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Chapter D. Spectral type coding

The spectral type of a star consists of 4 parts:

• A temperature class, with the following order
  1. Stars with subtypes: from O3 to M9

  2. White dwarfs: DC to DM

  3. Stars without subtypes: from O to M, and R, N, S, C

  4. Composite stars.

• A luminosity class. The possible values are listed below:

          unknown   Ia        Iab-b     II        III/IV    V
          Ia-O      Ia/ab     Ib        II/III    IV        V/VI
          Ia-O/Ia   Iab       Ib-II     III       IV/V      VI
  

• Precisions
  • Inaccuracy on temperature or luminosity class: colon (:) written just after the concerned field.
  • Incompleteness of the Simbad spectral type: ellipsis (...) written at the end of the spectral class. It generally means that additional pecularities (like the list of the enhanced elements, or subtypes of peculiar classes) are not included in the Simbad spectral type.
  • Indication related to the spectrum:
    • Overlap : X
    • Particular source : *
    • Quality : 0 - 7

• Peculiarities

  Each of them is represented by one or more letters placed after temperature and luminosity classes:

       variable spectrum                  :  v
       spectrum with emission lines       :   e
       spectrum interpreted like a
         shell star                       :   sh
       peculiar spectrum                  :   p
           
       spectrum with peculiar profile:      
                             sharp         :    s
                          nebulous         :    n
                     very nebulous         :    nn
             
       spectrum with peculiar elements:  
                       peculiar CN         :    CN
                         weak line         :    w
                    metallic lines         :    m