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NORMAL STARS SPECTRA


Spectral classes:

O - B - A - F - G - K - M


Type F stars
Stars of this spectral class encompass a temperature range that goes from 7000 to 9000 K.
Class F stars can be considered in transition between the hot and cold stars infact many physical properties changes abruptly along F spectral class.
As an example, the rotation speed goes from few Km/sec for G-K-M cold stars to 100 Km/sec for A stars.
Moreover the main termonuclear reaction became the C-N-O where carbon plays the role of catalyst, while in colder classes, the main termonuclear reaction is the direct fusion of hydrogen (proton-proton reaction).
Thus it should be no surprise if the main instability region of the HR diagram - the cepheid stripe - lies within the F region.

Among the more representative dwarfs:
g Vir (F0 V), p 3 Ori , n And (F8 V)

Among the giants:
z Leo (F0 III), b Cas (F2 III), d Gem (F2IV), Procyon (F5 IV), 50 And (F8 IV)

Among the supergiants:
Canopo (F0 Ib), e Aur (F0 Ia), a Per (F5 Ia), g Cyg (F8 Ib), r Cas (F8 Ia), Polaris (F8 Ib)

From the spectroscopic point of view, class F stars show spectra filled of lines that comes both from neutral and ionized elements. Among the neutral elements that are more easy to detect we find Fe, Mg and Ca. But the ionized Ca lines (H and K) are also very prominent in the far violet region of the spectrum.
In the spectra of the late F subclasses it is also possible to see the first weak molecular band due to CH.

Picture 1: Spectrum of Sadr ( g Cyg - F8 Ib) between 3800 e 4700 ┼ recorded with 2 ┼ resolution. The spectrum is not corrected for atmospheric transmission and spectrograph spectral response.


Picture 2: Spectrum of Sadr ( g Cyg - F8 Ib) between 4800 e 5700 ┼ recorded with 2 ┼ resolution. The spectrum is not corrected for atmospheric transmission and spectrograph spectral response.


Picture 3: Spectrum of Sadr ( g Cyg - F8 Ib) between 5700 e 6600 ┼ recorded with 2 ┼ resolution. The spectrum is not corrected for atmospheric transmission and spectrograph spectral response.




Goto other spectral classes:

O - B - A - G - K - M





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28/02/2002