Zheng-Long Wang | Search arXiv

arXiv2026

Binary-pulsar Timing: A 3D Solar-System Accelerometer and Unknown-Source Probe

The acceleration of the Solar System barycenter (SSB) offers a unique precision probe of the local gravitational environment, enabling searches for otherwise invisible gravitating sources such as Planet Nine and nearby (primordial) black holes. Using the binary-pulsar timing measurements, we develop an analysis framework that combines the line-of-sight differential accelerations of 26 binary pulsars to jointly reconstruct the three-dimensional acceleration of the SSB and place directional upper limits. Across three smooth Galactic-potential baselines, the residual acceleration is consistent with zero. We obtain directional 95\% upper limits of $0.198$, $0.262$, and $0.693~μ\mathrm{as}\,\mathrm{yr}^{-1}$ over 50\%, 75\%, and all sampled directions, respectively. These limits are tighter by factors of 3.5, 3.6, and 1.6 than a matched Gaia EDR3 benchmark and improve previous pulsar constraints by more than an order of magnitude. We further extend the framework to the full SSB--pulsar two-endpoint response, enabling direct position-dependent mass constraints on unknown gravitational sources. A $10\,M_\odot$ object is excluded within 0.39, 0.34, and 0.21 pc over the same sky fractions. Our unknown-mass limits surpass the tidal-equivalent INPOP19a reference beyond 0.2 pc by about an order of magnitude over most of the sky at 1 pc.

astro-ph.GA↗

arXiv2026

Challenges in Binary Pulsar Timing Detection of Dark Matter Subhalos

Recently, binary pulsar timing has been proposed as a viable probe of dark matter subhalos with masses of $\sim 10^7\,M_{\odot}$ in the solar neighborhood. We present a comprehensive analytical framework that incorporates the subhalo mass function, projection effects of line-of-sight acceleration, and the spatiotemporal geometric requirements for joint detection by binary systems, enabling a quantitative evaluation of the detectability of nearby subhalos. Applying this framework to the current binary pulsar sample, we find a probability $\leq 1.7 \times 10^{-4}$ of detecting at least one subhalo within the effective volume. An independent timing residual analysis shows no statistically significant excess in line-of-sight accelerations beyond predictions from data-driven Galactic gravitational potential models. These results place stringent constraints on detecting $<10^8~M_{\odot}$ dark matter subhalos with existing pulsar timing data, aligning with the theoretical expectation that such subhalos have a low survival probability in the solar neighborhood. A low detection prospect still holds even for future Square Kilometre Array observations.

astro-ph.HE↗