

Correlated time variability of multicomponent high-velocity outflows in J162122.54+075808.4

ABSTRACT We present a detailed analysis of time variability of two distinct C iv broad absorption line (BAL) components seen in the spectrum of J162122.54+075808.4 (zem = 2.1394) using observations from SDSS, NTT, and SALT taken at seven different epochs spanning about 15 yr. The blue-BAL component (with an ejection velocity, $v_{\rm e}\sim 37\, 500$ km s−1) is an emerging absorption that shows equivalent width variations and kinematic shifts consistent with acceleration. The red-BAL component ($v_{\rm e} \sim 15\, 400$ km s−1) is a three-component absorption. One of the components is emerging and subsequently disappearing. The two other components show kinematic shifts consistent with acceleration coupled with equivalent width variability. Interestingly, we find the kinematic shifts and equivalent width variability of the blue- and red-BAL components to be correlated. While the C iv emission-line flux varies by more than 17 per cent during our monitoring period, the available light curves (covering rest frame 1300–2300 Å) do not show more than a 0.1 mag variability in the continuum. This suggests that the variations in the ionizing flux are larger than that of the near-ultraviolet flux. However, the correlated variability seen between different BAL components cannot be explained solely by photoionization models without structural changes. In the framework of disc wind models, any changes in the radial profiles of density and/or velocity triggered either by disc instabilities or by changes in the ionizing radiation can explain our observations. High-resolution spectroscopic monitoring of J1621+0758 is important to understand the physical conditions of the absorbing gas and thereby to constrain the parameters of disc wind models.

Probing the Disk–Corona Systems and Broad-line Regions of Changing-look Quasars with X-Ray and Optical Observations

Abstract “Changing-look” quasars are a new class of highly variable active galactic nuclei that have changed their spectral type over surprisingly short timescales of just a few years. The origin of this phenomenon is debated, but is likely to reflect some change in the accretion flow. To investigate the disk–corona systems in these objects, we measure optical/UV–X-ray spectral indices ( α OX ) and Eddington ratios ( λ Edd ) of 10 previously discovered changing-look quasars at two or more epochs. By comparing these data with simulated results based on the behavior of X-ray binaries, we find possible similarities in spectral indices below the 1% Eddington ratio. We further investigate the Eddington ratios of changing-look quasars before and after their spectral type changes, and find that changing-look quasars cross the 1% Eddington ratio boundary when their broad emission lines disappear/emerge. This is consistent with the disk-wind model as the origin of broad emission lines.

Multi-scale view of star formation in IRAS 21078+5211: from clump fragmentation to disk wind

Context. Star formation (SF) is a multi-scale process in which the mode of fragmentation of the collapsing clump on scales of 0.1–1 pc determines the mass reservoir and affects the accretion process of the individual protostars on scales of 10–100 au. Aims. We want to investigate the nearby (located at 1.63 ± 0.05 kpc) high-mass star-forming region IRAS 21078+5211 at linear scales from ~1 pc down to ~10 au. Methods. We combine the data of two recent programs: the NOrthern Extended Millimeter Array large project CORE and the Protostellar Outflows at the EarliesT Stages (POETS) survey. The former provides images of the 1 mm dust continuum and molecular line emissions with a linear resolution of ≈600 au covering a field of view up to ≈0.5 pc. The latter targets the ionized gas and 22 GHz water masers, mapping linear scales from a few 103 au down to a few astronomical units. Results. In IRAS 21078+5211, a highly fragmented cluster (size ~0.1 pc) of molecular cores is observed, located at the density peak of an elongated (size ~1 pc) molecular cloud. A small (≈1 km s−1 per 0.1 pc) LSR velocity (VLSR) gradient is detected across the major axis of the molecular cloud. Assuming we are observing a mass flow from the harboring cloud to the cluster, we derive a mass infall rate of ≈10−4 M⊙ yr−1. The most massive cores (labeled 1, 2, and 3) are found at the center of the cluster, and these are the only ones that present a signature of protostellar activity in terms of emission from high-excitation molecular lines or a molecular outflow. The masses of the young stellar objects (YSOs) inside these three cores are estimated in the range 1–6 M⊙. We reveal an extended (size ~0.1 pc), bipolar collimated molecular outflow emerging from core 1. We believe this is powered by the compact (size ≲1000 au) radio jet discovered in the POETS survey, ejected by a YSO embedded in core 1 (named YSO-1), since the molecular outflow and the radio jet are almost parallel and have a comparable momentum rate. By means of high-excitation lines, we find a large (≈14 km s−1 over 500 au) VLSR gradient at the position of YSO-1, oriented approximately perpendicular to the radio jet. Assuming this is an edge-on, rotating disk and fitting a Keplerian rotation pattern, we determine the YSO-1 mass to be 5.6 ± 2.0 M⊙. The water masers observed in the POETS survey emerge within 100–300 au from YSO-1 and are unique tracers of the jet kinematics. Their three-dimensional (3D) velocity pattern reveals that the gas flows along, and rotates about, the jet axis. We show that the 3D maser velocities are fully consistent with the magneto-centrifugal disk-wind models predicting a cylindrical rotating jet. Under this hypothesis, we determine the jet radius to be ≈ 16 au and the corresponding launching radius and terminal velocity to be ≈ 2.2 au and ≈ 200 km s−1, respectively. Conclusions. Complementing high-angular resolution, centimeter and millimeter interferometric observations in thermal tracers with Very Long Baseline Interferometry of molecular masers, is invaluable in studying high-mass SF. The combination of these twodatasets allows us to connect the events that we see at large scales, as clump fragmentation and mass flows, with the physical processes identified at small scales, specifically, accretion and ejection in disk-jet systems.

