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Journal articles on the topic 'Accretion disks'

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Published: 4 June 2021

Last updated: 16 June 2025

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1

Narayan, R. "Advective Disks." International Astronomical Union Colloquium 163 (1997): 75–89. http://dx.doi.org/10.1017/s0252921100042524.

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AbstractRecent work on advection-dominated accretion flows (ADAFs) is reviewed. The article concentrates on an optically thin branch of ADAFs which is present at mass accretion rates below a critical value ~ (10−2– 10−1) the Eddington rate. Models based on this branch have been quite successful at explaining a number of low-luminosity X-ray binaries and galactic nuclei, and some brighter systems. Some progress has also been made toward understanding the various spectral states of accreting black holes. It is argued that ADAFs may provide one of the best techniques for demonstrating the reality of event horizons in black holes.

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2

Haerken 哈斯铁, Hasitieer 尔·哈尔肯, Guang-Wei 广伟 Li 李, Min 敏. Li 李, Fuqing 福庆 Duan 段, and Yongheng 永恒 Zhao 赵. "Discovery of Two Different Full Disk Evolutionary Patterns of M-type T Tauri Stars with LAMOST DR8." Astrophysical Journal 960, no. 1 (2023): 58. http://dx.doi.org/10.3847/1538-4357/ad04d3.

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Abstract The full disk, full of gas and dust, determines the upper limit of planet masses, and its lifetime is critical for planet formation, especially for giant planets. In this work, we studied the evolutionary timescales of the full disks of T Tauri stars (TTSs) and their relations to accretion. Combined with Gaia EDR3, Two Micron All Sky Survey, and Wide-field Infrared Survey Explorer data, 1077 disk-bearing TTS candidates were found in LAMOST DR8, and stellar parameters were obtained. Among them, 783 are newly classified by spectra as classical T Tauri stars (CTTSs; 169) or weak-lined T Tauri stars (WTTSs). Based on EW and FWHM of Hα, 157 TTSs in accretion were identified, with ∼82% also having full disks. For TTSs with M < 0.35M ☉, about 80% seem to already lose their full disks at ∼0.1 Myr, which may explain their lower mass, while the remaining 20% with full disks evolve at similar rates of non-full disks within 5 Myr, allowing enough time and material to form giant planets. The fraction of accreting TTSs to disk-bearing TTSs is stable at ∼10% and can last ∼5–10 Myr, suggesting that full disks and accretion evolve with similar rates as non-full disks. For TTSs with M > 0.35 M ☉, almost all full disks can survive more than 0.1 Myr, most for 1 Myr and some even for 20 Myr. For TTSs with M > 0.35 M ☉, almost all full disks can survive more than 0.1 Myr, most for 1 Myr, and some even for 20 Myr, which implies planets are more likely to be formed in their disks than those of M < 0.35 M ☉, and thus M dwarfs with M > 0.35 M ☉ can have more planets. The fraction of full-disk TTSs to disk-bearing TTSs decreases with age following the relation f ∝ t −0.35, and similar relations existed in the fraction of accreting TTSs and the fraction of full-disk CTTSs, suggesting faster full disks and accretion evolution than non-full disks. For full-disk stars, the ratio of accretion of lower-mass stars is systematically lower than that of higher-mass stars, confirming the dependence of accretion on stellar mass, which may be reflective of an observational bias in the detection of accretion levels, with the lower-mass stars crossing below the detection threshold earlier than higher-mass stars.

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3

Gárate, Matías, Timmy N. Delage, Jochen Stadler, et al. "Large gaps and high accretion rates in photoevaporative transition disks with a dead zone." Astronomy & Astrophysics 655 (November 2021): A18. http://dx.doi.org/10.1051/0004-6361/202141444.

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Context. Observations of young stars hosting transition disks show that several of them have high accretion rates, despite their disks presenting extended cavities in their dust component. This represents a challenge for theoretical models, which struggle to reproduce both features simultaneously. Aims. We aim to explore if a disk evolution model, including a dead zone and disk dispersal by X-ray photoevaporation, can explain the high accretion rates and large gaps (or cavities) measured in transition disks. Methods. We implemented a dead zone turbulence profile and a photoevaporative mass-loss profile into numerical simulations of gas and dust. We performed a population synthesis study of the gas component and obtained synthetic images and SEDs of the dust component through radiative transfer calculations. Results. This model results in long-lived inner disks and fast dispersing outer disks that can reproduce both the accretion rates and gap sizes observed in transition disks. For a dead zone of turbulence αdz = 10−4 and an extent rdz = 10 AU, our population synthesis study shows that 63% of our transition disks are still accreting with Ṁg ≥ 10−11 M⊙ yr−1 after opening a gap. Among those accreting transition disks, half display accretion rates higher than 5.0 × 10−10 M⊙ yr−1. The dust component in these disks is distributed in two regions: in a compact inner disk inside the dead zone, and in a ring at the outer edge of the photoevaporative gap, which can be located between 20 and 100 AU. Our radiative transfer calculations show that the disk displays an inner disk and an outer ring in the millimeter continuum, a feature that resembles some of the observed transition disks. Conclusions. A disk model considering X-ray photoevaporative dispersal in combination with dead zones can explain several of the observed properties in transition disks, including the high accretion rates, the large gaps, and a long-lived inner disk at millimeter emission.

