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/stellar.spec.ts

@@ -160,9 +160,10 @@ describe('effectiveTemperatureK', () => {
   });
 
   it('reads a colour past the table at its end where there is no type, and the type where there is', () => {
-    // An ultracool dwarf redder than M8.5, a white dwarf bluer than B9, and an O star B−V puts at B0.
+    // An ultracool dwarf redder than M8.5, a white dwarf bluer than B9 at the 19 012 K Gentile
+    // Fusillo et al. (2021) measure at its colour, not B9's 10 700, and an O star B−V puts at B0.
     expect(effectiveTemperatureK({ magnitude: 14.005, distancePc: 4.005, spectralType: 'Unknown', magnitudeBand: 'G', colorIndex: 5.113, colorSystem: 'BP-RP' })).toBe(2420);
-    expect(effectiveTemperatureK({ magnitude: 14, distancePc: 25, spectralType: 'Unknown', magnitudeBand: 'G', colorIndex: -0.25, colorSystem: 'BP-RP' })).toBe(10700);
+    expect(effectiveTemperatureK({ magnitude: 14, distancePc: 25, spectralType: 'Unknown', magnitudeBand: 'G', colorIndex: -0.25, colorSystem: 'BP-RP' })).toBeCloseTo(19012, 6);
     expect(effectiveTemperatureK({ magnitude: 7, distancePc: 121, spectralType: 'O8', colorIndex: -0.31, colorSystem: 'B-V' })).toBe(31400);
     // HD 49748, G5 V at B−V −0.32: the colour is the one that is wrong.
     const g5 = effectiveTemperatureK({ magnitude: 9, distancePc: 184, spectralType: 'G5V', colorIndex: null })!;
@@ -184,6 +185,15 @@ describe('radiusFromLuminositySolar', () => {
     expect(radius / 0.104).toBeLessThan(1.2);
   });
 
+  it('gives a white dwarf bluer than the table the radius its mass and gravity give', () => {
+    // Gaia DR3 6791196382856581376, 24.5 pc: 19 205 K, log g 8.07 and 0.66 M☉ in Gentile Fusillo et
+    // al. (2021), so 0.01245 R☉. At B9's 10 700 K it came out about 1.5 times that.
+    const star = { magnitude: 12.9198, distancePc: 24.5237, spectralType: 'Unknown', magnitudeBand: 'G', colorIndex: -0.2539, colorSystem: 'BP-RP' } as const;
+    const radius = radiusFromLuminositySolar(luminositySolar(star)!, effectiveTemperatureK(star)!);
+    expect(radius / 0.01245).toBeGreaterThan(1 / 1.2);
+    expect(radius / 0.01245).toBeLessThan(1.2);
+  });
+
   it('gives Sirius and TRAPPIST-1 their published radii from colour and brightness alone', () => {
     // 1.711 R☉ (Liebert et al. 2005) and 0.119 R☉ (Agol et al. 2021), each to within a fifth.
     for (const [star, published] of [