Constraints on dark matter annihilation from a nearby subhalo candidate

Abstract

A recent analysis of pulsar timing data has reported evidence for a massive ($\sim 6\times 10^7{M}_{\odot }$) dark matter subhalo located only $\sim 0.8$ kpc from Earth. This candidate implies an exceptionally large $J$-factor of $\sim 10^{23}\mathrm{Ge}{\mathrm{V}}^2\mathrm{c}{\mathrm{m}}^{-5}$, exceeding that of known classical dwarf spheroidal galaxies by orders of magnitude and rivaling the Galactic Center. In this work, we utilize more than 17 years of $\text{Fermi}$-LAT data to search for gamma-ray emission from this subhalo. We identify a tentative excess in the region with ambiguous origin. Adopting a conservative strategy, we retain this excess without modeling additional astrophysical components, treating it instead as unmodeled background to derive upper limits on the dark matter annihilation cross-section for the $b\bar{b}$ and ${\tau }^{+}{\tau }^{-}$ channels. Despite this conservative treatment, the resulting limits remain stringent due to the exceptionally large $J$-factor. Subject to the dynamical confirmation of the subhalo, these constraints are potentially orders of magnitude stronger than those obtained from combined analyses of dwarf spheroidal galaxies and blind subhalo searches.

7 pages, 2figures