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4

Daemgen, Sebastian, Monika G. Petr-Gotzens, and Serge Correia. "T Tauri Binaries in Orion: Evidence for Accelerated and Synchronized Disk Evolution." Proceedings of the International Astronomical Union 7, S282 (2011): 452–53. http://dx.doi.org/10.1017/s1743921311028043.

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AbstractIn order to trace the role of binarity for disk evolution and hence planet formation, we started the currently largest spatially resolved near-infrared photometric and spectroscopic study of the inner dust and accretion disks of the individual components of 27 visual, 100–400 AU binaries in the Orion Nebula Cluster (ONC). We study the frequency of Brackett-γ (2.165μm) emitters to assess the frequency of accretion disk-bearing stars among the binaries of the ONC: only 34±9% of the binary components show signs of accretion and, hence, the presence of gaseous inner disks—less than the fraction of gas accretion disks among single stars of the ONC of ~50%. Additionally, we find a significant difference between binaries above and below 200 AU separation: no close systems with only one accreting component are found. The results suggest shortened disk lifetimes as well as synchronized disk evolution.

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5

Khaibrakhmanov, Sergey A., Alexander E. Dudorov, and Andrey M. Sobolev. "Rising magnetic flux tubes as a source of IR-variability of the accretion disks of young stars." Proceedings of the International Astronomical Union 14, S345 (2018): 295–96. http://dx.doi.org/10.1017/s1743921319001431.

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AbstractWe investigate dynamics of slender magnetic flux tubes (MFT) in the accretion disks of young stars. Simulations show that MFT rise from the disk and can accelerate to 20-30 km/s causing periodic outflows. Magnetic field of the disk counteracts the buoyancy, and the MFT oscillate near the disk’s surface with periods of 10-100 days. We demonstrate that rising and oscillating MFT can cause the IR-variability of the accretion disks of young stars.

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6

Dittmann, Alexander J., and Geoffrey Ryan. "The Evolution of Accreting Binaries: From Brown Dwarfs to Supermassive Black Holes." Astrophysical Journal 967, no. 1 (2024): 12. http://dx.doi.org/10.3847/1538-4357/ad2f1e.

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Abstract Circumbinary accretion occurs throughout the universe, from the formation of stars and planets to the aftermath of major galactic mergers. We present an extensive investigation of circumbinary accretion disks, studying circular binaries with mass ratios (q ≡ M 2/M 1) from 0.01 to 1 and at each mass ratio probing the effects of disk thickness and viscosity. We study disks with aspect ratios H/r ∈ {0.1, 0.05, 0.03} and vary both the magnitude and spatial dependence of viscosity. Although thin accretion disks have previously been found to promote rapid inspirals of equal-mass binaries, we find that gravitational torques become weaker at lower mass ratios and most binaries with 0.01 ≤ q ≤ 0.04 outspiral, which may delay the coalescence of black hole binaries formed from minor mergers and cause high-mass exoplanets to migrate outward. However, in a number of cases, the disks accreting onto binaries with mass ratios ∼0.07 fail to develop eccentric modes, leading to extremely rapid inspirals. Variability in black hole accretion correlates with disk eccentricity, and we observe variability above the ∼10% level even for mass ratios of 0.01. We demonstrate that the spatial dependence of the viscosity (e.g., α vs. constant ν) significantly affects the degree of preferential accretion onto the secondary, resolving discrepancies between previous studies. Colder circumbinary disks remain eccentric even at q ∼ 0.01 and sustain deep, asymmetric cavities.

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7

Hure, J. M., and D. Richard. "Accretion Discs in AGN, Viscosity and Structure of Accretion Disks." EAS Publications Series 1 (2001): 53–61. http://dx.doi.org/10.1051/eas:2001008.

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8

Burke, Colin J., Yue Shen, Omer Blaes, et al. "A characteristic optical variability time scale in astrophysical accretion disks." Science 373, no. 6556 (2021): 789–92. http://dx.doi.org/10.1126/science.abg9933.

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Accretion disks around supermassive black holes in active galactic nuclei produce continuum radiation at ultraviolet and optical wavelengths. Physical processes in the accretion flow lead to stochastic variability of this emission on a wide range of time scales. We measured the optical continuum variability observed in 67 active galactic nuclei and the characteristic time scale at which the variability power spectrum flattens. We found a correlation between this time scale and the black hole mass extending over the entire mass range of supermassive black holes. This time scale is consistent with the expected thermal time scale at the ultraviolet-emitting radius in standard accretion disk theory. Accreting white dwarfs lie close to this correlation, suggesting a common process for all accretion disks.

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9

Kitabatake, Etsuko, and Jun Fukue. "Cloudy Accretion Disks." Publications of the Astronomical Society of Japan 55, no. 6 (2003): 1115–20. http://dx.doi.org/10.1093/pasj/55.6.1115.

