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Author name code: wilson-olin
ADS astronomy entries on 2022-09-14
author:"Wilson, Olin C."
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Title: VizieR Online Data Catalog: Ca II H and K Measurements Made
at MWO (Duncan+ 1991)
Authors: Duncan, D. K.; Vaughan, A. H.; Wilson, O. C.; Preston,
G. W.; Frazer, J.; Lanning, H. H.; Misch, A.; Mueller, J.; Soyumer,
D.; Woodard, L.; Baliunas, S. L.; Noyes, R. W.; Hartmann, L. W.;
Porter, A.; Zwaan, K.; Middelkoop, F.; Rutter, R.; Mihalas, D.
2005yCat.3159....0D Altcode:
Summaries are presented of the photoelectric measurements of stellar
CaII H and K line intensity made at Mount Wilson Observatory during
the years 1966-1983. These results are derived from 65,263 individual
observations of 1296 stars. For each star, for each observing season,
the maximum, minimum, mean, and variation of the instrumental H and
K index "S" are given, as well as a measurement of the accuracy of
observation. A total of 3110 seasonal summaries are reported. <P />These
observations were obtained with two instruments, HKP-1 and HKP-2. The
HKP-2 instrument is a four-channel chopping spectrometer which records
counts in 1.09{AA} FWHM triangular bandpasses centered in the H and
K lines as well as in two 20{AA} reference bandpasses centered on
3901.067 and 4001.067{AA}. The stellar activity is expressed by the
index S defined as <P />S = {alpha} (Nh+Nk)/(Nr+Nv) <P />where Nh and
Nk are the counts (corrected from background) in the H and K lines,
Nr and Nv those in the reference continuum bandpasses, and {alpha}
is a constant of proportionality used to correct for night-to-night
instrumental variations. Higher values of S generally correspond to
higher levels of chromospehric activities. <P />Factors which effect the
ability to detect stellar activity variations and accurately measure
their amplitudes such as the accuracy of the H and K measurements and
scattered light contamination are discussed. Relations are given which
facilitate intercomparison of "S" values with residual intensities
from ordinary spectrophotometry, and for converting measurements to
absolute fluxes. <P />(1 data file).
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Title: Chromospheric Variations in Main-Sequence Stars. II.
Authors: Baliunas, S. L.; Donahue, R. A.; Soon, W. H.; Horne, J. H.;
Frazer, J.; Woodard-Eklund, L.; Bradford, M.; Rao, L. M.; Wilson,
O. C.; Zhang, Q.; Bennett, W.; Briggs, J.; Carroll, S. M.; Duncan,
D. K.; Figueroa, D.; Lanning, H. H.; Misch, T.; Mueller, J.; Noyes,
R. W.; Poppe, D.; Porter, A. C.; Robinson, C. R.; Russell, J.; Shelton,
J. C.; Soyumer, T.; Vaughan, A. H.; Whitney, J. H.
1995ApJ...438..269B Altcode:
The fluxes in passbands 0.1 nm wide and centered on the Ca II H
and K emission cores have been monitored in 111 stars of spectral
type F2-M2 on or near the main sequence in a continuation of an
observing program started by O. C. Wilson. Most of the measurements
began in 1966, with observations scheduled monthly until 1980, when
observations were scheduled sevral times per week. The records, with
a long-term precision of about 1.5%, display fluctuations that can be
identified with variations on timescales similar to the 11 yr cycle of
solar activity as well as axial rotation, and the growth and decay of
emitting regions. We present the records of chromospheric emission and
general conclusions about variations in surface magnetic activity on
timescales greater than 1 yr but less than a few decades. The results
for stars of spectral type G0-K5 V indicate a pattern of change in
rotation and chromospheric activity on an evolutionary timescale, in
which (1) young stars exhibit high average levels of activity, rapid
rotation rates, no Maunder minimum phase and rarely display a smooth,
cyclic variation; (2) stars of intermediate age (approximately 1-2
Gyr for 1 solar mass) have moderate levels of activity and rotation
rates, and occasional smooth cycles; and (3) stars as old as the Sun
and older have slower rotation rates, lower activity levels and smooth
cycles with occasional Maunder minimum-phases.
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Title: CA II H and K Measurements Made at Mount Wilson Observatory,
1966--1983
Authors: Duncan, Douglas K.; Vaughan, Arthur H.; Wilson, Olin C.;
Preston, George W.; Frazer, James; Lanning, Howard; Misch, Anthony;
Mueller, Jean; Soyumer, David; Woodard, L.; Baliunas, Sallie L.;
Noyes, Robert W.; Hartmann, Lee W.; Porter, Alain; Zwaan, Cornelis;
Middelkoop, Frans; Rutten, Rene G. M.; Mihalas, Dimitri
1991ApJS...76..383D Altcode:
Summaries are presented of the photoelectric measurements of stellar
Ca II H and K line intensity made at Mount Wilson Observatory during
the years 1966-1983. These results are derived from 65,263 individual
observations of 1296 stars. For each star, for each observing season,
the maximum, minimum, mean, and variation of the instrumental H and
K index 'S' are given, as well as a measurement of the accuracy of
observation. A total of 3110 seasonal summaries are reported. Factors
which affect the ability to detect stellar activity variations and
accurately measure their amplitudes, such as the accuracy of the H and K
measurements and scattered light contamination, are discussed. Relations
are given which facilitate intercomparison of 'S' values with residual
intensities derived from ordinary spectrophotometry, and for converting
measurements to absolute fluxes.
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Title: Ca II H and K Flux Monitoring in Cool Stars: Rotation and
Activity Cycles
Authors: Robinson, C. R.; Baliunas, S. L.; Bennett, W.; Briggs, J.;
Frazer, J.; Noyes, R. W.; Shelton, C.; Woodard, L.; Vaughan, A. H.;
Wilson, O. C.
1989BAAS...21.1115R Altcode:
No abstract at ADS
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Title: The Mount Wilson Observatory HK Project: The Continuing
Analysis of Rotation and Stellar Magnetic Cycles
Authors: Baliunas, S. L.; Bennett, W.; Briggs, J.; Frazer, J.; Noyes,
R. W.; Robinson, C. R.; Shelton, C.; Woodard, L.; Vaughan, A. H.;
Wilson, O. C.
1988BAAS...20Q.994B Altcode:
No abstract at ADS
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Title: Stellar Activity Cycles and Rotation in Cool Stars Observed
from Mt. Wilson Observatory
Authors: Baliunas, S. L.; Briggs, J.; Frazer, J.; Noyes, R. W.;
Robinson, C. R.; Carroll, S.; Donahue, R. A.; Shelton, C.; Woodard,
L.; Vaughan, A. H.; Wilson, O. C.
1988BAAS...20Q.697B Altcode: 1988BAAS...20Z.697B
No abstract at ADS
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Title: Recognition and classification of strong-CN giants.
Authors: Keenan, Philip C.; Yorka, Sandra B.; Wilson, Olin C.
1987PASP...99..629K Altcode:
Fifty of the stars designated as super-metal-rich by Spinrad and
Taylor (1969) are classified here on the Revised MK System. Positive
CN indices are assigned in recognition of the characteristic excesses
of carbon and nitrogen in their atmospheres, as compared to normal
Population I stars. For only a few of the stars, an abnormal strength
of the iron lines or of Ca 4226 A is so noticeable that they need to
be distinguished by positive indices for these metals.
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Title: Activity Cycles of Lower Main-Sequence Stars: Eighteen Years
of Research
Authors: Baliunas, S. L.; Donahue, R. A.; Horne, J. H.; Noyes, R. W.;
Porter, A.; Gilliland, R.; Duncan, D. K.; Frazer, J.; Lanning, H.;
Misch, A.; Mueller, J.; Soyumer, D.; Vaughan, A. H.; Wilson, O. C.;
Woodard, L. A.
1984BAAS...16R.899B Altcode:
No abstract at ADS
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Title: Photoelectric measures of chromospheric H and K and He in
giant stars.
Authors: Wilson, O. C.
1982ApJ...257..179W Altcode:
The coude scanner of the 100-inch telescope was used to measure
the fluxes at the centers of H and K of Ca II and at the position of
H-epsilon, and its antiposition, in about 200 late-type giant stars. For
the large majority of class III giants, it was found that the total
chromospheric radiation of H and K and of H-epsilon is constant in
amount for G8 to early M-type stars with respect to the energy in
the V band, and that the two Ca II lines together emit about three
times as much energy as does H-epsilon. In the Hyades main sequence
the efficiency of the transfer of energy from the total outflow
into the chromosphere increases from the bluer to the redder stars,
whereas the converse is true in the normal giants. Evidence is given
that main-sequence stars with H and K emission also have emission
in H-epsilon that is considerably weaker, with respect to H and K,
than in the giants.
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Title: Activity Cycles in Other Stars
Authors: Wilson, O.; Vaughan, A.; Kraft, R.; Preston, G.
1981S&T....62..312W Altcode:
No abstract at ADS
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Title: The activity cycles of stars.
Authors: Wilson, O. C.; Vaughan, A. H.; Mihalas, D.
1981SciAm.244b..82W Altcode: 1981SciAm.244...82W
No abstract at ADS
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Title: The activity cycles of stars
Authors: Wilson, O. C.; Vaughan, A. H.; Mihalas, D.
1981SciAm.244b.104W Altcode: 1981SciAm.244..104W
The activity cycle of the sun is reviewed with attention to the
contributions of Galileo, Schwabe, Wolf, Maunder, Carrington, Hale,
Babcock and Parker. The use of the H-K photometer in the observation of
the chromospheric variability of 91 sun-like stars at the Mount Wilson
Observatory is discussed. It is estimated that more than half of the
main-sequence stars less massive than 1.5 solar masses may show cyclic
behavior. The chromospheric variations for 12 sunlike stars are given.
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Title: Stellar Spectroscopy - Stellar Chromospheres - Magnetic
Ap-Star - Dwarf Novae - Variable Stars
Authors: Wilson, O.; Vaughan, A.; Preston, G.; Wolff, S. C.; Borne, K.;
Wade, R.; Greenstein, J.; Schneider, D. P.; Mochnacki, S.; Oke, J. B.
1979haob.rept..724W Altcode:
No abstract at ADS
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Title: Chromospheric variations in main-sequence stars.
Authors: Wilson, O. C.
1978ApJ...226..379W Altcode:
An analysis is given of fluxes measured in 1-A bands centered on the Ca
II H and K lines for a sample of 91 main-sequence stars, extending from
about F5 to M2, over time intervals of nine to 11 years. The results are
discussed separately for a set of 18 stars with minimal chromospheric
fluxes used as standards, the program stars of spectral types F7 to G3,
the program stars of types G5 and later, as well as the sun. K/H ratios
are determined and compared for the different groups of stars. It is
tentatively concluded that: (1) no stellar chromospheres are likely
to be constant in time; (2) short-term fluctuations tend to increase
in size with average flux; (3) cyclical variations occur with periods
ranging from about 7 years to probably at least twice as long; (4) the
stellar cycles observed in H and K flux should be regarded as evidence
for analogs of the solar cycle; and (5) the incidence of complete or
probable partial cycles increases toward later spectral types.
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Title: Flux measurements of Ca II and K emission.
Authors: Vaughan, A. H.; Preston, G. W.; Wilson, O. C.
1978PASP...90..267V Altcode:
A four-channel photon-counting spectrophotometer (designated HKP-2)
is described which is designed for measuring stellar chromospheric
calcium emission. The HKP-2 is calibrated, and its performance and
accuracy evaluated, by observing 63 of Wilson's (1968) program stars
on the same nights with both the HKP-2 and a coude scanner designated
HKP-1. The results of the observations are discussed in terms of
the calibration of mean H-K flux indices, variations in individual
stellar fluxes, the flux ratio for H and K, and the instrument color
index. It is shown that the HKP-2 provides satisfactory performance in
the measurement of stellar chromospheric emission in a manner closely
analogous to the method of Wilson and that a single observation yields
a color index as well as flux indices for H and K that can be calibrated
and transferred unambiguously to Wilson's system of measurement.
