{
  "kind": "Own fitted aggregate predictive calibration; no original or transformed star rows",
  "version": "ac27-fixed-scale-three-anchor-v1",
  "anchors": [
    {
      "cluster": "Praesepe",
      "age_gyr": 0.67,
      "stars": 64,
      "coefficients": [
        2.2840439512425372,
        -0.29169230461913803,
        -0.03418655430030381,
        -0.007813279988135854
      ],
      "temperature_range_k": [
        4202.23,
        5971.6
      ],
      "effective_log_scatter": 0.04785120007853288,
      "minimum_predictive_period_width_days": 1.0
    },
    {
      "cluster": "NGC 6811",
      "age_gyr": 1.0,
      "stars": 103,
      "coefficients": [
        2.4062285301459294,
        -0.01689272540175968,
        0.029145694460345623,
        -0.17758399739460606
      ],
      "temperature_range_k": [
        4245.37,
        5953.13
      ],
      "effective_log_scatter": 0.038586619271600016,
      "minimum_predictive_period_width_days": 1.0
    },
    {
      "cluster": "Ruprecht 147",
      "age_gyr": 2.7,
      "stars": 24,
      "coefficients": [
        3.1627680823707003,
        -0.03909723454263105,
        -0.30855345319046384,
        -0.11143182875226355
      ],
      "temperature_range_k": [
        4241.68,
        5832.12
      ],
      "effective_log_scatter": 0.05961855130077957,
      "minimum_predictive_period_width_days": 2.0
    }
  ],
  "common_temperature_support_k": [
    4245.37,
    5832.12
  ],
  "age_support_gyr": [
    0.67,
    2.7
  ],
  "temperature_coordinate": "(Teff-5100)/900",
  "interpolation": "Linear log period and effective log width in log age; no forced monotonicity or hidden extrapolation",
  "width_qualification": "Effective predictive width combines residual MAD and source-inspired one/two-day dispersion; not a measured intrinsic scatter or homogeneous period-error estimate",
  "holdouts": [
    "NGC 6819",
    "NGC 752"
  ],
  "scale": "Fixed published0.67/1.0/2.7Gyr conditioning; NGC6819 stays a2.5Gyr external cluster holdout, not an invented low-temperature anchor",
  "limits": "Shared source temperature/extinction and membership assumptions retained; no external age-scale propagation or absolute precision claim"
}