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10

Lovelace, R. V. E., and Tom Chou. "Counterrotating Accretion Disks." Astrophysical Journal 468, no. 1 (1996): L25—L28. http://dx.doi.org/10.1086/310232.

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11

Abramowicz, M. A., B. Czerny, J. P. Lasota, and E. Szuszkiewicz. "Slim accretion disks." Astrophysical Journal 332 (September 1988): 646. http://dx.doi.org/10.1086/166683.

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12

Fukue, Jun, and Masayuki Ioroi. "Hoyle-Lyttleton Accretion onto Accretion Disks." Publications of the Astronomical Society of Japan 51, no. 1 (1999): 151–59. http://dx.doi.org/10.1093/pasj/51.1.151.

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13

Maeda, Natsuho, Keiji Ohtsuki, Takayuki Tanigawa, Masahiro N. Machida, and Ryo Suetsugu. "Delivery of Gas onto the Circumplanetary Disk of Giant Planets: Planetary-mass Dependence of the Source Region of Accreting Gas and Mass Accretion Rate." Astrophysical Journal 935, no. 1 (2022): 56. http://dx.doi.org/10.3847/1538-4357/ac7ddf.

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Abstract Gas accretion onto the circumplanetary disks and the source region of accreting gas are important to reveal dust accretion that leads to satellite formation around giant planets. We performed local three-dimensional high-resolution hydrodynamic simulations of an isothermal and inviscid gas flow around a planet to investigate the planetary-mass dependence of the gas accretion bandwidth and gas accretion rate onto circumplanetary disks. We examined cases with various planetary masses corresponding to M p = 0.05–1M Jup at 5.2 au, where M Jup is the current Jovian mass. We found that the radial width of the gas accretion band is proportional to M p 1 / 6 for the low-mass regime with M p ≲ 0.2M Jup while it is proportional to M p for the high-mass regime with M p ≳ 0.2M Jup. We found that the ratio of the mass accretion rate onto the circumplanetary disk to that into the Hill sphere is about 0.4 regardless of the planetary mass for the cases we examined. Combining our results with the gap model obtained from global hydrodynamic simulations, we derive a semi-analytical formula of mass accretion rate onto circumplanetary disks. We found that the mass dependence of our three-dimensional accretion rates is the same as the previously obtained two-dimensional case, although the qualitative behavior of accretion flow onto the circumplanetary disk is quite different between the two cases.

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14

Jiao, Cheng-Liang, and Xue-Bing Wu. "Outflows from Accretion Disks around Compact Objects." Proceedings of the International Astronomical Union 8, S290 (2012): 82–85. http://dx.doi.org/10.1017/s1743921312019266.

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AbstractWe solve the set of hydrodynamic equations for accretion disks in the spherical coordinates (rθφ) to obtain the explicit structure along the θ direction. The results display thinner, quasi-Keplerian disks for Shakura-Sunyaev Disks (SSDs) and thicker, sub-Keplerian disks for Advection Dominated Accretion Flows (ADAFs) and slim disks, which are consistent with previous popular analytical models, while an inflow region and an outflow region always exist, which supports the results of some recent numerical simulation works. Our results indicate that the outflows should be common in various accretion disks and stronger in slim disks and ADAFs.

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15

Dudorov, Alexander E., Sergey A. Khaibrakhmanov, Sergey Yu Parfenov, and Andrey M. Sobolev. "Large-scale magnetic field of the accretion disks of T Tauri stars." Proceedings of the International Astronomical Union 14, S345 (2018): 297–98. http://dx.doi.org/10.1017/s1743921319001443.

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AbstractThe large-scale magnetic field in the accretion disks of young stars is investigated. Main features of our magnetohydrodynamical (MHD) model of the accretion disks and typical simulation results are presented. We discuss the role of MHD effects, ionization structure, magnetic field geometry and strength of the accretion disks.

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16

Venuti, Laura, Ann Marie Cody, Giacomo Beccari, et al. "Circumstellar Disk Accretion Across the Lagoon Nebula: The Influence of Environment and Stellar Mass." Astronomical Journal 167, no. 3 (2024): 120. http://dx.doi.org/10.3847/1538-3881/ad1f65.

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Abstract Pre-main-sequence disk accretion is pivotal for determining the final stellar properties and the early conditions for close-in planets. We aim to establish the impact of internal (stellar mass) and external (radiation field) parameters on the disk evolution in the Lagoon Nebula massive star-forming region. We employ simultaneous u, g, r, i, Hα time-series photometry, archival infrared data, and high-precision K2 light curves to derive the stellar, disk, and accretion properties for 1012 Lagoon Nebula members. We estimate that of all young stars in the Lagoon Nebula, 34%–37% have inner disks traceable down to ∼12 μm, while 38%–41% are actively accreting. We detect disks ∼1.5 times more frequently around G, K, and M stars than around higher-mass stars, which appear to deplete their inner disks on shorter timescales. We find tentative evidence for a faster disk evolution in the central regions of the Lagoon Nebula, where the bulk of the O/B population is located. Conversely, disks appear to last longer at the nebula outskirts, where the measured fraction of disk-bearing stars tends to exceed that of accreting and disk-free stars. The derived mass accretion rates show a nonuniform dependence on stellar mass between ∼0.2 and 5 M ⊙. In addition, the typical accretion rates appear to differ across the Lagoon Nebula extension, with values twice lower in the core region than at its periphery. Finally, we detect tentative radial density gradients in the surface accretion shocks, leading to lags in the appearance of light curve brightness features as a function of wavelength that can amount to ∼7%–30% of the rotation period.