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Title: Stellar chromospheres for fun and profit.
Authors: Wilson, O. C.
1977BAAS....9..585W Altcode:
No abstract at ADS
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Title: Effects of heavy element abundance on spectroscopic
luminosities of G5 - K0 giants.
Authors: Keenan, P. C.; Wilson, O. C.
1977ApJ...214..399K Altcode:
Spectral classification has been carried out on coude' spectrograms
(9 A mm -1) for 13 semibarium stars (stars with slight excesses of
heavy metals) and for two barium stars. The luminosity classes assigned
from ratios of lines of iron-peak elements should be independent of
chemical composition. These luminosity classes place the observed
semibarium stars on, or very slightly above, the main giant sequence,
in agreement with the K-line absolute magnitudes. The two barium stars
(o Vir and HD 205011) are also typical giants in luminosity. Subject
headings: stars: abundances - stars: late-type - stars: luminosities
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Title: Absolute magnitudes of stars from widths of chromospheric Ca
II emission lines.
Authors: Wilson, O. C.
1976ApJ...205..823W Altcode:
Absolute magnitudes of about 700 late-type subgiants, giants, and
supergiants are derived from measures of the widths of the chromospheric
emission components of the Ca ii K line. They are tabulated along
with other pertinent information. The data are essentially complete
for all suitable stars down to m = 5.0 and declination 250. The moduli
derived from the Mv(K) are plotted against the trigonometric parallaxes
for all stars for which the latter have weights >20. It is found
that there is a systematic difference in the fit to the m - M = -s -
5 log curve for stars with b < 250 compared to those with b >
250. Since the numbers of stars in these two groups are equal, the
difference is believed to originate with the parallaxes. Estimates
against nearby Fe i lines have been made for the strength of Sr ii
A4077, which is a luminosity criterion for these stars. When the
logarithms of the A4077 intensities are plotted against the Mv(K),
the bulk of the stars in the diagram fall approximately along a linear
relationship. However, there is a group of stars between Mv(K) =
+1.5 and -3 for which the estimated A4077 intensities are too strong,
compared to the average for the other stars, by amounts well in excess
of the errors of estimation. Further investigation indicates that the
G-K stars in this group are probably barium stars, but M-type stars
also participate in the Sr ii anomaly. The color-magnitude diagram
constructed from the Mv(K) has several interesting features which are
discussed in the text. In particular, the C-M diagram of NGC 188 by
Sandage forms an excellent lower boundary to the assemblage of field
stars. Subject headings: Ca ii emission - stars: late-type - stars:
luminosities
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Title: Chromospheric Variations in Main Sequence Stars
Authors: Wilson, O. C.
1976IAUS...71..447W Altcode:
No abstract at ADS
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Title: Ira S. Bowen (1898-1973)
Authors: Wilson, O. C.
1973S&T....45..212W Altcode:
No abstract at ADS
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Title: Summary
Authors: Wilson, O. C.
1973NASSP.317..305W Altcode: 1973stch.coll..305W; 1973IAUCo..19..305W
No abstract at ADS
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Title: I. S. Bowen 1898 - 1973 Februar 6th.
Authors: Wilson, O. C.
1973S&T....45R.212W Altcode:
No abstract at ADS
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Title: Ira Sprague Bowen (1898 - 1973).
Authors: Wilson, O. C.
1973S&T....45Q.212W Altcode:
No abstract at ADS
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Title: A Preliminary Investigation of the Dependence of Mv (K) on
[Fe/H]
Authors: Wilson, O. C.; Olsen, E. H.; Kjaergaard, P.
1972QJRAS..13..161W Altcode:
No abstract at ADS
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Title: Widths of CA II Chromospheric Emission Lines as a Measure of
Stellar Luminosity
Authors: Wilson, Olin C.
1970PASP...82..865W Altcode:
No abstract at ADS
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Title: Dependence of Chromospheric Emission upon Bolometric Luminosity
for the Hyades
Authors: Wilson, O. C.
1970ApJ...160..225W Altcode:
Fluxes in the centers of the H and K lines were measured for sixty-five
Hyades stars between F4 and KS. Analysis of these measures shows that,
in terms of bolometric luminosity, theradiation in the chromospheric
H and K emission lines increases by a factor of 2 between B - V =
0.45 and B - V = 1.25. Other results give the emission as a function
of the local continuum, as well as the true emission ratios for stars
in this color range.
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Title: Calcium emission intensities as indicators of stellar age.
Authors: Wilson, O.; Woolley, R.
1970MNRAS.148..463W Altcode:
Fresh data are presented concerning the calcium emission intensities
of 325 main-sequence late-type stars estimated by one of the authors
(0. W.). These are compared with parameters of the galactic orbits
of the stars according to methods worked out at R.G.O. A very clear
correlation is found between the calcium emission intensities and
the eccentricities and box angles (inclinations) of the orbits. This
reinforces the view that main-sequence stars with strong calcium
reversals are young stars, and have near circular orbits with low
inclinations to the galactic plane; while stars with feeble emissions
are old stars which have, statistically, high eccentricities and high
inclinations to the galactic plane.
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Title: High-Dispersion Classification of K2-M6 Giants of High and
Low Velocity
Authors: Deutsch, A. J.; Wilson, O. C.; Keenan, P. C.
1969ApJ...156..107D Altcode:
The classification of early M-type giants by the usual criteria of TiO
band strengths has been tested by estimating ratios of weak atomic
lines on coudé spectrograms of scale 9-10 A mm1. No systematic
dif- ferences are found between the types given by the two methods
for Population I stars and for high- velocity stars of intermediate
Population II. Published V - I and U - I colors also give sequences in
agreement with the spectral types. Although there is thus no evidence
that TiO bands differ in strength between giants of the two popula-
tions studied, in several of the M stars of high velocity a slight
weakening of the stronger atomic lines ap- pears to be present. In
several stars representing both populations, the absorption lines at
Hy and Ho show intensity changes on a time scale of weeks or months;
but other absorption lines and bands appear not to vary
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Title: Calibration Apparatus at Mt. Wilson and Mt. Palomar
Authors: Wilson, Olin C.
1969BAAS....1..154W Altcode:
No abstract at ADS
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Title: Chromospheric variations in main-sequence stars
Authors: Wilson, O. C.
1969lls..symp..103W Altcode:
No abstract at ADS
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Title: Flux Measurements at the Centers of Stellar H- and K-Lines
Authors: Wilson, O. C.
1968ApJ...153..221W Altcode:
The coudé scanner of the 100-inch telescope has been used as a
two-channel photometer to measure the fluxes at the centers of stellar
H- and K-lines, for the purpose of initiating a search for stellar
ana- logue~ of the solar cycle. From the Stromgren-Perry catalogue
139 stars previously observed at 10 A mm1 dispersion were selected for
this purpose and included most of those in which H-K emission had been
seen on the spectrograms. Reasonable agreement between eye-estimated
intensities and the photometric results shows that the procedure adopted
is suitable for specifying chromospheric activity, but with an accuracy
much improved over eye estimates. The probable error of a single
measurement of a line is a little less than 2 per cent. No undoubted
variations have been observed during a year's observation. However,
the measures are discussed in connection with the Stromgren-Perry
photometric parameters b - y, in1, C1. In this way it is possible to
trace in some detail the course of chromospheric evolution as stars
begin to move off the zero-age main sequence (ZAMS) toward the giant
region. Doublet ratios of the chromospheric compo- nents of H and K are
one of the by-products of the observations. They show that, in general,
the optical thickness of the gas masses involved cannot be very great
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Title: Radial velocities of dK and dM stars.
Authors: Wilson, O. C.
1967AJ.....72..905W Altcode:
No abstract at ADS
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Title: Distance of the Hyades and Relation between Luminosity and
CA II Emission-Line Widths
Authors: Wilson, O. C.
1967PASP...79...46W Altcode:
No abstract at ADS
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Title: Dwarf k- and m- Stars from the Catalogue of Vyssotsky et AL.
Authors: Wilson, O. C.
1967IAUS...30..145W Altcode:
No abstract at ADS
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Title: The masses of nine visual binary systems
Authors: Wilson, O. C.
1967mamt.book..241W Altcode:
No abstract at ADS
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Title: Age-Helium Content Correlations for Two Low-Mass Field
Binary Systems
Authors: Faulkner, John; Iben, Icko, Jr.; Wilson, Olin C.
1966ApJ...146..271F Altcode:
It is shown that knowledge of a well-determined mass for a star
ascending the subgiant branch would provide an important test
of theories of stellar evolution. Recently determined masses for
the systems ADS 755 and ADS 11479 suggest that the component stars
formed from material that was richer in helium than would be thought
appropriate to the relevant period of formation. In particular, the
assumption that these stars are as old as the Galaxy itself implies
initial helium contents >= 30 per cent, in agreement with a recently
proposed theory of the evolution of Population II stars.
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Title: Stellar Convection Zones, Chromospheres, and Rotation
Authors: Wilson, O. C.
1966ApJ...144..695W Altcode:
This paper is an attempt to connect the rotations of main-sequence
stars with their chrom osheric properties and, hence, with the extent
of their hydrogen convection zones. It is based on 10/mm spectrograms
of 308 stars, with b - y > 0 240 from the -Perry catalogue. On
the zero-age main sequence it is found that rotational velocities of
the order of V sin i > 50 km/sec set in very abruptly at b - y =
0.285, and Kraft's observations show that this is true also in the
Hyades. However, similar rotational velocities are found among the field
stars at the upper edge of the main- sequence band among spectral types
G0-G5, and it is logical to suppose that these objects have evolved
from the zero-age line near b - y = 0.285. A curve can be drawn in the
(b - y) - Ci plane which separates the large from the small rotations,
and this curve, therefore, approximates the evolutionary track of
stars originating at b - y = 0.285 on the zero-age line. This curve,
which divides the larger from the smaller angular momenta, applies
to the members of spectroscopic binary systems as well as to single
stars. Stars showing emission at H and K have a strong concentration to
the zero-age line and extend up the main sequence to b - y = 0.30. It
cannot be stated definitely that stellar chromospheres terminate
near this point, but the evidence indicates that it is quite possible
that they do. If so, the close agreement between the onset of larger
rotations and the termination of chromospheres is very suggestive
of the braking mechanism described by Schatzman. The implication,
then, is that deep hydrogen convection ends at b - y = 0 285 on the
zero-age line (spectral type F4), and the observations show that the
change from deep to shallow convection must occur within a mass range
of the order of 5 per cent.
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Title: Stellar Chromospheres
Authors: Wilson, O. C.
1966Sci...151.1487W Altcode:
No abstract at ADS
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Title: Chromospheric Activity as a Function of Age in Main-Sequence
Stars
Authors: Wilson, O. C.; Skumanich, A.
1966IAUS...24...40W Altcode:
No abstract at ADS
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Title: A Preliminary Investigation of Lithium in Main Sequence
Visual Binaries
Authors: Wilson, O. C.; Baum, W. A.; Ford, W. K., Jr.; Purgathofer, A.
1965PASP...77..359W Altcode:
No abstract at ADS
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Title: Stellar Chromospheres and Ca II H and K Emission
Authors: Wilson, O. C.
1965SAOSR.174..381W Altcode:
No abstract at ADS
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Title: The Strength of the li i Line in the Spectra of Main-Sequence
f- and G-Type Stars.
Authors: Kraft, Robert P.; Wilson, Olin C.
1965ApJ...141..828K Altcode:
No abstract at ADS
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Title: Dependence of Chromospheric Activity upon Age in Main-Sequence
Stars: Additional Evidence.
