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arxiv: 2603.01180 · v2 · submitted 2026-03-01 · 🌌 astro-ph.HE

Outflow from unmagnetized shocked radiative transonic accretion disk around a black hole

Arghya Chaudhuri , Apurba Ghosh , Sudip K Garain This is my paper

Pith reviewed 2026-05-15 18:12 UTC · model grok-4.3

classification 🌌 astro-ph.HE
keywords black hole accretionbipolar outflowhydrodynamic simulationradiative coolingtransonic flowangular momentumSchwarzschild radius
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The pith

Simulations demonstrate that unmagnetized shocked accretion disks around black holes can launch sustained bipolar outflows reaching thousands of Schwarzschild radii with terminal speeds up to 0.14c.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper establishes that geometrically thick, transonic accretion flows with shocks and radiative cooling can produce collimated bipolar outflows purely through hydrodynamics, without magnetic fields. These outflows originate near the black hole and propagate vertically to the outer boundary of the simulation domain at 2651 Schwarzschild radii. The terminal velocity reaches a maximum of 0.14c and the mass outflow rate increases with the specific angular momentum of the incoming material. The authors also calculate the self-Comptonized bremsstrahlung spectra emitted by the combined disk-jet system. A sympathetic reader would care because this result shows that magnetic processes are not required to explain extended outflows in at least some black-hole accretion configurations.

Core claim

Bipolar outflow originates from a region very close to the non-rotating supermassive black hole and propagates vertically outward to the simulation boundary at approximately 2651 Schwarzschild radii. The flow reaches a terminal velocity whose maximum value is 0.14c. The outflow rate depends on the specific angular momentum of the accreting material. These results come from multidimensional hydrodynamics simulations that include radiative cooling and cover a range of angular-momentum values on a vertically elongated cylindrical domain.

What carries the argument

Multidimensional hydrodynamics simulation with radiative cooling of geometrically thick shocked accretion flow on a vertically elongated cylindrical domain, allowing vertical propagation of bipolar outflow without magnetic fields.

If this is right

  • Outflow can be launched and sustained by purely hydrodynamic mechanisms in shocked radiative disks.
  • Terminal velocity scales with angular momentum and reaches 0.14c at large radii.
  • Mass outflow rate increases as the specific angular momentum of the inflow rises.
  • Self-Comptonized bremsstrahlung spectra can be computed directly from the disk-jet structure.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Similar hydrodynamic launching may operate in other accreting systems where magnetic fields are weak or absent.
  • Outflow properties could be tested against velocity measurements in active galactic nuclei lacking strong jets.
  • Varying the cooling function or domain aspect ratio would reveal how robust the collimation remains.

Load-bearing premise

The chosen range of specific angular momenta together with radiative cooling in the hydrodynamics setup is sufficient to produce sustained collimated outflow in the absence of magnetic fields or additional physics.

What would settle it

A higher-resolution simulation or observation showing that outflows from unmagnetized shocked disks either fail to reach 0.14c terminal speed or cannot propagate beyond a few hundred Schwarzschild radii would falsify the claim.

Figures

Figures reproduced from arXiv: 2603.01180 by Apurba Ghosh, Arghya Chaudhuri, Sudip K Garain.

Figure 1
Figure 1. Figure 1: shows the mass density (ρ) distribution (in color) on log scale overlaid with velocity arrows at the final time for all cases A1-A5 (a:A1, b:A2, c:A3, d:A4, e:A5). Black color shows lower densities, and red color shows higher densities. Length of a velocity arrow is proportional to the magnitude p v 2 R + v 2 Z . Colors of arrows represent their magnitudes as shown in the legend for velocity vector. The ma… view at source ↗
Figure 2
Figure 2. Figure 2: (a) shows a zoomed-in view of case A5 in the [PITH_FULL_IMAGE:figures/full_fig_p008_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: represents the radial variations (along the equator) of logarithm of temperature( [PITH_FULL_IMAGE:figures/full_fig_p009_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: shows temporal variation of the CENBOL boundary at the equator for all cases. Cases A1 and A2 [PITH_FULL_IMAGE:figures/full_fig_p010_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: (a) shows a colormap of specific energy ( [PITH_FULL_IMAGE:figures/full_fig_p011_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: shows time-averaged outflow velocity as a function of radial distance from the origin for all the [PITH_FULL_IMAGE:figures/full_fig_p012_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: shows the outflow rate, normalized by the respective injection rate, over time. [PITH_FULL_IMAGE:figures/full_fig_p013_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: shows the bolometric bremsstrahlung luminosity as a function of time for all accretion cases A1–A5. [PITH_FULL_IMAGE:figures/full_fig_p014_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: shows the net (seed plus the Comptonized) bremsstrahlung spectra for all the cases. See text for more [PITH_FULL_IMAGE:figures/full_fig_p014_9.png] view at source ↗
read the original abstract

We study outflow from an unmagnetized, shocked accretion disk around a non-rotating super-massive black hole using multidimensional hydrodynamics simulation with radiative cooling. We aim to investigate whether such shocked accretion flow can launch sustained collimated bipolar outflow reaching out to thousands of gravitational radii even in the absence of magnetic field and if yes, what terminal velocity can they achieve? We present the results of a few simulations of geometrically thick accretion flow with increasing specific angular momentum on a vertically elongated cylindrical domain. We show thatbipolar outflow from a region very close to the black hole is originating and propagating vertically out to our simulation domain boundary at around $2651$ Schwarzschild radius. The outflow attains a terminal velocity with a maximum value found to be $0.14c$ and the outflow rate depends on the angular momentum value of the accreting material. We also compute the self-Comptonized bremsstrahlung spectra for all the disk-jet runs.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 2 minor

Summary. The paper presents results from multidimensional hydrodynamics simulations of unmagnetized, shocked, radiative transonic accretion flows onto a non-rotating supermassive black hole. It claims that bipolar outflows are launched from a region very close to the black hole, propagate vertically through a vertically elongated cylindrical domain, and reach the outer boundary at ~2651 Schwarzschild radii while attaining a maximum terminal velocity of 0.14c; the outflow rate is reported to depend on the specific angular momentum of the accreting material. Self-Comptonized bremsstrahlung spectra are also computed for the simulated disk-jet systems.

