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Table 2
Properties of spectral indices.
| Index | Description | Indicator type |
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| μ1 − μ7 | TiO and CaH bands | Teff late-type (μ7 also log g) |
| αw | Hα wings | Teff early-type, CTTS if αw> 1.1 |
| αc | Hα core | chromospheres |
| βt | metal line “quintet” λλ6493 − 6500 | Teff intermediate type |
| β c | low-gravity “quintet” lines | log g |
| ζ 1 | Fe I lines λλ 6625–6635 | Teff intermediate type |
| γ 1 | low-gravity lines λλ 6758–6776 | log g |
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| μ | 0.25(μ1 + μ3 + μ5 + μ7) | Teff late-type |
| β | 1 − βc/βt | log g |
| τ | min(αw,1) − βt − ζ1 + 3 × μ | Teff all types |
| γ | β + γ1 | log g all types |
| ζ | ζ1 − βt | metallicity |
| ζ r | ζ/Z(τ) | Teff-corrected metallicity |
| γ ′z |
|
Teff- and z-corrected gravity |
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