abt

explanation blue bibcodes open ADS page with paths to full text

Author name code: abt
ADS astronomy entries on 2022-09-14
author:"Abt, Helmut A." OR author:"Abt, Arthur"

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Title: The Lifetimes of Astronomical Papers and the Completeness of
the ADS
Authors: Abt, Helmut A.
2019BAAS...51d0207A Altcode:
By counting the numbers of citations received after publication, we can
determine how long astronomical papers are remembered. Those from 1955
have a half-life of 71 years and in 1960 it was 25 years. After 1970
the half-life has been a steady 10 years, telling us that astronomical
results are now appreciated quickly and then replaced quickly. However,
average astronomical papers have been receiving increased total
citations. Tests for astronomical journals showed that ADS has a
completeness of 94%, although it does not include most observatory
publications and books.

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Title: Lifetime Data on Astronomical Papers and Citations
Authors: Abt, Helmut A.
2019RNAAS...3...93A Altcode: 2019RNAAS...3g..93A
No abstract at ADS

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Title: VizieR Online Data Catalog: The evolutionary status of GK
subgiants (Abt, 2019)
Authors: Abt, H. A.
2019yCat..51570177A Altcode:
The Snowden-Young (2005ApJS..157..126S) sample of GK class IV
stars north of -20° decl. was selected from the Yale Catalog
of Bright Stars (Hoffleit 1964, Cat. V/50). In addition, Snowden
&amp; Young observed 14 additional stars as controls. They were GK
III standards of radial velocities and three known spectroscopic
binaries: HD 102928 (Massarotti et al. 2008, J/AJ/135/209), HD 150680
(Katoh et al. 2013, J/AJ/145/41), and HD 170829 (Katoh et al. 2013,
J/AJ/145/41). Most of the new radial velocities of these bright stars
were obtained with the 1.53 m Harvard Tillinghast telescope at the
Oak Ridge Station. The original digital spectrograph, which gave
velocity accuracies of σ~+/-0.3 km/s, was replaced in 2011 with an
echelle spectrograph (Tillinghast Reflector Echelle Spectrograph)
giving α=+/-0.10 km/s. The individual velocities can be found at
http://www.cfa.harvard.edu/~latham/snowden/snowden.orb. (4
data files).

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Title: The Evolutionary Status of GK Subgiants
Authors: Abt, Helmut A.
2019AJ....157..177A Altcode:
Snowden &amp; Young suggested that the reason why there are GK subgiants
is because they are members of binaries, which would bring them above
the main sequence in an Hertzsprung-Russell (HR) diagram. They studied
a sample of 30 G0-K1 IV stars and were disappointed to find only two
to be spectroscopic binaries. With more accurate radial velocities I
found seven binaries in their samples of subgiants and control stars;
orbital elements are given for those seven. Using Hipparcos parallaxes
and SIMBAD data, I found that nearly all of the G0-K1 IV stars fall on
the evolutionary tracks by Garardi et al. for Population I stars with
masses of 0.9-1.9 M ⊙ and ages of up to 1010
yr, which are normal parameters for nearby field stars. Therefore
there is no problem regarding the existence of GK subgiants.

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Title: Publication Changes during the IAU History
Authors: Abt, Helmut A.
2019IAUS..349..397A Altcode:
During the 100 years of the International Astronomical Union,
the worldwide astronomical publications have grown exponentially,
converted almost entirely to English, and changed format from
observatory publications to journals to online publications. Observatory
publications, conference proceedings, and individual theses have nearly
disappeared in usefulness for research.

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Title: Principles of Editing
Authors: Abt, Helmut A.
2019BAAS...51a0201A Altcode: 2019BAAS...51.0201A
During my 29 years (1971-1999) as Editor-in-Chief of The Astrophysical
Journal, I learned or developed various principles and policies for
editing that seem scientifically sound, fair, and effective.

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Title: Spectroscopic Orbits for Late-type Stars. II
Authors: Fekel, Francis C.; Willmarth, Daryl W.; Abt, Helmut A.;
Pourbaix, Dimitri
2018AJ....156..117F Altcode:
We have determined spectroscopic orbital elements for 13 systems—10
single-lined binaries and three double-lined binaries. For the
three binaries with previously published spectroscopic orbits, we
have computed improved or comparable elements. While two systems
have relatively short periods between 10 and 19 days, the remaining
systems have much longer periods ranging from 604 to 9669 days. One
of the single-lined systems, HD 142640, shows both short-period and
long-period velocity variations and so is triple. For three systems—HD
59380, HD 160933, and HD 161163—we have combined our spectroscopic
results with Hipparcos astrometric observations to obtain astrometric
orbits. For HD 14802 we have determined a joint orbital solution from
spectroscopic velocities and interferometric observations. The orbits
given here will be useful in combination with future interferometric
and Gaia satellite observations.

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Title: The life and times of Aden and Marjorie Meinel; a biography
Authors: Breckinridge, James B.; Abt, Helmut
2018iau3.book...33B Altcode:
We are collecting information on Professor Aden and Marjorie Pettit
Meinel for their biography. Aden Baker Meinel, an astronomer, optical
scientist, astrophysicist, atmospheric physicist, and telescope
designer, died in Henderson, Nevada, on 2 October 2011. He was the
founding director of Kitt Peak National Observatory (1955-1960) and the
Optical Science Center (1965-1971) of the University of Arizona. He was
also the director of Steward Observatory from 1963 to 1965. Marjorie
was a daughter of Mt. Wilson astronomer Edison Pettit. Aden was very
active in the IAU and was president of the commission on telescopes and
instruments, which is no longer active. During his long career he was a
consultant on the Chinese LAMOST and a 48-inch telescope in Hyderabad,
India. We would like to discuss your experiences with them. Please
send an email to James B. Breckinridge at jbreckin@caltech.edu to help
us. Aden developed an interest in astronomy in high school. At 19
he entered Caltech as a sophomore. In 1942 Aden dropped out of school
to join the US Navy's Caltech rocket program. He went to Europe in
1944 to investigate the German V-2 rocket factory at Nordhausen and its
underwater-rocket testing facility at Toplitzsee. Upon his return
in 1946 he entered graduate school of astronomy at the University of
California, Berkeley, where he earned his Astronomy PhD in 3 years. His
advisor was C. D. Shane. Aden designed and built a Schmidt telescope
and used it to make the first observations of the IR emission bands
of molecular oxygen and hydrogen in the atmosphere to demonstrated
that auroras are produced by solar protons. He graduated in 1949 and
accepted an appointment to Yerkes Observatory at the University of
Chicago in 1950. In 1955 NSF appointed Aden to search potential
sites for a national observatory to provide telescope access for
astronomers in the US. The result was Kitt Peak National Observatory,
and Aden its first director. He proved the practicality of segmented
telescope mirrors with his design of the MMT. Aden recognized
the need for an interdisciplinary academic center of excellence in
optical science. In 1964 he became the first director of the UA's
Optical Sciences Center and created a graduate degree program in
optics. Today this College of Optical Sciences has more than 2,500
graduates and 100 faculty teaching more than 90 courses. Aden joined
NASA's Jet Propulsion Laboratory (JPL) in 1983. His work laid the
foundation for JWST. In 1986, Aden concluded that detecting exoplanets
was feasible and NASA created the exoplanet program. During an active
research career that spanned almost 70 years, Aden published more than
250 papers and 6 books. Among his awards were the AAS Helen B. Warner
Prize in 1954 and the OSA's Adolph Lomb medal in 1952 the Frederic
Ives Medal in 1980. He and Marjorie Meinel, his wife and long-time
research collaborator, jointly received three awards from SPIE.

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Title: What Fraction of Papers in Astronomy and Physics Are Not
Cited in 40 Years?
Authors: Abt, Helmut A.
2018PASP..130g4506A Altcode:
Of 4000 papers published in astronomy and in physics in the past
40 years, 40.3%, and 23.4%, respectively, have not been cited
(referenced). However, if we limit this to the final research papers
(excluding announcements, book reviews, proposals for funding, and
observing time, obituaries, etc.), the fractions are 1.4% and 1.5%,
respectively. So virtually all the papers in these two sciences are
useful. These data also tell us that the productivities of astronomers
peak at age 40.4 years. and that 43.0% were published after the age
of 50 years. For physicists, the peak occurs at 36.6 years. and only
33.7% were published after the age of 50 years. Therefore physicists
peak about four years earlier than astronomers and they produce 9%
fewer citations after the age of 50 years.

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Title: An earlier explosion date for the Crab Nebula supernova
Authors: Abt, Helmut A.; Fountain, John W.
2018RAA....18...37A Altcode:
The Chinese first reported the Crab Nebula supernova on 1054 July
5. Ecclesiastical documents from the near east reported it in April
and May of 1054. More than 33 petroglyphs made by Native Americans
in the US and Mexico are consistent with sightings both before and
after conjunction with the Sun on 1054 May 27. We found a petroglyph
showing the new star close to Venus and the Moon, which occurred on
1054 April 12 and April 13, respectively. Collins et al., using the
four historical dates, derived a light curve that is like that of a
Type Ia supernova. The only remaining problem with this identification
is that this supernova was near maximum light for 85 d, which is unlike
the behavior of any known supernova.

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Title: The Most Productive Years of Average Astronomers
Authors: Abt, Helmut A.
2017PASP..129k4505A Altcode:
We learned previously that geniuses and outstanding scientists have
peak productivities in their 30s but produce little late in life. This
time we consider average astronomers who have completed their careers
(25 American Astronomical Society members who died recently) and found
that they peak in their mid 40s and did half of their life's important
output after age 50.

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Title: VizieR Online Data Catalog: Shape parameters for 154 Galactic
open clusters (Zhai+, 2017)
Authors: Zhai, M.; Abt, H.; Zhao, G.; Li, C.
2017yCat..51530057Z Altcode:
The data used are from database WEBDA
(http://www.univie.ac.at/webda/). We have found 946 open clusters with
equatorial coordinates for each cluster member. Since cluster members
are easily contaminated by field stars, we have only adopted stars
with membership probabilities higher than 70% as cluster members. It
is rarely possible to determine a cluster's shape with a small number
of members, so we have only considered relatively richer clusters,
which host more than 20 of the most probable member stars. After these
selections, there are 154 clusters left. (1 data file).

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Title: VizieR Online Data Catalog: Radial velocities of NGP wide
binaries (Latham+, 1991)
Authors: Latham, D. W.; Mazeh, T.; Davis, R. J.; Stefanik, R. P.;
Abt, H. A.
2017yCat..51010625L Altcode:
All 244 stars brighter than V magnitude 12.0 in a magnetic tape version
of the Weistrop catalog (1980, private communication) were observed
with the CfA digital speedometers. Three of the stars near the
faint limit of the sample turned out to be close visual pairs, with
angular separations between 1.4 and 4.0 arcsec. Although we do not
have accurate photometry of the individual components in these pairs,
we estimate that they are all fainter than the 12.0mag limit of the
survey. Thus our data table has 247 entries. (5 data files).

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Title: What Happens to Am Stars After They Leave the Main Sequence?
Authors: Abt, Helmut A.
2017PASP..129d4201A Altcode:
The Am, or “Metallic-line,” stars have too strong line strengths
of the iron peak elements for their temperatures and too weak He, Ca,
etc. Michaud showed that the A4-F2 V stars, which occur in the same
area of the main sequence as the Am stars, have radiative zones below
their photospheres where diffusion acts to push metals upward into the
photospheres by radiation pressure and lets Ca, etc. sink downward,
but only if the stars are slow rotators. Slow rotation can be caused
by the formation of disks or by tidal interactions in binaries. The Am
stars are rich in binaries with P &lt; 100 days; the rapidly rotation
A4-F2 V stars have no such binaries. The special peculiarities do not
occur in stars above the luminosity class V stars, except among the ρ
Puppis stars, so the radiative zones must disappear and the atmospheres
become well mixed with the interiors. The suggestion that the ρ Puppis
stars are the descendents of the Am stars fails because there are too
few ρ Puppis stars by a factor of about 100. Then by searching for
binaries among evolved stars I conclude that the Am stars plus A4-F2 V
normal stars evolve into A7-F9 IV stars and then into F2-F9 (or later)
III stars with normal abundances.

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Title: Citations and Team Sizes
Authors: Abt, Helmut A.
2017PASP..129b4008A Altcode:
I explore whether small or large teams produce the most important
astronomical results, on average, using citation counts as our metric. I
present evidence that citation counts indicate the importance of
papers. For the 1343 papers published in A&amp;A, ApJ, and MNRAS in
2012 January-February, I considered 4.5 years worth of citations. In
each journal, there are larger citation counts for papers from large
teams than from small teams by a factor of about 2. To check whether the
results from 2012 were unusual, I collected data from 2013 for A&amp;A
and found it to be the same as that for 2012. Could the preponderance
of papers by large teams be due to self-citations (i.e., citing and
cited papers sharing one or more authors)? To answer this, I looked at
136 papers with one to 266 authors and discovered a linear relation
that ranges from a 12.7% self-citation rate for single-author papers
to a 45.9% self-citation rate for papers with 100 authors. Correcting
for these factors is not enough to explain the predominance of the
papers with large teams. Then I computed citations per author. While
large teams average more citations than small ones by a factor of 2,
individuals on small teams average more citations than individuals
on large teams by a factor of 6. The papers by large teams often
have far more data, but those by small teams tend to discuss basic
physical processes.

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Title: The Shape Evolution of Galactic Open Clusters from Observations
Under Galactic External Forces
Authors: Zhai, Meng; Abt, Helmut; Zhao, Gang; Li, Chengdong
2017AJ....153...57Z Altcode:
We present the Galactic characteristics of 154 open clusters using
the stellar statistics method with data from the WEBDA database. We
find that all clusters in our sample are elongated in shape, which
indicates that the spherical clusters are stretched out to be ellipsoid
as a function of age ({log}({age}/{year})=6.64{--}9.7). By dividing a
cluster into a central core and an outer part, we have computed the
apparent ellipticities of these two parts respectively. The scale
relations between ellipticities and age indicate that the outer
parts of open clusters become more elliptical while the central
cores remain circular. We suppose that the outer parts become more
elliptical because they are more subjected to the external forces,
e.g., Galactic differential rotation, while the central cores form
a circular shape under the domination of stellar dynamics. We have
also performed an analysis of the crucial influence of cluster mass
and location on its shape.

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Title: VizieR Online Data Catalog: Spectroscopic orbits for 15
late-type stars (Willmarth+, 2016)
Authors: Willmarth, D. W.; Fekel, F. C.; Abt, H. A.; Pourbaix, D.
2016yCat..51520046W Altcode:
The radial velocities used here are mainly from four sources: those
obtained during the aforementioned work of Abt &amp; Willmarth
2006 (Cat. J/ApJS/162/207), an earlier survey of solar-type stars
(1986-1990, Julian Days 2546708-2550885) reported in Abt &amp;
Willmarth (1992ASPC...32...82A), subsequent observations by the
first author (DW) using the same spectrograph, and observations by
the second author (FF) that were acquired at Fairborn Observatory
(Fekel et al. 2009AJ....137.3900F). The observations of Abt
&amp; Willmarth 2006 (Cat. J/ApJS/162/207) were obtained with the
Kitt Peak National Observatory (KPNO) 0.9m auxillary coude feed
telescope and the coude spectrograph, which was originally built
for the KPNO 2.1m telescope. The observations reported in Abt &amp;
Willmarth (1992ASPC...32...82A) employed the same equipment, except
the "B" grating was used yielding approximately half the resolution
used in Abt &amp; Willmarth 2006 (Cat. J/ApJS/162/207). Subsequent
observations obtained by DW used either the "A" grating as in Abt &amp;
Willmarth 2006 (Cat. J/ApJS/162/207) or a 31.6grooves/mm echelle grating
cross-dispersed by grisms. The latter combination yields a resolving
power λ/Δλ=72000 for 2 pixels. Spectroscopic observations
with the 2m Tennessee State University telescope and fiber-fed echelle
spectrograph at Fairborn Observatory in southeast Arizona were described
in detail in Fekel et al. 2015 (Cat. J/AJ/149/63), and provide the
majority of the more recent radial velocities. (3 data files).

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Title: At What Ages Did Astronomers Write Their Most Important Papers?
Authors: Abt, Helmut A.
2016PASP..128i4501A Altcode:
In 1983 I found that the most productive ages for research
astronomers was 40-75 years, contradicting the frequent statement
that a scientist’s best work is done before the age of 35. Now most
scientists work in small to large teams, unlike the individual research
usually done previously. How has that affected the productive careers
of astronomers? A new study of 14 recent Russell Lecturers shows a peak
in productivity at age 33 and more than half that peak during 25-56
years, in agreement with results in other sciences. Nevertheless, 33%
of their best work was done after the age of 50 years.

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Title: Spectroscopic Orbits for 15 Late-type Stars
Authors: Willmarth, Daryl W.; Fekel, Francis C.; Abt, Helmut A.;
Pourbaix, Dimitri
2016AJ....152...46W Altcode:
Spectroscopic orbital elements are determined for 15 stars with
periods from 8 to 6528 days with six orbits computed for the first
time. Improved astrometric orbits are computed for two stars and one
new orbit is derived. Visual orbits were previously determined for
four stars, four stars are members of multiple systems, and five stars
have Hipparcos “G” designations or have been resolved by speckle
interferometry. For the nine binaries with previous spectroscopic
orbits, we determine improved or comparable elements. For HD 28271
and HD 200790, our spectroscopic results support the conclusions of
previous authors that the large values of their mass functions and lack
of detectable secondary spectrum argue for the secondary in each case
being a pair of low-mass dwarfs. The orbits given here may be useful in
combination with future interferometric and Gaia satellite observations.

