The specta of B-type stars are dominated by the Balmer lines of hydrogen and lines of neutral Helium, He I.
The Balmer lines strenghten throw the B-type stars into the A-type stars, coming to a maximum for A2 spectral type
The neutral helium lines strengthen through the O-type stars, come to a maximum at a spectral type of B2 and then weaken, finaly disappearing at a spectral type of about A0
Parameters for the B-type stars of the main sequence
|
Mass |
Radius |
Temperature |
Luminosity |
Main sequence |
High range |
2.4 |
1.55 |
7100 K |
|
|
Low range |
1.6 |
1.87 |
9700 K |
|
|
|
|
Plank curve for T = 20000 K and T = 10500 K |
Comparison of radius of extreme B-type main stars (blue) and Sun (Orange) |
Peculiars A-Type stars :
Helium anomalies |
Helium strong stars |
HeI strong |
Sigma Ori E Delta Ori C |
Photometric and spectroscopic variations of the ordrer of days |
Helium weak Stars |
HeI weak + unusual strenghts of ceratin metalic lines (Si II, ...) |
|
|
Emission lines |
Be Stars |
Emission of one or more Balmer lines
|
|
|
B[e] Stars |
Forbidden emission lines [FeII] and [OI] |
|
|