Read a white dwarf past the table's blue end at the temperature white dwarfs of its colour have

31e0c04 clamped an untyped star bluer than BP−RP −0.12 to the table's B9 row, so every one of the
110 white dwarfs within 50 pc was drawn at 10 700 K. Gentile Fusillo et al. (2021, MNRAS 508, 3877)
fit 104 of them at 14 266 to 39 304 K, and the radius their mass and gravity give was a median
0.65 of the one drawn. Past the table's end, dwarfSequenceAtColor now reads BP−RP off the median
pure-hydrogen temperature they fit in bins of ±0.025 around −0.15 to −0.40 (15 369 to 28 585 K,
counted again from the cross-match: 27, 24, 22, 15, 10 and 2 stars), and the correction and G−V
off the table's own rows at that temperature, through a new dwarfSequenceAtTemperature that
temperatureToColorIndex now shares.

Against GF21's R = sqrt(GM/g) over the same 104, the drawn radius goes from a median 1.53 (p10
1.33, p90 1.96) to 0.96 (0.94, 1.05), and the temperature from 0.59 of theirs to 1.00 (0.88,
1.02). Gaia DR3 6791196382856581376 is now 19 251 K and 0.0120 R☉, against their 19 205 K and
0.01245.

Tests: stellar.spec's −0.25 case now expects 19 012 K where it pinned 10 700, and a new case gives
that white dwarf its radius to within a fifth; spectral.spec reads −0.15, −0.13 and −0.6, keeps
the red end and B−V's blue end at their rows, and covers dwarfSequenceAtTemperature. Controls:
no white-dwarf branch, the bin's temperature without interpolating, B9's correction kept at the
new temperature, and the temperature read the wrong way round each fail the named test.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/app/shared/astro/spectral.spec.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest';
 
-import { dwarfSequenceAtColor, isGiant, parseSpectralClass, spectralClassification, SPECTRAL_CLASSES, spectralTypeFromColor, spectralTypeToColorIndex, temperatureToColorIndex } from './spectral';
+import { dwarfSequenceAtColor, dwarfSequenceAtTemperature, isGiant, parseSpectralClass, spectralClassification, SPECTRAL_CLASSES, spectralTypeFromColor, spectralTypeToColorIndex, temperatureToColorIndex } from './spectral';
 
 describe('parseSpectralClass', () => {
   it('reads a clean class and subclass', () => {
@@ -180,7 +180,26 @@ describe('dwarfSequenceAtColor', () => {
 
   it('reads the row at the end a colour is past, when asked to', () => {
     expect(dwarfSequenceAtColor(2.2, 'B-V', true)).toEqual({ bMinusV: 2.16, temperatureK: 2420, bolometricCorrectionV: -5.78, gMinusV: -3.09 });
-    expect(dwarfSequenceAtColor(-0.15, 'BP-RP', true)).toEqual({ bMinusV: -0.07, temperatureK: 10700, bolometricCorrectionV: -0.42, gMinusV: 0.018 });
+    expect(dwarfSequenceAtColor(5.3, 'BP-RP', true)).toEqual({ bMinusV: 2.16, temperatureK: 2420, bolometricCorrectionV: -5.78, gMinusV: -3.09 });
+    expect(dwarfSequenceAtColor(-0.4, 'B-V', true)).toEqual({ bMinusV: -0.301, temperatureK: 31400, bolometricCorrectionV: -2.99, gMinusV: null });
     expect(dwarfSequenceAtColor(null, 'B-V', true)).toBeNull();
   });
+
+  it("reads a white dwarf bluer than BP−RP's end at the temperature measured at its colour, and the table's correction there", () => {
+    // Gentile Fusillo et al. (2021): 15 369 K at −0.15, where B9's row had 10 700; between B6 and B5.
+    const point = dwarfSequenceAtColor(-0.15, 'BP-RP', true)!;
+    expect(point.temperatureK).toBeCloseTo(15369, 6);
+    expect(point.bolometricCorrectionV).toBeCloseTo(-1.13 - 0.21 * (869 / 1200), 6);
+    expect(dwarfSequenceAtColor(-0.13, 'BP-RP', true)!.temperatureK).toBeCloseTo(15369 - 4669 * (2 / 3), 6);
+    expect(dwarfSequenceAtColor(-0.6, 'BP-RP', true)!.temperatureK).toBeCloseTo(28585, 6);
+  });
+});
+
+describe('dwarfSequenceAtTemperature', () => {
+  it("is a type's own row at its temperature, between two rows between them, and the end row past either end", () => {
+    expect(dwarfSequenceAtTemperature(5770)).toEqual({ bMinusV: 0.65, temperatureK: 5770, bolometricCorrectionV: -0.085, gMinusV: -0.165 });
+    expect(dwarfSequenceAtTemperature(3615).bolometricCorrectionV).toBeCloseTo(-1.51, 6);
+    expect(dwarfSequenceAtTemperature(50000).temperatureK).toBe(31400);
+    expect(dwarfSequenceAtTemperature(1000).temperatureK).toBe(2420);
+  });
 });