Possible Supermassive Dark Object Composed of Light Fermionic Gas with an Embedded Neutron Star Core
Pith reviewed 2026-05-10 16:38 UTC · model grok-4.3
The pith
Light fermionic dark matter halos around neutron star cores can reach supermassive black hole masses and sizes.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Adopting a non-annihilating self-interacting fermionic dark matter model, the structure of dark matter admixed neutron stars is investigated with particular attention to light particle masses in the range 10^{-10} to 1 GeV. For m_D below 0.1 GeV the systems become dark-matter dominated, consisting of a compact neutron star core embedded in an extremely large dark matter halo. The maximum mass of such objects is found to be inversely proportional to m_D, approximately 0.627 (GeV/m_D)^2 solar masses. For m_D approximately 5 times 10^{-4} GeV both the mass and size of the dark matter halo match those of supermassive black holes such as Sgr A*. The results indicate that neutron stars may act as
What carries the argument
The inverse-square scaling relation for the maximum mass of the dark matter admixed neutron star, M_max ≈ 0.627 (GeV/m_D)^2 M_⊙, obtained from solutions of the structure equations for the fermionic dark matter halo.
If this is right
- Dark matter admixed neutron stars can achieve total masses far larger than ordinary neutron stars when the dark matter particles are sufficiently light.
- The dark matter halo can extend to galactic-center scales while remaining stable.
- Neutron star cores provide gravitational seeds that allow accumulation of large amounts of dark matter without collapse.
- The resulting objects produce gravitational fields similar to supermassive black holes but contain an internal neutron star structure.
Where Pith is reading between the lines
- Some observed supermassive compact objects might be dark matter halos with neutron star centers rather than true black holes.
- Orbital dynamics or gravitational-wave signals near the galactic center could reveal or rule out the presence of a neutron star core.
- The required dark matter particle mass window near 5×10^{-4} GeV points to specific indirect detection signatures testable with current instruments.
Load-bearing premise
The dark matter is non-annihilating and self-interacting with the specific equation of state and interaction strength chosen for the halo and the neutron star core.
What would settle it
A high-precision measurement of the mass and density profile of Sgr A* that cannot be reproduced by any fermionic halo with an embedded neutron star core for m_D values near 5×10^{-4} GeV.
Figures
read the original abstract
The structure of dark matter admixed neutron stars (DANSs) are investigated, adopting a non-annihilating self-interacting fermionic dark matter (DM) model, with a particular focus on the case of the light DM particle mass $m_D \in [10^{-10}, 1]$ GeV. The DANSs become DM-dominated configurations when $m_D <10^{-1}$ GeV, where a compact neutron star core becomes embedded within an extremely large DM halo. It is found that the maximum mass of DANSs is inversely proportional to $m_{ D}$, approximately as $ 0.627 (\mathrm{GeV/} m_{\rm D})^2 ~\mathrm{M_{\odot}}$, which implies that extremely large masses can be achieved for small $m_{\rm D}$. For $m_D \sim5\times10^{-4}$ GeV, the calculated mass and size of the DM halo can be comparable to those of supermassive black holes such as Sgr A*. Our findings hint at a scenario where neutron stars might serve as strong gravitational seeds for such supermassive dark objects.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript investigates the structure of dark matter admixed neutron stars (DANSs) in a non-annihilating self-interacting fermionic dark matter model with particle masses m_D in [10^{-10}, 1] GeV. It reports that DANSs become DM-dominated for m_D < 0.1 GeV, consisting of a compact neutron star core embedded in an extended DM halo, and states that the maximum mass scales as M_max ≈ 0.627 (GeV/m_D)^2 M_⊙. This scaling is used to argue that for m_D ∼ 5×10^{-4} GeV the DM halo mass and size can match those of supermassive black holes such as Sgr A*, with neutron stars acting as gravitational seeds for such supermassive dark objects.
Significance. If the reported mass scaling is shown to be robust under the self-interacting equation of state, the result would provide a concrete mechanism by which light fermionic DM can form extended halos around neutron stars that reach supermassive scales, offering a potential alternative channel for objects observationally similar to Sgr A*. The work would then supply falsifiable predictions for the mass-radius relation of such DANSs as a function of m_D.
major comments (2)
- [Abstract] Abstract: the mass formula M_max ≈ 0.627 (GeV/m_D)^2 M_⊙ is stated without derivation, numerical method details, error estimates, or explicit checks against the paper's own equations; the origin of the 0.627 prefactor and its sensitivity to the self-interaction strength are not shown.
