Strömgren photometric system

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.

Mean wavelength and half-widths of response functions

	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

Indices

b-y, m₁, c₁, β

m₁ = (v - b) - (b - y)

c₁ = (u - v) - (v - b)

β = β_narrow-β_wide

y magnitudes are well-correlated with Johnson-Morgan V magnitudes. b-y is sensitive to stellar temperature (measure of Paschen continuum). c₁ is sensitive to the surface gravity (measures Balmer discontinuity strength). m₁ is sensitive to the metallicity (measure of line blanketing).

See also

• Stellar classification

References

• Strömgren, Bengt, 1956, Two-dimensional spectral classification of F stars through photoelectric photometry with interference filters, Vistas in Astronomy, Vol. 2, Issue 1, pp. 1336–1346
• Crawford, David L., 1958, Two-Dimensional Spectral Classification by Narrow-Band Photometry for B Stats in Clusters and Associations, Astrophysical Journal, Vol. 128 (September 1958), pp. 185–206

External links

• The Asiago Database on Photometric Systems
• The uvby photometric system
• Stromgren photometric system tutorial
• SAGA: Strömgren survey for Asteroseismology and Galactic Archaeology