Accretion of Primordial Black Holes in Stellar Interiors
5 affiliations
- 1Flatiron Institute
- 2Princeton University
- 3Massachusetts Institute of Technology
- 4New York University
- 5Stanford University
Abstract
We study spherical accretion onto primordial black holes (PBHs) embedded in the core of a solar-type star. We compute the radiative efficiency self-consistently for the first time across more than 6 decades in black hole mass (10 −16.5 –10 ⁻¹⁰ M ⊙ ) with time-dependent simulations, and follow the growth up to 10 ⁻² M ⊙ using an analytical photon-trapping prescription above 5 × 10 ⁻¹³ M ⊙ . Near the Schwarzschild radius ( r S ∼ 10 ⁻¹¹ cm for a 10 ⁻¹⁶ M ⊙ PBH), gas compressed to T ∼ 10 ¹¹ K radiates through microphysical processes that fundamentally alter the classical adiabatic Bondi solution. We solve the time-dependent spherical Euler equations with an implicit cooling source term, determining M ̇ , the Bondi-normalized radiative efficiency η = L / ( M ̇ B c 2 ) , and the flow structure self-consistently. We identify three regimes for spherical accretion: a hot Bondi regime ( M BH ≲ 10 ⁻¹⁴ M ⊙ ) in which bremsstrahlung cooling is dynamically negligible; a bremsstrahlung-cooling regime (10 ⁻¹⁴ –5 × 10 ⁻¹³ M ⊙ ) driving the flow toward isothermal with η ≈ 10 ⁻² ; and a photon-trapping regime above 5 × 10 ⁻¹³ M ⊙ , in which the Bondi sphere is optically thick and the accretion rate remains close to the Bondi value. Cooling enhances M ̇ by a factor of ∼1.5–7, keeping growth superexponential throughout the spherical regime. The radiative efficiency is an order of magnitude lower than previously assumed, and the critical initial PBH mass required to consume a solar-mass star within a Hubble time is M 0,crit ∼ 10 ⁻¹⁶ M ⊙ .
Related
- Inflaton accretion onto primordial black holes during reheating
- Satellite stellar-to-halo mass relations in primordial black hole universes
- Search for subsolar primordial black holes in low mass-ratio binaries with LIGO-Virgo O2 data and implications for the primordial black hole dark matter fraction
- Theory-constrained hierarchical inference of primordial black holes in f(Q, T) gravity with GWTC-3
- Gravitational wave signals from primordial black holes orbiting solar-type stars
BibTeX
@article{cantiello2026accretion,
title = {{Accretion of Primordial Black Holes in Stellar Interiors}},
author = {Matteo Cantiello and Ore Gottlieb and Cameron Norton and Matthew Kleban and Ken Van Tilburg},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aea0d2},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea0d2},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Accretion of Primordial Black Holes in Stellar Interiors
AU - Matteo Cantiello
AU - Ore Gottlieb
AU - Cameron Norton
AU - Matthew Kleban
AU - Ken Van Tilburg
PY - 2026
DA - 2026/10/15
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aea0d2
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aea0d2
AB - We study spherical accretion onto primordial black holes (PBHs) embedded in the core of a solar-type star. We compute the radiative efficiency self-consistently for the first time across more than 6 decades in black hole mass (10 −16.5 –10 ⁻¹⁰ M ⊙ ) with time-dependent simulations, and follow the growth up to 10 ⁻² M ⊙ using an analytical photon-trapping prescription above 5 × 10 ⁻¹³ M ⊙ . Near the Schwarzschild radius ( r S ∼ 10 ⁻¹¹ cm for a 10 ⁻¹⁶ M ⊙ PBH), gas compressed to T ∼ 10 ¹¹ K radiates through microphysical processes that fundamentally alter the classical adiabatic Bondi solution. We solve the time-dependent spherical Euler equations with an implicit cooling source term, determining M ̇ , the Bondi-normalized radiative efficiency η = L / ( M ̇ B c 2 ) , and the flow structure self-consistently. We identify three regimes for spherical accretion: a hot Bondi regime ( M BH ≲ 10 ⁻¹⁴ M ⊙ ) in which bremsstrahlung cooling is dynamically negligible; a bremsstrahlung-cooling regime (10 ⁻¹⁴ –5 × 10 ⁻¹³ M ⊙ ) driving the flow toward isothermal with η ≈ 10 ⁻² ; and a photon-trapping regime above 5 × 10 ⁻¹³ M ⊙ , in which the Bondi sphere is optically thick and the accretion rate remains close to the Bondi value. Cooling enhances M ̇ by a factor of ∼1.5–7, keeping growth superexponential throughout the spherical regime. The radiative efficiency is an order of magnitude lower than previously assumed, and the critical initial PBH mass required to consume a solar-mass star within a Hubble time is M 0,crit ∼ 10 ⁻¹⁶ M ⊙ .
SN - 0004-637X
SN - 1538-4357
ER -