Radius of the innermost stable circular orbit of black-holes with localized Astrophysical Dark Matter halo
Abstract
We investigate the geodesic structure of a static, spherically symmetric black-hole in the background of a localized Astrophysical Dark Matter (ADM)-halo. The halo is modeled by a core-radius (r0), regularized density profile that vanishes at the event horizon and exponential factor ensures the finite total halo mass. We solved the Einstein field equations numerically with equation of state with p=wρ for stiff matter w=1 scenario. By analyzing the effective potential and its first and second derivatives, we evaluated the characteristic radius of the time-like innermost stable circular orbit (rISCO) of massive particle in the vicinity of hairy black-hole. Our numerical analysis is consistent with the recently proposed theoretical upper bound rISCO ≤ 6 normalized to unit mass black-hole. We showed that the ADM-halo shifts rISCO inward with respect to the Schwarzschild (bald) scenario and the shifts are larger for larger halo core-radius. In particular our numerical finding enumerate rISCO are approximately $5.97$, $5.61$, $5.53$ for r0=2.0,10.0,20.0 respectively. We believe that our analysis with ADM-halo model shed light on probing black-hole hair through high-energy astrophysical observables.
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BibTeX
@misc{karekar2026radius,
title = {{Radius of the innermost stable circular orbit of black-holes with localized Astrophysical Dark Matter halo}},
author = {Anup S. Karekar and Siba Prasad Das},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.24673},
eprint = {2610.24673},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.24673},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Radius of the innermost stable circular orbit of black-holes with localized Astrophysical Dark Matter halo
AU - Anup S. Karekar
AU - Siba Prasad Das
PY - 2026
DA - 2026/10/17
PB - arXiv
DO - 10.48550/arxiv.2610.24673
UR - https://arxiv.org/abs/2610.24673
AB - We investigate the geodesic structure of a static, spherically symmetric black-hole in the background of a localized Astrophysical Dark Matter (ADM)-halo. The halo is modeled by a core-radius (r_0), regularized density profile that vanishes at the event horizon and exponential factor ensures the finite total halo mass. We solved the Einstein field equations numerically with equation of state with p=wρ for stiff matter w=1 scenario. By analyzing the effective potential and its first and second derivatives, we evaluated the characteristic radius of the time-like innermost stable circular orbit (r_ISCO) of massive particle in the vicinity of hairy black-hole. Our numerical analysis is consistent with the recently proposed theoretical upper bound r_ISCO ≤ 6 normalized to unit mass black-hole. We showed that the ADM-halo shifts r_ISCO inward with respect to the Schwarzschild (bald) scenario and the shifts are larger for larger halo core-radius. In particular our numerical finding enumerate r_ISCO are approximately $5.97$, $5.61$, $5.53$ for r_0=2.0,10.0,20.0 respectively. We believe that our analysis with ADM-halo model shed light on probing black-hole hair through high-energy astrophysical observables.
ER -