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 s ...
, is a four-colour medium-
passband
A passband is the range of frequency, frequencies or wavelengths that can pass through a Filter (signal processing), filter. For example, a radio receiver contains a bandpass filter to select the frequency of the desired radio signal out of all t ...
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 s ...
plus Hβ (H-beta) filters for determining magnitudes and obtaining
spectral classification
''Spectral'' is a 2016 Hungarian-American military science fiction action film co-written and directed by Nic Mathieu. Written with Ian Fried & George Nolfi, the film stars James Badge Dale as DARPA research scientist Mark Clyne, with Max M ...
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
and
filters
without the effects of reddening, termed
and
.
Wavelength and half-width response functions
The 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).
Indices
There 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
Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...
(measure of
Paschen continuum).
*
is sensitive to the
surface gravity (measures
Balmer discontinuity strength).
*
is sensitive to the
metallicity
In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matt ...
(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 s ...
s
*
Stellar classification
In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction gratin ...
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