1980A&AS...42..283N

Nicolet (1980)

B0

A0F0

G0

K0

M0

B5

Color-Color Diagrams

U−B is sensitive to Hydrogen in n = 2 state (eg, A stars).

N = ~ 40,000 starsphotoelectric mags.

ASTR 511/O’Connell Lec 15 4

Location of the UBV Filters (Johnson & Morgan 1953)

1980A&AS...42..283N

Nicolet (1980)

A0

B0

F0

G0

B0

A0F0

G0

K0

M0

B5

Color-Color Diagrams

U−B is sensitive to Hydrogen in n = 2 state (eg, A stars).

Dust displaces data points along reddening vector.

Q = (U−B) − 0.72 (B−V)

Reddening-independent index:

N = ~ 40,000 starsphotoelectric mags.

(Supergiants are different b/cnarrow lines block less light.)

Can remove reddening effects for O and early B stars.