Authors: Wilson, O. C.; Skumanich, Andrew
1964ApJ...140.1401W Altcode:
Spectrograms of 10 A/mm dispersion have been obtained of 142 field
stars from the catalogue of Str6mgren and Perry for those objects with
b - y > 0.325. Mter elimination of known spectroscopic binaries
and stars of higher luminosity, a sample of 114 main-sequence stars
remains. In this sample seventeen stars showing H and K bright reversals
are found, and all but two of these lie close to the lower boundary
(zero-age edge) of the distribution in a Ci - (b - y) diagram. This
result is taken as evidence in support of the view that chromospheric
activity of main-sequence stars decreases with age. In particular,
it removes the possibility that stars formed in large clusters differ
significantly in respect to their chromospheric properties from those
formed in small groups or singly.
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Title: Chromospheric Activity and Lithium
Authors: Wilson, O. C.
1964PASP...76..238W Altcode:
No abstract at ADS
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Title: Retirement of Dr. Ira S. Bowen
Authors: Wilson, O. C.
1964PASP...76..193W Altcode:
No abstract at ADS
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Title: The Distribution of Intensities of Bright H and K in dK Stars
and the Rate of Star Production in the Galaxy
Authors: Wilson, O. C.
1964PASP...76...28W Altcode:
No abstract at ADS
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Title: Strength of the Li I Line in the Spectra of Main-Sequence F-
and G-Type Stars.
Authors: Kraft, Robert P.; Wilson, Olin C.
1964AJ.....69Q.549K Altcode:
The strength of the Li I feature at X6708 has been estimated against
X6703 of Fe I and X6718 of Ca I in the spectra of about 30 main-
sequence F- and G-type stars. The stars were selected from Stro~mgren
and Perry's photometric catalog on the b-y, c,, m1, system in the
interval 0.33<b-y<0.42, without regard to c, or m1, or Ca II
emission strength. From the limited material at hand, we conclude the
following: (1) All stars showing strong Ca II emission show strong Li
I in absorption, but Li I absorption occurs in strength in many stars
without Ca II emission. (2) If, following Stro~mgren, we interpret
the index c, as a nuclear age parameter, then there is no correlation
between Li I strength and nuclear age. (3) There is no correlation
between the Li I strength and the metal index mi.
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Title: The Spectrum of NGC 7027.
Authors: Aller, L. H.; Bowen, I. S.; Wilson, O. C.
1963ApJ...138.1013A Altcode:
Additional spectrograms of NGC 7027 have been obtained which
extend the observations to substantially fainter lines than earlier
studies. Photoelectric measurements were made of the stronger lines
in the region between X 3100 and X 4700 and were used to calibrate
the photographically determined intensities of all lines.
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Title: A Probable Correlation Between Chromospheric Activity and
Age in Main-Sequence Stars.
Authors: Wilson, O. C.
1963ApJ...138..832W Altcode:
Observation shows that the average intensity of H and K emission
is much higher for main-sequence stars of types G0-K2 in the Hyades,
Praesepe, Coma, and Pleiades clusters than for similar local field stars
and that it is appreciably higher for the Pleiades than for the other
clusters. It is also found, from observations of local visual binaries,
that the H-K intensities in the members of such pairs tend to be very
similar when allowance is made for spectral-type differences. It is
concluded that the most probable explanation of these facts is that
the H-K intensity in a main-sequence star and hence the general degree
of its chromospheric activity bear an inverse relationship to its
age. This concept of chromospheric evolution is consistent with all
the observations presented here, as well as with the known kinematical
differences between dMe and ordinary dM stars. If, however, stars can be
formed in the general field, as well as in clusters, then the observed
differences in chromospheric activity would be related to place of
origin rather than to age. The probable bearing of average surface
magnetic-field strength on the question of chromospheric activity is
discussed briefly.
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Title: Nebular absorption of He 3889 A.
Authors: Munch, G.; Wilson, O. C.
1963AJ.....68..287M Altcode:
No abstract at ADS
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Title: Lithium in a Main Sequence Star
Authors: Wilson, O. C.
1963PASP...75...62W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Nebular Absorption of He I λ3889.
Authors: Münch, G.; Wilson, O. C.
1963AJ.....68Q.287M Altcode:
The presence of an absorption line arising from the 2~5 metastable
level of neutral helium in the spectra of the stars imbedded in the
Orion Nebula was noticed long ago by 0. C. Wilson. Lately it has been
shown by G. Mu~nch and 0. C. Wilson (Z. Astrophys. 56, 127, 1962)
how the strength of this nebular absorption line may be related to
the surface brightness of a homogeneous emission nebula. The lack
of agreement between the surface brightness thus computed for the
Orion Nebula with the observed value, has been interpreted in terms
of density inhomogeneities in the nebula, independently postulated
by Osterbrock on other grounds. Because this interpretation has been
criticized by K. Wurm (Z. Astrophys. 52,149, 1961), new observational
evidence related to the line in question is being obtained. In this
communicatioi~, besides new data for the Orion stars, the results
of the search for the absorption line in other emission nebulae are
presented. So far the line has been detected in a number of stars in
the complex M8- M20, in BD +6601675, exciting NGC 6822, in BD +6002522
exciting NGC 7635, and in HD 64315, exciting star of NGC 2467. The stars
imbedded in 20 other H II regions do not have detectable He I nebular
absorption. Although a complete discussion of the data requires surface
brightness determinations (corrected for interstellar and internebular
extinction) not available yet, it is shown how the recent observations
fully support the interpretation advanced earlier by Wilson and Mu~nch.
---------------------------------------------------------
Title: Internal Motions in the Planetary Nebula IC 4997
Authors: Wilson, Olin C.; O'dell, C. R.
1962PASP...74..511W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Relationship Between Colors and Spectra of Late Main-Sequence
Stars.
Authors: Wilson, O. C.
1962ApJ...136..793W Altcode:
Spectrograms of 109 main-sequence stars of types G5 and later have
been obtained at a dispersion of 10 A/mm and have been used to derive
spectral types on the Yerkes system, based on ratios of metallic
lines. A plot of the revised types against the old Mount Wilson
types shows a very considerable scatter, which is believed to be
due chiefly to errors in the Mount Wilson values. Nevertheless, even
with the revised types, it is found that there is not a one-to-one
correspondence between spectral type and photoelectric color for these
field stars. Spectral types of 69 Hyades main-sequence stars have been
estimated from 38 A/mm spectrograms. For these objects the correlation
of type and color is appreciably closer than for the field stars. It
is suggested, following an argument based on the Vogt-Russell theorem,
that these facts imply a greater degree of chemical non-uniformity
in the local main sequence than in that of the Hyades. A number of
instances of anomalous intensities of the hydrogen lines and of CN
bands among the local main-sequence stars are indicated.
---------------------------------------------------------
Title: On the Structure of the Orion Nebula. A Reply to K. WURM. With
2 Figures in the Text
Authors: Münch, G.; Wilson, O. C.
1962ZA.....56..127M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: An Interpretation of the Late Main Sequence.
Authors: Wilson, O. C.
1961ApJ...133..457W Altcode:
Eggen's photoelectrically measured c6lors are plotted against spectral
type for the main sequence below AS. It is found that the distribution
of points in this diagram is fairly narrow from AS to G5, at which point
it begins to widen. This width, which extends at least as far as Mi,
is much too large to be attributable to errors in either the colors
or the spectral types. It is noted also that the widening occurs in
that region of the spectral sequence where the supply of electrons
fiom hydrogen is diminishing to the point where the metals are coming
into equilbrium with their own electrons. This leads to an attempt
to account for the major features of the (P- V) -type diagram on the
basis of a series of stellar atmospheres in which the metal-hydrogen
radio is not constant and within which,for a given spectral type, there
is an appreciable spread of temperature. The results are encouraging
to a considerable degree, and, where discrepancies occur in the range
G8-K2, they are in the sense to be reduced if differential blanketing
effects are still appreciable It turns out that among main-sequence
K-type stars a total range in the metal-hydrogen ratio of the order
1:100 is necessary to account for the observed spread in the plot
referred to above. Observations at 10 A/mm of stars of the same types
near the upper and lower boundaries of the diagram show that they are
spectroscopically distinguishable. All stars near the upper boundary
(red stars) have much stronger H and K emission than do stars of the
same types near the lower boundary (blue stars). Conversely, except at
G8, the blue stars of given types all have stronger Balmer absorption
lines than the corresponding red stars. These latter facts are accounted
for, semiquantitatively, by the same assumptions as those which explain
the spread in the (P - V) spectral-type diagram.
---------------------------------------------------------
Title: Spectrographic Observations of a Flare Star
Authors: Wilson, O. C.
1961PASP...73...15W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A New Scale of Stellar Distances
Authors: Wilson, O. C.
1961SciAm.204a.107W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observational Limitations to Mass Loss by Normal Late-Type
Giants.
Authors: Wilson, O. C.
1960ApJ...132..136W Altcode:
Spectroscopic observations of H and K lines of Ca ii in several hundred
late-type stars are discussed, and it is shown that the measured
displacements provide no evidence for ejection of matter from normal
giants earlier than MO. Also, some simple calculations show that the
absence of true circumstellar lines from the spectra of these objects
implies a rate of mass loss less than 10-10 0 per year. Hence if these
stars must lose a substantial portion of their masses before becoming
wbite dwarfs there appear to be only two alternatives: either they
all must eventually evolve to M-type stars and remain such long enough
to eject the necessary amount of matter; or they are ejecting matter
at present but by some unknown mechanism which permits the process to
escape observation. There is also a brief discussion of mass loss in
genera] and with reference to a Herculis in particular.
---------------------------------------------------------
Title: A Suggested Mechanism for the Ejection of Matter from M-Type
Stars.
Authors: Wilson, O. C.
1960ApJ...131...75W Altcode:
It is suggested that matter is ejected from M-type stars by the outward
force due to a strong chromospheric Ly-a radiation A brief examination
of the mechanism indicates that it may be capable of meeting the
requirements set by the observations of expanding envelopes around
these stars
---------------------------------------------------------
Title: Eclipses by Extended Atmospheres
Authors: Wilson, O. C.
1960stat.book..436W Altcode: 1960S&SS....6..436W; 1960stat.conf..436W
No abstract at ADS
---------------------------------------------------------
Title: A Color-Magnitude Diagram for Late-Type Stars Near the Sun.
Authors: Wilson, O. C.
1959ApJ...130..496W Altcode:
A color-magnitude diagram for late-type stars in the solar neighborhood
is derived from measures of the widths of the bright H and K reversals
in the spectra of stars for which photoelectric values of B - V are
available. The diagram is filled out by the inclusion of stars with
trigonometric parallaxes >0'oso. From the plotted points it is
possible to delineate with fair accuracy the limiting evolutionary
track for the oldest galactic stars and to estimate the location of
the break-off point from the main sequence. The corresponding age
of the galaxy is about lOiS years, but this estimate is subject to
improvement with the addition of further observations.
---------------------------------------------------------
Title: Accuracy of Absolute Magnitudes Derived from Widths of H and
K Emission Components.
Authors: Wilson, O. C.
1959ApJ...130..499W Altcode:
Measures of the dths of the bright reversals in H and K in the sun and
in the yellow giants of the Hyades are used to establish a calibration
of absolute visual magnitude as a function of emission-line width. For
giant and subgiant stars the probable error of a single measurement is
j 0.26 mag., and the probable error due to intrinsic scatter is about
I 0.20 mag. The latter quantity is determined from comparison with 24
stars for which dir/ir < 6 . A comparison with 29 main-sequence stars
gives larger values of both measuring error and intrinsic scatter. It is
suggested that the principal source of intrinsic scatter for all stars
may be rotational widening. Further comparison with H and K measures
in three supergiants in h and x Persei and in the K-type component of
Aurigae indicates that the calibration is valid for stars as bright
as Mv -6.
---------------------------------------------------------
Title: Location of Late Type High-Velocity Stars in the
Color-Magnitude Diagram
Authors: Wilson, O. C.
1959PASP...71..338W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Internal Kinematics of the Orion Nebula.
Authors: Wilson, O. C.; Minich, Guido; Flather, Edith; Coffeen, Mary F.
1959ApJS....4..199W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A preliminary color-magnitude diagram for late-type stars in
the solar neighborhood
Authors: Wilson, O. C.