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Title: Hot Gaseous Stellar Disks Avoid Regions of Low Interstellar
Densities
Authors: Abt, Helmut A.
2015PASP..127.1218A Altcode:
No abstract at ADS

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Title: VizieR Online Data Catalog: Bibliography of stellar radial
velocities (Abt+ 1972)
Authors: Abt, H. A.; Biggs, E. S.
2015yCat.3004....0A Altcode:
The data file contains a bibliography of 44,000 radial velocities
for about 25,000 stars, from a compilation of about 2340 publications
(see the "Note (3)" below). The authors estimate that 99% of stellar
radial velocities published by June 1970 are contained in the surveyed
volumes. (1 data file).

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Title: The Lifetimes of Astronomers
Authors: Abt, Helmut A.
2015PASP..127..713A Altcode:
No abstract at ADS

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Title: The Research Use of Astronomical Monographs
Authors: Abt, Helmut A.
2014PASP..126..409A Altcode:
No abstract at ADS

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Title: Joy, Alfred Harrison
Authors: Abt, Helmut A.
2014bea..book.1142A Altcode:
No abstract at ADS

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Title: Mayall, Nicholas Ulrich
Authors: Abt, Helmut A.
2014bea..book.1426A Altcode:
No abstract at ADS

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Title: Bohlin, Karl Petrus Teodor
Authors: Abt, Helmut A.
2014bea..book..256A Altcode:
No abstract at ADS

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Title: Scientific Efficiency of Ground-based Telescopes
Authors: Abt, Helmut A.
2012AJ....144...91A Altcode:
I scanned the six major astronomical journals of 2008 for all
1589 papers that are based on new data obtained from ground-based
optical/IR telescopes worldwide. Then I collected data on numbers
of papers, citations to them in 3+ years, the most-cited papers,
and annual operating costs. These data are assigned to four groups
by telescope aperture. For instance, while the papers from telescopes
with an aperture &gt;7 m average 1.29 more citations than those with
an aperture of 2 to &lt;4 m, this represents a small return for a
factor of four difference in operating costs. Among the 17 papers
that have received &gt;=100 citations in 3+ years, only half come from
the large (&gt;7 m) telescopes. I wonder why the large telescopes do
so relatively poorly and suggest possible reasons. I also found that
papers based on archival data, such as the Sloan Digital Sky Survey,
produce 10.6% as many papers and 20.6% as many citations as those based
on new data. Also, the 577.2 papers based on radio data produced 36.3%
as many papers and 33.6% as many citations as the 1589 papers based
on optical/IR telescopes.

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Title: The h- and a-Indexes in Astronomy
Authors: Abt, Helmut A.
2012opsa.book..245A Altcode:
Astronomers can compute h-indexes using either the Science Citation
Index (World of Science) or the Astrophysical Data System (ADS). These
two data systems sample different sets of publications.We compare the
different results from these and the advantages and disadvantages of
each.Because the Hirsch h-index is a steep function of time, their
values for young and old astronomers cannot be compared.We define an
a-index that is constant with time.Whether the h-index or a-index is
more indicative of important research depends upon how one accredits
the citation counts of authors in multi-author papers.We list current
mean h- and a-indexes for astronomers in four countries.We conclude
that on the average, individual astronomers in France, Germany, the
UK, and USA are doing equally well in research importance but those
in the first three countries are still not producing as much research
as those in the USA, relative to total populations.

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Title: The age of the local interstellar bubble
Authors: Abt, Helmut A.
2012AIPC.1452....9A Altcode:
No abstract at ADS

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Title: The Discovered Exoplanets Have The Same Orbital Elements As
Stellar Systems
Authors: Abt, Helmut A.
2012AAS...22012102A Altcode:
The Discovered Exoplanets Have the Same Orbital Elements as Stellar
Systems Helmut A. Abt Kitt Peak National Observatory,
Tucson, AZ 85726; abt@noao.edu&lt;/u&gt; There are two ways in
which planetary masses are formed. One is in debris disks like that
that produced the solar system. The other is as separate condensations
in stars clusters. We now know that the luminosity function extends
from stars through brown dwarfs to planetary masses. In the case of
separate condensations, many planetary masses will be captured to
become companions of stars. The exoplanet eccentricities are the same
as those of stellar companions, and are six times larger than those
of solar system planets. The exoplanet semi-major axes are like those
of stellar companions and are six times smaller than solar system
planets. We conclude that most of the exoplanets discovered to date
were produced as separate condensations like stars and not in disks.

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Title: The Age of the Local Interstellar Bubble
Authors: Abt, H. A.
2011ASPC..451..315A Altcode:
The Local Interstellar Bubble is an irregular-shaped region that happens
to be centered on the Sun. It has minimum and maximum radii of 50 and
150 pc. The density inside the bubble is 1/200 of that outside and
the temperature is about 1 million K. Therefore the density times the
temperature at the borders is constant, so the bubble is stable and can
be very old. It was evidently cleared of interstellar gas by one or
more supernovae. Because of the low density, no new stars could have
been formed in the bubble since the supernovae explosions. We looked
for the youngest stars within the bubble. In the central region they
are B7 so that region is about 160 million years old. The Pleiades lobe
has B3 stars so it is about 60 million years old. The lobe toward the
galactic center has O9.5 stars so it is about 4 million years old. In
fact, it has a pulsar with a spin-down time of 3.76 million years, so
that must be the remnant of the supernova that created that region. The
bubble has measureable OVI and CII lines, but no HI, confirming its
high temperature. The Sun was probably formed elsewhere and happened
to drift into the bubble some millions of years ago. The full text of
this talk was published in the Astronomical Journal (Abt 2011).

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Title: The Nature of the Exoplanets
Authors: Abt, Helmut A.
2011AIPC.1346...14A Altcode:
We wonder whether the exoplanets discovered to date were formed
in disk systems, like the Solar System, or like stellar and
brown-dwarf companions to stars. We show for large samples that
the stellar companions, brown-dwarf companions, and exoplanets have
large eccentricities (greater than 0.1 in half of the cases) but in
only one of the eight planets in the Solar System. Also the stellar,
brown-dwarf, and exoplanets usually are close to the primaries, unlike
in the Solar System. These suggest that the exoplanets discovered to
date were formed like stellar and brown dwarf companions, probably by
captures in three-body encounters, and not in disk systems. This is
confirmed in that binaries among metal-poor stars have a peak period
of 900 days, unlike the 20 days for metal-rich stars, so that explains
why few of the exoplanets discovered in the past few years occur around
metal-poor stars.

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Title: The Age of the Local Interstellar Bubble
Authors: Abt, Helmut A.
2011AJ....141..165A Altcode:
The Local Interstellar Bubble is an irregular region from 50
to 150 pc from the Sun in which the interstellar gas density is
10-2-10-3 of that outside the bubble and the
interstellar temperature is 106 K. Evidently most of the
gas was swept out by one or more supernovae. I explored the stellar
contents and ages of the region from visual double stars, spectroscopic
doubles, single stars, open clusters, emission regions, X-ray stars,
planetary nebulae, and pulsars. The bubble has three sub-regions. The
region toward the galactic center has stars as early as O9.5 V and
with ages of 2-4 M yr. It also has a pulsar (PSRJ1856-3754) with a
spin-down age of 3.76 Myr. That pulsar is likely to be the remnant
of the supernova that drove away most of the gas. The central lobe
has stars as early as B7 V and therefore an age of about 160 Myr or
less. The Pleiades lobe has stars as early as B3 and therefore an age
of about 50 Myr. There are no obvious pulsars that resulted from the
supernovae that cleared out those areas. As found previously by Welsh
&amp; Lallement, the bubble has five B stars along its perimeter that
show high-temperature ions of O VI and C II along their lines of sight,
confirming its high interstellar temperature.

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Title: The Tonantzintla Search for High Luminosity Stars
Authors: Abt, H. A.
2011RMxAC..39...65A Altcode:
Starting with the paper by G. González and G. González, 1952, BOTT,
1, 5, 1 in the first volume of the Bulletin, various Tonantzintla
astronomers worked for years to find the OB stars that delineate the
local spiral arms. Perhaps they became discouraged when the 21 cm radio
maps appeared, but they should not have been because the optical data
produce distances while the radio data measure only radial motions, that
need to be interpreted with a model of the motions in our Galaxy. Those
motions are more complicated than they thought, so their maps are very
inaccurate. The recent 4.5 μm infrared map shows our Galaxy to have
a central bar, two major spiral arms, and five small ones.

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Title: Symposium Summary
Authors: Abt, H. A.
2011RMxAC..39..117A Altcode:
No abstract at ADS

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Title: Astronomical Publication Rates in the US, UK, and Europe
Authors: Abt, Helmut A.
2011ASSP...24...77A Altcode: 2011ApSSP...1...77A
I explored the growth of astronomical research in the US, UK,
and four productive European countries to see if there has been any
leveling off. I counted pages in the four major astronomical journals,
and corrected for format changes and for contributions from other
countries. The four European countries were France, Germany, Italy,
and the Netherlands. In each area there has been no reduction in
output. However, the data show that the UK lags behind the US by 10
± 1 years and the four European countries lag the US by 12 ± 1 years.

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Title: The Origin of the Exoplanets
Authors: Abt, Helmut A.
2010PASP..122.1015A Altcode: 2010arXiv1008.4637A
We explore two ways in which objects of planetary masses can form. One
is in disk systems like the solar system. The other is in dense
clusters where stars and brown dwarfs form. We do not yet have the
instrumental accuracy to detect multiplanet systems with masses like
those in solar system; with our present technology from a distant
site, only the effects of Jupiter could be detected. We show that the
orbital characteristics (eccentricities and semimajor axes) of stellar,
brown dwarf, and exoplanet companions of solar-type stars are all the
same within our measuring accuracies and are very different than the
planets in the solar system. The period ratios in multiplanet systems
do not distinguish between the two models. We conclude that most of the
exoplanets found to date are formed like stellar companions and not
in disk systems like the solar system. This conclusion explains why
metal-poor stars lack planets: because metal-poor stars lack stellar
companions with short periods. The distribution of exoplanetary periods
for primaries having [Fe/H] &lt; -0.3 fits the distribution for stellar
companions of metal-poor stars and not of metal-rich stars.

---------------------------------------------------------
Title: Have We Reached a Maximum Astronomical Research Output?
Authors: Abt, Helmut A.
2010PASP..122..955A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: How Long Does It Take To Get A Paper Accepted For Publication
By The ApJ?
Authors: Abt, Helmut A.
2010AAS...21531605A Altcode: 2010BAAS...42R.317A
Publication after acceptance in the ApJ is now very fast. The first
papers are published in the on-line editions of Part 1 in 23 days after
acceptance and 19 days for the Letters. But what about the average
interval between submission and acceptance? Such data cannot be found
from the papers, but is available only in the editors’ logs. I
visited the Editor's ApJ office in Hamilton, Ontario and collected
data for 251 papers. It turns out that 6% of the papers are rejected,
5% are withdrawn, and 88% are eventually accepted for publication. The
average reviewing time is 44 days, average revision time is 53 days,
and editorial time is 12 days. Other pertinent data are given.

---------------------------------------------------------
Title: Stellar Rotation versus Duplicity in Open Cluster Early-Type
Stars
Authors: Abt, Helmut A.
2009PASP..121.1307A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Reviewing and Revision Times for The Astrophysical Journal
Authors: Abt, Helmut A.
2009PASP..121.1291A Altcode:
From a study of the editorial log for 251 manuscripts submitted in
2006, we learn that 6% are rejected, 5% are withdrawn, and 88% are
eventually accepted for publication. Of the accepted articles, 30%
are reviewed once, 58% twice, and 12% are reviewed 3-5 times. The mean
time for the first review is 31 days and for the first revision is
44 days. The spread in total reviewing times (dispersion of 16 days)
is much shorter than in total revision times (54 days). Important
articles, those receiving 31-193 citations in 2 yr, are not reviewed
more promptly than others nor revised more promptly. Only in the
subfield of high-energy objects do the authors revise their manuscripts
marginally more promptly than others.

---------------------------------------------------------
Title: VizieR Online Data Catalog: MK classifications of spectroscopic
binaries (Abt, 2009)
Authors: Abt, H. A.
2009yCat..21800117A Altcode:
The photographic spectra were obtained with the Meinel Cassegrain
spectrograph on the Kitt Peak 0.9m telescope. (1 data file).

---------------------------------------------------------
Title: The Difference between Metal-poor and Metal-rich Binaries
Authors: Abt, H. A.
2009ASPC..404..209A Altcode:
I explored the reason why many authors differed as to whether the field
metal-poor stars are deficient in spectroscopic binaries or have the
same frequency as metal-rich stars. From published studies of five
large samples of binaries, it is obvious that the distribution of
orbital periods of metal-poor stars peaks at 875 days while that of
metal-rich stars peaks at about 22 days. That means that if one uses
high-dispersion spectra, one will find many binaries in both samples
but if one uses low-dispersion spectra, one will fail to detect the
long-period binaries and will find more binaries among the metal-rich
stars. The reason for the difference in period distributions seems to
be that most of the metal-poor stars have left the globular clusters
quickly (within 10^6 yr), before most of them can form short-period
binaries in three-body encounters.

---------------------------------------------------------
Title: The Spectral-type Limits of the Barr Effect
Authors: Abt, Helmut A.
2009PASP..121..811A Altcode:
The Barr Effect is a nonrandom distribution of longitudes of periastron,
ω, in spectroscopic binary orbits. Physically one would not expect
elliptical binary orbits to show any preferred orientations. Aitken
and Struve have shown a preference for 0 &lt; ω &lt; 90° among 275
elliptical binary orbits of all primary types. Some eclipsing binaries
show inconsistencies between their light and velocity curves. Struve
showed that the velocity curves of some spectroscopic binaries
are distorted by absorption in gaseous streams flowing between the
components. I wondered about the occurrence of this effect for stars
of various spectral types and found that the effect occurs primarily
for B0-B3 V-lll primaries but may be present in a few of the remaining
BA stars. The B0-B3 region is also where the mean radial velocities
of stars (single plus binaries) in open clusters are systematically
larger than for other stars.

---------------------------------------------------------
Title: Why are There Normal Slow Rotators Among A-Type Stars?
Authors: Abt, Helmut A.
2009AJ....138...28A Altcode:
I wondered why there are still slowly rotating (V &lt; 120 km
s-1) normal A0-A9 field stars when such stars should
have become Ap or Am stars by a diffusion mechanism. My first guess
was that this was related to an unusually high binary frequency,
but the frequency turned out to be normal, as shown in a paper in
preparation. Next, I wondered whether all the slow rotators have had
enough time to become Ap or Am stars. That process is rapid for Ap(Si),
Ap(HgMn), and Am stars, but slow for Ap(SrCrEu) stars. For Ap(SrCrEu)
stars, it takes about half of their main-sequence lifetime to show
their abnormality. Under the assumption of a constant formation rate
of field A stars, about half of the eventual Ap(SrCrEu) will appear as
normal slow rotators. That is why there are still normal slow rotators
in A0-A3. That is the main conclusion of this study. I discuss recent
doubts about the length of time it takes to form an Ap(SrCr) star
and found that the doubts are inappropriate. For the A4-F0 stars,
I confirm that all the stars in binaries with orbital periods of
2-10 days became Am stars because their rotational velocities have
been reduced by tidal interactions below V = 120 km s-1,
a requirement for diffusion to act. It is also confirmed that all the
normal stars in binaries have orbital periods above ~100 days because
the tidal interactions in such binaries are inadequate to bring the
rotational velocities below 120 km s-1. However, both Am
and normal stars occur in binaries with orbital periods between 10
and 100 days, and at present we do not know why.

---------------------------------------------------------
Title: VizieR Online Data Catalog: MK spectral types of Visual
Multiples (Abt, 2008)
Authors: Abt, H. A.
2009yCat..21760216A Altcode:
Two-thirds of the current spectra were obtained with the Meinel
Cassegrain spectrograph on the Kitt Peak 0.9m telescope, with a
resolution of 2.5Å. The remaining one-third were obtained with the
Cassegrain spectrograph (also designed by Meinel) on the Kitt Peak
2.1m telescope, with a resolution of 0.8Å. (2 data files).

---------------------------------------------------------
Title: Reference Sources in Research Literature
Authors: Abt, Helmut A.
2009PASP..121..544A Altcode:
I looked at statistically large samples of references in the
Astrophysical Journal and Astronomy &amp; Astrophysics at approximately
decade intervals from 1952 to 2009. They show an increase of references
to journals from 76% to 90.0% at the expense of references to monographs
(down to 3.4%), conference papers (down to 2.6%), in-house papers
(down to 1.2%), theses (down to 0.3%), and private communications
(0.0%). References to preprints (1.3%) and review papers (1.2%) have
also increased. The general conclusion is that references that are
available online are increasing in usage while the remaining references
are decreasing.

---------------------------------------------------------
Title: Evidence that Most Binaries Do not Evolve after the Primaries
Reach the Main Sequence
Authors: Abt, Helmut A.
2009PASP..121..248A Altcode:
Assuming that binaries are formed in three-body interactions in
clusters, we wonder whether the process continues after the stars
reach the main sequence. We considered the 233 binaries with known
orbital elements that are main-sequence members in 69 open clusters,
and looked for changes (presumably decreases) in separations or periods
and eccentricities. We found none that are statistically significant,
indicating that most binaries are fully formed by the time that their
primaries reach the main sequence.

---------------------------------------------------------
Title: MK Classifications of Spectroscopic Binaries
Authors: Abt, Helmut A.
2009ApJS..180..117A Altcode:
New MK spectral classifications are given for 145 spectroscopic binaries
(SBs) with AF primaries because two-dimensional types are lacking for
more than one-third of the AF SBs with known orbital elements in the
current catalog. Compared with the classifications by Morgan, Keenan,
and their students, the new classifications give types that are 1.1 ±
0.2 subclasses later and 0.7 ± 0.1 luminosity classes fainter. Also
listed are selected published MK types from Brian Skiff's recent
compilation.

