Ryuichi Kurosawa

Max Planck Institute for Radio Astronomy

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Daniel Proga

University of Nevada, Las Vegas

M. M. Romanova

Cornell University

Tim J. Harries

University of Exeter

Neil H. Symington

University of St Andrews

D. J. Hillier

University of Pittsburgh

R. V. E. Lovelace

Cornell University

Alexander Kreplin

University of Exeter

G. Weigelt

Max Planck Institute for Radio Astronomy

G. V. Ustyugova

Keldysh Institute of Applied Mathematics

Agnieszka Janiuk

Polish Academy of Sciences

Cooperative Institutions

Centre National de la Recherche Scientifique

Max Planck Society

Institut de Planétologie et d'Astrophysique de Grenoble

Université Grenoble Alpes

Max Planck Institute for Astronomy

Cornell University

Max Planck Institute for Radio Astronomy

University of Exeter

National Institute for Astrophysics

Institute of Astronomy

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Radial velocity surveys of BDs in Upper Sco and rho Oph

Ryuichi Kurosawa

Radial velocity

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Outflows from AGN: Their Impact on Spectra and the Environment

Daniel Proga Ryuichi Kurosawa

We present a brief summary of the main results from our multi-dimensional, time-dependent simulations of gas dynamics in AGN. We focus on two types of outflows powered by radiation emitted from the AGN: disk winds and winds driven from large-scale inflows. We show spectra predicted by the simulations and discuss their relevance to observations of broad- and narrow-line regions of the AGN. We finish with a few remarks on whether these outflows can have a significant impact on their environment and host galaxy.

Line (geometry)

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Line formation in the inner winds of classical T Tauri stars: testing the conical-shell wind solution

Monthly Notices of the Royal Astronomical Society (2012)

Ryuichi Kurosawa M. M. Romanova

We present the emission-line profile models of hydrogen and helium based on the results from axisymmetric magnetohydrodynamics (MHD) simulations of the wind formed near the disc–magnetosphere boundary of classical T Tauri stars (CTTSs). We extend the previous outflow models of 'the conical-shell wind' by Romanova et al. to include a well-defined magnetospheric accretion funnel flow which is essential for modelling the optical and near-infrared hydrogen and helium lines of CTTSs. The MHD model with an intermediate mass-accretion rate shows outflows in conical-shell shape with a half opening angle ∼35°. The flow properties such as the maximum outflow speed in the conical-shell wind, maximum inflow speed in the accretion funnel, mass accretion and mass-loss rates are comparable to those found in a typical CTTS. The density, velocity and modified temperature from the MHD simulations are used in a separate radiative transfer model to predict the line profiles and test the consistency of the MHD models with observations. The line profiles are computed with various combinations of X-ray luminosities, temperatures of X-ray-emitting plasma and inclination angles. A rich diversity of line profile morphology is found, and many of the model profiles are very similar to those found in observations. We find that the conical-shell wind may contribute to the emission in some hydrogen lines (e.g. Hα, Hβ, Paβ and Paγ) significantly when the temperature in the wind is relatively high (e.g. ∼104 K); however, the wind contribution decreases rapidly when a lower wind temperature is adopted. The model well reproduces a relatively narrow and low-velocity blueshifted absorption component in He i λ10830, which are often seen in observations.

Outflow

10.1111/j.1365-2966.2012.21853.x

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MHD simulations of disk-star interaction

Proceedings of the International Astronomical Union (2007)

M. M. Romanova Min Long A. K. Kulkarni Ryuichi Kurosawa G. V. Ustyugova

We discuss a number of topics relevant to disk-magnetosphere interaction and how numerical simulations illuminate them. The topics include: (1) disk-magnetosphere interaction and the problem of disk-locking; (2) the wind problem; (3) structure of the magnetospheric flow, hot spots at the star's surface, and the inner disk region; (4) modeling of spectra from 3D funnel streams; (5) accretion to a star with a complex magnetic field; (6) accretion through 3D instabilities; (7) magnetospheric gap and survival of protoplanets. Results of both 2D and 3D simulations are discussed.

Funnel

Accretion disc

Protoplanet

10.1017/s1743921307009635

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THREE-DIMENSIONAL SIMULATIONS OF DYNAMICS OF ACCRETION FLOWS IRRADIATED BY A QUASAR

The Astrophysical Journal (2009)

Ryuichi Kurosawa Daniel Proga

We study the axisymmetric and non-axisymmetric, time-dependent hydrodynamics of gas that is under the influence of the gravity of a super massive black hole (SMBH) and the radiation force produced by a radiatively efficient flow accreting onto the SMBH. We have considered two cases: (1) the formation of an outflow from the accretion of the ambient gas without rotation and (2) that with weak rotation. The main goals of this study are: (1) to examine if there is a significant difference between the models with identical initial and boundary conditions but in different dimensionality (2-D and 3-D), and (2) to understand the gas dynamics in AGN. Our 3-D simulations of a non-rotating gas show small yet noticeable non-axisymmetric small-scale features inside the outflow. The outflow as a whole and the inflow do not seem to suffer from any large-scale instability. In the rotating case, the non-axisymmetric features are very prominent, especially in the outflow which consists of many cold dense clouds entrained in a smoother hot flow. The 3-D outflow is non-axisymmetric due to the shear and thermal instabilities. In both 2-D and 3-D simulations, gas rotation increases the outflow thermal energy flux, but reduces the outflow mass and kinetic energy fluxes. Rotation also leads to time variability and fragmentation of the outflow in the radial and latitudinal directions. The collimation of the outflow is reduced in the models with gas rotation. The time variability in the mass and energy fluxes is reduced in the 3-D case because of the outflow fragmentation in the azimuthal direction. The virial mass estimated from the kinematics of the dense cold clouds found in our 3-D simulations of rotating gas underestimates the actual mass used in the simulations by about 40 %. (Abbreviated)