A variable magnetic disc wind in the black hole X-ray binary GRS 1915+105?

Context. GRS 1915+105 being one of the brightest transient black hole binaries (BHBs) in the X-rays offers a unique testbed for the study of the connection between accretion and ejection mechanisms in BHBs. In particular, this source can be used to study the accretion disc wind and its dependence on the state changes in BHBs. Aims. Our aim is to investigate the origin and geometry of the accretion disc wind in GRS 1915+105. This study will provide a basis for planning future observations with the X-ray Imaging Spectroscopy Mission (XRISM), and may also provide important parameters for estimating the polarimetric signal with the upcoming Imaging X-ray Polarimetry Explorer (IXPE). Methods. We analysed the spectra of GRS 1915+105 in the soft ϕ and hard χ classes using the high-resolution spectroscopy offered by Chandra HETGS. In the soft state, we find a series of wind absorption lines that follow a non-linear dependence of velocity width, velocity shift, and equivalent width with respect to ionisation, indicating a multiple component or stratified outflow. In the hard state we find only a faint Fe XXVI absorption line. We model the absorption lines in both the states using a dedicated magneto-hydrodynamic (MHD) wind model to investigate a magnetic origin of the wind and to probe the cause of variability in the observed line flux between the two states. Conclusions. The MHD disc wind model provides a good fit for both states, indicating the possibility of a magnetic origin of the wind. The multiple ionisation components of the wind are well characterised as a stratification of the same magnetic outflow. We find that the observed variability in the line flux between soft and hard states cannot be explained by photo-ionisation alone but is most likely due to a large (three orders of magnitude) increase in the wind density. We find the mass outflow rate of the wind to be comparable to the accretion rate, suggesting an intimate link between accretion and ejection processes that lead to state changes in BHBs.

Bow shocks, nova shells, disc winds and tilted discs: the nova-like V341 Ara has it all

ABSTRACT V341 Ara was recently recognized as one of the closest (d ≃ 150 pc) and brightest (V ≃ 10) nova-like cataclysmic variables. This unique system is surrounded by a bright emission nebula, likely to be the remnant of a recent nova eruption. Embedded within this nebula is a prominent bow shock, where the system’s accretion disc wind runs into its own nova shell. In order to establish its fundamental properties, we present the first comprehensive multiwavelength study of the system. Long-term photometry reveals quasi-periodic, super-orbital variations with a characteristic time-scale of 10–16 d and typical amplitude of ≃1 mag. High-cadence photometry from theTransiting Exoplanet Survey Satellite (TESS) reveals for the first time both the orbital period and a ‘negative superhump’ period. The latter is usually interpreted as the signature of a tilted accretion disc. We propose a recently developed disc instability model as a plausible explanation for the photometric behaviour. In our spectroscopic data, we clearly detect antiphased absorption and emission-line components. Their radial velocities suggest a high mass ratio, which in turn implies an unusually low white-dwarf mass. We also constrain the wind mass-loss rate of the system from the spatially resolved [O iii] emission produced in the bow shock; this can be used to test and calibrate accretion disc wind models. We suggest a possible association between V341 Ara and a ‘guest star’ mentioned in Chinese historical records in AD 1240. If this marks the date of the system’s nova eruption, V341 Ara would be the oldest recovered nova of its class and an excellent laboratory for testing nova theory.

