The Peat photometric system

Basic Reference

Peat D.W. 1964, MNRAS 128, 435

Abstract

Observations are presented of the strength of the Halpha line the spectra of approximately 600 northern stars of spectral types G and K. High velocity giant stars have systematically stronger Halpha absorption than low velocity giant stars of the same magnesium b line strength, and this result is ascribed to metal deficiency in the high velocity stars. At spectral types later than G0, reduction of metal content reduces the opacity and so strengthens the core of the Halpha absorption; pressure broadening mechanisms have little effect on the Halpha profile in late-type giant stars. Similarly, G and K supergiants have stronger Halpha than giants of the same effective temperature. The sodium D lines are shown theoretically to be independent of luminosity in K type giants and supergiants, and the Halpha-Na D diagram shows a separation of giants from supergiants. The spectral classification of the MKK standard star, gamma Draconis, is rediscussed in terms of this result. The importance of a classification parameter, independent of metal abundance for late-type stars, is emphasized.

Content

Access to the data and references

Asiago Database on Photometric System (ADPS)

Peat realisation
I. Census parameters for 167 photometric system
II. Band and reddening parameters

Andrews realisation
I. Census parameters for 167 photometric system
II. Band and reddening parameters

Indices and Parameters

Ralpha

Ralpha = (B / BL) / (A / AL)

where B and A are the output for the side band and Halpha, and BL and AL the corresponding fluxes for the lamp.

Filters

The integrated light intensity within a band defined by the wavelength limits 6545-6580 Å. centered on Halpha was measured on one photomultiplier (A). The combined integrated light-intensity within the two comparison regions defined repsectively by the wavelength limits 6477.5 to 6495.0 Å and 6630.0 to 6647.5 Å was measured by a second photomultiplier (B).

Photomultipliers

EMI 9558A
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Jean-Claude.Mermilliod@obs.unige.ch
Last update: 21 May 1996
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