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II/24 H-alpha Photometry of Northern Late-Type Stars I. (Peat 1964)
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Beginning of ReadMe :II/24 H-alpha Photometry of Northern Late-Type Stars I. (Peat 1964)
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H-alpha Photometry of Late-Type Stars. I.
F-, G- and K-Type Stars North of the Equator
Peat D.W.
<Mon. Not. R. Astron. Soc., 128, 435 (1964)>
=1964MNRAS.128..435P
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ADC_Keywords: Photometry, H-alpha; Stars, late-type; Stars, dwarfs
Description:
Observations are presented of the strength of the H-alpha absorption
line in the spectra of approximately 600 northern F, G and K stars of
differing luminosities and chemical compositions. Most of the stars in
this catalogue were previously observed by Griffin and Redman
(1960MNRAS.120..287G), Deeming (1960MNRAS.121...52D), and Griffin
(1961MNRAS.122..181G). Data given in this catalog include HD number,
MK spectral classification, high velocity, (B-V) color index,
magnesium b ratio, sodium D line ratio and H-alpha ratio.
Introduction: (Peat, 1964)
The integrated light-intensity within a band defined by the wavelength
limits 6545-6580A, centered on the wavelength of H-alpha, was
measured by one photomultiplier. The combined integrated light
intensity within the two comparison regions defined respectively by
the wavelength limits 6477.5 to 6495.0A and 6630.0 to 6647.5A was
measured by a second photomultiplier. The wavelengths were monitored
using the bright neon emission at lambda 6402 produced by a neon
discharge tube, and were held constant to within +-0.5A. Errors of the
order of +- 2A in the wavelength setting, however, were found
experimentally to have no effect on the results, and corrections for
the Doppler shift due to the stellar radial velocity were therefore
unnecessary.
The "H-alpha ratio" R, was defined by the expression R =
[B/B(L)]/[A/A(L)] where B, A represent the photomultiplier output
counts for a star, in the side bands and H-alpha band respectively,
and B(L), A(L) represent the corresponding counts for the lamp. One
might expect this ratio to be partially determined by features, other
than H-alpha, situated within the central and comparison regions of
the stellar spectrum, but examination of a high resolution spectrogram
of Arcturus (a K2 giant star typical of the stars on the observing
program) taken by Griffin (1962) showed that these other features
affected the H-alpha ratio by less than 0.3%. This is only of the
same order as the estimated observational error in the H-alpha
ratios, and we shall assume therefore that the H-alpha ratio is
determined solely by the strength of the H-alpha absorption line.
Griffin (1961MNRAS.122..181G) describes the three-channel
spectrophotometer with which observations were made at the coude focus
of the Cambridge Observatory 36 in reflecting telescope. Griffin and
Redman (1960MNRAS.120..287G), Deeming (1960MNRAS.121...52D), and
Griffin (1961MNRAS.122..181G) describe the method of Observation and
reduction.