---------------------------------------------------------
Title: The Kitt Peak 2.1-meter Telescope: An Unusually Innovative
Telescope
Authors: Abt, Helmut A.
2009AAS...21320008A Altcode: 2009BAAS...41..187A
The 2.1-meter telescope (1964) had the following innovations:
(1) an unusually fast f/2.6 primary and f/8 Cassegrain focus that
allowed for a small cheaper dome, (2) Ritchey-Chretien coma-free
optics, (3) a Pyrex mirror made with the slumping process that was
ground and polished in 1.5 years, (4) a flip-top secondary allowing
5-minute conversion between Cassegrain and coude foci, and (5) fast
high-resolution spectrographs. Those features led to the discovery
of the Lyman-alpha forest, the first gravitational lens, the first
pulsating white dwarf, and the realization that most solar-like stars
have companions. Such discoveries were possible because of (1) fast
high-resolution equipment, (2) competitive time scheduling, and (3)
relatively long observing runs that allowed for experimentation.

---------------------------------------------------------
Title: Why Are There Normal Slow Rotators among A-type Stars?
Authors: Abt, Helmut A.
2009AAS...21336302A Altcode: 2009BAAS...41..513A
Michaud (1970) found that main-sequence A-type stars have radiative
layers below their atmospheres where diffusion can act and produce Ap
and Am stars if their rotational velocities are below 120 km/s. But
among field stars there are some normal slow rotators. Why? Studies (Abt
1979) of stars in open clusters of various ages show that the Ap(Si),
Ap(HgMn), and Am stars develop their atmospheric abnormalities in a few
million years, but the Ap(SrCrEu) stars take about 186 million years
to develop their abnormalities. Because they stay on the main sequence
only 424 million years, they spend nearly half of their main-sequence
lifetimes as normal stars before their peculiarities appear. Numerically
that explains the numbers of normal field stars observed.

---------------------------------------------------------
Title: Do Astronomical Journals Still Have Extensive Self-referencing?
Authors: Abt, Helmut A.
2009PASP..121...73A Altcode:
Now that all the major astronomical journals are available online and
search engines allow astronomers to find pertinent papers regardless
of where they are published, do papers in those journals still have
a strong tendency to reference papers in the same journals? Current
statistics show that all the general astronomical journal papers still
have 9% self-referencing, as they did 21 years ago. Equally disturbing
is the large decrease (from 41.6% to 22.8%) in the past 21 years in
citations to papers outside these eight major ones, even though the
others can also be found in electronic searches.

---------------------------------------------------------
Title: Evidence That the Mean Radial Velocities of Many B0-B3 Stars
Are Systematically Incorrect
Authors: Abt, Helmut A.
2008PASP..120..715A Altcode:
Furenlid &amp; Young showed that in main-sequence B0-B3 stars the Hα
line profiles are distorted, showing shortward absorption evidently
due to mass loss. Earlier, others have found evidence of mass loss in
UV ionic lines in such stars. Are the radial velocities of B0-B3 stars
in the optical region distorted by such effects? We looked at all the
10 young open clusters (log age &lt;7.5 yr) with sufficient numbers
of measured radial velocities, many of them measured with CORAVEL,
and found that in each case that the main-sequence B0-B3 stars have
larger velocities than earlier or later stars. However, that difference
is in the wrong sense to be explained by mass loss effects. Could the
distorted radial velocities be due to the Barr Effect in binaries? This
study does not prove that the radial velocities of B0-B3 stars are
misleading because of an uncertainty about what the cross-correlation
measures represent. However, some previously published studies plus
this one provide a warning that the radial velocities may be uncertain.

---------------------------------------------------------
Title: Visual Multiples. IX. MK Spectral Types
Authors: Abt, Helmut A.
2008ApJS..176..216A Altcode:
In this third of three parts of MK classifications of the components
brighter than about B = 8 mag in Aitken's Catalogue, new classifications
are given for 546 stars. Included in this section are 15 Ap stars,
33 Am stars, 18 stars with composite spectra, three stars with shell
spectra, and two SB2s.

---------------------------------------------------------
Title: The Difference Between Metal-Poor and Metal-Rich Binaries
Authors: Abt, Helmut A.
2008AJ....135..722A Altcode:
In the past there have been many discrepant studies about whether
metal-poor (Population II) stars were deficient in binaries or had
approximately the same binary frequency as metal-rich stars. We
consider here the distributions of periods in five samples of
binaries: (1) 138 field halo binaries with low metal abundances
([Fe/H] &lt; -0.30) observed by Latham et al. and Goldberg et al.,
(2) 42 blue metal-poor binaries discovered by Preston &amp; Sneden,
(3) all 145 known FG dwarf binaries with [Fe/H] &gt; -0.30 as listed
on-line by Pourbaix, (4) 31 binaries among the well-studied FG dwarfs
within 25 pc of the Sun, and (5) binaries in three open clusters
with ages of 108-109 yr. The main result is
that the metal-poor stars lack short-period binaries relative to the
metal-rich stars; the period distributions are very different. This
tells us two things. First, the determination of the frequency of
discovered binaries for metal-poor and metal-rich stars will depend
upon the equipment used: if one uses low-resolution spectrographs,
one will detect many of the short-period binaries but not many of
the long-period binaries and conclude that the metal-poor stars are
deficient in binaries. If one uses higher resolution, as did Latham
et al., one will detect many more binaries and conclude that there is
no difference in binary frequency between metal-poor and metal-rich
stars. Second, if binaries are formed in three-body interactions in
clusters and, as n-body simulations show, the longer they remain in
dense cluster environments, the harder (shorter periods) they become.

---------------------------------------------------------
Title: New Data on A-Type Disk Stars
Authors: Abt, Helmut A.
2008ApJS..174..499A Altcode:
After a review of what has been learned to date about the Ti II
disk lines at λλ3759 and 3761 in the spectra of rapidly rotating A
dwarfs, new measures obtained during the past 10 yr are given. They
show stars with quasi-periodic variations of 15-30 yr (as in Be stars)
and probably longer. The star HR 10 has double disk lines that change
relative strengths during 9 yr, consistent with the behavior found by
others. They support the model by others of erratic longward components
representing material falling onto the star.

---------------------------------------------------------
Title: The Future of Single-authored Papers
Authors: Abt, Helmut A.
2007AAS...211.7105A Altcode: 2007BAAS...39..862A
For four sciences (astronomy, biology, chemistry, physics) I counted the
fractions of single-authored papers in four journals for each science
and during 1975-2005. The occurrences are best fit with exponential
decays that never reach zero, implying that single-authored papers
will continue to be published in the foreseeable future. This is
contradictory to the predictions of their demise.

---------------------------------------------------------
Title: Observed Orbital Eccentricities
Authors: Abt, Helmut A.
2007IAUS..240..414A Altcode: 2006IAUS..240E.500A
For binaries with periods of more than a few weeks, nearly all
eccentricities from zero (circular) to nearly one (highly elliptical)
are possible. What are the average characteristics and limiting
values? I considered the 1169 spectroscopic and visual systems
with known orbital elements and B0-M5 dwarf primaries. The average
eccentricities as a function of orbital period show a very systematic
behavior. For systems with periods greater than about 1000 days, all
eccentricities are equally probable, showing that in the process of
binary formation, no specific eccentricities are favored. It is well
known that for periods of a few days, all systems have been circularized
by tidal interactions. For periods between a few days and 1000 days,
the mean eccentricities increase from zero to a mean asymptotic
value of 0.5. The upper limiting eccentricities are 0.8 for periods
of months, 0.7 for periods of weeks, and 0.3 for periods around one
week. Double-lined binaries tend to have higher mean eccentricities
than single-lined ones of the same periods in accord with Kepler's
third law because they have greater total masses and hence larger
separations. Systems with giant primaries have the same behavior except
they are circularized for periods less than about 70 days.

---------------------------------------------------------
Title: Tidal Effects in Binaries
Authors: Abt, H. A.
2007ASPC..362...92A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Editor's Forum
Authors: Abt, Helmut A.
2007fpca.conf..239A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Changing Sources for Research Literature
Authors: Abt, Helmut A.
2007fpca.conf..177A Altcode:
Including material published previously, I considered all the references
listed in the January issues of Astronomy &amp; Astrophysics and
the Astrophysical Journal in decade intervals from 1952 to 2006. The
results are that journal papers, preprints, and reviews are growing in
the frequency in which they are cited, while observatory publications,
private communications, theses, conference papers, and monographs
are decreasing in cited frequency. The last two are surprising in
view of the rapidly increasing numbers of conferences and monographs
published annually. It appears that sources of information that are
readily available on-line are greatly preferred over sources that are
not available on the internet.

---------------------------------------------------------
Title: The Numbers of Scientific Papers Depend Only on the Numbers
of Scientists
Authors: Abt, Helmut A.
2006AAS...20910803A Altcode: 2006BAAS...38.1057A
For five sciences (physics, astronomy, geophysics, mathematics,
and chemistry) I counted the numbers of papers published annually
in 1970-2004 in 5-27 major journals in each field. The totals
were divided by the numbers of members in the appropriate American
societies, e.g. The American Physical Society. Corrections were made for
non-American papers. The quotients (American papers per society member
per year) are generally constants and show no jumps due to improved
instrumentation (e.g. CCDs, Hubble, Keck, computer speeds). These tell
us that the numbers of papers depend only on the numbers of research
scientists, although the quality and content of those papers improve
with technical improvements.

---------------------------------------------------------
Title: Observed Orbital Eccentricities. II. Late-Type Stars
Authors: Abt, Helmut A.
2006ApJ...651.1151A Altcode:
The distribution of individual eccentricities for binaries shows a
large scatter between zero (circular orbits) and nearly 1 (highly
elliptical), but mean eccentricities show systematic effects. For 296
F0-M5 IV or V primaries with known spectroscopic orbital elements
and 482 similar primaries with known visual orbital elements, I
collected mean eccentricities as a function of orbital periods. The
results show complete circularization for periods up to 1.4 days
for B dwarfs, 1.6-2.2 days for A dwarfs, 2.0 days for F dwarfs,
and 4.3 days for G-M dwarfs. However, the evidence of maximum
circularization periods of 4.3 to 18 days for late-type stars with
increasing age suggests that these limiting periods depend primarily
on age, rather than on primary mass. The mean eccentricities as a
function of period approach e=0.52+/-0.02 asymptotically for the
longest periods and for all types of stars. For long periods the
distribution of eccentricities is statistically flat, indicating
that for wide binaries, all eccentricities are equally probable,
as was found previously for BA dwarfs in binaries. For intermediate
periods the higher eccentricities disappear, and for short periods
all eccentricities are zero. Double-lined spectroscopic binaries have
statistically larger eccentricities than single-lined ones of the same
periods, consistent with Kepler's third law. Late-type giants follow
similar distributions, with complete circularization occurring below
70 days.

---------------------------------------------------------
Title: An anomalous journal impact factor
Authors: Abt, H. A.
2006AN....327..737A Altcode:
The impact factor (average number of citations per paper) for the
Astrophysical Journal Supplement Series jumped between 2003 and 2004
from 6.247 to 15.231, giving it the world's second highest impact
factor for an astronomical journal in 2004. Was this change due to a
computing error or to an unusual occurrence? It is shown that it was
due to the extremely high citation rates (average of 160 citations
per year) for 13 papers in the special issue devoted to the Wilkinson
Microwave Anisotropy Probe.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Radial velocities of solar-type
stars (Abt+, 2006)
Authors: Abt, H. A.; Willmarth, D.
2006yCat..21620207A Altcode:
We used the Kitt Peak 0.9m auxiliary feed telescope and the coude
spectrograph built for the 2.1m telescope. Also used were a Bausch &amp;
Lomb grating (302x361mm2 and 632grooves/mm) and F3KB CCD,
yielding 0.11{AA}/pixel and covering 320{AA} centered on 5200{AA}. (2 data files).

---------------------------------------------------------
Title: A Comparison of the Citation Counts in the Science Citation
Index and the NASA Astrophysics Data System
Authors: Abt, Helmut A.
2006ASSL..335..169A Altcode: 2006osa6.book..169A
From a comparison of 1000+ references to 20 papers in four fields of
astronomy (solar, stellar, nebular, galaxy), we found that the citation
counts in Science Citation Index (SCI) and Astrophysics Data System
(ADS) agree for 85% of the citations. ADS gives 15% more citation counts
than SCI. SCI has more citations among physics and chemistry journals,
while ADS includes more from conferences. Each one misses less than 1%
of the citations.

---------------------------------------------------------
Title: The Secondaries of Solar-Type Primaries. I. The Radial
Velocities
Authors: Abt, Helmut A.; Willmarth, Daryl
2006ApJS..162..207A Altcode:
We studied for duplicity the 167 F7-G8 IV or V primaries within 25 pc of
the Sun according to their Hipparcos parallaxes and between declinations
of -30° and +75°. We obtained an average of 13 coudé radial
velocities with an accuracy of +/-0.10 km s-1. Combining
these measures with published data, we obtained 39 single-lined and
12 double-lined binaries with orbital elements. This material will
be combined in a later paper with the known visual binaries to derive
the secondary mass frequencies.

---------------------------------------------------------
Title: National Astronomical Productivities
Authors: Abt, Helmut A.
2005BAAS...37.1540A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Observed Orbital Eccentricities
Authors: Abt, Helmut A.
2005ApJ...629..507A Altcode:
For 391 spectroscopic and visual binaries with known orbital
elements and having B0-F0 IV or V primaries, we collected the derived
eccentricities. As has been found by others, those binaries with periods
of a few days have been circularized. However, those with periods up to
about 1000 or more days show reduced eccentricities that asymptotically
approach a mean value of 0.5 for the longest periods. For those binaries
with periods greater than 1000 days their distribution of eccentricities
is flat from 0 to nearly 1, indicating that in the formation of binaries
there is no preferential eccentricity. The binaries with intermediate
periods (10-100 days) lack highly eccentric orbits.

---------------------------------------------------------
Title: Estimated Completeness of the Science Citation Index
Authors: Abt, Helmut
2005BAAS...37..551A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Erratum: “Spectral Classification of Stars
in A Supplement to the Bright Star Catalogue” (<A
href="bib_query?2004ApJS...155..175A">ApJS, 155, 175 [2004]</A>)
Authors: Abt, Helmut A.
2005ApJS..157..174A Altcode:
Some object names are in error in Table 1:For:Read:HD 7781HD 89269HD
59950HD 57950HD 133517HD 135517HD 136100HD 136140HD 170099HD 170991HD
222718ABHD 223718AB I very much appreciate Brian Skiff's careful
study of my types and the discovery of these errors.

---------------------------------------------------------
Title: Information Obtainable from Bibliometric Studies
Authors: Abt, Helmut A.
2005coas.conf....2A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Peer Reviewing
Authors: Abt, Helmut A.
2005coas.conf...19A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Formation of Planets
Authors: Abt, H. A.
2004AAS...205.3903A Altcode: 2004BAAS...36R1406A
We determined the luminosity function for the secondaries of solar-type
stars, based on observations of the 170 F7-G8 IV or V stars with
Hipparcos parallax distances within 25 pc and declinations of -30 to
+75 deg. Like the Van Rhijn function, it shows an increase in numbers
of secondaries down to 0.4 solar masses and then a decline to the 10
extrasolar planets in this sample. It is shown that the eccentricities
and orbital periods of the extrasolar planets found to date fit those
in this sample and not those of the solar system. We conclude that
the extrasolar planets found to date were formed in approximately
spherical multiple star systems, not in disk systems like the solar
system. We appreciate funding from the Research Corp.

---------------------------------------------------------
Title: VizieR Online Data Catalog: MK Classification of Bright Star
Supplement (Abt, 2004)
Authors: Abt, H. A.
2004yCat..21550175A Altcode:
MK spectral types are given for about 584 stars in "A Supplement to
the Bright Star Catalogue" (Hoffleit et al., 1983, Cat. V/36). The
spectra were obtained at Kitt Peak in 1983 on Eastman IIaO emulsions,
15% with the Cassegrain spectrograph on the 2.1m telescope and the rest
with a Cassegrain spectrograph on the 0.9m telescope. The spectral
types are compared with Hipparcos parallaxes to check the reliability
of those classifications. The estimated errors are +/-1.2 subtypes,
and 10% of the luminosity classes may be wrong. (1 data file).

---------------------------------------------------------
Title: Tidal Effects in Binaries of Various Periods
Authors: Abt, Helmut A.; Boonyarak, Chayan
2004ApJ...616..562A Altcode:
We found in the published literature the rotational velocities
for 162 B0-B9.5, 152 A0-A5, and 86 A6-F0 stars, all of luminosity
classes V or IV, that are in spectroscopic or visual binaries with
known orbital elements. The data show that stars in binaries with
periods of less than about 4 days have synchronized rotational and
orbital motions. Stars in binaries with periods of more than about
500 days have the same rotational velocities as single stars. However,
the primaries in binaries with periods of between 4 and 500 days have
substantially smaller rotational velocities than single stars, implying
that they have lost one-third to two-thirds of their angular momentum,
presumably because of tidal interactions. The angular momentum losses
increase with decreasing binary separations or periods and increase
with increasing age or decreasing mass.

