Flyby Survival Simulator

Full radius-sweep reimplementation of Paper E, Figure 1: per-bin Monte Carlo of gravitationally focused stellar flybys across the whole feasibility envelope, median & 16–84% survival band. For a single-point (one mass, one radius) version, see flyby-survival.html.

Speculative register · MTH engineering
Not run yet — click ▶ run sweep.
Method (Paper E Appendix A, browser-reduced sample counts). For each log-spaced radius bin a ∈ [10⁻³, stripping radius] AU: draw encounters with impact parameter from the gravitationally focused distribution truncated at bmax = 30a, velocity from a Maxwellian at dispersion σ, and mass from the perturber mass function; compute the impulsive eccentricity-kick variance ⟨δ²⟩; convert to a survival time via the random-walk first-passage estimate n = ecross²/⟨δ²⟩ divided by the encounter rate, with CLT scatter giving the 16–84% band; cap at 12 Gyr. Deliberately conservative: no adiabatic suppression applied.

Perturber mass function & the fBH control (referee-M1 revision, Paper E v0.4). The background is two-component stellar (0.35 M☉ weight 0.70, 0.60 M☉ white-dwarf tail weight 0.30). A mass-segregated heavy-remnant extension adds neutron stars (1.4 M☉, fixed number fraction fNS = 2%) and stellar-mass black holes (10 M☉, segregated fraction f_BH, fiducial 1%, grid 0.1/1/3%). The 10 M☉ BH tail is the controlling perturber: heavy masses dominate the kick variance, so raising fBH shortens the floor sharply. This supersedes the stars-only result (a ~3×10⁹ yr floor comparable to the cluster age) that this page previously reported. At the fiducial fBH = 1% the envelope floor drops to ~3×10⁸ yr (the paper quotes ~1.5×10⁸–5×10⁸ yr across the grid). That stays well above the 10⁶ yr passive-safety criterion, though it is no longer comparable to the cluster lifetime. Set fBH = 0 to recover the superseded stars-only baseline.

Paper reference mode. Ticking paper reference plots the exact fiducial arrays from fig1_results.json verbatim (2×10⁵ encounter draws × 2×10⁴ histories × 40 bins, fixed seed 20260717, σ = 21 km/s, fig1_envelope.py, full bundle at /papers/source/): no live sampling, so it reproduces the published numbers rather than approximating them. The live MC trades sample count for interactivity; expect its median to sit inside the reference band, not land on it. The paper MC floor summary card always shows the published floor for the grid fBH nearest your setting, for side-by-side comparison. σ default from measurements.js clusterParams (18.2 km/s, cluster-averaged); Paper E adopts σ = 21 km/s, the midpoint of the 20–23 km/s central-region range of Baumgardt & Vasiliev (2021) and Nitschai et al. (2023). The difference lengthens survival times by tens of per cent and is inside the paper’s stated parameter variations.
→ single-point calculator → fuel budget → Paper E, Section 2 (the envelope)