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17

Laune, JT, Rixin 日新 Li 李, and Dong Lai. "Migration of Accreting Planets and Black Holes in Disks." Astrophysical Journal 975, no. 2 (2024): 296. http://dx.doi.org/10.3847/1538-4357/ad7117.

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Abstract Nascent planets are thought to lose angular momentum (AM) to the gaseous protoplanetary disk via gravitational interactions, leading to inward migration. A similar migration process also applies to stellar-mass black holes (BHs) embedded in the disks of active galactic nuclei. However, AM exchange via accretion onto the planet/BH may strongly influence the migration torque. In this study, we perform 2D global hydrodynamic simulations of an accreting planet/BH embedded in a disk, where AM exchange between the planet/BH and disk via gravity, accretion, pressure, and viscosity are considered. When accretion is turned off, we recover the linear estimate for Type I migration torque. However, for the two planet masses we investigated with our accreting simulations, we find outward migration due to the positive AM deposited onto the accreting body by the disk gas. Our simulations achieve the global steady state for the transport of mass and AM: The mass and AM fluxes are constant across the disk except for jumps ( Δ M ̇ and Δ J ̇ ) at the planet’s location, and the jumps match the accretion rate and torque on the planet. Our findings suggest that caution is needed when applying the standard results of disk migration to accreting planets and BHs.

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18

Czerny, B. "Emission of Accretion Disks." Symposium - International Astronomical Union 159 (1994): 261–70. http://dx.doi.org/10.1017/s0074180900175138.

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Accretion disks surrounding massive black hole is an attractive scenario of nuclear activity. A number of arguments support it although there is no unquestionable proof of the existence of accretion disks in active galactic nuclei. Meaningful comparison of the disk model prediction with the data can only be made if emission of accretion disks is calculated taking into account the existence of optically thin parts responsible for the emission of x-ray radiation. Nonlocal reprocessing phenomena have to be also included. Since we have no real understanding of the viscous processes operating in accretion disks some ad hoc parameterization of these processes has to be used and its applicability should be checked by broad band comparison of predictions for continuum emission and spectral features with available data.

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19

Pudritz, Ralph E., and Colin A. Norman. "Hydromagnetic winds from accretion disks." Canadian Journal of Physics 64, no. 4 (1986): 501–6. http://dx.doi.org/10.1139/p86-094.

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We present a hydromagnetic wind model for molecular and ionized gas outflows associated with protostars. If the luminosity of protostars is due to accretion, then centrifugally driven winds that arise from the envelopes of molecular disks explain the observed rates of momentum and energy transport. Ionized outflow originates from disk radii r ≤ 1015 cm inside of which Ly-continuum photons from the protostellar accretion shock are intercepted. Observed molecular outflows arise from the cool disk envelope at radii 1015 ≤ r ≤ 1017 cm. The mass-loss rates of these two component outflows are [Formula: see text] and [Formula: see text]. These winds solve the angular-momentum problem of star formation. We propose that the collimation of such outflows is due to "hoop" stresses generated by the increasingly toroidal magnetic field in the wind and suggest that the structure of the underlying disks makes self-similar solutions for these outflows likely. Finally, we apply this analysis to other accreting systems such as cataclysmic variables.

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20

Gu, Wei-Min, and Ju-Fu Lu. "Bimodal Accretion Disks: Shakura-Sunyaev Disk–Advection-dominated Accretion Flow Transitions." Astrophysical Journal 540, no. 1 (2000): L33—L36. http://dx.doi.org/10.1086/312864.

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21

Li 李, Ya-Ping 亚平, Yi-Xian 逸贤 Chen 陈, and Douglas N. C. 潮. Lin 林. "Concurrent Accretion and Migration of Giant Planets in Their Natal Disks with Consistent Accretion Torque." Astrophysical Journal 971, no. 2 (2024): 130. http://dx.doi.org/10.3847/1538-4357/ad5a06.