---------------------------------------------------------
Title: Spectral Classification of Stars in A Supplement to the Bright
Star Catalogue
Authors: Abt, Helmut A.
2004ApJS..155..175A Altcode:
MK spectral types are given for about 584 stars in A Supplement to the
Bright Star Catalogue. These are compared with Hipparcos parallaxes to
check the reliability of those classifications. The estimated errors
are +/-1.2 subtypes, and 10% of the luminosity classes may be wrong.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Visual multiples. VIII. (Abt+,
1985)
Authors: Abt, H. A.
2004yCat..20590095A Altcode:
A total of 1000 new classifications are given for stars brighter
than B=8.0mag in the Aitken double star catalog. The classifications
supplement 865 classifications obtained in 1981 and 1984. Among
the newly discovered stars are 12 new Ap stars, eight Lambda Bootis
stars, one Ba II star, and 60 Am stars. A detailed list of the new
classifications is given. (1 data file).

---------------------------------------------------------
Title: The Mass Distribution of Secondaries to Solar-Type Stars
Authors: Abt, H. A.; Willmarth, D. W.
2004RMxAC..21...37A Altcode: 2004IAUCo.191...37A
Two previous studies of the secondary mass function in spectroscopic
binaries by Abt &amp; Levy (1976) and by Duquennoy &amp; Mayor (1991)
are shown to be in good agreement if they are both plotted with the same
abscissa scale. A new study of 271 main-sequence stars later than F6 V
made with a radial-velocity accuracy of ±0.10 km s-1 yielded 10 new
sets of orbital elements in addition to the 59 published ones. The
resulting secondary mass function is nearly flat and shows that
2.2±1.5% of the primaries have low-mass (0.01-0.10 M⊙)
companions. In contrast, the secondary mass function for visual binaries
with separations &gt;500 AU fits a van Rhijn function, as was shown
previously by Abt and Levy.

---------------------------------------------------------
Title: Dedication to Arcadio Poveda
Authors: Abt, H. A.
2004RMxAC..21....1A Altcode: 2004IAUCo.191....1A
It is appropriate that this meeting about double and multiple stars
be dedicated to Arcadio Poveda, who has derived so many results about
such systems. This dedication mentions some of those results, as well
as some other details of his research and accomplishments.

---------------------------------------------------------
Title: VizieR Online Data Catalog: MK Classification of Visual
Multiples (Abt, 1981)
Authors: Abt, H. A.
2004yCat.3106....0A Altcode:
The spectral types listed here represent about one-third of a program of
MK classification of all the Northern (Dec&gt;-30deg) visual components
brighter than B~8.0mag. The spectra used were obtained in 1969-1980
with the Cassegrain spectrograph attached to the Kitt Peak No.2 91-cm
telescope. The grating spectra have a dispersion of 128{AA}/mm, and
are 1.2mm wide; they are overexposed and underdeveloped to minimize
grain. The spectra were classified against standards of the "Revised
MK Spectral Atlas for stars earlier than the Sun" by Morgan, Abt and
Tapscott (Yerkes Obs. 1978) and of the "Spectral classification" of
Morgan and Keenan (1973ARA&amp;A..11...29M). Accurate positions,
V magnitudes rounded to 0.1 mag, and remarks were added by B. Skiff
in June 2004 as the file "more.dat"; some typos in the catalog were
also corrected (see the "History" section below). (2 data files).

---------------------------------------------------------
Title: Post Main-Sequence Changes in Rotational Velocities
Authors: Abt, H. A.
2004IAUS..215..154A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Evidence for an Interstellar Origin for Hot Inner Disks around
Rapidly Rotating Early-type Stars
Authors: Abt, H. A.
2004AAS...204.2401A Altcode: 2004BAAS...36..690A
At any one time, about one quarter of the rapidly rotating early-type
stars show sharp absorption lines due to hot inner disks (temperatures
10,000 K). The lines appear and disappear on time scales of decades,
indicating that they are ephemeral, not primordial. Because no such
lines occur around stars with projected rotational velocities less than
about 200 km/s, the lines are formed in disks, not spherical shells. We
looked in the cores of H alpha for disk lines in 181 rapidly rotating
B9-A5 V or IV stars and all 97 northern shell stars listed in the
Bright Star Catalogue. It was found that the 145 stars without disk
lines are well distributed in galactic coordinates, but the 87 stars
with disk lines avoid the core of the local interstellar bubble. A
working model is that in dense regions these stars may accrete disks,
but where the interstellar density is less than 10% than that outside
the bubble, the stars loose them due to strong winds.

---------------------------------------------------------
Title: What Kind of Astronomical Papers are Still Referenced 50
Years After Publication?
Authors: Abt, Helmut A.
2004BAAS...36..948A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Evidence for an Interstellar Origin of Stellar Shells
Authors: Abt, Helmut A.
2004ApJ...603L.109A Altcode:
It is shown that the hot inner disks around rapidly rotating BA
dwarfs (stars conventionally called shell stars) are accreted from
the interstellar medium because such disks rarely occur around stars
within the heart of the local interstellar bubble, which has less than
10% of the density surrounding it. A working model is one in which
stars accrete disks in dense interstellar regions, but in regions
of low interstellar density, such as the local interstellar bubble,
the stellar winds exceeds the accretion rate.

---------------------------------------------------------
Title: The Institute for Scientific Information and the Science
Citation Index
Authors: Abt, H. A.
2003ASSL..296..197A Altcode: 2003osa4.book..197A
No abstract at ADS

---------------------------------------------------------
Title: Foreword
Authors: Abt, H. A.
2003ASSL..290D...7A Altcode: 2003asco.bookD...7A
No abstract at ADS

---------------------------------------------------------
Title: Scientific Impact of Small Telescopes
Authors: Abt, Helmut A.
2003ASSL..287...55A Altcode: 2003fst1.book...55A
No abstract at ADS

---------------------------------------------------------
Title: Changes in Astronomical Publications During the 20th Century
Authors: Abt, H. A.
2003ASSL..285..127A Altcode: 2003iha..book..127A
Among the major changes in astronomical publication during the 20th
century are the virtual demise of observatory publication, the growth
of conference proceedings, and the continuing dominance of journal
publications. The numbers of research papers were found to depend only
on the number of researchers and not upon the speed of new detectors and
computers or the availability of large telescopes. Papers have grown
in average length by a factor of 5 but their lengths have leveled off
because many data are published on-line only. The fraction of papers
with authors from two or more countries is currently 40% and growing
by 1% per year. After trying various publication methods (microfiche,
CD-ROMs, videos), the trend is toward on-line publication. With the
growth and complexity of science, it is increasingly important to
obtain independent reviews of papers. Current auxiliary tools include
search engines, the Science Citation Index, and preprint servers.

---------------------------------------------------------
Title: Post-Main-Sequence Changes in Rotational Velocities
Authors: Abt, Helmut A.
2003ApJ...582..420A Altcode:
For 1377 dwarfs and 381 giants of types B and A, we present mean
observed projected rotational velocities for normal plus abnormal
spectral types combined. For the dwarfs, Vsini is statistically constant
at 127+/-15 km s-1 from B0 V to A5 V. Using the interior
models of Bertelli et al., we predict the rotational velocities of
the giants. We assume an age of 30×106 yr for the observed
dwarfs. The predicted giant rotational velocities agree well with the
observed values if angular momentum is conserved in rigid-body rotation;
the observed minus the computed is -7+/-4 km s-1. Significant
loss of angular momentum by mass loss (stellar winds) cannot occur
because the observed rotational velocities of the giants are already at
the maximum level allowed by either conservation mechanism. Comparison
with three other studies indicates that angular momentum is conserved
by rigid-body rotation if the expansion is less than a factor of 4,
but conserved in shells if the expansion is more.

---------------------------------------------------------
Title: Spectra Comparators
Authors: Abt, Helmut
2003gafe.conf..123A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotational velocities of B stars
Authors: Abt, Helmut A.; Levato, Hugo; Grosso, Monica
2003ASSL..298..165A Altcode: 2003sath.conf..165A
We measured projected rotational velocities for nearly 1100 B stars with
these results. (1) They average substantially less than those published
in the Bright Star Catalogue and are about one-quarter of the break-up
velocities. (2) For the late B stars the deconvolved distribution in
V is bimodal; one lobe consists of rapidly-rotating normal stars and
the other lobe of slowly-rotating Ap stars. This is consistent with
diffusion theory by Michaud. (3) Using interior models by Bertelli et
al. we predicted rotational velocities of giants and found that they
agree with observational ones for rigid-body rotation. Combining this
with other data, we conclude that if the expansion of post-main sequence
stars is a factor of &lt;4, the conservation of angular momentum is
by rigid-body rotation but for factors &gt;4, it is in shells. (4) In
binaries the primaries have synchronized rotational and orbital motions
for periods &lt;2.4 days. For the A stars studied by Abt &amp; Morrell
the limit is 5.0 days. (5) In binaries the orbits are circularized
for periods &lt;1.5 days and for A star &lt;2.5 days. For binaries of
107.5 - 1010.2yr the maximum circularized period
is 0.0016 A0.40 days.

---------------------------------------------------------
Title: Solving Olin Wilson's Mystery
Authors: Abt, Helmut
2003gafe.conf...47A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Production and Distribution Times for Conference
Proceedings
Authors: Abt, Helmut A.
2002BAAS...34.1354A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: How to write a good astronomical paper
Authors: Abt, Helmut A.
2002PABei..20..299A Altcode:
Some suggestions are given about writing an astronomical paper for
an international audience. For each of the parts of a paper (title,
abstract, introduction, main text, figures, references) we give ideas on
how to write concisely but to be clear yet informative. These are based
on my years of being an editor and reading both good and weak papers.

---------------------------------------------------------
Title: Rotational Velocities of B Stars
Authors: Abt, Helmut A.; Levato, Hugo; Grosso, Monica
2002ApJ...573..359A Altcode:
We measured the projected rotational velocities of 1092 northern B stars
listed in the Bright Star Catalogue (BSC) and calibrated them against
the 1975 Slettebak et al. system. We found that the published values
of B dwarfs in the BSC average 27% higher than those standards. Only
0.3% of the stars have rotational velocities in excess of two-thirds
of the breakup velocities, and the mean velocity is only 25% of
breakup, implying that impending breakup is not a significant factor
in reducing rotational velocities. For the B8-B9.5 III-V stars the
bimodal distribution in V can be explained by a set of slowly rotating
Ap stars and a set of rapidly rotating normal stars. For the B0-B5
III-V stars that include very few peculiar stars, the distributions
in V are not bimodal. Are the low rotational velocities of B stars
due to the occurrence of frequent low-mass companions, planets, or
disks? The rotational velocities of giants originating from late B
dwarfs are consistent with their conservation of angular momentum in
shells. However, we are puzzled by why the giants that originate from
the early B dwarfs, despite having 3 times greater radii, have nearly
the same rotational velocities. We find that all B-type primaries in
binaries with periods less than 2.4 days have synchronized rotational
and orbital motions; those with periods between 2.4 and 5.0 days
are rotating within a factor 2 of synchronization or are “nearly
synchronized.” The corresponding period ranges for A-type stars are
4.9 and 10.5 days, or twice as large. We found that the rotational
velocities of the primaries are synchronized earlier than their orbits
are circularized. The maximum orbital period for circularized B binaries
is 1.5 days and for A binaries is 2.5 days. For stars of various ages
from 107.5 to 1010.2 yr the maximum circularized
periods are a smooth exponential function of age.

---------------------------------------------------------
Title: Solving Olin Wilson's Mystery
Authors: Abt, Helmut A.
2002PASP..114..559A Altcode:
Wilson showed that G8-M1 dwarfs have a range of 0.30 mag in P-V color
whereas the color range for earlier stars is 0.12 mag. He attributed
the increased range for the later stars to differing hydrogen-to-metal
ratios in the temperature region where most of the electrons come
from the metals. I explored those stars using Hipparcos parallaxes
and photometry and with MK types. His effect can be explained without
resorting to abundance differences, which are not confirmed elsewhere,
by poorer spectral classification from unwidened spectra for the fainter
stars and the use of maximum color ranges, rather than dispersions. I
also considered, with negative results, the possibility that the Ca
II H and K emission lines or chromospheric activity could cause the
large ranges in colors. Different amounts of chromospheric activity
do not affect the colors significantly.

---------------------------------------------------------
Title: Rotational Velocities of B Stars
Authors: Abt, H. A.; Levato, H.; Grosso, M.
2002RMxAC..14..111A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Productivity of Ground-Based Optical Telescopes of
Various Apertures
Authors: Abt, H. A.
2001AAS...19914501A Altcode: 2001BAAS...33.1524A
We scanned the papers published in the first quarter of 1996 in A&amp;A,
AJ, ApJ, Icarus, and MNRAS and counted those that were partly or fully
based on new observations from optical ground-based telescopes. We
found that 82% of the papers came from telescopes with apertures &lt;4
meters. Then we counted citations since 1996 to those papers and found
that 75% of the citations were to those papers from telescopes &lt;4
meters. Dividing these two similar distributions shows that the average
citations per paper are a linear function of aperture but with a small
slope, e.g. papers from telescopes of 5-10 meters average only twice
as many citations as papers from telescopes of 1-2 meters. Finally we
counted papers in the first quarter of 2001 in the same journals and
found that 79% of the papers came from telescopes &lt;4 meters in
aperture. These numbers tell us that the bulk of our astronomical
papers and of the most important results come from telescopes
&lt;4 meters. That situation is likely to continue throughout this
decade. Therefore the failure of the decadal survey to emphasize the
dominant importance of small telescopes and make recommendations for
their improvement shows that that panel did not assess realistically
the sources of contemporary optical ground-based results.

---------------------------------------------------------
Title: Publication Statistics for Recent Papers from the Hubble
Space Telescope
Authors: Abt, Helmut A.; Stevens-Rayburn, Sarah
2001BAAS...33..935A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Are Stellar Rotational Axes Distributed Randomly?
Authors: Abt, Helmut A.
2001AJ....122.2008A Altcode:
Stellar line widths yield values of Vsini, but the equatorial
rotational velocities, V, cannot be determined for individual stars
without knowledge of their inclinations, i, relative to the lines of
sight. For large numbers of stars we usually assume random orientations
of rotational axes to derive mean values of V, but we wonder whether
that assumption is valid. Individual inclinations can be derived only
in special cases, such as for eclipsing binaries where they are close
to 90° or for chromospherically active late-type dwarfs or spotted
(e.g., Ap) stars where we have independent information about the
rotational periods. We consider recent data on 102 Ap stars for which
Catalano &amp; Renson compiled rotational periods from the literature
and Abt &amp; Morrell (primarily) obtained measures of Vsini. We find
that the rotational axes are oriented randomly within the measuring
errors. We searched for possible dependence of the inclinations on
Galactic latitude or longitude, and found no dependence.

---------------------------------------------------------
Title: Are Stellar Rotational Axes Oriented Randomly?
Authors: Abt, H. A.
2001AAS...198.4708A Altcode: 2001BAAS...33..850A
Stellar line widths yield values of V sin i, but the equatorial
rotational velocities, V, cannot be determined for individual
stars without knowledge of their inclinations, i, relative to the
lines of sight. For large numbers of stars we generally assume
random orientations, but is that valid? For eclipsing binaries i
is known. For spotted stars we have independent information about
rotational periods. We considered data for 140 Ap stars for which
Catalano and Renson compiled rotational periods from the literature and
we used the line widths by Abt and Morrell. We found that rotational
axes are oriented randomly. Also they show no dependence upon galactic
latitude or longitude.

---------------------------------------------------------
Title: Electronic access to journals
Authors: Abt, Helmut A.
2001IAUGA..24..354A Altcode:
The use made of electronic access to journals by astronomers in some
developing countries is estimated and compared with the use made of
it by astronomers in developed countries.

---------------------------------------------------------
Title: Comments on Refereeing
Authors: Abt, H. A.
2001ASSL..266..197A Altcode: 2001osa2.book..197A
No abstract at ADS

---------------------------------------------------------
Title: Does Rotation Alone Determine Whether an A-Type Star's Spectrum
Is Abnormal or Normal?
Authors: Abt, Helmut A.
2000ApJ...544..933A Altcode:
As noted by Abt &amp; Morrell, virtually all of the metallic line (Am)
and peculiar A (Ap) stars have equatorial rotational velocities less
than 120 km s-1, and most of the normal A0-F0 main-sequence
stars have equatorial rotational velocities greater than 120 km
s-1. However, at all spectral types there are some (10%-20%)
of the normal stars that have smaller rotational velocities. If this
overlap is real, then a star's rotational velocity is insufficient
to explain its abnormal or normal spectra. We studied the A5-F0 and
A2-A4 stars and found in both cases that there are stars classified as
“normal” that have unusually weak Ca II K lines and/or that occur
in short-period binaries. Therefore, the overlap seems to be due to
undetected marginal abnormal stars. Among the A0-A1 stars we find that
our inability to distinguish consistently the class IV from the class
V stars can explain the overlap because the class IV stars have lower
rotational velocities than class V stars. We conclude from statistical
arguments that rotation alone can explain the appearance of an A star
as either abnormal or normal.

---------------------------------------------------------
Title: Astronomical Publication in the Near Future
Authors: Abt, Helmut A.
2000PASP..112.1417A Altcode:
A study is made of the number of astronomical papers, number of pages,
mean paper lengths, authors per paper, and international authorship in
recent decades, and this produces predictions for the coming decade
or two. The first significant result is that the number of published
research papers worldwide shows no abrupt changes due to increased
technical and scientific capabilities, such as major increases in
equipment sensitivity, new telescopes, breakthroughs in computing
and publication techniques, or our ability to generate huge amounts of
data. The second major result is that the number of papers is a function
only of the number of astronomers. This Essay is one of a series of
invited contributions which will appear in the PASP throughout the
year 2000 to mark the upcoming millennium. (Eds.)

