Is there any way you can tell if a star is either hydrogen shell burning or helium burning in its core (entered the horizontal branch or blue loop)

[kingsbishop]

Hello I am wondering is there a way you can tell by using the spectral class of a star or any other way I can find out if a star has entered the horizontal branch or blue loop phase or if it’s on the hydrogen shell burning phase or if it’s on the top or bottom line of the horizontal branch or blue loop phase?

[dan_adi]

6 hours ago, kingsbishop said:

Hello I am wondering is there a way you can tell by using the spectral class of a star or any other way I can find out if a star has entered the horizontal branch or blue loop phase or if it’s on the hydrogen shell burning phase or if it’s on the top or bottom line of the horizontal branch or blue loop phase?

I guess looking at the spectra of the star should give this information