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III/169A Photometric Atlas of Procyon for 314-747 nm (Griffin+ 1979)
The following files can be converted to FITS (extension .fit .fgz or .fiZ)
procyon.dat
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Beginning of ReadMe :III/169A Photometric Atlas of Procyon for 314-747 nm (Griffin+ 1979)
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A Photometric Atlas of the Spectrum of Procyon (3140 - 7470 Angstroem)
Griffin R.E., Griffin R.
<R. & R. Griffin, publishers, Cambridge, U.K.(1979)>
=1979pmas.book.....G
=1996yCat.3169....0G
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ADC_Keywords: Stars, F-type; Spectrophotometry
Description:
This atlas contains intensities, expressed in terms of the continuum
as 100, in steps of 5 milli Angstroem of the F5 star Procyon. The
spectral range is from 3140 to 7469.995 Angstroems.
Introduction:
The Atlas covers the spectrum of Procyon from 314.0 nm to 747.0 nm.
Spectra from 314.0 nm to 540.0 nm are generally exposed on fourth- and
third-order plates and from 540.0 nm to 747.0 nm mostly on
second-order plates. All wavelengths are in the rest-frame of the
star, i.e., they have been reduced to zero radial velocity.
This is one of three classical spectrophotometric atlasses, the others
being, 'A Photometric Atlas of the Spectrum of Arcturus' (Griffin
1968), and the Utrecht 'Photometric Atlas of the Solar Spectrum'
(Minnaert et al. 1940) which are both only in printed form available.
The Sun and Arcturus are of spectral types G2 and K2 respectively;
Procyon is an F5 type star.
This Atlas is based upon photographic spectrograms obtained at the
coude' spectrograph of the Mount Wilson 100-inch reflector during
three observing seasons.
The instrumental profile is carefully described and illustrated in the
Introduction to the Arcturus Atlas, and applies equally to the present
Atlas. Numerical representations of the central part of the profile at
particular wavelengths in the second and third orders of diffraction
have been published elsewhere (Mackle et al., 1975).
Twenty-eight spectrograms exposed on the Eastman Kodak emulsion IIa,
IIa-D, IIa-F and 103a have been used in the production of the Atlas.
The calibration was done by exposing the plates with either a wedge
slit or a stepped entrance aperture. It provided a calibration curve
spanning 1.7 logarithmic units and defined at intervals of 0.1 unit.
The various slit widths were distributed at random, in an effort to
avoid systematic effects.
The wavelength scale was linearized by interpolation. The wavelengths
used were either those resulting from actual measurement of the
complete plate, or failing that were solar wavelengths adopted from
the catalogue by Pierce and Breckinridge (1973). Individual lines
typically give residuals of the order of 3 milli-Angstroem (=0.0003
nm), and in parts of the Procyon spectrum which have many good lines
the wavelength scale is expected to be accurate to this order of
precision. Inevitably, there may be greater errors in the barren
regions of the spectrum which occur at longer wavelengths.
The continuous spectrum of Procyon appears to be visible throughout
the region covered by this Atlas, at least in the sense that there are
frequent high points lying on, or close to, a common locus. This
continuum has been drawn by eye on the raw intensity plots, and then
normalized to a uniform value of 100.
A substantial difficulty arises with the hydrogen lines and Ca II H
and K owing to their great extent: the lower members of the Balmer
series cover something like 10.0 nm, and the wings of the higher
members overlap to such an extent that the lines effectively merge
into a pseudo-continuum at a wavelength (about 368.0 nm) still well
above the series limit of 364.6 nm. In the wavelength region of
364.6-400.0 nm we have adopted, for the purposes of the Atlas, an
operational definition of the continuum as being the locus of the
maxima of the _local_ continuum drawn in the overlapping wings of the
Balmer lines. In the near-ultraviolet, therefore, the true continuum
must lie far above the Atlas continuum, and moreover it has a large
discontinuity (the Balmer Jump) at 364.6 nm. Proceeding shortwards
from the red, the true continuum probably begins to diverge from the
Atlas value near 400.0 nm, if not before, and to rise increasingly
steeply to a level of perhaps 150-200 per cent in the vicinity of
368.0 nm, a level from which it returns stepwise to the Atlas
continuum at 364.6 nm.
To obtain a good continuum definition near the hydrogen and H and K
lines, a spectrum with a very compressed wavelength scale have been
used. The bridging process is easily accomplished where the lines are
comparatively close together, but difficult for the first four Balmer
lines where the distance to be bridged is of the order of 10.0 nm,
corresponding to 6-10 cm of plate, and for this purpose very high
dispersion is a distinct disadvantage.
The first few pages in this Atlas cover a region of the spectrum where
telluric ozone absorption is increasing rapidly towards shorter
wavelengths -- indeed, for ground-based observers the absorption
becomes effectively infinite only 20.0 nm beyond the shortward limit
of the Atlas. The onset of ozone absorption is not smooth, but seems
to include bands, typically several Angstroems (0.1nm) wide and of
irregular profiles, where the absorption is several per cent greater
than would be expected on the basis of interpolation on a smooth
curve. The bands are too narrow, and the data on their character too
scarce, for the continuum to be corrected for their presence: the
continuous spectrum used in normalizing the Atlas tracings has simply
been bridged, in this region just as elsewhere, between local maxima
in the observed intensities. Band absorption by ozone is probably
significant for present purposes only below 330.0 nm.
Objects:
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RA (J2000) DE Designations(s) (File)
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07 39 18.1 +05 13 30 Procyon = Alpha CMi = HR 2943 (procyon.dat)
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