---------------------------------------------------------
Title: What Can We Learn from Publications Studies?
Authors: Abt, Helmut A.
2000ASSL..256...77A Altcode: 2000osa1.book...77A
No abstract at ADS

---------------------------------------------------------
Title: The Maximum Age of Trapezium Systems
Authors: Abt, Helmut A.; Corbally, Christopher J.
2000ApJ...541..841A Altcode:
We sought to determine the maximum age of Trapezium systems by studying
possible trapezium systems that were selected independently of their
occurrence in H II regions. We started with the unpublished catalog by
Allen, Tapia, &amp; Parrao of all the known visual systems having three
or more stars in which the maximum separation is less than 3.0 times
the minimum separation. Their catalog has 968 such systems whose most
frequent primary type is F, which does not describe young systems. With
a CCD on the Kitt Peak 0.9 m telescope we obtained UBV frames for 265
systems accessible with our equipment on Kitt Peak. The frames were
used to obtain UBV photometry for about 1500 stars with an accuracy
of +/-0.04 mag between V=7 and 14 mag. Also these frames were used
to obtain astrometry with an accuracy of +/-0.015d in position angle
and +/-0.01" in separation. For the brightest star in each system we
obtained a spectral type to determine the distance and reddening to the
system. The measures were used to determine physical membership from
stars that (1) fit a single color-magnitude diagram, (2) fit a common
color-color diagram, and (3) show no astrometric motion compared to
visual measures made (mostly) a century ago. Combining the results
with spectroscopic data for 20 additional Allen et al. systems by
Abt, we found that 126 systems had only optical companions to the
primaries, 116 systems contained only a single physical pair, 13 were
hierarchical systems with 3-6 members and having separation ratios of
more than a factor of 10, two were small clusters, and only 28 fitted
the criteria of Trapezium systems. However, as shown by Ambartsumian,
about 9% of the hierarchical systems should appear to be Trapezium
systems in projection. Those, like other hierarchical systems, have a
broad distribution of primary spectral types. We isolated 14 systems
that seem to be true Trapezium systems. They have primary types of
B3 or earlier, indicating a maximum age of about 5×107
yr. This upper limit is consistent with the estimate made by Allen
&amp; Poveda for an age of several million years for these dynamically
unstable systems. These Trapezia are also large with a median radius
of 0.2 pc and a maximum radius of 2.6 pc. We asked why the sample of
285 possible Trapezium systems yielded only 14 true ones, despite the
attempt made by Allen et al. to eliminate optical companions with a
“1% filter,” i.e., demanding that each companion have less than a 1%
chance of being a field star of that magnitude within a circle of its
radius from the primary. The explanation seems to be that the double
star catalogs are based mostly on BD magnitudes that, fainter than
V=12 mag, are systematically too faint by 1 mag.

---------------------------------------------------------
Title: The Most Frequently Cited Astronomical Papers Published During
the Past Decade
Authors: Abt, Helmut A.
2000BAAS...32..937A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Completion of a Survey for Disk Lines Around Rapidly-Rotating
A Stars
Authors: Abt, Helmut A.; Willmarth, Daryl W.
2000noao.prop...56A Altcode:
We wish to complete our survey of 178 A northern stars in the Bright
Star Catalogue that have projected rotational velocities &gt; 200 km/s
to search for disk lines of Ti II near 3700 A. They indicate hot inner
disks. During semester 2000A we found 11 out of 92 to have disk lines
(but with an unexpected galactic longitude distribution). We also had
time to find disk absorption cores in Ca II H&amp; K and H delta in
the same 11 stars, but not in the other stars. Those will allow us,
with assumptions about abundances, to derive temperatures and disk
masses. Are all these disks similar in dimensions and temperatures? We
wonder about the production method for the disks, but our data may
not tell us that.

---------------------------------------------------------
Title: A redetermination of the projected axial rotational velocities
for the northern - B-type stars of the Bright Star Catalogue %b We
have redetermined with a resolution of 0.21 Å /px, the V sin i values
of 1060 B-type stars of the northern hemisphere brighter than V =
6.5. We have also included some southern objects to the north of -31
degees for overlapping with the southern survey which is underway. The
V sin i values were derived by comparison with standard stars in the
Slettebak system and we have used for such purpose 4471 and 4481
lines from HeI and MgII respectively. We have also measured the
equivalent widths of the lines. A statistical analysis will follow.
Authors: Abt, H.; Levato, H.; Grosso, M.
2000BAAA...44...43A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Does rotation alone determine whether an A-type star's spectrum
is abnormal or normal?
Authors: Abt, Helmut A.; Willmarth, Daryl W.
2000ASSL..254..175A Altcode: 2000stas.conf..175A
No abstract at ADS

---------------------------------------------------------
Title: Book Review: The Astrophysical Journal; American Astronomical
Society Centennial Issue (Abt)
Authors: Schmidt-Kaler, Theodor; Abt, Helmut A.
2000AcHA...10..232S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Do Important Papers Produce High Citation Counts?
Authors: Abt, H. A.
1999AAS...19513001A Altcode: 1999BAAS...31.1560A
It is generally thought that citation counts measure importance
and/or usefulness of scientific papers, although they do not tell us
into which category a paper falls. Here we ask the inverse question,
namely do important papers invariably produce high citation counts? In
honor of the AAS centennial we asked 53 senior astronomers to select
the most important papers published in the AJ or ApJ this century and
to write commentaries about them. The original papers and commentaries
will be published in a special part of the ApJ. We counted citations
in 1955-1989 to those paper and to 106 adjacent papers as controls. We
found that the important papers averaged 6.7 times as many citations
as the controls. Ninety-four percent of the important papers produced
more citations than the average for the controls. Thus important papers
almost invariably produce high citation counts. We also found that
the lifetimes of the important papers were 2.5 times longer on the
average than for the controls. KPNO is funded by the National Science
Foundation through a grant to AURA, Inc.

---------------------------------------------------------
Title: Binaries in the Praesepe and Coma Star Clusters and Their
Implications for Binary Evolution
Authors: Abt, Helmut A.; Willmarth, Daryl W.
1999ApJ...521..682A Altcode:
This completes a study of the evolution of binary systems in five open
clusters of various ages. Among 21 stars observed in Praesepe, eight are
found or confirmed to be spectroscopic binaries and orbital elements are
derived, while one more shows long-term binary motion. Among 18 stars
observed in the Coma Berenices cluster, five are found or confirmed
to be spectroscopic binaries and orbital elements are derived, while a
sixth has tentative elements. Among five clusters studied we searched
for three expected evolutionary effects, namely an increase with age
in the mass ratios, a decrease with age of the binary periods, and an
increase in binary frequencies. We find that there is a progression
(at the 3 σ level) from no binaries out of 10 with mass ratios greater
than 0.5 in the youngest cluster (combined with the published results
for NGC 6193) to 25% such stars in the intermediate-age clusters to
43% such stars in these two oldest clusters. There is no evidence for
an increase in short-period binaries with age. And there is slight
evidence (at the 1 σ level) for an increase with age from 15% to 28%
in the fraction of large-amplitude binaries. These results are mostly
consistent with the idea that most binaries are formed or modified in
three-body interactions, and successive generations of formation and
disruptions tend to form binaries with larger mass ratios. However,
part of the initial generation of binaries is probably primordial.

---------------------------------------------------------
Title: Announcement: New Editor-In-Chief, Robert C. Kennicutt, Jr.
Authors: Abt, Helmut A.
1999ApJ...518....1A Altcode:
Effective 1999 July 1, all new manuscripts for Part 1 of The
Astrophysical Journal and The Astrophysical Journal Supplement Series
should be sent to Dr. Robert C. Kennicutt, Jr., Editor-in-Chief The Astrophysical Journal Steward Observatory University
of Arizona Tucson, AZ 85721-0065 The other means of
contact are telephone, (520) 621-5145 FAX, (520) 621-5153 and e-mail,
apj@as.arizona.edu. For express packages please use the street address
of 933 North Cherry Avenue. Dr. Kennicutt will be assisted by several
of my loyal coworkers, who will move across the street. Manuscripts
received before July 1 will be handled by the current editor until most
of their problems have been resolved, at which point the remainder
will be sent to Dr. Kennicutt's office. Manuscripts for the
Letters should, as before, be sent directly to Dr. Alex Dalgarno at the
Center for Astrophysics in Cambridge, MA. We are fortunate that a
person with as much experience in research and proven good judgment as
Dr. Kennicutt is willing to accept this difficult and time-consuming
responsibility. He will be only the seventh Managing Editor or
Editor-in-Chief that this Journal has had in its 104 years. Please give
him the cooperation and help that you have given the current editor. It has been my privilege to work for 28 years with many of the best
astrophysicists in the world and to publish their papers. This was
done with the help of the AAS Publications Board and AAS officers, the
efforts of Peter Boyce and Evan Owens who made the on-line edition of
the Journal possible, three Associate Editors, a score of Scientific
Editors, a hardworking staff of six in Tucson, up to 25 production
controllers and manuscript editors at the University of Chicago Press,
and the thousands of astronomers throughout the world who served as
referees. The original masthead called this journal “An International
Review of Spectroscopy and Astronomical Physics.” That subtitle is
no longer appropriate because we do not publish review papers, and
spectroscopy is only one of many techniques used in astrophysics, but
it was prophetic in that the Journal has become a truly international
endeavor, with more than a third of the papers coming from abroad
and many of the referees residing outside the United States. The
past Managing Editor, Dr. S. Chandrasekhar, established a tradition
of first-class research. When he stepped down in 1971, he realized
that in order to accommodate for the rapid growth of the Journal, a
person with organizational ability was needed. That led to editing by
about 15 Scientific Editors with diversified specialized knowledge,
an on-line edition that is slowly replacing the printed edition in
importance and completeness, and facilities (subject headings, indexing,
yellow pages, and instant recall of references in the on-line edition)
for improved information retrieval. The next step for Dr. Kennicutt
will be to make use of the current computing opportunities to provide
a more efficient flow of manuscripts and to push for faster and less
expensive publication. And who can predict the options that will be
available in publication and data retrieval in the coming years? HELMUT A. ABT Editor-in-Chief

---------------------------------------------------------
Title: Announcement: New Editor-In Robert C. Kennicutt
Authors: Abt, Helmut A.
1999ApJS..122.....A Altcode:
Effective 1999 July 1, all new manuscripts for Part 1 of The
Astrophysical Journal and The Astrophysical Journal Supplement
Series should be sent to Dr. Robert C. Kennicutt, Editor-in-Chief
The Astrophysical Journal Steward Observatory University of Arizona
Tucson, AZ 85721-0065 The other means of contact are telephone, (520)
621-5145 FAX, (520) 621-5153 and e-mail, apj@as.arizona.edu. For
express packages please use the street address of 933 North Cherry
Avenue. Dr. Kennicutt will be assisted by several of my loyal coworkers,
who will move across the street. Manuscripts received before July 1
will be handled by the current editor until most of their problems
have been resolved, at which point the remainder will be sent to
Dr. Kennicutt's office. Manuscripts for the Letters should, as before,
be sent directly to Dr. Alex Dalgarno at the Center for Astrophysics in
Cambridge, MA. We are fortunate that a person with as much experience in
research and proven good judgment as Dr. Kennicutt is willing to accept
this difficult and time-consuming responsibility. He will be only the
seventh Managing Editor or Editor-in-Chief that this Journal has had
in its 104 years. Please give him the cooperation and help that you
have given the current editor. It has been my privilege to work for 28
years with many of the best astrophysicists in the world and to publish
their papers. This was done with the help of the AAS Publications Board
and AAS officers, the efforts of Peter Boyce and Evan Owens who made
the on-line edition of the Journal possible, three Associate Editors,
a score of Scientific Editors, a hardworking staff of six in Tucson,
up to 25 production controllers and manuscript editors at the University
of Chicago Press, and the thousands of astronomers throughout the world
who served as referees. The original masthead called this journal “An
International Review of Spectroscopy and Astronomical Physics.” That
subtitle is no longer appropriate because we do not publish review
papers, and spectroscopy is only one of many techniques used in
astrophysics, but it was prophetic in that the Journal has become
a truly international endeavor, with more than a third of the papers
coming from abroad and many of the referees residing outside the United
States. The past Managing Editor, Dr. S. Chandrasekhar, established
a tradition of first-class research. When he stepped down in 1971,
he realized that in order to accommodate for the rapid growth of the
Journal, a person with organizational ability was needed. That led to
editing by about 15 Scientific Editors with diversified specialized
knowledge, an on-line edition that is slowly replacing the printed
edition in importance and completeness, and facilities (subject
headings, indexing, yellow pages, and instant recall of references
in the on-line edition) for improved information retrieval. The next
step for Dr. Kennicutt will be to make use of the current computing
opportunities to provide a more efficient flow of manuscripts and to
push for faster and less expensive publication. And who can predict
the options that will be available in publication and data retrieval
in the coming years? HELMUT A. ABT Editor-in-Chief

---------------------------------------------------------
Title: Announcement: New Editor-in-Chief Robert C. Kennicutt
Authors: Abt, Helmut A.
1999ApJS..122...19A Altcode:
Effective 1999 July 1, all new manuscripts for Part 1 of The
Astrophysical Journal and The Astrophysical Journal Supplement Series
should be sent to Dr. Robert C. Kennicutt, Editor-in-Chief The Astrophysical Journal Steward Observatory University
of Arizona Tucson, AZ 85721-0065 The other means of
contact are telephone, (520) 621-5145 FAX, (520) 621-5153 and e-mail,
apj@as.arizona.edu. For express packages please use the street address
of 933 North Cherry Avenue. Dr. Kennicutt will be assisted by several
of my loyal coworkers, who will move across the street. Manuscripts
received before July 1 will be handled by the current editor until most
of their problems have been resolved, at which point the remainder
will be sent to Dr. Kennicutt's office. Manuscripts for the
Letters should, as before, be sent directly to Dr. Alex Dalgarno at the
Center for Astrophysics in Cambridge, MA. We are fortunate that a
person with as much experience in research and proven good judgment as
Dr. Kennicutt is willing to accept this difficult and time-consuming
responsibility. He will be only the seventh Managing Editor or
Editor-in-Chief that this Journal has had in its 104 years. Please give
him the cooperation and help that you have given the current editor. It has been my privilege to work for 28 years with many of the best
astrophysicists in the world and to publish their papers. This was
done with the help of the AAS Publications Board and AAS officers, the
efforts of Peter Boyce and Evan Owens who made the on-line edition of
the Journal possible, three Associate Editors, a score of Scientific
Editors, a hardworking staff of six in Tucson, up to 25 production
controllers and manuscript editors at the University of Chicago Press,
and the thousands of astronomers throughout the world who served as
referees. The original masthead called this journal “An International
Review of Spectroscopy and Astronomical Physics.” That subtitle is
no longer appropriate because we do not publish review papers, and
spectroscopy is only one of many techniques used in astrophysics, but
it was prophetic in that the Journal has become a truly international
endeavor, with more than a third of the papers coming from abroad
and many of the referees residing outside the United States. The
past Managing Editor, Dr. S. Chandrasekhar, established a tradition
of first-class research. When he stepped down in 1971, he realized
that in order to accommodate for the rapid growth of the Journal, a
person with organizational ability was needed. That led to editing by
about 15 Scientific Editors with diversified specialized knowledge,
an on-line edition that is slowly replacing the printed edition in
importance and completeness, and facilities (subject headings, indexing,
yellow pages, and instant recall of references in the on-line edition)
for improved information retrieval. The next step for Dr. Kennicutt
will be to make use of the current computing opportunities to provide
a more efficient flow of manuscripts and to push for faster and less
expensive publication. And who can predict the options that will be
available in publication and data retrieval in the coming years? HELMUT A. ABT Editor-in-Chief

---------------------------------------------------------
Title: The American Astronomical Society and The Astrophysical Journal
Authors: Abt, Helmut A.
1999aasf.book..176A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Electronic publication in 1997.
Authors: Abt, H. A.
1998PABei..16...87A Altcode:
Publication and distribution techniques for scientific journals
are changing rapidly. The author describes the use of the electronic
submission of manuscripts, primarily to the Astrophysical Journal, and
that Journal's on-line edition. Progress toward more rapid reviewing
and very rapid publication are also described.

---------------------------------------------------------
Title: Announcement: embedded halftones.
Authors: Abt, H. A.; Dalgarno, A.
1998ApJ...499..525A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Is the Astronomical Literature Still Expanding Exponentially?
Authors: Abt, Helmut A.
1998PASP..110..210A Altcode:
Have the recent reductions in funding for astronomy resulted in a
significant decrease in the exponential growth of our astronomical
publications? I studied the growth of five American and European
journals (A&amp;A, AJ, ApJ, MNRAS, and PASP) that publish papers on a
broad range of astronomical topics. For each, I counted the numbers of
normalized pages and papers published at 10 intervals in 1960-1996. The
average numbers of pages showed an exponential increase of 11% per
year before the mid-1970s and 6% per year thereafter. The average
number of papers increased exponentially by 9% before the mid-1970s
and by 4% per year thereafter. The difference between these two sets
of numbers is caused by an increase in average paper lengths from
six normalized pages in 1960 to a constant 12 pages per paper during
the last decade. Thus, the average paper lengths have asymptotically
reached a constant value. However, there is no sign of a leveling
off in the growth of our literature. The number of different authors
also increased steadily. Over the past 36 years there have been few
systematic shifts from one journal to another, implying that few authors
have changed their habitual choices of journals. The numbers of papers
in the three American journals has been directly proportional to the
numbers of AAS members at 0.41 papers per year per member during
the past 36 years. Therefore, the growth in our numbers of papers
is entirely due to the growth in the numbers of astronomers, and the
additional growth in pages is due to the growth in paper lengths.

