The Strömgren photometric system, abbreviated also 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[1] and was extended by his colleague the American astronomer David L. Crawford in 1958.[2]
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.[3] This system also allows calculation of parameters from the and filters without the effects of reddening, termed and .[3]
Wavelength and half-width response functions
editThe following table shows the characteristics of each of the filters used (represented colors are only approximate):
Note: colors are only approximate and based on wavelength to sRGB representation (when possible).[4]Strömgren photometric system filter 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
Indices
editThere are four main highly applied and technical indices: ; ; ; and .
Where;
- magnitudes are well-correlated with Johnson-Morgan V magnitudes (its V band).
- is sensitive to stellar temperature (measure of Paschen continuum).
- is sensitive to the surface gravity (measures Balmer discontinuity strength).
- is sensitive to the metallicity (measure of line blanketing).
See also
editReferences
edit- ^ 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 Stars in Clusters and Associations". Astrophysical Journal. 128: 185–206. Bibcode:1958ApJ...128..185C. doi:10.1086/146536.
- ^ a b Paunzen, 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.
- ^ "Light wavelength to RGB Converter". www.johndcook.com. Retrieved 2023-07-28.