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Abstract Migration commonly occurs during the epoch of planet formation. For emerging gas giant planets, it proceeds concurrently with their growth through the accretion of gas from their natal protoplanetary disks. A similar migration process should also be applied to the stellar-mass black holes embedded in active galactic nucleus disks. In this work, we perform high-resolution 3D and 2D numerical hydrodynamical simulations to study the migration dynamics for accreting embedded objects over the disk viscous timescales in a self-consistent manner. We find that an accreting planet embedded in a predominantly viscous disk has a tendency to migrate outward, in contrast to the inward orbital decay of nonaccreting planets. 3D and 2D simulations find the consistent outward migration results for the accreting planets. Under this circumstance, the accreting planet’s outward migration is mainly due to the asymmetric spiral arms feeding from the global disk into the Hill radius. This is analogous to the unsaturated corotation torque although the imbalance is due to material accretion within the libration timescale rather than diffusion onto the inner disk. In a disk with a relatively small viscosity, the accreting planets clear deep gaps near their orbits. The tendency of inward migration is recovered, albeit with suppressed rates. By performing a parameter survey with a range of disks’ viscosity, we find that the transition from outward to inward migration occurs with the effective viscous efficiency factor α ∼ 0.003 for Jupiter-mass planets.

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22

Manara, C. F., C. Mordasini, L. Testi, et al. "Constraining disk evolution prescriptions of planet population synthesis models with observed disk masses and accretion rates." Astronomy & Astrophysics 631 (October 11, 2019): L2. http://dx.doi.org/10.1051/0004-6361/201936488.

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While planets are commonly discovered around main-sequence stars, the processes leading to their formation are still far from being understood. Current planet population synthesis models, which aim to describe the planet formation process from the protoplanetary disk phase to the time exoplanets are observed, rely on prescriptions for the underlying properties of protoplanetary disks where planets form and evolve. The recent development in measuring disk masses and disk-star interaction properties, i.e., mass accretion rates, in large samples of young stellar objects demand a more careful comparison between the models and the data. We performed an initial critical assessment of the assumptions made by planet synthesis population models by looking at the relation between mass accretion rates and disk masses in the models and in the currently available data. We find that the currently used disk models predict mass accretion rate in line with what is measured, but with a much lower spread of values than observed. This difference is mainly because the models have a smaller spread of viscous timescales than what is needed to reproduce the observations. We also find an overabundance of weakly accreting disks in the models where giant planets have formed with respect to observations of typical disks. We suggest that either fewer giant planets have formed in reality or that the prescription for planet accretion predicts accretion on the planets that is too high. Finally, the comparison of the properties of transition disks with large cavities confirms that in many of these objects the observed accretion rates are higher than those predicted by the models. On the other hand, PDS70, a transition disk with two detected giant planets in the cavity, shows mass accretion rates well in line with model predictions.

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23

Zhou, Shuying, Mouyuan Sun, Tong Liu, Jian-Min Wang, Jun-Xian Wang, and Yongquan Xue. "Stellar Black Holes Can “Stretch” Supermassive Black Hole Accretion Disks." Astrophysical Journal Letters 966, no. 1 (2024): L9. http://dx.doi.org/10.3847/2041-8213/ad3c3f.

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Abstract Stellar black holes (sBHs) are widely believed to exist in the accretion disks of active galactic nuclei (AGNs). Previous studies often focus on the transient emission produced by embedded sBHs. Here, we explore the possible observational consequences of an AGN accretion disk that contains a population of accreting sBHs. Embedded accreting sBHs change the effective temperature distribution of the AGN accretion disk by heating gas in the outer regions. Two possible observational consequences are presented. First, the spectral energy distribution has a turnover feature at ∼4700 Å when the supermassive black hole mass is ∼108 M ⊙, which can help explain the observed shallow spectral shape at wavelengths >5000 Å for the Sloan Digital Sky Survey quasar composite spectrum. Second, the half-light radius of a given relatively long wavelength is significantly larger than for an AGN disk without sBHs, which can be tested by microlensing observations. With appropriate sBH distributions, the model can be reconciled with quasar microlensing disk sizes. We propose that the half-light radius–wavelength relation can be utilized to investigate the distributions of embedded sBHs in AGN accretion disks.

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Kurmanov, Yergali, Talgar Konysbayev, Gulnara Suliyeva, et al. "Radiative characteristics of accretion disksaround rotating regular black holes." International Journal of Mathematics and Physics 15, no. 1 (2024): 57–67. http://dx.doi.org/10.26577/ijmph.2024v15i1a7.

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Our research focuses on examining the characteristics of thin accretion disks encircling rotating regular black holes. In this study, we investigate the important features of accretion disks surrounding Bardeen's regular black holes, which play a crucial role in addressing the singularity issue. The horizon configuration of rotating Bardeen black holes is analyzed in details, as well as the innermost stable circular orbits related to this spacetime. The primary goal is to derive quantitively the radiative flux, differential and spectral luminosities of the accretion disk. Within the specified gravitational field, particularly, by taking the parameter r_0*>0 and fixing the j=0.2, our findings show that the corresponding accretion disk’s luminosity exceeds that one predicted by the Kerr metric at identical value of spin parameter ( j=0.2). Making the juxtaposition of Bardeen’s black hole parameter with the spin parameter of the Kerr black hole we reveal that the spacetime corresponding to the non-rotating Bardeen black holes, in some certain cases, can imitate the Kerr spacetime.