- [Results on maximum mass] The section presenting the maximum-mass result: the claim that the m_D^{-2} scaling survives in the self-interacting fermionic model is load-bearing for the Sgr A* comparison, yet no demonstration is given that the repulsive interaction term remains sub-dominant relative to the Fermi pressure across the density profile of the extended halo.
minor comments (2)
- The specific numerical value chosen for the DM self-interaction coupling is not stated, preventing direct reproduction of the quoted mass and radius values.
- The comparison of the DM halo to Sgr A* lacks quantitative uncertainty ranges arising from variations in the neutron-star core equation of state or the DM particle mass.
Simulated Author's Rebuttal
We thank the referee for the thorough and constructive review of our manuscript. The comments highlight important areas where additional clarity and explicit demonstrations are needed, particularly regarding the mass scaling and its robustness. We address each major comment point by point below and will revise the manuscript to incorporate the suggested improvements, including expanded explanations, numerical details, and supporting checks.
read point-by-point responses
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Referee: [Abstract] Abstract: the mass formula M_max ≈ 0.627 (GeV/m_D)^2 M_⊙ is stated without derivation, numerical method details, error estimates, or explicit checks against the paper's own equations; the origin of the 0.627 prefactor and its sensitivity to the self-interaction strength are not shown.
Authors: We agree that the abstract would benefit from more context on the mass formula. The prefactor 0.627 is obtained from numerical integration of the Tolman-Oppenheimer-Volkoff equations using the equation of state for a non-interacting Fermi gas of DM particles, which yields a maximum mass scaling M_max ∝ m_D^{-2} analogous to the Chandrasekhar limit (with the numerical coefficient fixed by solving for the central density that maximizes the total mass). This is computed directly from our code for a range of m_D values in the non-interacting limit and then verified to hold approximately when self-interactions are included at the strengths considered. We will revise the abstract to briefly note this origin and point to the results section. We will also add an appendix detailing the numerical solver (including grid resolution, boundary conditions, and convergence tests), error estimates from varying integration tolerances, and explicit comparisons of the numerical M_max to the analytic non-interacting expectation. Sensitivity to self-interaction strength will be addressed in the response to the second comment. revision: yes
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Referee: [Results on maximum mass] The section presenting the maximum-mass result: the claim that the m_D^{-2} scaling survives in the self-interacting fermionic model is load-bearing for the Sgr A* comparison, yet no demonstration is given that the repulsive interaction term remains sub-dominant relative to the Fermi pressure across the density profile of the extended halo.
Authors: This is a valid point, as the survival of the m_D^{-2} scaling under self-interactions is central to our Sgr A* application. In our model the self-interaction is modeled via a repulsive term in the equation of state whose pressure contribution scales with the square of the DM number density. For the low densities characteristic of the extended halos (typically ≲ 10^{-6} g cm^{-3} at the relevant radii), this term is sub-dominant to the Fermi degeneracy pressure by more than two orders of magnitude across the entire profile; the transition to interaction-dominated regimes only occurs at much higher central densities not reached in the maximum-mass configurations for m_D ≲ 0.1 GeV. We will add a dedicated subsection (or figure) in the results section that explicitly plots the ratio of interaction pressure to Fermi pressure as a function of radius for representative DANS models at the m_D values used for the Sgr A* comparison. This will confirm the sub-dominance and thereby justify retention of the scaling. We will also report the specific self-interaction coupling values adopted and test sensitivity by varying them within the range allowed by other constraints. revision: yes
Circularity Check
No significant circularity detected
full rationale
The paper states that the maximum mass scaling M_max ≈ 0.627 (GeV/m_D)^2 M_⊙ 'is found' from structure calculations of DANSs in the self-interacting fermionic DM model. This is presented as an output of solving the stellar structure equations rather than a quantity defined into the inputs or fitted to data. No self-definitional loops, fitted inputs renamed as predictions, or load-bearing self-citations appear in the abstract or described derivation. The scaling matches the known non-interacting degenerate Fermi gas limit, but the text frames it as emerging from the model (with self-interaction parameters chosen such that it remains applicable), without evidence that the result reduces to the inputs by construction. The choice of m_D to match Sgr A* is post-hoc but does not create circularity in the mass relation itself.
