The Washington photometric system
Basic Reference
Canterna R. 1976, Astron. J. 81, 228
Abstract
A new broad-band photometric system C, M, T1, T2 was developed specifically to
obtain accurate temperatures, metal abundances, and a CN index for G and K
giants. This new system is more efficient than the UBVRI system. The
temperature index T1-T2 is a linear function of R-I. Metal abundances derived
from the index delta (M-T1) are uncertain by a factor of 2. The system is
capable of separating the effects of blanketing by the molecular CN band
system from those of the metallic lines in the ultraviolet. A cyanogen band
index delta I(CN) can distinguish between strong CN stars (CN +3, +2) and
weak CN stars (CN -3, -2) for giants with [Fe/H] > 1.0. Delta I(CN) has been
found to be linearly related to the DDO CN band strength index delta Cm.
Observations of M67 giants and several SMR giants show that (I) M67 is
slightly metal deficient compared to normal and not super metal rich, and (2)
the large ultraviolet deficiencies of SMR stars are a result of a slight
enrichment of metals and anomalously strong CN bands. Finally, the
applicability of the C, M, T1, T2, system for abundance studies of G-type
dwarfs is promising. The indices delta (M-T1) and delta (C-M) are
monotonically related to delta (U-B) for G-type dwarfs and the temperature
index is less sensitive to blanketing than B-V or V-r. The effects of
reddening and luminosity on the parameters delta (M-T1) and delta I(CN)
are discussed.
Content
Access to the data and references
Asiago Database on Photometric System (ADPS)
Indices and Parameters
V, C-M, M-T1, V-T1, M51
Filters
- C : 4 mm Corning CS-7-59 + 2.5 mm 80% CuSO4-H2O
- Effective wavelength : 3910Å ; Width : 1100Å
- M : 3 mm Schott GG455 + 5 mm Corning CS-4-96
- Effective wavelength : 5085Å ; Width : 1050Å
- T1 : 1.5 mm Schott BG38 + 3mm Schott OG 590
- Effective wavelength : 6330Å ; Width : 800Å
- T2 : 3 mm Schott RGN 9
- Effective wavelength : 7885Å ; Width : 1400Å
Photomultiplier
RCA C31034 Ga-As
Calibrations
The calibrations have been revised
recently.
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commentsto epaunzen@physics.muni.cz
epaunzen@physics.muni.cz
Last update: 13 September 2002