Outflow

Inflow

Rotational energy

10.1088/0004-637x/693/2/1929

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Citations (57)

3D simulations of rotationally-induced line variability from a classical T Tauri star with a misaligned magnetic dipole

Monthly Notices of the Royal Astronomical Society (2008)

Ryuichi Kurosawa M. M. Romanova Tim J. Harries

We present 3D simulations of rotationally induced line variability arising from complex circumstellar environment of classical T Tauri stars (CTTS) using the results of the 3D magnetohydrodynamics (MHD) simulations of Romanova et al., who considered accretion on to a CTTS with a misaligned dipole magnetic axis with respect to the rotational axis. The density, velocity and temperature structures of the MHD simulations are mapped on to the radiative transfer grid, and corresponding line source function and the observed profiles of neutral hydrogen lines (Hβ, Paβ and Brγ) are computed using the Sobolev escape probability method. We study the dependency of line variability on inclination angles (i) and magnetic axis misalignment angles (Θ). We find the line profiles are relatively insensitive to the details of the temperature structure of accretion funnels, but are influenced more by the mean temperature of the flow and its geometry. By comparing our models with the Paβ profiles of 42 CTTS observed by Folha & Emerson, we find that models with a smaller misaligngment angle (Θ < ∼15°) are more consistent with the observations which show that majority of Paβ are rather symmetric around the line centre. For a high inclination system with a small dipole misalignment angle (Θ≈ 15°), only one accretion funnel (on the upper hemisphere) is visible to an observer at any given rotational phase. This can cause an anticorrelation of the line equivalent to the width in the blue wing (v < 0) and that in the red wing (v > 0) over half of a rotational period, and a positive correlation over the other half. We find a good overall agreement of the line variability behaviour predicted by our model and those from observations.

Line (geometry)

10.1111/j.1365-2966.2008.13055.x

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Citations (35)

Three-dimensional dust radiative-transfer models: the Pinwheel Nebula of WR 104

Monthly Notices of the Royal Astronomical Society (2004)

Tim J. Harries John D. Monnier Neil H. Symington Ryuichi Kurosawa

We present radiative-transfer modelling of the dusty spiral Pinwheel Nebula observed around the Wolf–Rayet/OB-star binary WR 104. The models are based on the three-dimensional radiative-transfer code torus, modified to include an adaptive mesh that allows us to adequately resolve both the inner spiral turns (subau scales) and the outer regions of the nebula (distances of 104 au from the central source). The spiral model provides a good fit to both the spectral energy distribution and Keck aperture masking interferometry, reproducing both the maximum entropy recovered images and the visibility curves. We deduce a dust creation rate of 8 ± 1 × 10−7 M⊙ yr−1, corresponding to approximately 2 per cent by mass of the carbon produced by the Wolf–Rayet star. Simultaneous modelling of the imaging and spectral data enables us to constrain both the opening angle of the wind–wind collision interface and the dust grain size. We conclude that the dust grains in the inner part of the Pinwheel Nebula are small (∼100 Å), in agreement with theoretical predictions, although we cannot rule out the presence of larger grains (∼1 μm) further from the central binary. The opening angle of the wind–wind collision interface appears to be about 40°, in broad agreement with the wind parameters estimated for the central binary. We discuss the success and deficiencies of the model, and the likely benefits of applying similar techniques to the more complex nebulae observed around other WR/O star binaries.

Spectral energy distribution

10.1111/j.1365-2966.2004.07668.x

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Citations (93)

25a-B-1 Reduction Growth of Silver Microcrystals I

春の分科会講演予稿集 (1991)

Kiyoshi Kishi Ryuichi Kurosawa Mitsuhiro Tamura Masahiro Bunyo Masahiko Takeuchi

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3-D Simulations Of AGN Feedback via Radiation and Radiation-driven Outflows

American Astronomical Society Meeting Abstracts #213 (2009)

Ryuichi Kurosawa Daniel Proga

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STABLE AND UNSTABLE REGIMES OF MASS ACCRETION ONTO RW AUR A

The Astrophysical Journal (2016)

M. Takami Yujie Wei Mei-Yin Chou Jennifer L. Karr Tracy L. Beck

ABSTRACT We present monitoring observations of the active T Tauri star RW Aur, from 2010 October to 2015 January, using optical high-resolution ( R ≥ 10,000) spectroscopy with Canada–France–Hawaii Telescope/ESPaDOnS. Optical photometry in the literature shows bright, stable fluxes over most of this period, with lower fluxes (by 2–3 mag) in 2010 and 2014. In the bright period our spectra show clear photospheric absorption, complicated variation in the Ca ii λ 8542 emission profile shapes, and a large variation in redshifted absorption in the O i λλ 7772 and 8446 and He i λ 5876 lines, suggesting unstable mass accretion during this period. In contrast, these line profiles are relatively uniform during the faint periods, suggesting stable mass accretion. During the faint periods, the photospheric absorption lines are absent or marginal, and the averaged Li i profile shows redshifted absorption due to an inflow. We discuss (1) occultation by circumstellar material or a companion and (2) changes in the activity of mass accretion to explain the above results, together with near-infrared and X-ray observations from 2011 to 2015. Neither scenario can simply explain all the observed trends, and more theoretical work is needed to further investigate their feasibilities.

Occultation

10.3847/0004-637x/820/2/139

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Citations (13)