---------------------------------------------------------
Title: Disks that appear and disappear around rapidly rotating
A-type stars
Authors: Abt, H. A.; Tan, H.; Zhou, H.
1998ASPC..138....3A Altcode: 1998stas.conf....3A
No abstract at ADS

---------------------------------------------------------
Title: Access to Journals
Authors: Abt, H. A.
1998HiA....11..929A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Hot Inner Disks that Appear and Disappear Around Rapidly
Rotating A-Type Dwarfs
Authors: Abt, Helmut A.; Tan, Huisong; Zhou, Hongnan
1997ApJ...487..365A Altcode:
At any one time, approximately one-quarter of the most rapidly rotating
normal A-type dwarfs (V sin i &gt;= 200 km s-1) show shell
lines of Ti II in the near-ultraviolet. Our observations during 22 years
show that the lines appear and disappear on timescales of decades but
do not display significant changes within 1 year. This implies that
they are not remnants of the star formation but rather are probably
caused by sporadic mass-loss events. A working hypothesis is that all
A-type stars that are rotating near their limits have these shells,
but for only one-quarter of the time. Because these lines do not appear
in stars with smaller sin i, the shells must be disks. These are hot
inner disks that may or may not be related to the cool outer disks
seen by Smith and Terrile around β Pic or through infrared excesses
around Vega and other A-type dwarfs. The similar, limited line widths
indicate that the disks are ~7 R* above the stellar surfaces.

---------------------------------------------------------
Title: How do Binaries in Clusters Change with Age?
Authors: Abt, Helmut A.; Willmarth, Daryl W.
1997ASPC..130..117A Altcode: 1997rdbs.conf..117A
No abstract at ADS

---------------------------------------------------------
Title: Access to Journals
Authors: Abt, H. A.
1997IAUJD..20E..31A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Maximum Ages of Trapezium Systems
Authors: Abt, H. A.; Corbally, C. J.
1997ASSL..223..127A Altcode: 1997vdsf.conf..127A
No abstract at ADS

---------------------------------------------------------
Title: How Long Are Astronomical Papers Remembered?
Authors: Abt, Helmut A.
1996PASP..108.1059A Altcode:
For the 165 papers published in the Astrophysical Journal and
Supplements in 1954, we counted the citations during 1955-1994. They
show an exponential decay with a halflife of 29 yr. Papers receiving
more citation than others during the first five years do not have
longer halflives. This sample shows that observational papers have an
average halflife (35 yrs) that is somewhat longer than for theoretical
papers (22 yrs). Longer papers, such as Supplement ones, are cited more
frequently on the average than short ones, such as Journal papers and,
especially, Notes. Excluding Notes, 57% of the 1954 papers are still
cited in 1990-1994. These durations are so long primarily because the
field has been growing so rapidly--by a factor of 24 in 40 years. If
normalized to a constant literature output, the average halflife would
have been 6 yr. Another pertinent effect is caused by the changing
fields of interest. Because studies of extragalactic objects, relative
to other fields, are now 7 times more frequent than in 1954, citations
to them have remained nearly constant in 40 years while citations
to papers in other fields have dropped off more quickly. (SECTION:
Astronomical Sociology)

---------------------------------------------------------
Title: HD 105262, A Newly-Discovered HR 4049 Star with a Large
Proper Motion
Authors: Abt, Helmut A.
1996PASP..108..844A Altcode:
HD 105262 has a spectrum like that of HR 4049 in having Balmer liens
as in a Ib supergiant but very weak lines due to He I, Ca II, Si II, Ti
II, fe I, Fe II, and Mg II. It has a published proper motion of 0.057"
+/- 0.011" yr^-1. If the star had the luminosity of a Ib supergiant,
its space motion would be several times the escape velocity from
the Galaxy. HD 105262 does not have the spectral appearance of a
horizontal-branch or post AGB star. The most likely explanation for the
spectrum is the model proposed for HR 4049 by Lamers et al. (1986),
Waelkens et al. (1987), and Lambert et al. (1988), namely a low-mass
proto-planetary nebula star in which the narrow Balmer lines are formed
in an extended atmosphere. (SECTION: Stars)

---------------------------------------------------------
Title: Announcement: additional scientific editors.
Authors: Abt, H. A.
1996ApJ...466..603A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Announcement: faster publication times for electronic
manuscripts and other changes.
Authors: Abt, Helmut A.
1996ApJ...465....1A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: What Fraction of Astronomers Become Relatively Inactive in
Research after Receiving Tenure?
Authors: Abt, Helmut A.; Zhou, Hongnan
1996PASP..108..375A Altcode:
We ask how many astronomers publish substantially fewer papers after
receiving tenure than before and what are their characteristics that
would have allowed us to predict their decreased productivity? This
is answered by a study of 214 tenured astronomers at 17 of the major
astronomical centers in the U.S. It is reassuring that 48% of the
astronomers published more papers per year after receiving tenure
than before and 33% published between half and the same number of
papers per year as before tenure. Only 19% published less than half
as many papers per year after tenure than before; among those, 1.8%
published no first-author papers after receiving tenure, even though
that occurred several decades ago in some cases. However the pre-tenure
rates of publication and the current citations to those papers were not
significantly different for the 19% less active researchers than for the
remaining 81%. We found no numerical characteristics that allow one to
predict who will become relatively inactive in research after receiving
tenure. Those 19% do not favor any specific decade when they received
tenure (1960s, 1970s, or 1980s) and they are well distributed among
the 17 institutions. A few have heavy administrative responsibilities,
but some others with at least as heavy responsibilities are among
the most productive researchers after tenure. The 17 institutions
averaged a constant number of new tenure assignments per year during
1970-1995. (SECTION: Astronomical Sociology)

---------------------------------------------------------
Title: VizieR Online Data Catalog: A-type stars rotation and spectral
peculiarities (Abt+ 1995)
Authors: Abt, H. A.; Morrell, N. I.
1996yCat..20990135A Altcode:
We obtained new data to determine whether the spectral appearance of
A-type stars is entirely determined by their rotational velocities. For
this purpose we derived rotational velocities for 1700 northern A-type
stars from CCD coude spectra, calibrated with the new Slettebak et
al. system, and new MK classifications based on wide photographic
Cassegrain spectra for 2000 northern and some southern stars in the
Bright Star Catalogue. In addition we determined the equivalent widths
of the lambda 4481 Mg II lines in the coude spectra. Tables and graphs
show variations of rotational velocities and lambda 4481 line strengths
as functions of type and luminosity, and frequencies of the normal
and abnormal stars. After deconvolutions of the rotational velocities,
assuming random orientations of rotational axes, we find that all rapid
rotators have normal spectra and nearly all slow rotators have abnormal
spectra (Ap or Am). Those abnormalities are generally attributed to
diffusion and can occur only with little rotational mixing. However
at all types there are overlaps of these distributions, implying that
a given intermediate rotational velocity is insufficient to determine
whether the star should have a normal or abnormal spectrum. However,
we realized that (1) some of our "standards," such as Vega and Alpha
Dra, are really abnormal, causing us to classify similar peculiar
stars as "normal," (2) many of the "normal" stars near A2 IV have the
characteristics of peculiar stars such as low rotational velocities and
weak 4481 Mg II and K lines, and (3) the mean rotational velocities
of "normal" stars are depressed just at those types where the Ap and
Am stars are most frequent. Therefore we conclude that the overlaps
are due to our failure to detect all the abnormal stars and that a
specific rotational velocity is probably enough to determine whether
a star will have a normal or abnormal spectrum. (1 data file).

---------------------------------------------------------
Title: Keynote Address: Questions for the Present and Future
Authors: Abt, H. A.
1996ASPC...90...15A Altcode: 1996oedb.conf...15A
No abstract at ADS

---------------------------------------------------------
Title: What Happens to My Electronic Manuscript Submission to the
AAS-affiliated Journals?
Authors: Barnes, J.; Abt, H. A.; Avrett, E. H.; Dalgarno, A.; Hodge, P.
1996AAS...187.3806B Altcode: 1996BAAS...28..755B
No abstract at ADS

---------------------------------------------------------
Title: Informe sobre el avance del proyecto de determinaciones de
V sen i para todas las estrellas B más brillantes que 6.5 mag.
Authors: Abt, H.; Levato, H.
1996BAAA...40...24A Altcode:
Se ha finalizado con la determinación de V sen i para todas las
estrellas B más brillantes que 6.5 mag y al norte de -30 grados
de declinación. Esta muestra involucra casi 1000 estrellas. Las
observaciones fueron realizadas desde KPNO. Mientras tanto, se
ha completado desde CASLEO la observación de 350 estrellas B
más brillantes que 6.5 mag. al sur de -30 grados. Además de la
determinación de la rotación axial se determinan, en los casos
posibles, los anchos equivalentes de las líneas 4471 Ådel He I y
4481 Ådel Mg II.

---------------------------------------------------------
Title: Observational Evidence of Binary Evolution in Open Clusters
Authors: Abt, H. A.; Willmarth, D. W.
1996ASPC...90..105A Altcode: 1996oedb.conf..105A
No abstract at ADS

---------------------------------------------------------
Title: Some Statistical Highlights of the Astrophysical Journal
Authors: Abt, Helmut A.
1995ApJ...455..407A Altcode:
We start by scanning the first 25 volumes of the Astrophysical
Journal and listing some of the famous scientists who contributed
papers. Then we scan the whole 100 years of the Journal to find when
major changes were made. The more prolific authors with the longest
publication records are listed, as well as the most prolific ones
before 1944. Finally, in giving data on pages and papers published,
we find that the largest impact on astrophysical publication was not
due to the post-Sputnik era or periods of high funding; rather, it
was due to the development of atomic physics in the 1930s and earlier.

---------------------------------------------------------
Title: Obituary - Chandrasekhar, Subrahmanyan 1910-1995 Managing
Editor - 1952-1971
Authors: Abt, H. A.
1995ApJ...454..551A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Relation between Rotational Velocities and Spectral
Peculiarities among A-Type Stars
Authors: Abt, Helmut A.; Morrell, Nidia I.
1995ApJS...99..135A Altcode:
We obtained new data to determine whether the spectral appearance of
A-type stars is entirely determined by their rotational velocities. For
this purpose we derived rotational velocities for 1700 northern A-type
stars from CCD coudé spectra, calibrated with the new Slettebak et
al. system, and new MK classifications based on wide photographic
Cassegrain spectra for 2000 northern and some southern stars in the
Bright Star Catalogue. In addition we determined the equivalent widths
of the λ4481 Mg II lines in the coudé spectra. Tables and graphs
show the variations of rotational velocities and λ4481 line strengths
as functions of type and luminosity, and frequencies of the normal and
abnormal stars. After deconvolutions of the rotational velocities,
assuming random orientations of rotational axes, we find that all rapid
rotators have normal spectra and nearly all slow rotators have abnormal
spectra (Ap or Am). Those abnormalities are generally attributed to
diffusion and can occur only with little rotational mixing. However
at all types there are overlaps of these distributions, implying that
a given intermediate rotational velocity is insufficient to determine
whether the star should have a normal or abnormal spectrum. However,
we realized that (1) some of our "standards," such as Vega and α
Dra, are really abnormal, causing us to classify similar peculiar
stars as "normal," (2) many of the "normal" stars near A2 IV have the
characteristics of peculiar stars such as low rotational velocities and
weak 4481 Mg II and K lines, and (3) the mean rotational velocities
of "normal" stars are depressed just at those types where the Ap and
Am stars are most frequent. Therefore we conclude that the overlaps
are due to our failure to detect all the abnormal stars and that a
specific rotational velocity is probably enough to determine whether
a star will have a normal or abnormal spectrum.

---------------------------------------------------------
Title: Some Highlights of the Astrophysical Journal
Authors: Abt, Helmut A.
1995AAS...186.1403A Altcode: 1995BAAS...27..830A
We first name some prominent authors during the first 25 volumes. Then
we list the major changes made in the Journal during the past
100 years. The authors with the longest publication records are
listed, as well as the most prolific ones before 1944 and other such
records. Finally based on counts of papers and pages published annually,
we found that the sudden growth of astrophysics did not occur after
World War II or after Sputnik, but at a financially disadvantageous
time that will surprise you.

---------------------------------------------------------
Title: Changing Sources of Published Information
Authors: Abt, Helmut A.
1995PASP..107..401A Altcode:
We looked at the types of references in papers published during the
first month of 1972, 1982, and 1992 in the Astrophysical Journal and
Astronomy &amp; Astrophysics; also those published in the former
journal during the first half-years of 1952 and 1962. Some of the
results are qualitatively predictable, such as the decrease (from
12% to 1%) in references to observatory publications and inhouse
technical reports, and the increase (from 1% to 10%) in references to
conference papers. But what are surprising are (1) the low (less than
3%) reference rate to preprints, showing that they are not replacing
journal papers (78%) as the primary source for reliable information,
(2) the low (1%) reference rate to theses, showing that they are not
cited more frequently than average research papers, (3) the low (1%)
reference rate to review papers, showing that contrary to popular
belief, very few people cite review papers instead of the original
research papers, and (4) the slightly decreasing reference rate (from
6% to 4%) to monographs, showing that despite their greatly increased
publication rate, they are gradually being quoted less for research use
(as contrasted to tutorial use). (SECTION: Astronomical Sociology)

---------------------------------------------------------
Title: First Radial Velocities for 146 Bright F- and G-Type Stars
Authors: Abt, Helmut A.; Willmarth, Daryl W.
1994ApJS...94..677A Altcode:
We have obtained an average of 5.7 radial velocities for 146 northern
stars of types F and G (all luminosity classes) listed in 'A Supplement
to the Bright Star Catalogue' as having no previously known radial
velocity measures. Those were obtained with charge coupled devices
(CCDs) and a cross-correlation technique; the intrinsic velocity
accuracy, based on stars of apparently constant velocity, is probably
less than +/- 0.3 km/s per mean. Of those stars 14% are newly discovered
SB2 stars. The prevelance of rapid profile variations (in minutes or
hours) in most of the broad-lined F-type stars makes it difficult to
obtain accurate measures for them.

---------------------------------------------------------
Title: The Current Burst in Astronomical Publications
Authors: Abt, Helmut A.
1994PASP..106.1015A Altcode:
The Astrophysical Journal grew in numbers of papers during 1972-1986
at about the same rate as the growth in members of the AAS. However
since 1987 it has grown at twice that rate. By classifying papers
we found that half the excess growth is due to a doubling of papers
from spacecraft and the other half from theoretical papers, probably
those that interpret these data. The number of papers based on
ground-based data has stayed nearly constant. These changes did not
occur in the Astronomical Journal, which has a different proportion
in types of papers. Nor do Icarus, MNRAS, A&amp;A, PASP show recent
increases greater than the growth in numbers of astronomers. (SECTION:
Astronomical Sociology)

---------------------------------------------------------
Title: Announcement - the Centennial Challenge
Authors: Abt, H. A.
1994ApJ...430..445A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Institutional Productivities 1993
Authors: Abt, H. A.
1994PASP..106..107A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: MK Spectra of the Bright A-Type Stars
Authors: Abt, H. A.
1994ASPC...60...99A Altcode: 1994mpyp.conf...99A
No abstract at ADS

---------------------------------------------------------
Title: Report of IAU Commission 26: Double and multiple stars
(Etoiles doubles et multiples).
Authors: Abt, H. A.
1994IAUTA..22..239A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Obituary: Goro Ishida, 1924-1992
Authors: Abt, Helmut A.
1993BAAS...25.1497A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Institutional Productivities
Authors: Abt, Helmut A.
1993PASP..105..794A Altcode:
We considered the 5707 research papers published in ApJ, AJ, and
PASP in 1952, 1962, 1972, 1982, and 1992. For each paper we noted the
affiliations and, assuming that each of n authors should get credit
for one n^-1 paper for his/her institution, we determined the numbers
of ppaers published by 38 pre-selected institutions, the remaining
other U.S. institutions, and non-U.S. institutions. The 10 or 20 most
productive institutions are listed for each year. In many cases the
institutions with the largest staffs are at the top of the lists. Then
we determined the numbers of AAs members at each institution and
computed the mean numbers of papers per AAS member. We found that pure
research organizations have the highest productivity per AAS member and
average decrease as we progress to institituions whose staff members
have many other than commitments in addition to research. (SECTION:
Astronomical Sociology)

---------------------------------------------------------
Title: The Growth of Multiwavelength Astrophysics
Authors: Abt, Helmut A.
1993PASP..105..437A Altcode:
We scanned all the papers in the first halves of 1962, 1972, 1982, and
1992 in the Astrophysical Journal and Supplements, the Astronomical
Journal, and these Publications of the Astronomical Society of the
Pacific. The papers were classified as (O) containing new observations,
(R) being rediscussions of published data, (T) theoretical, or (L)
laboratory data or instrumentation. The proportions were 57:12:28:4,
respectively, with no significant changes in 30 years. The papers
containing new observations were classified by wavelength regions. All
regions showed increased numbers of papers with time. However the
predominance of papers (79%) from the optical region in 1962 gave way
by 1992 to 1% in gamma rays, 9% in X-rays, 6% in UV, and 15% in IR,
leaving 46% in optical. The radio papers remained at 20%. The fractions
of papers involving two or more wavelength regions grew from 1% in
1962-1972 to 6% in 1982-1992. (SECTION: Astronomical Sociology)

---------------------------------------------------------
Title: Announcement - E-Mail Addresses
Authors: Abt, H. A.
1993ApJ...406..359A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: CCD Observations of Possible Trapezium Systems
Authors: Abt, H. A.; Corbally, C. J.
1993ASPC...38...72A Altcode: 1993nfbs.proc...72A
No abstract at ADS

---------------------------------------------------------
Title: Rotational Velocities for the Brighter A-Type Stars
Authors: Abt, H. A.; Morrell, N. I.
1993ASPC...44..384A Altcode: 1993IAUCo.138..384A; 1993pvnp.conf..384A
No abstract at ADS

---------------------------------------------------------
Title: Announcement - Proposed Cd-Rom Series
Authors: Abt, H. A.
1993ApJ...402....1A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Astronomical Publications
Authors: Abt, H. A.
1993ASPC...38..466A Altcode: 1993nfbs.proc..466A
No abstract at ADS

---------------------------------------------------------
Title: The Astrophysical Journal Videotapes
Authors: Abt, H. A.
1992ApJ...393....1A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectroscopic Binaries in the alpha Persei Cluster
Authors: Morrell, Nidia; Abt, Helmut A.
1992ApJ...393..666M Altcode:
An average of 16 radial velocity measures for each of the 28 brightest
(B3-A2) cluster members and found four binaries was obtained. The
resulting binary frequency of 14 percent is, like the previous 20
percent for the B6-A1 stars in the Pleiades, unusually low compared with
a typical 30 percent for early-type field stars or with 30 percent or
more in other open clusters. These two clusters are the only known ones
with unusually high mean rotational velocities. It is suspected that
the mean rotational velocities are high either because these clusters
lack short-period binaries or are not old enough for synchronization
of rotational and orbital velocities to have occurred. The four Alpha
Persei binaries are all relatively wide ones (greater than 20 d) and
with small mass ratios (0.1-0.5). The same results apply to the young
Orion Nebula cluster. These results can be explained in terms of the
formation of binaries by capture in that during the first free-fall
time, capture will produce wide binaries with small mass ratios, as
in the Orion Nebula and Alpha Persei clusters, but repeated captures
and disruptions will produce more closely spaced binaries with many
mass ratios near 1.0, as in IC 4665.

