Observational Constraints on WIMP Mini-Spikes Around Stellar-Mass Primordial Black Holes with 17 Years of Fermi-LAT Data

Abstract

The quest to identify the true nature of dark matter remains one of the most pressing challenges in modern physics. We present a novel approach to probe the Weakly Interacting Massive Particle (WIMP) paradigm by analyzing density enhancements, or ``mini-spikes,'' around stellar-mass black holes (sBHs) using 17 years of data from the \textit{Fermi} Large Area Telescope. Motivated by the anomalous orbital decay observed in the black hole low-mass X-ray binaries A0620--00 and XTE J1118+480, we model these systems under the hypothesis of adiabatic spike formation around primordial black holes, incorporating the effects of tidal disruption in the Galactic disk. Finding no statistically significant gamma-ray excess at either location ($TS < 1$), we derive 95\% C.L. upper limits on the WIMP annihilation cross section. Our results exclude the canonical thermal relic cross section ($3 \times 10^{-26} \, \text{cm}^3\text{s}^{-1}$) across the 10~GeV to 10~TeV mass range for $b\bar{b}$ and $W^+W^-$ channels, and up to $\sim$6~TeV for the $τ^+τ^-$ channel. Recasting these results into a Galactic discovery reach, we demonstrate that \textit{Fermi}-LAT is sensitive to $10\,M_\odot$ mini-spikes even at distances surpassing the Galactic Center, provided the WIMP mass is below 1~TeV. These findings establish a significant tension between the dynamical friction interpretation of orbital decay in these systems and the WIMP hypothesis, providing robust observational constraints on the coexistence of primordial black holes and annihilating dark matter.

Figures (7)

• Figure 1: Dark matter density profiles around the stellar-mass black holes A0620--00 and XTE J1118+480 under the spike formation hypothesis, shown both with and without the effects of tidal disruption on the subhalo. The gray dotted line marks the saturation density corresponding to the adopted values of DM particle mass and annihilation cross section shown in the figure, and a system lifetime of $10^{10}$ yr.
• Figure 2: Residual TS map centered on the black hole A0620--00, covering an area of $10^\circ \times 10^\circ$. We find no statistically significant excess in 17 years of Fermi-LAT observations, neither in the point-source nor in the extended-source analysis at the position of A0620--00.
• Figure 3: Residual TS map centered on the black hole XTE J1118+480, covering an area of $10^\circ \times 10^\circ$. We find no statistically significant excess in 17 years of Fermi-LAT observations, neither in the point-source nor in the extended-source analysis at the position of XTE J1118+480.
• Figure 4: 95% CL upper limits on the flux for the source A0620--00. The spectral energy distribution and the likelihood profile are obtained in the energy range from 500 MeV to 1 TeV, assuming a point-like source morphology.
• Figure 5: 95% confidence level upper limits on the flux are shown for the source XTE J1118+480. The spectral energy distribution and the likelihood profile are obtained in the energy range from 500 MeV to 1 TeV, assuming a point-like source morphology.