Strömgren photometric system
title: "Strömgren photometric system" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["photometric-systems"] topic_path: "general/photometric-systems" source: "https://en.wikipedia.org/wiki/Strömgren_photometric_system" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0
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{{cite journal |last=Strömgren|first=Bengt |title=Two-dimensional spectral classification of F stars through photoelectric photometry with interference filters |date=1956 |journal=Vistas in Astronomy |volume=2 |issue=1 |pages=1336–1346 |doi=10.1016/0083-6656(56)90060-5 |bibcode=1956VA......2.1336S}} and was extended by his colleague the American astronomer David L. Crawford in 1958.{{cite journal |last=Crawford|first=D. L. |title=Two-Dimensional Spectral Classification by Narrow-Band Photometry for B Stars in Clusters and Associations |date=1958 |journal=Astrophysical Journal |volume=128 |pages=185–206 |doi=10.1086/146536 |bibcode=1958ApJ...128..185C}}
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.{{cite journal |last=Paunzen|first=E. |title=A new catalogue of Strömgren-Crawford uvbyβ photometry |date=2015 |journal=Astronomy and Astrophysics |volume=580 |pages=A23 |doi=10.1051/0004-6361/201526413 |bibcode=2015A&A...580A..23P |arxiv =1506.04568}} 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
The following table shows the characteristics of each of the filters used (represented colors are only approximate): :{| class="wikitable"
| +Strömgren photometric system filter wavelength and half-width response functions |
|---|
| ! |
| !u |
| !v |
| !b |
| !y |
| !βnarrow |
| !βwide |
| - |
| !Peak wavelength (nm) |
| 350 |
| style="background-color: ; color:#ffffff; text-align:center;" |
| style="background-color: ; color:#ffffff; text-align:center;" |
| style="background-color: ; color:#000000; text-align:center;" |
| style="background-color: ; color:#000000; text-align:center;" |
| style="background-color: ; color:#000000; text-align:center;" |
| - |
| ! align="center" |
| align="center" |
| align="center" |
| align="center" |
| align="center" |
| align="center" |
| align="center" |
| } Note: colors are only approximate and based on wavelength to sRGB representation (when possible). |
Indices
There are four main highly applied and technical indices: (b-y); m_1; c_1; and \beta.
- m_1 = (v-b) - (b-y)
- c_1=(u-v) - (v-b)
- \beta = \beta_{narrow} - \beta_{wide}
Where;
- y magnitudes are well-correlated with Johnson-Morgan V magnitudes (its V band).
- (b-y) is sensitive to stellar temperature (measure of Paschen continuum).
- c_1 is sensitive to the surface gravity (measures Balmer discontinuity strength).
- m_1 is sensitive to the metallicity (measure of line blanketing).
References
References
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