ALMA Observations and Modeling of the Rotating Outflow in Orion Source I

Abstract We present 29SiO(J = 8–7) ν = 0, SiS (J = 19–18) ν = 0, and 28SiO (J = 8–7) ν = 1 molecular line archive observations made with the Atacama Large Millimeter/Submillimeter Array (ALMA) of the molecular outflow associated with Orion Source I. The observations show velocity asymmetries about the flow axis that are interpreted as outflow rotation. We find that the rotation velocity (∼4–8 km s−1) decreases with the vertical distance to the disk. In contrast, the cylindrical radius (∼100–300 au), the expansion velocity (∼2–15 km s−1), and the axial velocity v z (∼−1–10 km s−1) increase with the vertical distance. The mass estimated of the molecular outflow M outflow ∼ 0.66–1.3 M ⊙. Given a kinematic time ∼130 yr, this implies a mass-loss rate M ⊙ yr−1. This massive outflow sets important constraints on disk wind models. We compare the observations with a model of a shell produced by the interaction between an anisotropic stellar wind and an Ulrich accretion flow that corresponds to a rotating molecular envelope in collapse. We find that the model cylindrical radii are consistent with the 29SiO(J = 8–7) ν = 0 data. The expansion velocities and the axial velocities of the model are similar to the observed values, except for the expansion velocity close to the disk (z ∼ ±150 au). Nevertheless, the rotation velocities of the model are a factor ∼3–10 lower than the observed values. We conclude that the Ulrich flow alone cannot explain the rotation observed and other possibilities should be explored, like the inclusion of the angular momentum of a disk wind.

Inner dusty regions of protoplanetary discs – II. Dust dynamics driven by radiation pressure and disc winds

ABSTRACT We explore dust flow in the hottest parts of protoplanetary discs using the forces of gravity, gas drag, and radiation pressure. Our main focus is on the optically thin regions of dusty disc, where the dust is exposed to the most extreme heating conditions and dynamical perturbations: the surface of optically thick disc and the inner dust sublimation zone. We utilize results from two numerically strenuous fields of research. The first is the quasi-stationary solutions on gas velocity and density distributions from mangetohydrodynamical (MHD) simulations of accretion discs. This is critical for implementing a more realistic gas drag impact on dust movements. The second is the optical depth structure from a high-resolution dust radiation transfer. This step is critical for a better understanding of dust distribution within the disc. We describe a numerical method that incorporates these solutions into the dust dynamics equations. We use this to integrate dust trajectories under different disc wind models and show how grains end up trapped in flows that range from simple accretion on to the star to outflows into outer disc regions. We demonstrate how the radiation pressure force plays one of the key roles in this process and cannot be ignored. It erodes the dusty disc surface, reduces its height, resists dust accretion on to the star, and helps the disc wind in pushing grains outwards. The changes in grain size and porosity significantly affect the results, with smaller and porous grains being influenced more strongly by the disc wind and radiation pressure.