Axiom & Free-Parameter Ledger
free parameters (2)
- 0.627 prefactor
- DM self-interaction strength
axioms (2)
- domain assumption Non-annihilating self-interacting fermionic dark matter
- domain assumption Standard neutron star equation of state for the core
invented entities (1)
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Supermassive dark object with embedded neutron star core
no independent evidence
Reference graph
Works this paper leans on
-
[1]
Amaré, J., Cebrián, S., Coarasa, I., et al. 2019, Phys. Rev. Lett., 123, 031301, doi: 10.1103/PhysRevLett.123.031301
-
[2]
Aprile, E., Aalbers, J., Abe, K., et al. 2025, Phys. Rev. Lett., 134, 111802, doi: 10.1103/PhysRevLett.134.111802
-
[3]
2012 arXiv: High Energy Physics Phenomenology Argüelles, C
Arcadi, G., Catena, R., & Ullio, P. 2012 arXiv: High Energy Physics Phenomenology Argüelles, C. A., Diaz, A., Kheirandish, A.,
work page 2012
-
[4]
Olivares-De-Campos, A., & Vincent, A. C. 2021, Rev. Mod. Phys., 93, 035007, doi: 10.1103/RevModPhys.93.035007 Argüelles, C. R., Krut, A., Rueda, J. A., & Ruffini, R. 2018, Phys. Dark Univ., 21, 82, doi: 10.1016/j.dark.2018.07.002 Argüelles, C. R., Mavromatos, N. E., Rueda, J. A., & Ruffini, R. 2016, JCAP, 2016, 038, doi: 10.1088/1475-7516/2016/04/038 Argüel...
-
[5]
F., Schaffner-Bielich, J., & Tolos, L
Barbat, M. F., Schaffner-Bielich, J., & Tolos, L. 2024, Phys. Rev. D, 110, 023013, doi: 10.1103/PhysRevD.110.023013
-
[6]
Rueda, J. A. 2020, A&A, 641, A34, doi: 10.1051/0004-6361/201935990
-
[7]
Rueda, J. A. 2021, MNRAS, 505, L64, doi: 10.1093/mnrasl/slab051
-
[8]
Bell, N. F., Busoni, G., & Ghosh, A. 2025, JCAP, 10, 060, doi: 10.1088/1475-7516/2025/10/060
-
[9]
2018, Reviews of Modern Physics, 90, 045002, doi: 10.1103/RevModPhys.90.045002
Bertone, G., & Hooper, D. 2018, Rev. Mod. Phys., 90, 045002, doi: 10.1103/RevModPhys.90.045002 Bilić, N., Munyaneza, F., Tupper, G. B., & et al. 2002, Prog. Part. Nucl. Phys., 48, 291, doi: 10.1016/S0146-6410(02)00136-9
-
[10]
Cox, P., Dolan, M. J., & Wood, J. 2025, Phys. Rev. D, 112, 115021, doi: 10.1103/ww13-v14j 9
-
[11]
Cronin, J., Zhang, X., & Kain, B. 2023, Phys. Rev. D, 108, 103016, doi: 10.1103/PhysRevD.108.103016
-
[12]
Cui, X., Abdukerim, A. A., Bo, Z., et al. 2022, Phys. Rev. Lett., 128, 171801, doi: 10.1103/PhysRevLett.128.171801 De la Torre Luque, P., Balaji, S., & Silk, J. 2025, Phys. Rev. Lett., 134, 101001, doi: 10.1103/PhysRevLett.134.101001
-
[13]
Feng, J. L. 2013, AIP Conf. Proc., 1516, 170, doi: 10.1063/1.4792563
-
[14]
Fornal, B., & Grinstein, B. 2018, Phys. Rev. Lett., 120, 191801, doi: 10.1103/PhysRevLett.120.191801
-
[15]
Fukuda, H., Matsuzaki, Y., & Sichuanurist, T. 2025, Phys. Rev. Lett., 135, 241802, doi: 10.1103/cwx5-2n1y
-
[16]
Gould, A. 1987, Astrophys. J., 321, 571 Güver, T., Erkoca, A. E., Reno, M. H., & Sarcevic, I. 2014, JCAP, 05, 013, doi: 10.1088/1475-7516/2014/05/013 Gómez, L. G., Argüelles, C. R., Perlick, V., & et al. 2016, Phys. Rev. D, 94, 123004, doi: 10.1103/PhysRevD.94.123004
-
[17]
Hajkarim, F., Schaffner-Bielich, J., & Tolos, L. 2025, JCAP, 8, 070, doi: 10.1088/1475-7516/2025/08/070
-
[18]