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25

Stepinski, T. "Kinematic Dynamo in Turbulent Circumstellar Disks." Symposium - International Astronomical Union 157 (1993): 203–7. http://dx.doi.org/10.1017/s0074180900174121.

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Many circumstellar disks associated with objects ranging from protoplanetary nebulae to accretion disks around compact stars allow for the generation of magnetic fields by an αω dynamo. We have applied kinematic dynamo formalism to geometrically thin accretion disks. We calculate, in the framework of an adiabatic approximation, the normal mode solutions for dynamos operating in disks around compact stars. We then describe the criteria for a viable dynamo in protoplanetary nebulae, and discuss the particular features that make accretion disk dynamos different from planetary, stellar, and galactic dynamos.

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26

McCray, Richard. "Compact Binary X-Ray Sources." International Astronomical Union Colloquium 89 (1986): 184–97. http://dx.doi.org/10.1017/s0252921100086085.

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AbstractCompact binary X-ray sources include white dwarfs, neutron stars, and black holes that are accreting matter from a companion star. The X-ray emission from these systems is produced by the accreting matter as it flows through an accretion disk and strikes the surface of the compact object. The emitting regions have opacities dominated by electron scattering, and radiation pressure is likely to play an important role in the hydrodynamics. Strong magnetic fields greatly modify the hydrodynamics and radiation transfer in the pulsating neutron star sources. Accretion disks have complex structure, including an electron scattering corona, a cool outer region, and possibly a thick torus in their inner region. The structure and stability properties of accretion disks are only partially understood. Major problems exist with the interpretation of the spectra and luminosities of the X-ray burst sources. The pulsed X-ray emission from the pulsating binary X-ray sources probably comes from “mounds” of accreting gas at the magnetic poles of neutron stars, in which the accreting matter is decelerated by radiation pressure. The physics of these systems is reviewed, with an emphasis on problems for which hydrodynamical simulations may be especially useful.

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27

Coroniti, F. V. "Accretion Disk Electrodynamics." Symposium - International Astronomical Union 107 (1985): 453–69. http://dx.doi.org/10.1017/s007418090007594x.

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Accretion disk electrodynamic phenomenae are separable into two classes: 1) disks and coronae with turbulent magnetic fields; 2) disks and black holes which are connected to a large-scale external magnetic field. Turbulent fields may originate in an α - ω dynamo, provide anomalous viscous transport, and sustain an active corona by magnetic buoyancy. The large-scale field can extract energy and angular momentum from the disk and black hole, and be dynamically configured into a collimated relativistic jet.

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Pugliese, D., and Z. Stuchlík. "RINGED ACCRETION DISKS: INSTABILITIES." Astrophysical Journal Supplement Series 223, no. 2 (2016): 27. http://dx.doi.org/10.3847/0067-0049/223/2/27.

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29

Mineshige, Shin, Atsunori Yonehara, and Toshihiro Kawaguchi. "Black-Hole Accretion Disks." Progress of Theoretical Physics Supplement 136 (1999): 235–50. http://dx.doi.org/10.1143/ptps.136.235.

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30

Bertin, G. "Self-regulated Accretion Disks." Astrophysical Journal 478, no. 2 (1997): L71—L74. http://dx.doi.org/10.1086/310555.

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31

Abramowicz, M. A., A. Lanza, E. A. Spiegel, and E. Szuszkiewicz. "Vortices on accretion disks." Nature 356, no. 6364 (1992): 41–43. http://dx.doi.org/10.1038/356041a0.

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32

Smak, J. "Accretion Disks in Algols." International Astronomical Union Colloquium 107 (1989): 107–16. http://dx.doi.org/10.1017/s0252921100087716.

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33

Kuperus, Max. "Magnetohydrodynamics of accretion disks." Computer Physics Reports 12, no. 4 (1990): 275–87. http://dx.doi.org/10.1016/0167-7977(90)90014-w.

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34

Krishan, V., S. Ramadurai, and P. J. Wiita. "Microflares in accretion disks." Astronomy & Astrophysics 398, no. 3 (2003): 819–23. http://dx.doi.org/10.1051/0004-6361:20021695.

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35

Hawley, John F. "Turbulence in Accretion Disks." Astrophysics and Space Science 292, no. 1-4 (2004): 383–94. http://dx.doi.org/10.1023/b:astr.0000045042.06099.19.

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36

Bjoernsson, Gunnlaugur, Marek A. Abramowicz, Xingming Chen, and Jean-Pierre Lasota. "Hot Accretion Disks Revisited." Astrophysical Journal 467 (August 1996): 99. http://dx.doi.org/10.1086/177587.

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37

Hawley, John F., and Steven A. Balbus. "Transport in accretion disks." Physics of Plasmas 6, no. 12 (1999): 4444–49. http://dx.doi.org/10.1063/1.873730.

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38

Bertin, G., and G. Lodato. "Self-Gravitating Accretion Disks." Physica Scripta T84, no. 1 (2000): 143. http://dx.doi.org/10.1238/physica.topical.084a00143.