The Ionized Warped Disk and Disk Wind of the Massive Protostar Monoceros R2-IRS2 Seen with ALMA

Abstract Theories of massive star formation predict that massive protostars accrete gas through circumstellar disks. Although several cases have been found already thanks to high angular-resolution interferometry, the internal physical structure of these disks remains unknown, in particular whether they present warps or internal holes, as observed in low-mass protoplanetary disks. Here, we report very high angular-resolution observations of the H21α radio recombination line carried out in Band 9 with the Atacama Large Millimeter/submillimeter Array (beam of 80 mas × 60 mas, or 70 au × 50 au) toward the IRS2 massive young stellar object in the Monoceros R2 star-forming cluster. The H21α line shows maser amplification, which allows us to study the kinematics and physical structure of the ionized gas around the massive protostar down to spatial scales of ∼1–2 au. Our ALMA images and 3D radiative transfer modeling reveal that the ionized gas around IRS2 is distributed in a Keplerian circumstellar disk and an expanding wind. The H21α emission centroids at velocities between −10 and 20 km s−1 deviate from the disk plane, suggesting a warping for the disk. This could be explained by the presence of a secondary object (a stellar companion or a massive planet) within the system. The ionized wind seems to be launched from the disk surface at distances ∼11 au from the central star, consistent with magnetically-regulated disk wind models. This suggests a similar wind-launching mechanism to that recently found for evolved massive stars such as MWC349A and MWC922.

Molecule formation in dust-poor irradiated jets

Context. Recent ALMA observations suggest that the highest velocity part of molecular protostellar jets (≳80 km s−1) are launched from the dust-sublimation regions of the accretion disks (≲0.3 au). However, the formation and survival of molecules in inner protostellar disk winds, in the presence of a harsh far-ultraviolet radiation field and the absence of dust, remains unexplored. Aims. We aim to determine if simple molecules, such as H2, CO, SiO, and H2O, can be synthesized and spared in fast and collimated dust-free disk winds or if a fraction of dust is necessary to explain the observed molecular abundances. Methods. This work is based on a recent version of the Paris-Durham shock code designed to model irradiated environments. Fundamental properties of the dust-free chemistry are investigated from single point models. A laminar 1D disk wind model was then built using a parametric flow geometry. This model includes time-dependent chemistry and the attenuation of the radiation field by gas-phase photoprocesses. The influence of the mass-loss rate of the wind and of the fraction of dust on the synthesis of the molecules and on the attenuation of the radiation field is studied in detail. Results. We show that a small fraction of H2 (≤10−2), which primarily formed through the H− route, can efficiently initiate molecule synthesis, such as CO and SiO above TK ~ 800 K. We also propose new gas-phase formation routes of H2 that can operate in strong visible radiation fields, involving CH+ for instance. The attenuation of the radiation field by atomic species (e.g., C, Si, and S) proceeds through continuum self-shielding. This process ensures the efficient formation of CO, OH, SiO, and H2O through neutral–neutral reactions and the survival of these molecules. Class 0 dust-free winds with high mass-loss rates (Ṁw ≥ 2 × 10−6 M⊙ yr−1) are predicted to be rich in molecules if warm (TK ≥ 800 K). Interestingly, we also predict a steep decrease in the SiO-to-CO abundance ratio with the decline of mass-loss rate, from Class 0 to Class I protostars. The molecular content of disk winds is very sensitive to the presence of dust, and a mass-fraction of surviving dust as small as 10−5 significantly increases the H2O and SiO abundances. Conclusions. Chemistry of high velocity jets is a powerful tool to probe their content in dust and uncover their launching point. Models of internal shocks are required to fully exploit the current (sub)millimeter observations and prepare future JWST observations.

HST/COS Observations of Quasar Outflows in the 500–1050 Å Rest Frame. IV. The Largest Broad Absorption Line Acceleration

Abstract We present an analysis of the broad absorption line (BAL) velocity shift that appeared in one of the outflow systems in quasar SDSS J1042+1646. Observations were taken by the Hubble Space Telescope/Cosmic Origins Spectrograph in 2011 and 2017 in the 500–1050 Å rest frame. The outflow’s velocity centroid shifted by ∼−1550 km s−1 from −19,500 km s−1 to −21,050 km s−1 over a rest-frame time of 3.2 yr. The velocity shift signatures are most apparent in the absorption features from the Ne viii λλ770.41 and 780.32 doublet and are supported by the absorption troughs from O v λ629.73 and the Mg x λλ609.79 and 624.94 doublet. This is the first time where a quasar outflow velocity shift is observed in troughs from more than one ion and in distinct troughs from a doublet transition (Ne viii). We attribute the velocity shift to an acceleration of an existing outflow as we are able to exclude photoionization changes and motion of material into and out of the line of sight as alternate explanations. This leads to an average acceleration of 480 km s−1 yr−1 (1.52 cm s−2) in the quasar rest frame. Both the acceleration and the absolute velocity shift are the largest reported for a quasar outflow to date. Based on the absorption troughs of the O v* multiplet, we derive a range for the distance of the outflow (R) from the central source, 0.05 pc < R < 54.3 pc. This outflow shows similarities with the fast X-ray outflow detected in quasar PG 1211+143. We use the acceleration and velocity shift to constrain radiatively accelerated active galactic nucleus disk–wind models and use them to make predictions for future observations.

