A system of intermediate-band photometry in which the names, wavelengths, and bandwidths of the filters are: u, 352 and 31 nm; v, 410 and 17 nm; b, 469 and 18 nm; and y, 548 and 23 nm. Strömgren photometry is often supplemented by two interference filters to measure the strength of the Hβ line (see hydrogen spectrum). They share the same central wavelength of 486 nm, but have different bandwidths of 15 and 3 nm. The difference in the two magnitudes is the Hβ index, symbol β. The different colours can be combined to determine the temperature, luminosity, and reddening of stars of spectral types O and B. The metallicity can also be determined for stars of spectral types A and F. The system is named after its originator, B. G. D. Strömgren.
Subjects: Astronomy and Astrophysics.