The Strömgren photometric system, abbreviated also as
uvbyβ or simply
uvby, and sometimes referred as Strömgren - Crawford
photometric system
In astronomy, a photometric system is a set of well-defined passbands (or optical filters), with a known sensitivity to incident radiation. The sensitivity usually depends on the optical system, detectors and filters used. For each photometric sy ...
, is a four-colour medium-
passband
A passband is the range of frequencies or wavelengths that can pass through a filter. For example, a radio receiver contains a bandpass filter to select the frequency of the desired radio signal out of all the radio waves picked up by its antenn ...
photometric system
In astronomy, a photometric system is a set of well-defined passbands (or optical filters), with a known sensitivity to incident radiation. The sensitivity usually depends on the optical system, detectors and filters used. For each photometric sy ...
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
In astronomy, extinction is the absorption and scattering of electromagnetic radiation by dust and gas between an emitting astronomical object and the observer. Interstellar extinction was first documented as such in 1930 by Robert Julius Trump ...
.
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
:
Indices
There are four main highly applied and technical indices: (b−y); m
1; c
1; and β.
m
1 = (v−b) − (b−y)
c
1 = (u−v) − (v−b)
β = β
narrow−β
wide
Where;
y magnitudes are well-correlated with
Johnson-Morgan V magnitudes (its V band).
(
b−
y) is sensitive to stellar
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer.
Thermometers are calibrated in various Conversion of units of temperature, temp ...
(measure of
Paschen continuum).
c
1 is sensitive to the
surface gravity
The surface gravity, ''g'', of an astronomical object is the gravitational acceleration experienced at its surface at the equator, including the effects of rotation. The surface gravity may be thought of as the acceleration due to gravity experien ...
(measures
Balmer discontinuity strength).
m
1 is sensitive to the
metallicity (measure of
line blanketing).
See also
*
Photometric system
In astronomy, a photometric system is a set of well-defined passbands (or optical filters), with a known sensitivity to incident radiation. The sensitivity usually depends on the optical system, detectors and filters used. For each photometric sy ...
s
*
Stellar classification
References
External links
The Asiago Database on Photometric SystemsStromgren photometric system tutorialSAGA: Strömgren survey for Asteroseismology and Galactic Archaeology
{{DEFAULTSORT:Stromgren photometric system
Photometric systems