1959IAUS...10...39W Altcode: 1959SAnAp...8...39W
No abstract at ADS
---------------------------------------------------------
Title: Some Theoretical Apsects of H and K Emission in Late-Type
Stars.
Authors: Hoyle, F.; Wilson, O. C.
1958ApJ...128..604H Altcode:
A velocity is defined in the subphotospheric convection zones of
late-type stars that varies from star to star in the same way as the
width of the emission lines H and K of Ca ii The quantity is tentatively
identified as the velocity of hydromagnetic waves.
---------------------------------------------------------
Title: Internal Kinematics of the Planetary Nebulae
Authors: Wilson, O. C.
1958RvMP...30.1025W Altcode: 1958IAUS....8.1025W
No abstract at ADS
---------------------------------------------------------
Title: Limitations on Physical Theories of H and K Emission Lines.
Authors: Wilson, O. C.
1957ApJ...126..525W Altcode:
A satisfactory physical theory of the H and K emission lines in the
sun and stars has not yet been developed. By consideration of existing
observations, certain requirements of and limitations upon such theories
are established. If rO is the optical thickness in the line center, N
the number of Ca ii ions per square centimeter vertical column, L the
luminosity (visual), and AXD the Doppler width, the following items
must be accounted for: A. Emission produced in optically thin layers
(ro 1). (1) AXD L1/6. (2) N unrestricted except for upper limit on
ro. (3) Mechanism for adequate emission from thin layers. B. Emission
produced in optically thick layers (10 < ro <- l0 ). (1) Both
AXD and N must vary appropriately with L. (2) The rate of variation
of AXD with L must lie within the maximum and minimum rates, which,
together with the corresponding variations of N, are, respectively,
AXD L1/5, N L-1/4, and AXD L1/9, N L1/2.
---------------------------------------------------------
Title: H Emission in Late-Type Star.
Authors: Wilson, O. C.
1957ApJ...126...46W Altcode:
Intensities of HE emission are estimated in 185 late-type stars
and compared with those of the K line of Ca ii. Although there is
a statistical tendency toward a correlation between the HE and K
intensities, there is also a large scatter, indicating that the ratio
of HE to K is widely variable.
---------------------------------------------------------
Title: H and K Emission in Late-Type Stars: Dependence of Line Width
on Luminosity and Related Topics.
Authors: Wilson, O. C.; Vainu Bappu, M. K.
1957ApJ...125..661W Altcode:
The H and K emission lines of Ca II have been studied on 10-A/mm
spectrograms of 185 stars of types G, K, and M. Nearly all stars of
type G0 or later in the list of MK standards (Johnson and Morgan 1953)
have been included. Emission-line widths have been measured, as well
as displacements of the emission and absorption components. Tb e
displacements are determined with respect to nearby low-excitation
reversing- layer absorption lines. <P />When the logarithms of the
emission-line widths (corrected for instrumental width) are plotted
against the Yerkes absolute spectroscopic magnitudes, the points define
a straight line which extends over a 15-mag. range of M<SUB>v</SUB>
and which indicates that the line width varies as the one-sixth
power of the luminosity. Stars with weak or strong lines and of all
spectral types later than G0 seem to fit the linear relationship equally
well. The widths therefore cannot be dependent upon line intensity or
stellar surface temperature. <P />Evidence from the solar spectrum,
from ζ Aurigae, from Hyades stars, and from four visual binaries
point to the conclusion that the relationship described here is not
of a statistical nature. Therefore, it is probable that the Ca II
emission-line widths can be used as luminosity indicators. Internal
consistency considerations indicate that one good spectrogram should
fix the absolute magnitude of any late-type star with suitable lines
to within ±05 mag. <P />It is found that,for displacements within ±6
km/sec, negative values are more frequent than positive for the emission
components of H and K. On the other hand, between +4 and -4 km/sec,
positive values are more common for the absorption components. The
naive interpretation is that the emitting layer is rising and that
the absorbing material is falling slowly inward. Statistics of the
larger displacements common among the intrinsically luminous stars are
discussed briefly. In particular, it is found that among the M-type
giants and supergiants the negative displacements of the absorption
components are not correlated with absolute magnitude.
---------------------------------------------------------
Title: The Analysis of the Chromosphere of Zeta Aurigae
Authors: Wilson, O. C.
1957JRASC..51...70W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Simultaneous Spectrographic and Photometric Observations of
the Short-Period Variables SX Phoenicis and CC Andromedae.
Authors: Wilson, O. C.; Walker, Merle F.
1956ApJ...124..325W Altcode:
Radial velocity-curves and light-curves in three colors are derived
from simultaneous spectrographic and photoelectric observations made
at Palomar in 1953 and 1954. For both SX Phoenicis and CC Andromedae
maximum brightness lags behind maximum size, as deduced from the
radial velocities, by a quarter-period, as is true of the cepheid
variables. The light-amplitude of SX Phoenicis is widely variable, but
corresponding variations in the velocity-amplitude cannot be established
with certainty. On the other hand, there is an obvious relationship
between the light- and velocity-amplitudes of CC Andromedae, which
seems to be the same as that for Scuti. It is probable that these two
stars, together with DQ Cephei, belong to the same class of variable
and that they may be considerably brighter than main-sequence stars
of the same spectral type.
---------------------------------------------------------
Title: The New Cassegrain Spectrograph for the Mount Wilson 60-Inch
Telescope
Authors: Wilson, O. C.
1956PASP...68..346W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Proportionality of Nebular Red Shifts to Wave Length.
Authors: Minkowski, R.; Wilson, O. C.
1956ApJ...123..373M Altcode:
Measures of the red shift /Xo for the colliding galaxies Cygnus A give
the value 16812 + 9 km/sec for the mean wave length 3830 A and 16798 +
7 km/sec for the mean wave length 6472 A. The relative change in the red
shift with wave length is less than 3 X 10- per 1000 A. Combination of
the optical results with those by Lilley and McClain for the 21-cm
hydrogen line shows that the relative change is lessthan3 X 10-
per 1000A
---------------------------------------------------------
Title: Complex Lines in the Spectrum of RW Cephei.
Authors: Merrill, Paul W.; Wilson, Olin C.
1956ApJ...123..392M Altcode:
The spectrum of this extreme supergiant M-type star observed with
dispersion of 9 A/mm shows many absorption lines apparently with
two components separated by a narrow central maximum. The maximum is
probably actual emission superposed on an absorption line considerably
widened by turbulence. In certain lines, especially the resonance
lines of Ca i, Cr i, Mn 1, and Sr ii, the shortward component is
greatly reinforced by the absorption of an upper expanding shell
of gas. Shortward of X 4000 A there appear numerous narrow emission
lines, chiefly of Fe i and Ti 1, without accompanying dark lines. The
peculiar relative intensities of these lines are probably due to strong
differential . The spectrum is compared with that of a Orionis.
---------------------------------------------------------
Title: The Radial Velocity of DQ Cephei = HD 199908.
Authors: Sahade, J.; Struve, O.; Wilson, O. C.; Zebergs, V.
1956ApJ...123..399S Altcode:
The radial velocities measured on 215 spectrograms taken on sixteen
nights confirm Walker's photoelectric period of 0.0788650 day. The
mean velocity of the star is - 21 9 km/sec. There is a beat period of
0.3751 day. The total range of the principal oscillation is 9.2 km/sec;
that of the interfering oscillation is 2.6 km/sec. The period of the
interfering oscillation is 0 06516 or 0.09986 day. The spectrum is
approximately Fl IV-V. The maximum brightness occurs halfway on the
descending branch of the velocity- curve. Near minimum radial velocity
a narrow space of continuous spectrum is visible between Ca H and
HE. This feature is absent at other phases.
---------------------------------------------------------
Title: Award of the Bruce Gold Medal to Dr. Albrecht Unsöld
Authors: Wilson, O. C.
1956PASP...68...89W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Possible Occurrence of λ5876 of He I in Absorption in
the Spectra of Certain Late-Type Stars
Authors: Wilson, O. C.; Aly, M. K.
1956PASP...68..149W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Award of the Bruce Gold Medal to Dr. Walter Baade
Authors: Wilson, O. C.
1955PASP...67...57W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Introductory remarks: THE ATMOSPHERES OF GIANT AND SUPERGIANT
STARS
Authors: Wilson, O. C.
1955stat.conf..147W Altcode: 1954stat.conf..147W
No abstract at ADS
---------------------------------------------------------
Title: Chromospheric Structure of the K-Type Component of Zeta
Aurigae.
Authors: Wilson, O. C.; Abt, Helmut A.
1954ApJS....1....1W Altcode:
Spectrograms of 10 A/mm dispersion taken during the 1947-1948 eclipse
have been measured for line intensities and for radial velocities,
and the results are compared with those obtained previously for the
1939-1940 eclipse. Egress of 1947-1948 is found to he quite similar
to ingress and egress of 1939-1940; ingress at the more recent eclipse
differs, however, from the other three transits in the direction of a
considerably slower gradient, particularly at the greater chromospheric
heights. This effect is found from lines of all types. However,
ingress of 1947-1948 is not distinguishable from the other transits in
the values of any of the derived parameters: excitation temperature,
turbulent velocity, or degree of ionization. It is shown that the
apparent rise of AXD with height found in 1939-1940 is really due
to a systematic difference in this quantity between the neutral and
ionized lines. Ions indicate slightly higher turbulent velocities than
do neutral atoms. The excitation temperature increases with height at
about the same rate as indicated by the earlier results. Ionization
in the chromosphere is studied in some detail, and 's theory of the
penetration of ionizing radiation from the B star into the chromosphere
of the K star is applied to the roblem. The outcome is that it appears
impossible to account for the spectroscopic phenomena on t e basis
of a smooth distribution of the chromospheric material. In fact,
it is necessary to assume that the matter occurs in condensations of
rather small size (thickness of the order of 10 km) and high density
(log n[H] = 13.8) in order to keep the ionization at the required level
and to avoid discordance with the solar abundance ratios. The model
is in accord with all but one of the observed spectroscopic features,
as well as with the recent interpretation of the photometric eclipse
by Roach and Wood.
---------------------------------------------------------
Title: Spectrophotometry of the Central Stars of Four Planetary
Nebulae.
Authors: Aller, L. H.; Wilson, O. C.
1954ApJ...119..243A Altcode:
An analysis of coud spectrograms of the nuclei of four planetary nebulae
with predoininanily absorption spectra, viz., IC 418, IC 2149, NGC 2392,
and IC 4593, yields spectral classes of on R. M. Petrie's system. The
proffles of the hydrogen lines are compared with those of the O9 star
10 Lacertae. Electron densities somewhat lower than those previously
obtained for other planetary nuclei with absorption4ine spectra seem
to be indicated. It is suggested that the He/H ratio can be greater in
the planetary nuclei than in normal 0 stars and that the excitation
temperatures can be systematically lower than those derived from
Petrie's scale. A final decision will requlre a much more detailed
analysis, involving the calculation of model atmospheres.
---------------------------------------------------------
Title: The Mass of the Globular Cluster M92.
Authors: Wilson, O. C.; Coffeen, Mary F.
1954ApJ...119..197W Altcode:
Radial-velocity measurements of 23 spectrograms of 15 red giant stars
in M92 are discussed. A mass of 3.3 X t 0 is derived for the cluster,
and the corresponding mass-to-luminosity ratio is 2.0 in solar units. It
is probable that there are intrinsic velocity variations in some of
the cluster stars.
---------------------------------------------------------
Title: Some Remarks on the Spatial and Kinematic Structure of the
Planetary Nebula IC 418.
Authors: Wilson, O. C.
1953ApJ...117..264W Altcode:
Recent high-dispersion spectrograms have resolved the [N ii] and [0 llJ
lines in this nebula which had appeared single with the lower dispersion
previously used. On collecting and discussing the kinematic data for
this low-excitation nebula and correlating them with the results from
slitless spectrograms, it becomes highly probable that IC 418 is built
upon the same spatiokinematic model as are the high-excitation ring
nebulae. A brief consideration of ring nebulae in general leads to two
alternative explanations for them: (1) If the density inside the shell
is higher than the density in the shell, then the flow of matter is from
the inner mass into the shell. In this case the electron temperature in
the inner mass must be much higher than that in the shell. (2) If, on
the other hand, the inner mass consists of matter expelled inward from
the shell, a relatively higher density in the shell, as compared to the
interior, is adequate to account for the appearance of the ring nebulae.
