Strömgren photometric system
Strömgren photometric system, abbreviated as uvbyβ or simply uvby, and sometimes referred as Strömgren - Crawford photometric system, is a four-colour medium-passband photometric system plus Hβ (H-beta) filters for determining magnitudes and obtaining spectral classification of stars. Its use was pioneered by the Danish astronomer Bengt Strömgren in 1956 and was extended by his colleague the American astronomer David L. Crawford in 1958.
It is often considered to be a powerful tool and successful investigating the brightness and effective temperature of stars. This photometric system also has a general advantage as it can be used to measure the effects of reddening and interstellar extinction. This system also allows calculation of parameters from the b and y filters (b − y) without the effects of reddening, termed m 1 and c 1.
Wavelength and half-width 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
There are four main indices : (b−y), m1, c1, β
m1 = (v − b) − (b − y)
c1 = (u − v) − (v − b)
β = βnarrow−βwide
- Strömgren, Bengt (1956). "Two-dimensional spectral classification of F stars through photoelectric photometry with interference filters". Vistas in Astronomy. 2 (1): 1336–1346. Bibcode:1956VA......2.1336S. doi:10.1016/0083-6656(56)90060-5.
- Crawford, D.L. (1958). "Two-Dimensional Spectral Classification by Narrow-Band Photometry for B Stats in Clusters and Associations". Astrophysical Journal. 128: 185–206. Bibcode:1958ApJ...128..185C. doi:10.1086/146536.
- Paunxen, E. (2015). "A new catalogue of Strömgren-Crawford uvbyβ photometry". Astronomy and Astrophysics. 580: A23. arXiv:1506.04568. Bibcode:2015A&A...580A..23P. doi:10.1051/0004-6361/201526413.