The WISSH quasars project

Hyper-luminous quasars (Lbol ≳ 1047 erg s−1) are ideal laboratories to study the interaction and impact of the extreme radiative field and the most powerful winds in the active galactic nuclei (AGN) nuclear regions. They typically exhibit low coronal X-ray luminosity (LX) compared to the ultraviolet (UV) and mid-infrared (MIR) radiative outputs (LUV and LUV); a non-negligible fraction of them report even ∼1 dex weaker LX compared to the prediction of the well established LX–LUV and LX–LUV relations followed by the bulk of the AGN population. In our WISE/SDSS-selected Hyper-luminous (WISSH) z = 2 − 4 broad-line quasar sample, we report on the discovery of a dependence between the intrinsic 2–10 keV luminosity (L2 − 10) and the blueshifted velocity of the CIV emission line (vCIV) that is indicative of accretion disc winds. In particular, sources with the fastest winds (vCIV ≳ 3000 km s−1) possess ∼0.5–1 dex lower L2 − 10 than sources with negligible vCIV. No similar dependence is found on LUV, LUV, Lbol, the photon index, or the absorption column density. We interpret these findings in the context of accretion disc wind models. Both magnetohydrodynamic and line-driven models can qualitatively explain the reported relations as a consequence of X-ray shielding from the inner wind regions. In case of line-driven winds, the launch of fast winds is favoured by a reduced X-ray emission, and we speculate that these winds may play a role in directly limiting the coronal hard X-ray production.

Kinematic signatures of reverberation mapping of close binaries of supermassive black holes in active galactic nuclei

Context. An unresolved region in the relative vicinity of the event horizon of a supermassive black holes (SMBH) in active galactic nuclei (AGN) radiates strongly variable optical continuum and broad-line emission flux. These fluxes can be processed into two-dimensional transfer functions (2DTF) of material flows that encrypt various information about these unresolved structures. An intense search for kinematic signatures of reverberation mapping of close binary SMBH (SMBBH) is currently ongoing. Aims. Elliptical SMBBH systems (i.e. both orbits and disc-like broad-line regions (BLR) are elliptic) have not been assessed in 2DTF studies. We aim to numerically infer such a 2DTF because the geometry of the unresolved region is imprinted on their optical emission. Through this, we determine their specific kinematical signatures. Methods. We simulated the geometry and kinematics of SMBBH whose components are on elliptical orbits. Each SMBH had a disc-like elliptical BLR. The SMBHs were active and orbited each other tightly at a subparsec distance. Results. Here we calculate for the first time 2DTF, as defined in the velocity-time delay plane, for several elliptical configurations of SMBBH orbits and their BLRs. We find that these very complex configurations are clearly resolved in maps. These results are distinct from those obtained from circular and disc-wind geometry. We calculate the expected line variability for all SMBBH configurations. We show that the line shapes are influenced by the orbital phase of the SMBBH. Some line profiles resemble observed profiles, but they can also be much deformed to look like those from the disc-wind model. Conclusions. First, our results imply that using our 2DTF, we can detect and quantify kinematic signatures of elliptical SMBBH. Second, the calculated expected line profiles share some intriguing similarities with observed profiles, but also with some profiles that are synthesised in disc-wind models. To overcome the non-uniqueness of the spectral line shapes as markers of SMBBH, they must be accompanied with 2DTF.

