Parameters
TRAPUM 90% CL: <10⁵ M☉ (formal likelihood analysis; more stringent than ratio-2 cutoff here).
Physics & citations
For a point mass M at the cluster centre, the maximum LOS acceleration at projected
distance r⊥ occurs at line-of-sight depth z = r⊥/√2 and equals
a_max = (2/3√3) × GM/r⊥² (the coefficient ≈ 0.3849).
The Plummer model softens the singularity by replacing r⊥² with (r⊥² + rc²), representing an extended dark cluster of scale radius rc.
The Hybrid model splits M equally between a point IMBH and a Plummer cluster, exploring the transition regime favoured by Bañares-Hernández et al. 2025.
Observed acceleration: a_obs = |ṗ / P| × c, where ṗ is the
measured spin-period derivative (including intrinsic spin-down, cluster mean field,
and IMBH contribution combined). Negative ṗ indicates the cluster is accelerating
the pulsar toward the observer.
Tension flag (a_max / a_obs > 2): the model predicts a maximum acceleration more than twice observed — geometrically improbable unless the IMBH exerts no force along that line of sight, which is unlikely for all pulsars simultaneously.
Pulsar timing: Chen et al. 2023, MNRAS 520:3847, doi:10.1093/mnras/stad029
IMBH upper limit: Bañares-Hernández et al. 2025, A&A 693:A104, doi:10.1051/0004-6361/202451763
amax model envelope vs. observed accelerations
| Pulsar | θ (′) | P (ms) | ṗ (10⁻²⁰ s/s) | |a_obs| (nm/s²) | a_max (nm/s²) | Ratio | Status |
|---|