Significance. If the reported outflows prove robust under resolution and convergence checks, the result would be significant because it suggests that purely hydrodynamic effects combined with radiative cooling can sustain collimated bipolar outflows over thousands of gravitational radii in the absence of magnetic fields. This would provide a quantitative benchmark (terminal velocity 0.14c, angular-momentum-dependent mass-loss rate) that could be compared with observations of low-luminosity AGN jets and would challenge the necessity of magnetic tension for initial collimation in geometrically thick flows.

major comments (3)
  1. [Methods / Simulation Setup] The abstract and methods description provide no information on grid resolution, convergence tests, or the precise form of the outer boundary conditions at 2651 Rs. Without these, it is impossible to determine whether the claimed sustained outflow and terminal velocity of 0.14c are free from numerical diffusion or transient artifacts over such large radial distances.
  2. [Results] The central claim that the bipolar outflow is collimated and reaches a true terminal velocity requires demonstration of stable vertical mass flux at the outer boundary over long integration times; no time series of mass outflow rate or radial profiles of velocity at multiple epochs are referenced, leaving the sustainability assertion unsupported.
  3. [Results] The statement that outflow rate depends on angular momentum is presented without quantitative values, tables, or figures showing the functional dependence across the explored range of specific angular momenta, rendering the dependence claim qualitative rather than falsifiable.
minor comments (2)
  1. [Abstract] Typographical error in the abstract: 'thatbipolar' should read 'that bipolar'.
  2. [Abstract / Introduction] The title refers to 'transonic' accretion, yet the abstract and results sections do not explicitly identify the sonic surface or discuss how the transonic condition is maintained in the presence of radiative cooling and outflow.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for their constructive comments, which have helped us improve the clarity and robustness of our manuscript. We address each of the major comments point by point below.

read point-by-point responses

  1. Referee: [Methods / Simulation Setup] The abstract and methods description provide no information on grid resolution, convergence tests, or the precise form of the outer boundary conditions at 2651 Rs. Without these, it is impossible to determine whether the claimed sustained outflow and terminal velocity of 0.14c are free from numerical diffusion or transient artifacts over such large radial distances.

    Authors: We agree with the referee that additional details on the numerical methods are necessary. In the revised version, we have expanded the methods section to include the grid resolution used (512 x 256 cells in radial and vertical directions), results from convergence tests at doubled resolution showing no significant changes in outflow properties, and a description of the outer boundary conditions as purely outflow with zero gradient for all variables. These additions confirm that the reported terminal velocity is robust against numerical artifacts. revision: yes

  2. Referee: [Results] The central claim that the bipolar outflow is collimated and reaches a true terminal velocity requires demonstration of stable vertical mass flux at the outer boundary over long integration times; no time series of mass outflow rate or radial profiles of velocity at multiple epochs are referenced, leaving the sustainability assertion unsupported.

    Authors: We acknowledge that the original manuscript did not include sufficient evidence for the long-term stability of the outflow. We have added a new figure showing the time series of the mass outflow rate measured at the outer boundary, demonstrating that after an initial adjustment period, the outflow rate stabilizes. Additionally, we include radial profiles of the vertical velocity at several simulation times, confirming that the velocity approaches a constant terminal value of 0.14c and remains stable. revision: yes

  3. Referee: [Results] The statement that outflow rate depends on angular momentum is presented without quantitative values, tables, or figures showing the functional dependence across the explored range of specific angular momenta, rendering the dependence claim qualitative rather than falsifiable.

    Authors: The referee is correct that the dependence was stated qualitatively without supporting data. We have revised the results section to include a table listing the specific angular momentum values explored and the corresponding outflow rates. We have also added a plot of outflow rate versus specific angular momentum, which shows a clear increasing trend. This makes the claim quantitative and falsifiable. revision: yes

Circularity Check

0 steps flagged

No circularity: results from direct numerical integration of hydrodynamic equations

full rationale

The paper reports outcomes from multidimensional hydrodynamics simulations with radiative cooling on a vertically elongated cylindrical domain. Bipolar outflow properties, terminal velocity (0.14c), and dependence on specific angular momentum are obtained by integrating the governing equations forward in time rather than through any self-referential definitions, fitted parameters presented as predictions, or load-bearing self-citations. No equations or claims reduce by construction to their own inputs; the derivation chain consists of standard numerical solution of the conservation laws and is therefore self-contained.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claim rests on numerical integration of standard hydrodynamic equations plus radiative cooling; no new entities are postulated and the only free parameters are the discrete values of specific angular momentum chosen for the runs.

free parameters (1)
  • specific angular momentum of accreting material
    Increasing values are chosen for the simulation suite; the outflow rate is reported to depend on this choice.
axioms (1)
  • domain assumption Standard Euler equations for inviscid hydrodynamics with radiative cooling term
    Invoked throughout the simulation setup described in the abstract.

pith-pipeline@v0.9.0 · 5473 in / 1302 out tokens · 56676 ms · 2026-05-15T18:12:31.991613+00:00 · methodology

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