---------------------------------------------------------
Title: Monochromatic isophotic contours of planetary nebulae.
Authors: Wilson, O. C.; Aller, L. H.
1953AJ.....58R.235W Altcode:
Slitless spectrograms of a number of bright planetary nebulae including
NGC 1535, 2392, 2440, 6210, 6752, 6741, 7009, 7662, and tC 418, 4593
were obtained with the coude' spectrograph and image rotator at the
100-inch telescope. Monochromatic images of EOIII~, LNe~IIj, ENevJ, Hei,
Heii, and H have been analyzed with the balanced-beam isophotometer
invented by Hiltner and Williams. A comparison of results secured by
tal~ing successive tracings across the image with the isophotic contours
traced by the machine showed good agreement. The greatest inacctiracy
in the contours is introduced by internal motions in the nebula which
prodtice a distortion of the slitless images. Direct photographs
obtained with suitable plate and filter combinations can overcome this
difficulty. Observations obtained with the multislit, which gives not
only the velocities of the forward and backward sides of the shell in
the line of sight, but also the relative amounts of material in the
two sides of the shell, may be combined with the isophotic contour
data to calculate three-dimensional models of some of the more regular
nebulae. When multislit data are not available, assumptions about the
symmetry of the nebula must be made. The contours obtained illustrate
single and double ring structures, single nuclear and binuclear
strticttires, as well as somewhat irregular objects. Observatory,
University of Michigan, Ann Arbor, Mich.
---------------------------------------------------------
Title: The Structure of the Planetary Nebula IC 418.
Authors: Wilson, O. C.; Aller, Lawrence H.
1951ApJ...114..421W Altcode:
Slitless coude' spectrograms of the small, low-excitation, planetary
nebula IC 418 are analyzed to determine the intensity distribution
across the disk in various monochromatic images. From an analysis
of these intensity distributions an attempt is made to find the
emission per unit volume. The emission in ergs/cm3/sec is expressed
in c.g.s. units, and the approximate ionic densities of H, He, N IT,
0 II, 0 III, Ne iii and Sir are derived.
---------------------------------------------------------
Title: The Of-Type Spectroscopic Binary BD+40°4220.
Authors: Wilson, O. C.; Abt, Arthur
1951ApJ...114..477W Altcode:
The components of the spectroscopic binary BD+ are of spectral types
Of and 09 and the period is 6.600 + 0.002 days. The mass of the 09
star (probably a giant or supergiant) is about four times that of the
Of. Rather pronounced periodic variations in visibility of some of
the spectral features are briefly discussed.
---------------------------------------------------------
Title: The structural features of certain planetary nebulae.
Authors: Aller, Lawrence H.; Wilson, Olin C.
1950AJ.....55...70A Altcode:
Guided slitless spectrograms obtained with the aid of an image
rotator at the coude' focus of the 100-inch reflector are used for a
study of the structure of NGC 6572 and NGC 7662. The outer portions
of NGC 6572 possess an amorphous structure. The nebula is not at
all elliptically symmetrical as earlier observations with smaller
telescopes indicated. Mg I X457I and S ii show a shell structure,
whereas N iii X4640 and A iv X4740 apparently do not. The intensity
distribution across the nebula, corrected for bad seeing and guiding,
has been obtained for lines of hydrogen and helium. Isophotal contours
of 0 iii X4959, Ne iii X3865, Hp, and Heii X4686 in NGC7662 have
been drawn. The two forbidden lines show similar contours whereas the
distribution of H and He ii is similar in the inner portions of the
nebula. A three-night exposure shows that He ii does not appear in the
outer shell at all. On the assumption that the structure of the nebula,
in the first approximation, can be represented as circularly symmetrical
in the plane containing the major axis of the ring and the observer,
the radial emission distribution is derived by a method employed by
Wallenquist in his study of star clusters. The hydrogen and Ne iii
shells appear to be hollow, whereas there is some suggestion that
He ii emission appears within the inner shell. Similar studies are
in progress for other planetary nebulae, among them XGC62Io, 7009,
and IC 418 and 4543. Observatory, University of Michigan, Ann Arbor,
Mich. and Mt. Wilson and Palomar Observatories, Pasadena, Ca 1sf.
---------------------------------------------------------
Title: A Survey of Internal Motions in the Planetary Nebulae.
Authors: Wilson, O. C.
1950ApJ...111..279W Altcode:
Slit spectrograms (dispersion 10 A/mm) of twenty-six bright planetary
nebulae have been obtained with the coude' spectrograph of the 100-inch
telescope. For thirteen of the nebulae, slitiess spectrograms have
been secured with the same instrument. he main observational results
are the separations of the components of the double nebular lines
and the dimensions of corresponding slitless images. Analysis of
these data leads to the following principal conclusions: 1. There
is no correlation between the relative intensities (V/R) of the red
and violet components of the nebular lines and the general level
of nebular excitation. 2. The number of nebulae with V/R> 1 is
about equal to the number with V/R < 1; hence the nebulae are
probably transparent in the observed wave4ength range. 3. The most
reliable measure of expansion velocity is shown to be the mean of
the values given by lines of H, [0 ni], and [Ne in]. There may be a
very weak positive correlation between this quantity and the level
of excitation. 4. Where differences in component separation exist
in the spectrum of a planetary nebula (and they are quite common),
tife particles show smaller separations than the low-excitation
particles. Extreme examples are [Ne v], for which the separations
are often close to zero, and [0 n] and [N n], which sometimes show
large separations. Hydrogen presents an outstanding exception to the
general run of separation with excitation, agreeing closely with [0 in]
and [Ne in]. Available evidence is against any marked dependence of
component separation upon transition probability. 5. There is generally
a positive correlation between component separation and monochromatic
image size. Usually, though not always, differences in image size are
much less than differences in separation. 6. Components of the nebular
lines are often quite sharp, their apparent width being frequently
determined by the resolving power of the emulsion; but components
of H lines are noticeably diffuse in all nebulae. By-products of the
investigation include improved wave lengths of twenty nebular lines and
radial velocities of twelve nebulae. Two models have been investigated
in attempting to explain the observations. The basic assumption of
the first model is that the velocity given by the lines of any ion
is a measure of the velocity of the abundant H and He in the region
where the lines in question are produced. In this model the material
is supposed to have originally a velocity equal to that measured for
[Ne v], which is, in some nebulae, probably less than 5 km/sec. The
increments in velocity between [Ne v] and He ii and between He ii and
H are assumed to be due to the increases in momentum flux carried by
the gas upon absorption of nuclear radiation below x 228 A and between
x 912 and x 228 A, respectively. Reasonable values of the radius and
temperature of the central star lead, on this model, to the correct
orders of magnitude both for the velocity changes and for the total
nebular brightness. The second model assumes that measured velocity
differences are due to selective forces acting upon some of the rare
ions and maintaining them in relative motion with respect to the
abundant H and He. It appears possible in this fashion to construct
a model which can account for the [Ne v] anomaly on the basis of an
inward flux of Lyman continuum from the bright hydrogen shell. This
model leads, however, to nebulae about 5 mag. too faint, and for this
reason the first one seems preferable.
---------------------------------------------------------
Title: Planetary Nebulae
Authors: Wilson, Olin C.
1950ASPL....6...20W Altcode: 1950ASPL..253.....W
No abstract at ADS
---------------------------------------------------------
Title: Proportionality of Nebular Red Shifts to Wave Length
Authors: Wilson, O. C.
1949PASP...61..132W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Wolf-Rayet Spectroscopic Binary HD 190918.
Authors: Wilson, O. C.
1949ApJ...109...76W Altcode:
The emission and absorption components of this star are of types
close to WN5 and BO, respectively. Many observations made in 1946,
1947, and 1948 have been combined by graphical methods to yield ap-
proximate spectrographic orbits. Only the X 4686 band of Heii was
measured in the W spectrum, while five or six absorption lines due
to the B-type component were regularly used. Derived constants of the
system are: YB = -21.8 km/sec, KB = 10.0 km/sec; ~yw = -f 88 km/sec,
K~ = 38 km/sec; (mB -f mw) sin3 i = 0.986 0. Since the spectra of the
components of HD 190918 are not very different from those of HD 193576,
whose minimum total masses are 35 0, it is probable that the value
of i for HD 190918 does not exceed 18°. It is concluded, therefore,
that the red shift of the X 4686 He ii band in WN stars is probably
inde- pendent of the orientation of the polar axes of the stars with
respect to the line of sight and that its origin is to be sought in
processes occurring within the WN atmospheres
---------------------------------------------------------
Title: Book Review: Centennial Symposia, December, 1946
Authors: Wilson, O. C.
1949PA.....57...48W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: No. 755. The Wolf-Rayet spectroscopic binary HD 190918.
Authors: Wilson, O. C.
1949CMWCI.755....1W Altcode: 1949QB4.M93n755....
No abstract at ADS
---------------------------------------------------------
Title: Three Interesting Spectroscopic Binaries
Authors: Wilson, O. C.
1948PASP...60..385W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Variations in the Spectrum of the Wolf-Rayet Star HD 50896
Authors: Wilson, O. C.
1948PASP...60..383W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Nova Serpentis 1948
Authors: Wilson, O. C.
1948PASP...60..327W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Nuclear and Nebular Spectra of the Planetary Nebula
NGC 2392.
Authors: Wilson, O. C.
1948ApJ...108..201W Altcode:
Eighteen stellar absorption lines and three wide emission lines
were measured on an excellent spectro- gram of the nucleus of NGC
2392. Seven nebular lines also were measured. The two nebular lines of
[Ne vi, X 3346 and X 3426, are single and nearly monochromatic. Other
nebular lines are double, with a separation of about 100 km/sec between
the components. Radial velocities of the system given by the single
[Ne vi lines, by means of the components of the double nebular lines,
and by the stellar emission lines are, respectively, +70.8, +71.1, and
+70.9 km/sec. When the stellar absorption lines are grouped according
to total excitation requirements, it is found that those of highest
excitation (N iv) give approximately the velocity of the system. Lines
of lower ex- citation show progressively larger displacements toward
the violet. The lines of lowest excitation (H) yield a velocity of +45
km/sec. These results indicate a variation of outward velocity with
depth in the atmosphere of the nuclear star such that the N iv lines
are formed at the greatest depth, those of H at the least depth. The
single nebular lines of [Ne v} are unexplained. A slitless spectrogram
indicates that these lines, as well as the double lines of [Ne m},
[011], etc., are all formed in the inner nebular ring. Some of the
obvious problems raised by these observations are mentioned
---------------------------------------------------------
Title: The Nuclear and Nebular Spectra of the Planetary Nebula
NGC 2392
Authors: Wilson, Olin C.
1948PASP...60..247W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Preliminary Lower Limit to the Ratio
C<SUP>12</SUP>/C<SUP>13</SUP> in Interstellar Matter
Authors: Wilson, O. C.
1948PASP...60..198W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Structure of the Atmosphere of the K-Type Component of
Zeta Aurigae.
Authors: Wilson, O. C.
