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.
Verdict rule (fixed 2026-09-24, audit P0-11; the previous a_max/a_obs > 2 "tension" mapping was inverted): the mass is excluded for a pulsar when a_max < |a_obs| — the model cannot produce the observed line-of-sight acceleration even at the LOS maximum; a_max above the observation is the compatible case. Comparisons use the intrinsic-Ṗ-corrected a_obs: the measured ṗ is total (intrinsic + cluster + Shklovskii), the intrinsic term is unknown at ~10⁻²⁰ s/s, so a_obs_corr = max(|ṗ| − 10⁻²⁰, 0)/P × c. That unknown caps usable sensitivity at ~10⁻⁹–10⁻¹⁰ m/s² (Paper H pulsar-leg floor).
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 |
|---|