Strömgren photometric system (uvby) (sometimes also referred as Strömgren - Crawford photometric system) is four-colour medium-band photometric system (plus H-beta filters) for stellar classification. It was pioneered by the Danish astronomer Bengt Strömgren in 1956 and extended by his colleague the American astronomer David L. Crawford in 1958.
Contents |
u | v | b | y | βnarrow | βwide | |
---|---|---|---|---|---|---|
Peak wavelength (nm) | 350 | 411 | 467 | 547 | 485.8 | 485 |
Half-width (nm) | 30 | 19 | 18 | 23 | 2.9 | 12.9 |
b-y, m1, c1, β
m1 = (v - b) - (b - y)
c1 = (u - v) - (v - b)
β = βnarrow-βwide
y magnitudes are well-correlated with Johnson-Morgan V magnitudes. b-y is sensitive to stellar temperature (measure of Pashen continuum). c1 is sensitive to the surface gravity (measures Balmer discontinuity strength). m1 is sensitive to the metallicity (measure of line blanketing).