1948ApJ...107..126W Altcode:
This investigation is based upon spectrograms of 10.4 A/mm dispersion
obtained during the 1939- 1940 eclipse. * Curves of growth were
constructed for four atmospheric levels observed during ingress and for
three during egress. Relative gf-values for Fe I lines were taken from
the laboratory data of King and King. For other elements the relative
gf's were calculated from the measures of lines in the solar-flash
spectrum made by H. H. Lane. Doppler widths, L~XD, of the theoretical
curves of growth which best fit the observations, range from 0.08 A
for a height above the limb of 0.8 X 106 km to 0.16 A for a height
of 20.6 X 1O°km, with cor- responding turbulent velocities of 6.5
and 13.0 km/sec, respectively. It appears, therefore, that the turbu-
lence increases with height in theatmosphere. Excitation temperatures
determined by comparison of the populations of the a~F and a3F states of
Fe i with that of the ground state, a5D, also increase with height. Mean
values range from 37800 at h = 0.8 X 106 km to 5660° at Ii = 13.5)<
10~ km. Density gradients in the atmosphere are readily evaluated by
means of the curves of growth. For all atomic and ionic states included
in this investigation the gradients are steepest at the lowest levels
and tend to become less steep with increasing height. Moreover, except
for Ca i in the lowest level, all the density gradients are nearly the
same. If the densities are expressed as a function of height by means
of the formula n = noe~, the observations yield a mean value of a = 2.3
X 1012 cm'. The observed gradient is compared with those calculated on
the assumption of hydrostatic equilibrium. The latter hypothesis leads
to gradients of the order of twenty times larger than observed for
H to one thousand times larger for Fe and elements of similar atomic
weight. McCrea's theory of turbulent support is also investigated. If
the turbulent velocities obtained from the curves of growth are used
in McCrea's equa- tion, the resulting gradient is still about ten
times too large. It cannot be decided at the present time whether this
discrepancy is real or due to an accumulation of errors in the data. The
ionization in the atmosphere of the K-type component is investigated,
chiefly at heights of 7 X 10~ km and 14 X 1O~ km, for which the data
appear most reliable. Thermodynamic equilibrium is first assumed; the
combination of the Boltzmann and Saha equations for H, together with
the standard ionization equation for Ca, then permit an evaluation of
the temperature, T. The latter is found to be nearly the same as that
of the K-type star itself, and the electron density at height 7 X 10~
km is 1O~ per cm3, on the assumption that hydrogen supplies effectively
all the electrons. It is next assumed that the ionization of Ca is
governed by the dilute radiation of the B-type star and Pannekoek's
equation is applied. It is shown that the observed ionization of Ca
requires a higher electron density than appears to be available for H,
and hence it is unlikely that the B-type star is responsible for the
ionization of Ca and atoms of similar I.P. This conclusion leads to an
investigation of the opacity of the atmosphere of the K-type star as a
function of wave length. Menzel's opacity formula is shown to provide
ample opacity at X «= 2000 A to screen most of the atmosphere from the
ionizing radiation of the companion, while still insuring transparency
in the regions ordinarily observed. On the basis of the same equation
it is suggested that the eclipses may begin appreciably earlier in the
ultraviolet than in the ordinary photo- graphic region. A tentative
explanation of the rise of excitation temperature with height is based
upon the metastability of the atomic states concerned and the variation
of atmospheric opacity with height and wave length. INTRODUCTIO
---------------------------------------------------------
Title: No. 749. The nuclear and nebular spectra of the planetary
nebula NGC 2392.
Authors: Wilson, O. C.
1948CMWCI.749....1W Altcode: 1948QB4.M93n749....
No abstract at ADS
---------------------------------------------------------
Title: No. 742. The structure of the atmosphereof the K-type component
of Zeta Aurigae.
Authors: Wilson, O. C.
1948CMWCI.742....1W Altcode: 1948QB4.M93n742....
No abstract at ADS
---------------------------------------------------------
Title: Components of Interstellar Sodium Lines
Authors: Merrill, Paul W.; Wilson, O. C.
1947PASP...59..132M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectrum of the Planetary Nebula NGC 3242
Authors: Wilson, O. C.
1946PASP...58..210W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Absolute Dimensions of a Wolf-Rayet Star and the
Expanding-Envelope Hypothesis.
Authors: Wilson, O. C.
1942ApJ....95..402W Altcode:
Measures of the equivalent width of the Hy absorption line of the
B-type component of RD 193576 have been made during and outside
of eclipse. These data, combined with a preliminary unpublished
light-curve by G. E. Kron and the spectrographic orbit by the writer,
permit the derivation of the abso- lute dimensions of the system with
fair accuracy. It is found that the Woif-Rayet star is the larger and
brighter of the pair, although it has the smaller mass, and Gaposchkin
has shown it to have the smaller surface brightness. The hypothesis
that the Woif-Rayet emission bands are formed in an expanding envelope
surrounding the star is discussed critically. Arguments based upon
observations, although not decisive, tend to throw doubt on the validity
of the hypothesis. The binary character of HD 193576 offers a means of
deciding whether or not the emission bands of the Woif-Rayet component
are produced in an expanding envelope. In view of the facts that the
band width corresponds to an ejection velocity of 2000 km/sec and that
the character of the Woif-Rayet spectrum is not seriously modified by
the presence of the companion, it is assumed that the ejected particles
follow linear trajectories. As a consequence of this assumption,
the radial velocity measured by the displacement of the emission
band must differ from the true radial velocity of the star. The chief
consequence of this transit-time effect is a difference between the
observed times of eclipse and the times predicted by the spectrographic
orbit. Formulae are derived from the transit-time effect and computa-
tions of its magnitude are made for three velocity distributions and for
a variety of inner and outer radii of the envelope, with the aid of the
absolute dimensions of the system derived in section I. Similar com-
putations are made of the magnitude of the violet shift of the bands
due to occultation. The existing observations limit the difference
between the observed and the computed times of eclipse to O.O1P, which
requires that the supposed envelope be so small as to lead to violet
shifts of some hundreds of km/sec. Since such shifts are not observed,
it is concluded that the emission bands are probably not formed in
an expanding envelope. The measured intensities of the X 4686 band of
He ix are investigated as a function of phase. The intensity is very
nearly the same at phases 0.25, 0.50, and 0.75, but the band is about
19 per cent weaker at primary minimum. Perhaps there is a "reflection
effect," which causes the Woif-Rayet star to radiate more strongly
in the X 4686 band from the hemisphere facing the companion. A few
tentative remarks are made concerning possible alternatives to the
expanding-envelope hy- pothesis, although no satisfactory solution
is found. A zone of turbulence might be invoked to account for the
great widths of the emission bands. This explanation, however, leads
to difficulties with the dis- placed absorption components sometimes
observed in Woif-Rayet spectra. Moreover, it leaves unex- plained the
red shift of the bands in HD 193576 and their periodic changes in shape
---------------------------------------------------------
Title: No. 660. Absolute dimensions of a Wolf-Rayet star and the
expanding-envelope hypothesis.
Authors: Wilson, O. C.
1942CMWCI.660....1W Altcode: 1942QB4.M93n660....
No abstract at ADS
---------------------------------------------------------
Title: Three Wolf-Rayet Spectroscopic Binaries
Authors: Wilson, O. C.
1941PASP...53..295W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Some Results from the 1939-40 Eclipse of ζ Aurigae
Authors: Wilson, O. C.
1941PASP...53..228W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Narrow Lines in the Spectrum of γ Cassiopeiae
Authors: Merrill, Paul W.; Wilson, O. C.
1941PASP...53..125M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Determination of Mass Ratios of Spectroscopic Binaries.
Authors: Wilson, O. C.
1941ApJ....93...29W Altcode:
A method is described which permits the determination of the mass
ratio and systemic velocity of a double-lined spectroscopic binary
from much less observational material than that required for a com-
plete orbit determination
---------------------------------------------------------
Title: Narrow lines in the spectrum of gamma Cassiopeiae.
Authors: Merrill, P. W.; Wilson, O. C.
1941PASP...53R.125M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: No. 640. On the determination of mass ratios of spectroscopic
binaries.
Authors: Wilson, O. C.
1941CMWCI.640....1W Altcode: 1941QB4.M93n640....
No abstract at ADS
---------------------------------------------------------
Title: A Wolf-Rayet Visual Binary
Authors: Wilson, O. C.
1940PASP...52..404W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Physical Characteristics of the Wolf-Rayet Stars.
Authors: Wilson, O. C.
1940ApJ....91..394W Altcode:
The red shift of the emission bands of the Woif-Rayet component
of HD 193576, noted in the preceding Con1ri&ut~on, suggests
that similar displacements may be a com- mon feature of Woif-Rayet
spectra. Examination of the wave lengths derived by Beals from measures
of a number of Woif-Rayet stars lends strong support to this view,
at least for stars of the nitrogen sequence. A discussion of the
possible origins of such a shift leads to the conclusion that only
two of them are at all likely. One of these possi- bilities, namely,
that the red shift is due to a weakening of the violet sides of the
bands by absorption of the light of the central star in the expanding
envelope, does not require any modification of the current view as to
the nature of a Woif-Rayet star. The other possible interpretation
is that the observed displacements represent a gravitational red
shift. If the latter is correct, the radii of the gaseous envelopes in
which the emission bands arise cannot exceed approximately one-tenth
that of the sun, and the nuclei themselves must be considerably
smaller and extremely dense. Some elementary com- putations of the
physical conditions in these small gaseous envelopes do not lead
to any inherent impossibilities. The one grave objection appears to
lie in the extraordinarily high surface temperatures demanded of the
nuclei in order to produce the observed continuous spectra. In fact,
it is suggested that, if the gravitational interpretation is adopted,
the continuous spectra cannot be the black-body radiations of the
nuclei at all but must be fluorescent spectra arising in the inner
portions of the gaseous envelopes. The data available at present are
insufficient to decide between the two possible interpretations of
the red shift. It may only be said that the absorption explanation
does not receive much support, since visual inspection of spectrograms
indicates that absorption components on the violet edges of He u bands
are quite rare. Probably careful photometric investigation of the
contours of emission bands in Woif-Rayet spectra wifi, in the future,
decide the question
---------------------------------------------------------
Title: The Wolf-Rayet Spectroscopic Binary HD 193576.
Authors: Wilson, O. C.
1940ApJ....91..379W Altcode:
Spectrographic orbits have been derived for the double-lined binary
HP 193576. The Woff-Rayet component is of type WN5, while that of the
absorption-line com- ponent is somewhat uncertainly estimated as Bi. The
minimum masses of the Wolf- Rayet and B-type components are 9.740 and
24.80, respectively. A curious feature of the results is that the y-axes
for the two stars differ by 90 km/sec, the two values being +56 and -34
km/sec, respectively, for the Woif-Rayet and the B components. Neither
erroneous wave lengths nor blends seem to afford an explanation of
this difference. Since a velocity for the system of -~4 km/sec is much
more in keeping with the velocities of other early-type stars in the
vicinity of HD 193576 than is one of +56 km/sec, it is probable that
the emission bands of the Woif-Rayet star are shifted toward the red
by an amount equal to the difference between the y-axes. The nature
of the red shift is discussed in the following Contribution. The
significance of certain rather minor periodic variations in the He Ii
4686 band is discussed. In particular, no evidence for an eclipse is
found in the spectrographic ma- terial, and, therefore, no est mate of
the inclination of the orbit plane is possible. The absolute magnitude
of the system has been previously derived from the intensi- ties of
the interstellar H and K lines. It is found necessary to assume the
stars to be 1-2 mag. brighter in order to bring the density of the
B-type component into line with the known densities of other massive
stars of early type. When this is done, the density of the Woif-Rayet
star is found to be of the same order as that of the sun, if it has
a surface temperature of 8o,ooo°. Also, the Woif-Rayet star appears
to be about 4 mag. brighter than would be estimated from its mass on
the basis of the empirical mass-luminosity relation
---------------------------------------------------------
Title: Relative Populations of 2^{1}S and 2^{3}S States of Helium
in the Orion Nebula.
Authors: Wilson, O. C.
1940ApJ....91..360W Altcode:
The observed equivalent width of X 3889 of He i produced by the Orion
nebula, together with the absence of X 3965, leads to a lower limit
for the ratio of populations of the 2~S and 2'S states of N3/Ni »=
25. This is considerably in excess of the values calculated by Struve
and Wurm on the assumption of strict metastabifity for both levels,
and thus points toward a shorter mean life for 2'S than for 2~S. The
matter may be complicated, however, by the selective absorption by
the nebula of the light from the Trapezium stars
---------------------------------------------------------
Title: No. 623. The Wolf-Rayet spectroscopic binary HD 193576.
