3
$\begingroup$

I know the luminosity classes are: Ia-0 ( Hypergiants ), Ia ( bright supergiants ), ... , VII ( white dwarf ).

I also have learned that you can use the presence of absorption lines ( ie. use spectral profiles ) to determine which spectral type a star belongs to: presence of helium lines imply O-type, and Hydrogen lines in A-type, getting fainter as the star gets cooler, etc.

I was told that one can use spectral profiles to determine luminosity class ( Ia-0, Ia, Ib, ... ), that the width of the spectral lines indicate the luminosity class: Ia stars have sharp lines, and V stars have broad lines... How about Ib, II, III, IV, VI, VII?

I mean... how can I distinguish between Ib and II? Given examples of Ia lines and V lines, you can tell whether an additional line is broader or sharper, but then guess that this additional line is Ib, II, III, or IV?

Is there a more concrete method of determining luminosity class from spectral profiles?

Improve this question
$\endgroup$
1
  • 1
    $\begingroup$ By definition, the luminosity class is simply determined by looking at the spectrum closely. There is indeed a (complex, temperature dependent) progression of line width with luminosity class. $\endgroup$
    – ProfRob
    Commented Nov 5, 2015 at 23:05

0

Reset to default

You must log in to answer this question.

Browse other questions tagged .