Class Taxonomy
AstroSpectro classifies stellar spectra into 5 primary classes based on the Harvard spectral classification system.
The five classes
| Class | T_eff range | Key spectral features | LAMOST count |
|---|---|---|---|
| A | 7,500–10,000 K | Strong Balmer absorption, weak Ca II | ~4,000 |
| F | 6,000–7,500 K | Moderate Balmer + Ca II transition | ~8,000 |
| G | 5,200–6,000 K | Strong Ca II H&K, moderate Balmer | ~15,000 |
| K | 3,700–5,200 K | Very strong Ca II, weak Balmer, metals | ~12,000 |
| M | < 3,700 K | TiO molecular bands, very weak Balmer | ~4,000 |
Class boundaries and known confusion
The F/G boundary (5,500–6,200 K) is the primary confusion zone. This is physically expected — the boundary is a continuous transition in stellar atmosphere physics, not a sharp discontinuity. The classifier's F/G confusion is a physically accurate reflection of this continuity, not a failure mode.
See F/G Confusion Analysis for details.
Rare classes (excluded from 5-class model)
The following classes appear in LAMOST DR5 but are excluded from the primary classifier due to insufficient sample size:
- B stars (T_eff > 10,000 K) — rare in LAMOST targeting
- M subdwarfs (sdM) — low surface gravity
- Carbon stars (C) — unusual molecular chemistry
- White dwarfs (DA/DB) — different physical regime