Authors: Wilson, O. C.
1940CMWCI.623....1W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: No. 625. Relative populations of 2<SUP>1</SUP>S and
2<SUP>3</SUP>S states of Helium in the Orion Nebula.
Authors: Wilson, O. C.
1940CMWCI.625....1W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Wolf-Rayet spectroscopic binary HD 193576.
Authors: Wilson, Olin Chaddock
1940wrsb.book.....W Altcode: 1940QB4.M93........
No abstract at ADS
---------------------------------------------------------
Title: No. 624. Physical characteristics of the Wolf-Rayet stars.
Authors: Wilson, O. C.
1940CMWCI.624....1W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Possible Applications of Supernovae to the Study of the
Nebular Red Shifts.
Authors: Wilson, O. C.
1939ApJ....90..634W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Intercomparison of Doublet Ratio and Line Intensity for
Interstellar Sodium and Calcium.
Authors: Wilson, O. C.
1939ApJ....90..244W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Doublet Ratio of Interstellar H and K and the Absolute
Magnitudes of Wolf-Rayet Stars.
Authors: Sanford, Roscoe F.; Wilson, O. C.
1939ApJ....90..235S Altcode:
Observations-The total absorptions of the interstellar Ca ii lines,
H and K, have been measured in 400 and B stars with weak H and in i8
Woif-Rayet stars (Table i). The difficulty so often encountered in
measuring the total absorption of H in the pres- ence of strong He
in absorption has therefore been largely obviated, and it is hoped
that these measures are an improvement upon earlier ones. Ratio of K
to H-K/H appears to be approximately 2 for very weak lines and to de-
crease, on the average, as lines of greater strength are considered,
reaching 1.56 for H 0.4 A, with little apparent tendency to diminish
thereafter. See Figures i and 2. Ratios D2/K and Di/H.-Twenty-f our
stars in Table i provide measures of the total absorptions of the
interstellar D2 and Di of Na I. The mean D2/K and Di/H derived therefrom
are 1.63 and 2.18, respectively, which closely check earlier results,
i.6 and the tentative value 2.1, respectively. Absolute magnitudes of
Woif-Rayet stars-The curve which relates distance with K- line intensity
has been used to derive the distances of the i8 Woif-Rayet stars
from which mean visual absolute magnitudes for 6 stars of the carbon
sequence and 12 of the nitrogen sequence have been derived. They are
-2.8 and -2.1, respectively. Masses of the Woif-Rayet stars-Plausible
values of temperature, together with our derived absolute magnitudes
and what appears to be a reasonable allowance for the contribution of
bright bands to the apparent magnitudes, give masses approximately
thirty times that of the sun. The assumptions and guesses involved
make such values highly speculative, even though the mass-luminosity
relation itself is unqualifiably ac- cepted
---------------------------------------------------------
Title: No. 613. On the doublet ratio of interstellar H and K and
the absolute magnitudes of Wolf-Rayet stars.
Authors: Sanford, Roscoe F.; Wilson, O. C.
1939CMWCI.613....1S Altcode: 1939QB4.M93n613....
No abstract at ADS
---------------------------------------------------------
Title: Velocities and intensities of absorption lines produced by
helium in the Orion Nebula
Authors: Wilson, O. C.
1939PAAS....9R.274W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: No. 614. Inter comparison of doublet ratio and line intensity
for interstellar sodium and calcium.
Authors: Wilson, O. C.
1939CMWCI.614....1W Altcode: 1939QB4.M93n614....
No abstract at ADS
---------------------------------------------------------
Title: Hɛ Emission in the Spectrum of Arcturus
Authors: Wilson, O. C.
1938PASP...50..245W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Radial Velocities of 600 Stars and Measures of 69
Spectroscopic Binaries.
Authors: Christie, William H.; Wilson, O. C.
1938ApJ....88...34C Altcode:
The radial velocities of 600 stars observed with the 60- and
100-inch reflectors are given. This list is in no way homogeneous
and contains stars from several observing lists made up for various
investigations. In addition, measures are given for 69 variable-velocity
stars, some of which have been observed elsewhere
---------------------------------------------------------
Title: Double Interstellar Sodium Lines
Authors: Sanford, R. F.; Merrill, P. W.; Wilson, O. C.
1938PASP...50...58S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: No. 582. Unidentified interstellar lines in the yellow and red.
Authors: Merrill, Paul W.; Wilson, O. C.
1938CMWCI.582....1M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: No. 593. The radial velocities of 600 stars and measures of
69 spectroscopic binaries.
Authors: Christie, William H.; Wilson, O. C.
1938CMWCI.593....1C Altcode: 1938QB4.M93n593....
No abstract at ADS
---------------------------------------------------------
Title: Unidentified Interstellar Lines in the Yellow and Red
Authors: Merrill, Paul W.; Wilson, O. C.
1938ApJ....87....9M Altcode:
Six unidentified interstellar lines (Table i) are discussed. Following
a brief history of previous observations, Tables 2 and 3 give widths
and central absorptions of three of the lines. The total intensity
of X 6284, which, in the mean, equals the average for the detached
lines Di and D2, shows a somewhat stronger correlation with stellar
color excess than does the intensity of the D lines. The widths of the
unidentified lines, which are rather diffuse and not sharp like the
D lines, and other facts make an atomic origin improbable. The lines
may be portions of molecular bands, as yet unidentified. Several facts,
however, suggest that the lines are produced by small solid particles,
per- haps closely related to those that cause space reddening
---------------------------------------------------------
Title: Helium Absorption Due to the Orion Nebula
Authors: Wilson, O. C.
1937PASP...49..338W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Intensities and Displacements of Interstellar Lines
Authors: Merrill, Paul W.; Sanford, Roscoe F.; Wilson, O. C.; Burwell,
Cora G.
1937ApJ....86..274M Altcode:
The main purpose of this ConirThution is to record measurements of
the intensities and displacements of the interstellar lines Di, D2, H,
and K in the spectra of numerous early-type stars. Intensities of the
unidentified lines XX 5780, 5797, and 6284 are in- cluded. Observational
methods and the technique of measurement are fully described, and the
accuracy of the results is discussed. Comparison of the Mount Wilson
values of the intensities of the D lines with those of Beals (Table 3,
Fig. i) indicates a fairly small accidental error in both series but
a con- siderable systematic difference between them. Displacements
of the D lines measured at various observatories (Table 7) are in
good agreement. The Catalogue, Table 6, includes 254 stars brighter
than apparent magnitude 7.0, 147 fainter stars, and, in addition,
3 novae. The numbers of objects with the various kinds of data are
as follows
---------------------------------------------------------
Title: Intensities of the Infrared Cα II Triplet in Stellar Spectra
Authors: Wilson, O. C.; Merrill, Paul W.
1937ApJ....86..162W Altcode:
The equivalent widths of the infrared Ca n triplet, XX 8498, 8542, and
8662, have been measured on spectrograms of the sun and of several stars
taken with a grating spectrograph having a dispersion of 33 A/mm. The
results for the solar lines agree well with those of other observers and
are nearly proportional to t~he square roots of the theore~ica1muitip1et
int~nsities. In the stars, however, particularly the late-type giants,
there is a strong tendency for the three lines to be more nearly equal
in strength. The cause of the variation in gradient is not clear,
and more extensive observations will be of interest
---------------------------------------------------------
Title: Forbidden Iron Lines in the Spectrum of the Companion of
α Scorpii
Authors: Wilson, O. C.; Sanford, R. F.
1937PASP...49..221W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Analysis of the Intensities of the Interstellar D Lines
Authors: Wilson, O. C.; Merrill, Paul W.
1937ApJ....86...44W Altcode:
Previous investigations of interstellar lines are briefly reviewed. The
interstellar D-line intensities measured at Mount Wilson in the spectra
of over 200 early-type stars are critically discussed with the object of
deducing the distribution and motions of the sodium atoms in space. If
the atoms are assumed to have no rela- tive motions other than those
due to temperature, the D-line intensities should follow a normal
curve of growth. This assumption is shown to be incorrect because
(i) the curve derived from the measured intensities does not have the
proper shape and (2) it leads to very improbable d~istances for the
stars with strong lines as compared to those with weak lines. The
introduction of galactic rotation gives a good representation of
the mean de- crease of the doublet ratio D2/DI from 2.0 to 1.2 with
increasing intensity. A more de- tailed examination proves conclusively,
however, that the rotational velocity gradient cannot be responsible
for the widths of the lines because, for a given distance, the line
intensities an~I the doublet ratio are essentially the same for all
galactic longitudes. The observations can be accounted for by making the
hypothesis that interstellar sodium occurs in discrete aggregations or
clouds, which, while participating in the gen- eral galactic rotation,
have in addition considerable random motions. This assumption requires
no dependence upon t~ie galactic longitude and succeeds in explaining
how the D lines can strengthen almost linearly with the distance,
while the ratio of D 2 to Di is only 1.2. By fitting computed curves to
the observational data, the following numerical results are obtained:
an upper limit to the temperature is 44,000°; the density of sodium
atoms in the ground state is approximately io-3' gm/cc; the linear
dimensions of the clouds, in the galactic plane, are of the order of
700 parsecs; and the spread of the ran- dom cloud velocities need not
exceed 15 or 20 km/sec
---------------------------------------------------------
Title: The System of β Capricorni
Authors: Adams, W. S.; Sanford, R. F.; Wilson, O. C.
1937PASP...49...25A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: No. 575. Intensities of the infrared CaII triplet in stellar
spectra.
Authors: Wilson, O. C.; Merrill, Paul W.
1937CMWCI.575....1W Altcode: 1937QB4.M93n575....
No abstract at ADS
---------------------------------------------------------
Title: No. 570. Analysis of the intensities of the interstellar
D-lines.
Authors: Wilson, O. C.; Merrill, Paul W.
1937CMWCI.570....1W Altcode: 1937QB4.M93n570....
No abstract at ADS
---------------------------------------------------------
Title: No. 576. Intensities and displacements of interstellar lines.
Authors: Merrill, Paul W.; Sanford, Roscoe F.; Wilson, O. C.; Burwell,
Cora G.
1937CMWCI.576....1M Altcode: 1937QB4.M93n576....
No abstract at ADS
---------------------------------------------------------
Title: The Blending of H and Hɛ in the Spectrum of α Lyrae
Authors: Wilson, O. C.; Thackeray, A. D.
1936PASP...48..329W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Radial Velocity Curves of Nova Lacertae 1936
Authors: Adams, W. S.; Sanford, R. F.; Wilson, O. C.
1936PASP...48..325A Altcode:
No abstract at ADS
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Title: Variations in the Spectrum of P Cygni
Authors: Wilson, O. C.
1936ApJ....84..296W Altcode:
An examination of spectrograms of P Cygni taken at the Lick and Mount
Wilson observatories has shown that the Balmer lines in this star
consist of an emission com- ponent and two absorption components,
instead of one, as formerly supposed. These two absorption components
vary in intensity (and probably in position) in such a way that on
some occasions both are visible, while on others only one or the other
is to be seen. No period for the variation can be deduced from the
available material, but it is demonstrated that significant changes have
occasionally occurred within intervals of the order of one month. The
helium lines also appear to pass through a similar cycle in step with
those of hydrogen
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Title: Note on the Absolute Magnitudes at Maximum of Nova Aquilae
1918 and Nova Cygni 1920
Authors: Wilson, O. C.
1936PASP...48..229W Altcode:
No abstract at ADS
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Title: Distance of Nova Lacertae 1936 Derived from the Intensities
of Interstellar Lines
Authors: Merrill, P. W.; Wilson, O. C.
1936PASP...48..230M Altcode:
No abstract at ADS
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Title: Contour or profile?
Authors: Wilson, O. C.; Williams, E. G.
1936Obs....59...49W Altcode:
No abstract at ADS
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Title: Intensities of interstellar lines
Authors: Merrill, P. W.; Wilson, O. C.