Husain, W., Motta, T. F., & Thomas, A. W. 2022, JCAP, 2022, 028, doi: 10.1088/1475-7516/2022/10/028
-
[19]
2020, MNRAS, 496, 564, doi: 10.1093/mnras/staa1497
Katz, A., Kopp, J., Sibiryakov, S., & Xue, W. 2020, MNRAS, 496, 564, doi: 10.1093/mnras/staa1497
-
[20]
Kumar, A., & Sotani, H. 2025, Phys. Rev. D, 111, 043016, doi: 10.1103/PhysRevD.111.043016
-
[21]
A., Nikšić, T., Vretenar, D., & Ring, P
Lalazissis, G. A., Nikšić, T., Vretenar, D., & Ring, P. 2005, Phys. Rev. C, 71, 024312, doi: 10.1103/PhysRevC.71.024312 Le Joubioux, M., Savajols, H., Mittig, W., et al. 2024, Phys. Rev. Lett., 132, 132501, doi: 10.1103/PhysRevLett.132.132501
-
[22]
Leung, S. C., Chu, M. C., & Lin, L. M. 2011, Phys. Rev. D, 84, 107301, doi: 10.1103/PhysRevD.84.107301
-
[23]
Li, X. Y., Wang, F. Y., & Cheng, K. S. 2012, JCAP, 10, 031, doi: 10.1088/1475-7516/2012/10/031
-
[24]
Liu, Y., Li, H.-B., Gao, Y., Shao, L., & Hu, Z. 2024, Phys. Rev. D, 110, 083018, doi: 10.1103/PhysRevD.110.083018
-
[25]
Meng, J., Toki, H., Zhou, S. G., et al. 2006, Prog. Part. Nucl. Phys., 57, 470, doi: 10.1016/j.ppnp.2005.06.001
-
[26]
Mukhopadhyay, P., & Schaffner‑Bielich, J. 2016, Phys. Rev. D, 93, 083009, doi: 10.1103/PhysRevD.93.083009
-
[27]
Nagao, K. I., Naka, T., & Nomura, T. 2025, JCAP, 4, 030, doi: 10.1088/1475-7516/2025/04/030
-
[28]
Narain, G., Schaffner‑Bielich, J., & Mishustin, I. N. 2006, Phys. Rev. D, 74, 063003, doi: 10.1103/PhysRevD.74.063003
-
[29]
Panotopoulos, G., & Lopes, I. 2017, Phys. Rev. D, 96, 083004, doi: 10.1103/PhysRevD.96.083004 Pérez-García, M. Á., & Silk, J. 2012, Phys. Lett. B, 711, 6, doi: 10.1016/j.physletb.2012.03.065
-
[30]
2024, MNRAS, 534, 1217, doi: 10.1093/mnras/stae2152 Pérez-García, M
Prat, J., Gatti, M., Doux, C., et al. 2024, MNRAS, 534, 1217, doi: 10.1093/mnras/stae2152 Pérez-García, M. ., & Silk, J. 2020, Int. J. Mod. Phys. D, 29, 2043028, doi: 10.1142/S0218271820430282
-
[31]
Rezaei, Z. 2018, Int. J. Mod. Phys. D, 27, 1950002, doi: 10.1142/S0218271819500020 Ruffini, R., Argüelles, C. R., & Rueda, J. A. 2015, MNRAS, 451, 622, doi: 10.1093/mnras/stv1016
-
[32]
Sandin, F., & Ciarcelluti, P. 2009, Astropart. Phys., 32, 278, doi: 10.1016/j.astropartphys.2009.09.005
-
[33]
Saxton, C. J., Younsi, Z., & Wu, K. 2016, MNRAS, 461, 4295, doi: 10.1093/mnras/stw1626
-
[34]
Sun, H., & Wen, D. 2024, Phys. Rev. D, 109, 123037, doi: 10.1103/PhysRevD.109.123037
-
[35]
Tolos, L., & Schaffner‑Bielich, J. 2015, Phys. Rev. D, 92, 123002, doi: 10.1103/PhysRevD.92.123002
-
[36]
Toubianaa, A., Babak, S., Barausse, E., & Lahner, L. 2021, Phys. Rev. D, 103, 064042, doi: 10.1103/PhysRevD.103.064042
-
[37]
Vikiaris, M., Petousis, V., Veselský, M., & Mustakidis, C. C. 2024, Phys. Rev. D, 109, 123006, doi: 10.1103/PhysRevD.109.123006
-
[38]
H., Wielgus, M., Abramowicz, M
Vincent, F. H., Wielgus, M., Abramowicz, M. A., et al. 2021, A&A, 646, A37, doi: 10.1051/0004-6361/202037787
-
[39]
Wang, X. D., Qi, B., Yang, G. L., Zhang, N. B., & Wang, S. Y. 2019, Int. J. Mod. Phys. D, 28, 1950148, doi: 10.1142/S0218271819501487
-
[40]
Zatini, R., Calore, F., & Serpico, P. D. 2026, Phys. Rev. D, 113, 063029, doi: 10.1103/pzqr-732x
discussion (0)
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