Stratified disc wind models for the AGN broad-line region: ultraviolet, optical, and X-ray properties

ABSTRACT The origin, geometry, and kinematics of the broad-line region (BLR) gas in quasars and active galactic nuclei (AGN) are uncertain. We demonstrate that clumpy biconical disc winds illuminated by an AGN continuum can produce BLR-like spectra. We first use a simple toy model to illustrate that disc winds make quite good BLR candidates, because they are self-shielded flows and can cover a large portion of the ionizing flux-density (ϕH-nH) plane. We then conduct Monte Carlo radiative transfer and photoionization calculations, which fully account for self-shielding and multiple scattering in a non-spherical geometry. The emergent model spectra show broad emission lines with equivalent widths and line ratios comparable to those observed in AGN, provided that the wind has a volume filling factor of fV ≲ 0.1. Similar emission line spectra are produced for a variety of wind geometries (polar or equatorial) and for launch radii that differ by an order of magnitude. The line emission arises almost exclusively from plasma travelling below the escape velocity, implying that ‘failed winds’ are important BLR candidates. The behaviour of a line-emitting wind (and possibly any ‘smooth flow’ BLR model) is similar to that of the locally optimally emitting cloud model originally proposed by Baldwin et al. (1995), except that the gradients in ionization state and temperature are large-scale and continuous, rather than within or between distinct clouds. Our models also produce UV absorption lines and X-ray absorption features, and the stratified ionization structure can partially explain the different classes of broad absorption line quasars.

Determining Quasar Orientation

Abstract Since the discovery of active galactic nuclei (AGN) and their subclasses, a unification scheme of AGN has been long sought. Orientation-based unified models predict that some of the diversity within AGN subclasses can be explained by the different viewing angles of the observer. Several orientation categorisations have been suggested, but a widely applicable measure has yet to be found. Using the properties of the ultraviolet and optical broad emission lines of quasars, in particular the velocity offsets and line widths of high-ionisation C iv and low-ionisation Mg ii lines, a correlation has been measured. It is postulated that this correlation is due to the viewing angle of the observer. Comparison with other orientation tracers shows consistency with this interpretation. Using a simulation of a wide angle disk-wind model for the broad emission line region, we successfully replicate the observed correlation with inclination. Future more detailed modelling will not only enable improved accuracy in the determination of the viewing angle to individual AGN, but will also substantially increase our understanding of the emitting regions of AGN.

GIARPS High-resolution Observations of T Tauri stars (GHOsT)

Context. The mechanism for jet formation in the disks of T Tauri stars remains poorly understood. Observational benchmarks to launching models can be provided by tracing the physical properties of the kinematic components of the wind and jet in the inner 100 au of the disk surface. Aims. In the framework of the GIARPS High-resolution Observations of T Tauri stars (GHOsT) project, we aim to perform a multi-line analysis of the velocity components of the gas in the jet acceleration zone. Methods. We analyzed the GIARPS-TNG spectra of six objects in the Taurus-Auriga complex (RY Tau, DG Tau, DL Tau, HN Tau, DO Tau, RW Aur A). Thanks to the combined high-spectral resolution (ℜ = 5°0 000−115 000) and wide spectral coverage (~400−2400 nm) we observed several O 0, S +, N 0, N +, and Fe + forbidden lines spanning a large range of excitation and ionization conditions. In four objects (DG Tau, HN Tau, DO Tau, RW Aur A), temperature (Te), electron and total density (ne, nH), and fractional ionization (xe) were derived as a function of velocity through an excitation and ionization model. The abundance of gaseous iron, X(Fe), a probe of the dust content in the jet, was derived in selected velocity channels. Results. The physical parameters vary smoothly with velocity, suggesting a common origin for the different kinematic components. In DG Tau and HN Tau, Te, xe, and X(Fe) increase with velocity (roughly from 6000 K, 0.05, 10%X(Fe)⊙ to 15 000 K, 0.6, 90%X(Fe)⊙). This trend is in agreement with disk–wind models in which the jet is launched from regions of the disk at different radii. In DO Tau and RW Aur A, we infer xe < 0.1, nH ~ 106−7 cm−3, and X(Fe) ≲ X(Fe)⊙ at all velocities. These findings are tentatively explained by the formation of these jets from dense regions inside the inner, gaseous disk, or as a consequence of their high degree of collimation.