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39

Smak, J. "Accretion disks in Algols." Space Science Reviews 50, no. 1-2 (1989): 107–16. http://dx.doi.org/10.1007/bf00215923.

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40

Horn, Susanne, and Wolfgang Kundt. "Magnetically tilted accretion disks." Astrophysics and Space Science 158, no. 2 (1989): 205–21. http://dx.doi.org/10.1007/bf00639725.

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41

Demidova, Tatiana V., and Vladimir P. Grinin. "Clumpy Accretion in Pre-main-sequence Stars as a Source of Perturbations in Circumstellar Disks." Astrophysical Journal 930, no. 2 (2022): 111. http://dx.doi.org/10.3847/1538-4357/ac53a6.

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Abstract The development of perturbations in the circumstellar disks of pre-main-sequence stars caused by clumpy accretion was investigated. Here we perform 3D smoothed particle hydrodynamics simulations of disks perturbed by a recent clump accretion event. These simulations are further explored by radiative transfer calculations to quantify the observational appearance of such disks. It was shown that the density waves in the disks were formed at the fall of the clump. After several revolutions they can transform into spirals and ring structures. Their images in millimeter wavelengths are very similar to those observed with Atacama Large Millimeter/submillimeter Array in some protoplanetary disks. We assume that clumpy accretion may be the source of such structures.

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42

Nakao, Yasushi. "Enhancement of Turbulent Viscosity by Global Magnetic Fields in Accretion Disks." Symposium - International Astronomical Union 188 (1998): 412. http://dx.doi.org/10.1017/s0074180900115773.

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A model of magnetohydrodynamic (MHD) turbulence in accretion disks with global magnetic fields is constructed using a second-order closure modeling of turbulence. The transport equations of the Reynolds stress tensor, the Maxwell stress tensor, and the cross-helicity tensor (the correlation of velocity fluctuation and magnetic fluctuation) are closed by second-order quantities using atwo-scale direct interaction approximation(TSDIA). The quantities appearing these equations are considered to be those averaged in the vertical direction of the disks. The turbulence is assumed to be stationary. We are interested only in the effects of the global magnetic fields on the turbulence in the disks, i.e., no dynamo processes are considered, and the global magnetic fields are supposed to be embedded in the diska priori.

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Pfalzner, S., S. Umbreit, and Th Henning. "Disk‐Disk Encounters between Low‐Mass Protoplanetary Accretion Disks." Astrophysical Journal 629, no. 1 (2005): 526–34. http://dx.doi.org/10.1086/431350.

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44

Wang, Xiao-Long, Min Fang, Yao Liu, Miao-Miao Zhang, and Wen-Yuan Cui. "LAMOST Reveals Long-lived Protoplanetary Disks." Astronomical Journal 169, no. 3 (2025): 141. https://doi.org/10.3847/1538-3881/ada8a7.

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Abstract While both observations and theories demonstrate that protoplanetary disks are not expected to live much longer than ∼10 Myr, several examples of prolonged disks have been observed in the past. In this work, we perform a systematic search for aged young stellar objects still surrounded by protoplanetary disks in the M-star catalog from the LAMOST archive. We identify 14 sources older than 10 Myr, still surrounded by protoplanetary disks and with ongoing accretion activities, significantly improving the census of the category known as the Peter Pan disks. The stellar parameters, variability, and accretion properties of these objects, as well as their spatial distribution, are investigated. Nearly all of these objects are distributed far away from nearby associations and star-forming regions but show evidence of being members of open clusters. Investigating the correlation between mass accretion rates and stellar masses, we find that these long-lived disks accrete at systematically lower levels, compared to their younger counterparts with similar stellar masses. Studying the evolution of mass accretion rates with stellar ages, we find that these aged disks follow a similar trend to young ones.

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Deinzer, W. "Dynamo–Action in Accretion Disks." Symposium - International Astronomical Union 157 (1993): 185–92. http://dx.doi.org/10.1017/s0074180900174091.

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Accretion disks are approximated by thin tori and the generation of magnetic fields by torus–dynamos is investigated. Solutions for the general α2ω–dynamo embedded into vacuum and into an ideally conducting medium are presented. Whereas the former solutions are qualitatively similar to those obtained for thin disks, there is a mode for the latter peculiar to torus–geometry. Excitation conditions for torus–dynamos are compared to those realized in accretion disks in cataclysmic variables, around T Tauri stars and in AGN's.

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Grant, Sierra L., Lucas M. Stapper, Michiel R. Hogerheijde, Ewine F. van Dishoeck, Sean Brittain, and Miguel Vioque. "The Ṁ –M _disk Relationship for Herbig Ae/Be Stars: A Lifetime Problem for Disks with Low Masses?" Astronomical Journal 166, no. 4 (2023): 147. http://dx.doi.org/10.3847/1538-3881/acf128.