---------------------------------------------------------
Title: What Fraction of Literature References Are Incorrect?
Authors: Abt, Helmut A.
1992PASP..104..235A Altcode:
From a systematic study of 1009 references in The Astrophysical Journal
it was found that 12.2% had errors. Only 0.4% of the referenced papers
could not be found at all; another 3.0% were found by searching in
volume, annual, and five-year indices and the remaining correctly
and incorrectly referenced papers were found right away. Another 8.3%
of the references have errors in the first authors' names or in the
journal names, and volume and page numbers such that they could be
misplaced in the Science Citation Index (S CI). However, the compilers
of SCI match all citations against a computerized file of the source
papers and correct some of the citations, so that only 3.6% of the
citations are missing or displaced in SCI.

---------------------------------------------------------
Title: Duplicity Among Solar-Type Stars
Authors: Abt, H. A.; Willmarth, D. W.
1992ASPC...32...82A Altcode: 1992cadm.conf...82A; 1992IAUCo.135...82A
No abstract at ADS

---------------------------------------------------------
Title: American On-Line Publication Tests and Long-Range Plans
Authors: Abt, H. A.
1992dpas.conf...47A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Closing Comments
Authors: Abt, H. A.
1992dpas.conf..223A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A noteworthy occasion
Authors: Abt, H. A.
1991Obs...111..251A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Further Observations of 9 Aurigae
Authors: Krisciunas, K.; Skillman, D. R.; Guinan, E. F.; Abt, H. A.
1991IBVS.3672....1K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Reinvestigation of the Binary Frequency in the Open Cluster
IC 4665
Authors: Morrell, Nidia; Abt, Helmut A.
1991ApJ...378..157M Altcode:
The radial velocities of 15 bright B3-A2 stars in the cluster IC 4665
are measured using a CCD. Only four of the 15 stars are spectroscopic
binaries, giving a binary frequency of 27 percent. Four of the
six sharp-lined stars are binaries, and none of the more rapidly
rotating stars are binaries with K at least 10 km/s. Statistically,
nearly all of the stars with low projected rotational velocities are
slow rotators, and most are binaries; two of the four binaries may
rotate synchronously. In two of the four binaries, the mass ratios
are near 1.0, as would be expected for binary formation in three-body
interactions after many crossing times. The measured cluster velcoity
dispersion is only 1.6 km/s, but most of that is still probably due
to measuring errors.

---------------------------------------------------------
Title: Science Citation and Funding
Authors: Abt, H. A.
1991Sci...251.1408A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Publication Practices in Various Sciences
Authors: Abt, H. A.
1991BAAS...23..961A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Search for Wide Binaries at the North Galactic Pole using
Precise Radial Velocities
Authors: Latham, David W.; Mazeh, Tsevi; Davis, Robert J.; Stefanik,
Robert P.; Abt, Helmut A.
1991AJ....101..625L Altcode:
Precise radial velocities are presented from a survey of 247 stars
centered on Selected Area 57 at the North Galactic Pole, complete
for late-type stars with V magnitude brighter than 12.0. The radial
velocities have a typical precision of 0.2-0.3 km/s. New spectral
types and distances estimates are presented for 120 of the stars in
the sample. All pairs of stars with angular separations between 1 and
600 arcsec have been considered, and 11 candidate pairs found with
velocity differences less than 1.5 km/s. It is estimated that 4 or 5
of the 11 candidate pairs are actually bound binaries, but none with
separations larger than 0.1 pc. The constraints imposed by these results
on the actual distribution of wide binaries in the Galaxy should now be
reanalyzed. The unusual precision of the velocities led to the discovery
of a new cluster associated with the multiple system ADS 8811 ABC.

---------------------------------------------------------
Title: Editorial - Changes to the Volume Index
Authors: Abt, H. A.
1991ApJ...366..341A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectroscopic Binaries in the Orion Nebula Cluster
Authors: Abt, Helmut A.; Wang, Ruyou; Cardona, Octavio
1991ApJ...367..155A Altcode:
A search was made for spectroscopic binaries among the 26 brightest
members of this very young cluster. Orbital elements are given for
four binaries (three known binaries, one newly discovered), and one
star is a probable binary. In agreement with published predictions
from n-body simulations for binary formation by capture, it is found
that the spectroscopic binaries have long periods (median of 20 days),
have low-mass companions, are not rotating synchronously with their
orbital motions even for a period of 6.5 days, and are probably not
concentrated toward the cluster center more than are the massive single
stars. The binary frequency is probably normal for a cluster with a
high mean rotational velocity.

---------------------------------------------------------
Title: A Search for Binaries in Two Open Clusters
Authors: Morrell, Nidia I.; Abt, Helmut A.
1991ASPC...13..433M Altcode: 1991fesc.book..433M
No abstract at ADS

---------------------------------------------------------
Title: Status of the profession
Authors: Boyce, Peter B.; Beichman, Charles A.; Abt, Helmut A.; Bauer,
Wendy Hagen; Burbidge, Geoffrey; Cochran, Anita L.; Dorfman, Robert;
Harris, Hugh; Havlen, Robert; Jones, Christine
1991aap..rept.....B Altcode:
The number of astronomers has grown by about 40 percent over the past
decade. The number of astronomers with jobs in industry, or with
long-term, non-tenured, jobs has increased dramatically compared
with traditional faculty positions. The increase in the number
of astronomers and the declining share of the NSF budget going to
astronomy has led to extreme difficulties in the NSF grant program
and in support of the National Observatories. In 1989, direct NASA
support of astronomers through the grants program exceeds that of NSF,
although the total of the NSF grants program over decade far exceeds
that of NASA. Access to major new telescopes will be important issue
for the 1990s. US astronomers, who once had a monopoly on telescopes
larger than 3 meters, will, by the year 2000, have access to just half
of the world's optical telescope area.

---------------------------------------------------------
Title: Publication Characteristics of Members of the AAS
Authors: Abt, Helmut A.
1990PASP..102.1161A Altcode:
For each of the 4995 persons listed in the 1989 American
Astronomical Society Membership Directory, we noted their total
1984-88 publications as listed in the Author Index of Astronomy and
Astrophysics Abstracts. The members are subdivided as retired (mean
of 0.61 paper/yr), foreign (3.89), Full (3.34), Division Affiliates
(1.76), Associate (1.48), and Junior (0.79) members. For Full members
the frequencies of various publication rates are listed; the median
is 2.28 papers/yr. The Full members are subdivided by affiliations,
namely private institutions (mean of 4.71 papers/yr), university
(3.89), government-funded (3.46), commercial company (1.81), and
unknown affiliations (0.84). We looked up the listed publications
for four high producers who each average 25.7 papers/yr. We found
that 55% of those are preprints, abstracts, conference papers, and
other secondary material. Furthermore, they average 4.2 authors per
original research paper. If we divide each original research paper
by the number of authors, these four average only the equivalent of
4.0 single-author research papers/yr. A sample of moderate producers
also have 53% of their publications as abstracts, conference papers,
etc., and they average 4.2 authors per original research paper. We
conclude that the average Full AAS member produces the equivalent of
1/2 single-author original-research paper/yr and 23% of them produce
more than 1 such paper/yr.

---------------------------------------------------------
Title: The Frequency and Formation Mechanism of B2--B5 Main-Sequence
Binaries
Authors: Abt, Helmut A.; Gomez, Ana E.; Levy, Saul G.
1990ApJS...74..551A Altcode:
Twenty coude spectra were obtained for each of the 74 B2-B5 IV or V
stars, and the results of their radial velocities were combined with
those of a previous study of 42 similar stars, to examine the frequency
and the formation mechanism of these binaries. New improved orbital
elements are listed for nine known double-lined and 26 single-lined
spectroscopic binaries. It is found that, systems with periods of 0.01
yr to 100,000 yrs, have secondary frequencies that fit the Salpeter
(1955) luminosity function (but not the van Rhijn function), indicating
that these systems were formed primarily by capture. For systems with
periods shorter than 0.01 yr, the separations of components are only
a few stellar radii, suggesting that these systems have undergone mass
transfer; their secondary masses have no direct information concerning
the formation mechanism.

---------------------------------------------------------
Title: Editorial - Style Changes for Most Astronomical Journals
Authors: Abt, H. A.
1990ApJ...357....1A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Refereed Conference Papers - Editorial
Authors: Abt, H. A.
1990ApJ...354....1A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Trends Toward Internationalization in Astronomical Literature
Authors: Abt, Helmut A.
1990PASP..102..368A Altcode:
For two American and three non-American astronomical journals,
we counted the numbers of papers during 1949-89 representing the
following authorships: purely national, mixed national and foreign,
and purely foreign. In the four major journals (ApJ, AJ, MNRAS, and
A&amp;A) the foreign input was constant from 1949 until the early 1970s
and it has increased steadily thereafter to reach a current level of
about 30%. There has also been a large increase in the numbers of mixed
national and foreign papers, showing that currently about one-quarter
of all the published papers represent multinational collaborations.

---------------------------------------------------------
Title: Editorial - Instrumentation Papers
Authors: Abt, H. A.
1989ApJ...346....1A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Journal Referencing
Authors: Abt, Helmut A.; Liu, Jinming
1989PASP..101..555A Altcode:
We have tested the complaint that authors in certain countries do
not adequately reference papers published elsewhere. We surveyed nine
general (i. e., nonspecialty) English-language astronomical journals
published in six countries and one region. For each we counted the
annual totals of references to papers in those nine journals. We found
in every case a preference to reference papers in the same journal. The
excess averages 7.7% of all the references, and that excess has not
changed since before 1980. Beyond that, the referencing patterns are
similar for all nine journals except some journals reference more
heavily than others the journals and monographs outside this set
of nine.

---------------------------------------------------------
Title: Developments in primary publishing:
Authors: Mitton, S.; Abt, H.; Wilkins, G. A.; Jaschek, C. O.
1989HiA.....8.....M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Future of Astronomical Literature
Authors: Abt, H. A.
1989lisa.conf...37A Altcode: 1989IAUCo.110...37A
No abstract at ADS

---------------------------------------------------------
Title: Growth Rates in Various Fields of Astronomy
Authors: Abt, Helmut A.
1988PASP..100.1567A Altcode:
We counted the original research papers published worldwide in 1970,
1975, 1980, and 1985 as listed in the Astronomy and Astrophysics
Abstracts. The numbers grew from 7772 papers in 1970 to 14,302 papers
in 1985, corresponding to a doubling time of 18.3 yr. In general
the growth of astronomical papers increases with the distance of
the objects from us, ranging from a doubling time of eight years
for galaxies and cosmology to a decline for planetary research. The
peak of interest has shifted from the planetary system in 1970-75 to
stars in 1980-85. An exception to the pattern is high-energy sources,
which show no growth in radio sources, quasars, pulsars, and cosmic
rays, and only a slow growth in X-rays and γ-rays; this constancy is
mostly due to a lack of new instrumentation. The American papers
show parallel effects except that only the field of stars is growing
(slightly) more rapidly than abroad. Research in interstellar matter,
high-energy sources, and the planetary system is growing much more
slowly than abroad. The doubling time for American papers is 26.2
yr and the American fraction of worldwide astronomical papers has
decreased from 38% in 1970 to a current 32%.

---------------------------------------------------------
Title: Maximum Separations among Cataloged Binaries
Authors: Abt, Helmut A.
1988ApJ...331..922A Altcode:
The author classified many of the widest common-motion binaries
listed in the Aitken catalog and lists 72 physical pairs with known
photoelectric photometry, 31 physical pairs without good photometry,
and 27 optical pairs. It is found that as a function of primary types,
the physical systems have upper limits to their separations that are
exceeded by some of the optical pairs. The fact that optical pairs
occur with larger separations implies that the limits are real ones
and not just catalog limitations. Those limits (in AU) are expressed
by 2500 M11.54 (M1 mass of the primary
in solar units) for B5 - K0 main-sequence primaries.

---------------------------------------------------------
Title: Editorial - Name Change - Letters
Authors: Abt, H. A.; Dalgarno, A.
1988ApJ...328L...1A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: What Happens to Rejected Astronomical Papers?
Authors: Abt, Helmut A.
1988PASP..100..506A Altcode:
We studied the histories of the 1039 papers submitted in 1984 to the
Pub. A. S.P., A.J., and Ap. J. (first half of 1984) and found that 90%
were eventually accepted and published in the initial journals. Of the
remainder, two-thirds never appeared in other journals and one-third
(32 papers) appeared in a large variety (18) of journals, mostly
nondomestic. These numbers do not differ significantly between the three
journals but differ drastically from journals in fields other than
the physical sciences where the acceptance rates are usually 10%-30%
and authors tend to submit rejected papers to other journals rather
than to revise them. Key words: publication-reviewing

---------------------------------------------------------
Title: Visual binary separations as functions of primary types,
ages, and locations
Authors: Abt, H. A.
1988Ap&SS.142..111A Altcode: 1988IAUCo..97..111A
We studied samples from theBright Star Catalogue of B1-B7, F3-G2,
and KM dwarfs for frequencies of visual companions and their
separations. The frequency of detected companions does not vary
significantly along the Main Sequence. But the most frequent separations
and the limiting separations vary markedly along the main sequence: the
limiting separations are 42000 AU for the B stars to 800 AU for the M
dwarfs. This confirms results found by Öpik in 1924. Stars off the Main
Sequence (giants, white dwarfs) show consistent results, as do membres
of Trapezium systems, hierarchical multiple-star systems, the widest
known cataloged binaries, and binaries in a moving cluster (Ursa Major
Stream). We propose a scenario in which binaries in open clusters can
have large separations, but after they leave the cluster environments,
chance encounters with field stars and molecular clouds will disrupt all
but the more compact systems. The comoving pairs discussed by Luyten,
Eggen, and others are seen as members of disrupting clusters and still
retaining the common cluster motions. However, the velocity dispersions
within clusters ensure that the comoving pairs have similar, but not
identical, motions, whereas members of truly bound binaries would have
motions that are indistinguishable. Appropriate measurements should
distinguish between wide binaries and the comoving pairs, which can
have separations up to the outer diameters or more of open clusters.

---------------------------------------------------------
Title: Erratum - Reference Frequencies in Astronomy and Related
Sciences
Authors: Abt, H. A.
1988PASP..100..156A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Interacting Am binaries.
Authors: Abt, H. A.
1988covp.conf....1A Altcode:
The author discusses and interprets a new study of binaries among Am
stars. Among the late A-type dwarfs, those with rotational velocities
≤100 km s-1 are Am's while the more-rapid rotators
have normal spectra. Diffusion in the former explain their abnormal
abundances. The author confirms that statistically all Am stars are
in binaries, mostly of short periods less than 100 days. It appears
that tidal braking in binaries with periods ≤100 days causes the
components to have low rotational velocities and thus become Am stars.

---------------------------------------------------------
Title: Reference Frequencies in Astronomy and Related Sciences
Authors: Abt, H. A.
1987PASP...99.1329A Altcode:
We explore the claim that citation rates for astronomers should not
be compared with those of other scientists because astronomers put
more references in their papers, causing their citation rates to be
artificially high. We scanned 2079 papers with 59,659 references in
13 journals: five American astronomical journals, three non-American
astronomical journals, and five journals in physics, chemistry, and
geophysics. We find a tight relation between mean numbers of references,
&lt;R&gt;, and mean paper lengths, , expressed in normalized
1000-word pages; it is &lt;R&gt; 9.9 + 2.18 . Except for review
papers and papers filled with many new data, this relation holds true
within 2-3 σ for 12 of the journals. The reason why American papers in
astronomy and geophysics have more references than papers in physics
and chemistry is because the former are approximately twice as long;
for papers of the same lenghts, the average numbers of references per
paper are the same among all four sciences.

---------------------------------------------------------
Title: Frequency of Binary Stars
Authors: Abt, H. A.
1987S&T....74..573A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Binary Frequency of High-Velocity Field Dwarfs as Obtained
with CCD Measures
Authors: Abt, Helmut A.; Willmarth, Daryl W.
1987ApJ...318..786A Altcode:
Published studies of high-velocity or weak-lined dwarfs have differed
in concluding that the binary frequency is either substantially lower
or similar to that of Population I dwarfs. The authors therefore made
a new spectroscopic study with 6 times the previous measuring accuracy
of 45 high-velocity FG dwarfs. They found five spectroscopic binaries
with derived orbital elements, including three previously known. The
resulting frequency of spectroscopic binaries with derived orbital
elements is 11%±5%, which is low relative to the 20% for Population I
dwarfs. In addition, ≡9%±3% of the high-velocity dwarfs have visual
companions, compared with 30% for Population I dwarfs.