1936PAAS....8R.249M Altcode:
No abstract at ADS
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Title: No. 550. Variations in the spectrum of P Cygni.
Authors: Wilson, O. C.
1936CMWCI.550....1W Altcode: 1936QB4.M93n550....
No abstract at ADS
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Title: Note on the recent eclipse of ζ Auriage
Authors: Christie, W. H.; Wilson, Olin C.
1935AN....257..183C Altcode:
No abstract at ADS
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Title: Absorption Lines due to an Expanding Star
Authors: Wilson, O. C.
1935ApJ....82..233W Altcode:
The modification of the shape of an absorption line produced by an
expansion or con- traction of a star is investigated. It is shown that
Carroll's approximation is valid only for small velocities and that for
large velocities important changes in the shape and strength of a line
occur. Applications to giant stars and Cepheid variables are discussed
briefly and to Woif-Rayet stars and novae with more detail. A method
is indicated by which, if the geometrical explanation of certain
features in the spectrum of Nova Her- culis is considered valid,
the linear dimensions of the star may be computed. A pre- liminary
calculation gives for the radius of the photosphere of Nova Herculis
in its earlier stages a value of the order of iooX 106 km
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Title: Radial velocities from absorption lines in the spectrum of
Nova Herculis.
Authors: Adams, W. S.; Christie, W. H.; Joy, A. H.; Sanford, R. F.;
Wilson, O. C.
1935PASP...47..205A Altcode:
No abstract at ADS
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Title: ζ Aurigae: the Structure of a Stellar Atmosphere
Authors: Christie, William H.; Wilson, O. C.
1935ApJ....81..426C Altcode:
From the measures of spectrograms of ~ Aurigae taken during the 1934
eclipse a ~iumber of new and interesting results have been obtained. By
combining the measures of the light of the star made at Mount Wilson
and Madi- son with the spectroscopic elements derived by Harper and
by the authors, new ele- ments for the system have been obtained. A
method has been devised whereby the effects of the light of the K star
in the corn- posite spectrum of the two bodies may be eliminated from
measures of microphotometer tracings of the spectra. This possibility
has enabled us to measure the total absorption of the continuous
spectrum of the B star produced by the various elements in the atmos-
phere of the K star. From a number of microphotometer tracings made
from the most suitable plates, the claanges in the total absorption have
been measured for nearly a hundred lines in the spectra. These measures
have been used to determine the effect of the B star shining through
the atmosphere of the K star alone, thus affording means of obtaining
the rela- tive numbers of atoms of the various elements existing at
different levels above the photosphere of the K star. These results
are grouped into six distinct classes: neutral metals; Mg; Ti~ (two
groups); H; Cat Comparison of these results with theory reveals that
there is, in most cases, no ade- quate hypothesis to account for the
observed distribution. The measures of the bydro- gen lines indicate
that the hydrogen shell surrounding the star is of uniform density
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Title: Cyanogen Absorption in the Spectrum of Nova Herculis, 1934
Authors: Wilson, O. C.; Merrill, P. W.
1935PASP...47...53W Altcode:
No abstract at ADS
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Title: No. 519. &Zeta Aurigae: The structure of a stellar
atmosphere.
Authors: Christie, William H.; Wilson, O. C.
1935CMWCI.519....1C Altcode: 1935QB4.M93n519....
No abstract at ADS
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Title: Spectrophotometry of RS Ophiuchi (nova Ophiuchi no.
Authors: Wilson, O. C.; Williams, E. G.
1934ApJ....80..344W Altcode:
From one good plate taken with the three-prism violet spectrograph
on August 30, 1933, the apparent color temperature of RS Ophiuchi is
found to be 4000° K. Contours of the hydrogen emission bandshave
been determined from several plates covering the period August
i6-September ii, ~ On the assumption that the red sides of the bands
present the true unmodified shapes, the following facts emerge: a)
The contours are roughly exponential in form. The earlier ones can
be represented approximately by the formula 1= e-(u/u~, where n-~
r+k(uo/u)-k and k =0.125. The value u0 decreases rapidly with time
at first, then more slowly, ftnally attaining a more or less constant
value; k also decreases and may be considered to vanish for the later
contours. b) In addition to a sharp absorption component present on the
short-wave-length sides of the band maxima in the early stages, there
appears to be a general deficiency of intensity over the violet halves
of the bands relative to that of the red halves. The sup- position that
this is due to the complete suppression of the continuous spectrum
under the violet sides is not in entire agreement with the facts,
but there may be complicating factors. This hypothesis would require
a large velocity range among the atoms directly in front of the star,
and leaves no room for the monochromatic hydrogen absorption components
or for the sharp nebular lines. It is suggested that the latter arise
in a quies- cent shell around the star left over from its previous
outburst. The Balmer decrement has been obtained from two accordant
plates, and is found to be appreciably faster than the mean of those
found by Plaskett and by Berman for planetary and diffuse nebulae. The
observed decrement is brought into good agreement with the latter by
applying the differential factors necessary to reduce a true tempera-
ture of 35,0000 to an apparent one of 40000. From several spectrograms
it appears that the ratio of the area of Hy to the intensity in the
underlying continuous spectrum did not vary greatly between August
i6 and September 2, 1933. Zanstra's method gives a photo-electric
temperature of 35,000°, calculated from the measures on plate V4o4,
August i8. If this is a real measure of the temperature, it fol-
lows from the preceding paragraph that, while the star decreased in
brightness by about two magnitudes from August i6 to September 2, its
temperature remained constant. This conclusion would imply that the
fading of the star was due to a shrinkage in the radiating surface. From
the measured intensity of the K line, with an approximate allowance for
a probable stellar blend, a distance of 95o parsecs is deduced. This is
shown to be fairly consistent with the recent results of Stebbins and
Huffer on the assumption that the difference between the photo-electric
and apparent temperatures is due to space redden- ing
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Title: The Analysis of Nova Emission Bands
Authors: Wilson, O. C.
1934ApJ....80..259W Altcode:
It is assumed, following Gerasimovi~ and Chandrasekhar, that nova
emission bands originate in spherical expanding gaseous envelopes having
internal velocity gradients; also that the matter in the envelope is
transparent to its own radiation and that Chandrasekhar's occultation
effect may be neglected. A method is then developed by which the
velocity gradient can easily be found from the observed band shapes;
all that is required is a simple integration. The analysis is applied
to the hydrogen emission contours recently measured in the spectrum
of RS Ophiuchi
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Title: Comparison of the Paschen and the Balmer Series of Hydrogen
Lines in Stellar Spectra
Authors: Merrill, Paul W.; Wilson, Olin C.
1934ApJ....80...19M Altcode:
Introduction-The structure of the hydrogen spectrum and previous
observations of the Paschen series are briefly described. The behavior
of the Paschen lines m= 12 to m = 24, recently photographed at Mount
Wilson in various types of stellar spectra, resembles in general
that of the Bahner lines in the same types. The Paschen series is
very conspicuous in the c stars $ Orionis and a Cygni. Photometric
data-Measurements of structure and intensity have been made by the usual
photometric methods on numerous lines in both hydrogen series in the
spectra of a Leonis B8n, a Lyrae Ao, a Canis Majoris Ao, j3 Orionis
cB8, and a Cygni cA2. Structure of lines-Most lines not affected
by the overlapping of neighboring lines have contours of the simple
exponential form, although in a Leonis the centers are flattened. In the
broad-line stars a Leonis and a Lyrae considerable departure from the
exponential form is exhibited by the wings of lines near the heads of
the series. In ~3 On- onis, a Cygni, a Leonis, and in the emission-line
stars `y Cassiopeiae and P Cygni the shapes of Balmer and Paschen
lines are similar, with the dimensions proportional to wave-length;
but this is not true of a Lyrae, in whose spectrum the Balmer lines
have relatively more intense wings. Central intensities-Measured
values for numerous lines are given in Table VI. In general the central
intensities of Paschen lines are less than those of the corresponding
Balmer lines. In a Leonis the Paschen series is relatively intense and
has a slow decre- ment. In j3 Orionis and a Cygni both series exhibit
slow decrements and little overlap- ping. Problem of overlapping
lines-The shapes as well as the central intensities of many lines,
particularly in the Balmer series, are probably seriously modified by
the over- lapping wings of adjacent lines. The problem is to find the
shapes and intensities of the "true" or original lines which by their
mutual interaction produce the observed curve. A physically reasonable
sequence of lines has been found which yields close ap- proximations
to the observed shapes and intensities in a Lyrae but gives too great
a reduction of the general intensity of the whole spectrum toward the
head of the series. This difficulty, which appears to be of a rather
general nature, is briefly discussed. Total line absorption-Measured
values for lines of both series in a Cygni, /3 Orionis, and a Leonis
are given in Table VII. From these data Unsold's equation gives
the num- bers of atoms in the second and third levels. The numbers
computed for a given level from various lines differ systematically,
indicating that the theory is incomplete. The maximum numbers, used in
Boltzmann's equation for thermal equilibrium, give reason- able values
of the temperature of the absorbing hydrogen. Intensities of emission
lines-Several bright lines in both series were measured in y Cassiopeiae
and P Cygni. The relative importance of induced and spontaneous emis-
sion is discussed. The photospheric temperatures computed from the
intensities of pairs of lines having a common upper level depend on the
assumed distribution of the atoms with respect to azimuthal quantum
number. An assumed distribution corresponding to thermal equilibrium
leads to reasonable temperatures for both stars. The possibility of
determining the amount of space absorption by comparison with other
data is pointed out. * Contributions from the Mount Wilson Observatory,
Carnegie Institution of Washing- ton, No. 494
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Title: No. 501. Spectrophotometry of RS Ophiuchi (Nova Ophiuchi
No. 3).
Authors: Wilson, O. C.; Williams, E. G.
1934CMWCI.501....1W Altcode: 1934QB4.M93n501....
No abstract at ADS
---------------------------------------------------------
Title: Comparison of the Balmer and Paschen series of hydrogen in
stellar spectra
Authors: Wilson, Olin Chaddock, Jr.
1934PhDT........16W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comparison of the Balmer and Paschen Series of Hydrogen in
Stellar Spectra.
Authors: Wilson, Olin C.
1934PhDT.........7W Altcode:
No abstract at ADS
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Title: No. 494. Comparison of the Paschen and the Balmer series of
hydrogen lines in stellar spectra.
Authors: Merrill, Paul W.; Wilson, Olin C., Jr.
1934CMWCI.494....1M Altcode: 1934QB4.M93n494....
No abstract at ADS
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Title: No. 500. The analysis of nova emission bands.
Authors: Wilson, O. C.
1934CMWCI.500....1W Altcode: 1934QB4.M93n500....
No abstract at ADS
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Title: Contours of Absorption Lines in Nova Aquilae 1918 before
Maximum
Authors: Wilson, O. C.
1932PASP...44..388W Altcode:
No abstract at ADS
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Title: An Application of the Radiometer: a Registering Microphotometer
Authors: Smith, Sinclair; Wilson, Olin C., Jr.
1932ApJ....76..117S Altcode:
A registering microphotometer is described in which a radiometer is
used as the light- sensitive element. The instrument has been made as
simple as possible without sacrifice of performance, and tests seem
to show that it is both fast and precise, besides being very easy to
operate. The details of construction are discussed and some typical
records are reproduced
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Title: The Velocity of Light
Authors: Wilson, Olin C.
1932Natur.130...25W Altcode:
IN NATURE for April 4, 1931, M. E. J. Gheury de Bray points out that
the determinations of the velocity of light made in this century seem
to tend towards smaller and smaller values the more recent the time
of observation.
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Title: Three New Be Stars
Authors: Wilson, Olin C., Jr.
1932PASP...44..124W Altcode:
No abstract at ADS
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Title: No. 454. An application of the radiometer: A registering
microphotometer.
Authors: Smith, Sinclair; Wilson, Olin. C., Jr.
1932CMWCI.454....1S Altcode: 1932QB4.M93n454....
No abstract at ADS