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Abstract The accretion of material from protoplanetary disks onto their central stars is a fundamental process in the evolution of these systems and a key diagnostic in constraining the disk lifetime. We analyze the relationship between the stellar accretion rate and the disk mass in 32 intermediate-mass Herbig Ae/Be systems and compare them to their lower-mass counterparts, T Tauri stars. We find that the M ̇ –M disk relationship for Herbig Ae/Be stars is largely flat at ∼10−7 M ☉ yr−1 over 3 orders of magnitude in dust mass. While most of the sample follows the T Tauri trend, a subset of objects with high accretion rates and low dust masses are identified. These outliers (12 out of 32 sources) have an inferred disk lifetime of less than 0.01 Myr and are dominated by objects with low infrared excess. This outlier sample is likely identified in part by the bias in classifying Herbig Ae/Be stars, which requires evidence of accretion that can only be reliably measured above a rate of ∼10−9 M ☉ yr−1 for these spectral types. If the disk masses are not underestimated and the accretion rates are not overestimated, this implies that these disks may be on the verge of dispersal, which may be due to efficient radial drift of material or outer disk depletion by photoevaporation and/or truncation by companions. This outlier sample likely represents a small subset of the larger young, intermediate-mass stellar population, the majority of which would have already stopped accreting and cleared their disks.

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47

Okuda, Toru, Mitsutaka Fujita, and Shiro Sakashita. "Two-Dimensional Accretion Disk Models: Inner Accretion Disks of FU Orionis Objects." Publications of the Astronomical Society of Japan 49, no. 6 (1997): 679–97. http://dx.doi.org/10.1093/pasj/49.6.679.

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48

Avramenko, R., S. Wolf, T. F. Illenseer, and S. Rehberg. "Selected aspects of the analysis of molecular line observations of edge-on circumbinary disks." Astronomy & Astrophysics 642 (October 2020): A127. http://dx.doi.org/10.1051/0004-6361/201935610.

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Context. Inner cavities, accretion arms, and density waves are characteristic structures in the density distribution of circumbinary disks. They are the result of the tidal interaction of the non-axisymmetric gravitational forces of the central binary with the surrounding disk and are most prominent in the inner region, where the asymmetry is most pronounced. Aims. The goal of this study is to test the feasibility of reconstructing the gas density distribution and quantifying properties of structures in the inner regions of edge-on circumbinary disks using multiple molecular line observations. Methods. The density distribution in circumbinary disks is calculated with 2D hydrodynamic simulations. Subsequently, molecular line emission maps are generated with 3D radiative transfer simulations. Based on these, we investigate the observability of characteristic circumbinary structures located in the innermost region for spatially resolved and unresolved disks. Results. We find that it is possible to reconstruct the inner cavity, accretion arms, and density waves from spatially resolved multi-wavelength molecular line observations of circumbinary disks seen edge-on. For the spatially unresolved observations only, an estimate can be derived for the density gradient in the transition area between the cavity and the disk’s inner rim.

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Kamali, F., C. Henkel, S. Koyama, et al. "Accretion disk versus jet orientation in H2O megamaser galaxies." Astronomy & Astrophysics 624 (April 2019): A42. http://dx.doi.org/10.1051/0004-6361/201834600.

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Context. An essential part of the paradigm describing active galactic nuclei is the alignment between the radio jet and the associated rotation axis of the sub-pc accretion disks. Because of the small linear and angular scales involved, this alignment has not yet been checked in a sufficient number of low luminosity active galactic nuclei (LLAGNs). Aims. The project examines the validity of this paradigm by measuring the radio continuum on the same physical scale as the accretion disks to investigate any possible connection between these disks and the radio continuum. Methods. We observed a sample of 18 LLAGNs in the 4.8 GHz (6 cm) radio continuum using the Very Long Baseline Array (VLBA) with 3.3–6.5 ms resolution. The sources were selected to show both an edge-on accretion disk revealed by 22 GHz H2O megamaser emission and signatures of a radio jet. Furthermore, the sources were previously detected in 33 GHz radio continuum observations made with the Very Large Array. Results. Five out of 18 galaxies observed were detected at 8σ or higher levels (Mrk 0001, Mrk 1210, Mrk 1419, NGC 2273, and UGC 3193). While these five sources are known to have maser disks, four of them exhibit a maser disk with known orientation. For all four of these sources, the radio continuum is misaligned relative to the rotation axis of the maser disk, but with a 99.1% confidence level, the orientations are not random and are confined to a cone within 32° of the maser disk’s normal. Among the four sources the misalignment of the radio continuum with respect to the normal vector to the maser disk is smaller when the inner radius of the maser disk is larger. Furthermore, a correlation is observed between the 5 GHz VLBA radio continuum and the [OIII] luminosity and also with the H2O maser disk’s inner radius.

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Kuperus, Max. "Accretion Disk Coronae." Highlights of Astronomy 8 (1989): 535–38. http://dx.doi.org/10.1017/s1539299600008248.

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SummaryAccretion disk coronae around compact objects are the result of strong magnetic activity in the inner regions of accretion disks. Part of the accreting energy is dissipated in te corona and can be observed as hard X-ray emission with a time variability caused by the coronal structures. The interaction of disk coronae with neutron stars and black holes may cause quaslperiodlc oscillations respectively flare type emission.

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