---------------------------------------------------------
Title: Implications for Solar-Type Binary Statistics of the
Morbey-Griffin Improved Binary Analysis
Authors: Abt, Helmut A.
1987ApJ...317..353A Altcode:
We do not contest the preceding results by Morbey and Griffin but
rather congratulate those authors on their improved instrumental
and statistical methods. We ask here about the effects upon the
binary statistics of solar-type stars of deleting the unconfirmed
binaries. Specifically we assumed, in accord with Morbey and Griffin's
recommendations, that all sharp-lined systems with orbital velocity
amplitudes K1 &lt; 8.0 km s-1 are undetected,
as well as all broad-lined systems with K1 &lt; 12.0
km s-1. After deleting 15 such binaries, there is some
compensation by deriving larger correction factors for undetected
binaries, namely six more. We find no significant change in the
binary frequency for periods of 10-3 - 1O-1
yr, a marginal reduction of 28% ± 24% in the numbers of binaries in
10-1 -10 yr, and no changes at all for longer periods. The
two forms of the secondary mass functions for periods greater than or
less than 100 yr are unchanged.

---------------------------------------------------------
Title: Duplicity among Stars with Strong Chromospheric CA II Emission
Lines: A Statistical Survey
Authors: Young, Arthur; Mielbrecht, Richard A.; Abt, Helmut A.
1987ApJ...317..787Y Altcode:
Using high-dispersion coudé spectrographs the authors have
made multiple observations of 38 stars, all of which have strong
emission-line core reversals in their Ca II H and K lines relative
to the majority of stars of their same spectral type and luminosity
class. Most of the sample stars are on the main sequence.The authors
have found four possible (new) close binaries in their sample based
upon detected variations of radial velocity. Comparing these results
with similar studies of active stars, the authors find that duplicity
may, in special circumstances, be sufficient but is not a necessary
condition to generate magnetically induced chromospheric activity.

---------------------------------------------------------
Title: Are Papers by Wellknown Astronomers Accepted for Publication
More Readily than Other Papers
Authors: Abt, H. A.
1987PASP...99..439A Altcode:
We considered the 242 papers published in 1977-86 in the Astrophysical
Journal by 49 well-known astronomers (i.e., the living Russell,
Warner, Pierce, and Heineman awardees and the AAS Presidents) plus
a control group of 242 papers selected at random. We found that the
numbers of reviews per paper were 1.34 and 1.37, respectively, or an
insignificant 0.5σ difference. The average reviewing time was 2.1σ
larger (42.7 days) for the papers by the well-known astronomers than
for the control (40.8 days), probably because the former are longer
papers on the average. The acceptance rate of 95% is higher for the
former than for the control (83%), as one would expect for papers by
more experienced authors. Thus, the papers by well-known astronomers
do not receive significantly fewer or more-rapid reviews, but a larger
fraction of them is eventually accepted.

---------------------------------------------------------
Title: Galactic Distribution, Kinematics, Locations in Clusters and
H-R Diagrams, and Duplicity of STARS Stars (review Paper)
Authors: Abt, Helmut A.
1987pbes.coll..470A Altcode: 1987IAUCo..92..470A
Present knowledge concerning Be stars in a number of areas is
reviewed. The Galactic distribution and kinematics of Be stars are
addressed. The occurrence of Be stars in open clusters and associations
and their locations in H-R diagrams are examined, taking into account
evidence for a preferred evolutionary stage, evidence for a dependence
upon age, and the frequencies in various clusters and in the field. The
issue of frequencies and kinds of binaries among Be stars is examined.

---------------------------------------------------------
Title: Spectral Classification of Weak-lined Stars Discovered
Photometrically
Authors: Abt, Helmut A.
1986ApJ...309..260A Altcode:
Olsen has compiled a mixed list of 800 weak-lined dwarfs plus 75
other interesting stars, found by obtaining Strömgren four-color
photometry for 14,816 A5 - G0 Henry Draper stars. The author has
obtained spectra of 140 of those, selected at random, and found that
97% of the proposed weak-lined dwarfs are indeed such; the remainder
are composities (1%) or normal, more luminous stars (2%). Spectral
types were generally obtained form the hydrogen line, iron-peak metals,
and G bands. Deficiencies in the metallic-line types are compared with
[Fe/H] values and Δm1 (metallic strength) indices.

---------------------------------------------------------
Title: The Ages and Dimensions of Trapezium Systems
Authors: Abt, H. A.
1986ApJ...304..688A Altcode:
MK spectral types and memberships were obtained for 120 stars in
31 systems thought to be Trapezium systems. Twenty-eight optical
components were found, after the removal of which, 17 systems are
hierarchical and three have no companions. Practically all of the
remaining Trapezium systems are either the same age or younger than the
Hyades, i.e., less than 10 to the 8.9th years old. The maximum radii
of Trapezium combined with hierarchical systems exhibit a dramatic
decrease with primary spectral type or age T, ranging from about
50,000 AU for OB primaries to 1000 AU for G dwarfs. If stars have an
observed binary separation of about 5000 AU, it is unlikely that the
sun would have a stellar companion at 92,000 AU. A Ba II star with a
physical companion, a star with strong double Ca II emission lines,
and a chance projection of a nearby quadruple hierarchical system on
a distant triple hierarchical system is discussed.

---------------------------------------------------------
Title: MK classification of the brighter Praesepe stars.
Authors: Abt, H. A.
1986PASP...98..307A Altcode:
MK classifications have been obtained for the 42 brightest stars
in the rich open cluster Praesepe. In the H-R diagram, 10 of the 12
stars brighter than V = 7.0 mag have luminosity classes brighter than
V or are Am stars. Only two of the stars fainter than V = 7.0 mag
are of luminosity class IV. The nine Am stars discovered by Bidelman
(1956) are confirmed. The frequency of these among the late A stars
is consistent with results for field stars, but there is only one Ap
star. The reasons for that deficiency are discussed.

---------------------------------------------------------
Title: The Binary Frequency Among Weak-Lined Dwarfs
Authors: Willmarth, D.; Abt, H. A.
1986BAAS...18..681W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: An Assessment of Research done at the National Optical
Observatories
Authors: Abt, H. A.
1985PASP...97.1050A Altcode:
We know that the national optical observatories produce hundreds of
papers yearly but we wonder whether these include a reasonable share of
major studies because some practices at those observatories, especially
before 1982, seemed to be biased against major long-term studies. We
considered the papers published in 1980 and 1981 and based on data
obtained primarily from four large telescopes, two at national and two
at university observatories. The former telescopes produce more papers,
but are they as useful to astronomy as judged by citation counts? There
is statistically no significant differences in the average citations
per paper for the four telescopes and the 5% most-cited papers came
from all four telescopes in statistically equal numbers.

---------------------------------------------------------
Title: Improved study of metallic-line binaries.
Authors: Abt, H. A.; Levy, S. G.
1985ApJS...59..229A Altcode:
For the sake of completeness, a new study has been made of the frequency
of binaries among classical metallic-line (Am) stars and of the
characteristics of these systems. For an initial sample of 60 Am stars,
about 20 coude spectra and radial velocities were obtained each. When
combined with excellent published orbital elements for some systems,
the new material yields 16 SB2s, 20 SB1s, and 20 visual and occultation
companions not already counted as spectroscopic companions. Extensive
details are given about the observations, radial velocities, and
binary orbits. Evolutionary expansion during their main sequence
lifetime is seen as an additional mechanism (besides tidal braking)
acting in close binaries to lower rotational velocities below 100 km/s.

---------------------------------------------------------
Title: Visual multiples. VIII. 1000 MK types.
Authors: Abt, H. A.
1985ApJS...59...95A Altcode:
A total of 1000 new classifications are given for stars brighter than
B = 8.0 mag in the Aitken double star catalog. The classifications
supplement 865 classifications obtained in 1981 and 1984. Among
the newly discovered stars are 12 new Ap stars, eight Lambda Bootis
stars, one Ba II star, and 60 Am stars. A detailed list of the new
classifications is given.

---------------------------------------------------------
Title: The spectra and ages of blue stragglers.
Authors: Abt, H. A.
1985ApJ...294L.103A Altcode:
A mechanism similar to Wheeler's 'quasi-homogeneous evolution' and Finzi
and Wolf's proposal for blue stragglers is proposed as the origin of
the blue stragglers in intermediate-age clusters. Blue stragglers are
stars whose positions in color-magnitude diagrams of open and globular
clusters are significantly above the turn-off points and in the region
of the (former) main sequence; they seem to represent a conflict with
the general conclusion that all stars in a cluster originated at about
the same time. It is concluded that there are at least two kinds of
blue stragglers: (1) those stars of types about B3-A2 are primarily Ap
stars and slow rotators, occur in the intermediate age clusters and
remain in the main sequence region probably through magnetic mixing;
and (2) the stars of type O6-B2 frequently have emission lines, are
rapid rotators, occur in the young cluster, and remain in the main
sequence region probably by rotational mixing.

---------------------------------------------------------
Title: Radial Velocities from CCD Detectors
Authors: Willmarth, Daryl W.; Abt, Helmut A.
1985srv..conf...99W Altcode: 1985LDP.....5...99W; 1985IAUCo..88...99W; 1985srv..proc...99W
The authors have developed a simple system to judge the suitability
and accuracy of CCD detectors for determining radial velocities. While
earlier studies determine the Doppler shift in Fourier space, the
method described here analyses the spectrum in data space, using a
straightforward technique that has been demonstrated to give accurate
reliable results.

---------------------------------------------------------
Title: Metallic Line Binaries
Authors: Abt, Helmut A.
1985srv..conf..275A Altcode: 1985IAUCo..88..275A; 1985srv..proc..275A; 1985LDP.....5..275A
A new radial-velocity study of 55 Am stars reveals 16 SB2s, 20 SB1s,
and 22 visual or occultation companions for a total of more than one
companion per primary. Only about 75% of the primaries are in binaries
with periods less than 100 days, even if one allows for unobservable
small inclinations and low-mass secondaries. Therefore it may not be
true that tidal interactions in close binaries is the only mechanism
necessary to produce the low rotational velocities that allow diffusion
to act, unless small reductions (factor of 1.4) in rotational velocities
occur in binaries of longer periods.

---------------------------------------------------------
Title: Spectroscopic tests of photoelectric stellar classification
of abnormal stars.
Authors: Abt, H. A.
1984ApJ...285..247A Altcode:
Spectroscopic classification is obtained for 169 northern A5-G0 stars
predicted by Olsen (1979, 1980) to have abnormal spectra on the basis
of Stromgren four-color photometry. The success in identifying reddened
early type stars was nearly 100 percent, for Am and early type weak
lined stars about 75 percent, for stars above main sequence about 50
percent, for composite spectra about 25 percent, and for Ap and Lambda
Boo stars 0 percent. Thus photoelectric photometry is a successful
first step in discovering stars of the more extreme spectroscopic
abnormalities.

---------------------------------------------------------
Title: Be stars in binaries.
Authors: Abt, H. A.; Cardona, O.
1984ApJ...285..190A Altcode:
The known companions to 80 Be stars and 355 B stars listed in the
Bright Star Catalogue in the range B1-B7 III-V and north of delta =
-30 deg are considered. The known near-absence of Be binaries with
periods less than 1/10 yr is confirmed. For longer periods up to the
limit of 10,000 AU of this survey, the Be and B stars do not differ in
binary frequencies. This result implies that during pre-main-sequence
contraction, the tidal braking in binaries wider than 0.5 AU was
inadequate to prevent the formation of stars with nearly the break-up
rotational velocities. The fraction of Be and B stars that have
companions is higher in clusters and associations (38 percent) than
among field stars (25 percent), confirming that escapees from clusters
tend to be single stars. There is some evidence that the companions
of Be stars that occur in the same luminosity range tend also to be
Be stars; that result was expected because in visual binaries there
is a known tendency for rapidly rotating primaries to have rapidly
rotating secondaries.

---------------------------------------------------------
Title: Citations to Single and Multiauthored Papers
Authors: Abt, H. A.
1984PASP...96..746A Altcode:
It is shown that on the average, the number of citations to papers
increases linearly with the number of authors. However, if team research
takes substantially more time to perform than individual research, the
advantage is lost. The larger citation rate for many-authored papers
is not due to the higher citation rate for longer papers because they
tend to be shorter than few-authored papers: it is also not due to
certain more-active fields more multiauthored papers. Longer papers
yield substantially larger numbers of citations than shorter papers,
but a single long paper still yields fewer citations than the total
for several shorter ones of the same combined lengths.

---------------------------------------------------------
Title: Additional radial velocities of the Cepheid binary W
Sagittarii.
Authors: Jacobsen, T. S.; Wallerstein, G.; Abt, H. A.
1984PASP...96..630J Altcode:
Radial-velocities of W Sgr from 28 coudespectrograms taken during
1980-1983 are presented, along with velocities of certain standard
stars. A mean velocity of -28.0 + or - 0.7 km/s for a mean epoch
of 1981.96 is found. The 1980-1983 data indicate that the orbital
period is longer than the 80 years previously suggested, and that
the spectroscopic orbit cannot be obtained at this time. Further
observations with high accuracy are required so as to obtain the
distance and mass of this speckle and spectroscopic binary.

---------------------------------------------------------
Title: Citations to Federally-Funded and Unfunded Research
Authors: Abt, H. A.
1984PASP...96..563A Altcode:
The 1409 papers published in 1974 in the three general American
astronomical research journals produced 21,106 citations (references)
during the years . Papers coming from most kinds of organizations
(universities, NSF and NASA centers, foundations, and miscellaneous
governmental and military organizations) have statistically the same
average citation rates, whereas papers from commercial companies
rank higher and foreign papers (in 1974) rank lower. Sloan Fellows
and university authors receiving most furms of auxiliary outside
funding (NASA, NSF) produce higher-cited papers than papers without
such funding.

---------------------------------------------------------
Title: The nature of the visual companions of AP and AM stars.
Authors: Abt, H. A.; Cardona, O.
1984ApJ...276..266A Altcode:
The stars in 43 visual multiples with Ap or Am primaries have been
classified, and the fraction of systems that have Ap or Am secondaries
is counted. The numbers of Ap secondaries are too few to be informative,
but an apparent excess of Am secondaries is found. That result is
understandable in terms of the (published) moderate correlation in
rotational velocities between components in visual multiples. But
in various open clusters, the variations in frequencies of Ap and Am
stars can be explained probably as statistical fluctuations in small
numbers of stars, indicating no tendency for abnormal stars to group
together for dimensions larger than those of visual multiples.

---------------------------------------------------------
Title: Discovery of λ Bootis Stars
Authors: Abt, H. A.
1984mpsc.conf..340A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Occurence of Peculiar Stars in Clusters and Visual Systems
Authors: Abt, H. A.
1984mpsc.conf..369A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: HD 164615 : A probable spotted single F type star.
Authors: Abt, H. A.; Bollinger, G.; Burke, E. W., Jr.
1983ApJ...272..196A Altcode:
This star shows light variations by 0.05 mag in a period of about 0.815
deg, but there are substantial differences from cycle to cycle. Various
possible explanations for the variations were explored. First, the
star is not an Ap variable because its spectrum is normal (F2 IV)
and it does not have the color variations that are typical of an Ap
star. It is not an ellipsoidal primary because the radial velocity does
not change; a lack of change in line widths excludes the possibility of
its being a double-lined binary with unresolved lines. It is probably
not a pulsating star because of the lack of color and velocity
changes. However, the hypothesis of a single rotating spotted star
fits because the rotational period (1.7 deg sin i) is compatible with
the light period (0.815 deg) and it offers a natural explanation for
changes from cycle to cycle in terms of changes in spot activity. It
has not been possible to determine whether the spots are bright or
dark ones in this rapid rotator.

---------------------------------------------------------
Title: Confirmation among visual multiples of an increase of AP
stars with age.
Authors: Abt, H. A.; Cardona, O.
1983ApJ...272..182A Altcode:
Open clusters with ages below certain threshold values contain no
Ap stars and those with greater ages contain numbers of Ap stars
that apparently increase with age. But in view of the few young
clusters studied, the data could also be interpreted in terms of random
differences in the frequencies of Ap stars between individual clusters,
rather than an age effect. Data on 77 field visual multiple systems
(that originated from many different clusters and associations)
in which the primaries are O5-A1 stars and the secondaries occur
in the absolute magnitude range of the Ap stars were, therefore,
obtained. Again spectral classification shows no Ap stars in systems
with ages not greater than 1,000,000 yr and a steady increase in Ap
stars thereafter. The numerical agreement with the cluster data is good,
confirming that the cluster data are exhibiting a real age effect.

---------------------------------------------------------
Title: At what Ages did Outstanding American Astronomers Publish
Their Most-Cited Papers
Authors: Abt, H. A.
1983PASP...95..113A Altcode:
We selected 22 outstanding American astronomers whose careers terminated
before 1970 and we counted the citations in 197() 79 to the papers
published throughout their careers. It turns out that most (84%) of
the citations are to papers published between the ages of 40 and 75
years. If we overcorrect for the fact that citations to outstanding
papers decreased exponentially after a peak, the change is small:
the years account for 77% of the citations and the years account for
94%. These results are not sensitive to the types of research done
by these astronomers. Two likely reasons for the high citation rates
in the later years are that astronomers tend to write reviews and do
major studies in later years, both of which are highly cited. These
results apply to outstanding normal astronomers and not necessarily
to the rare revolutionary scientist.

---------------------------------------------------------
Title: Accuracy of spectral classification
Authors: Abt, H. A.
1983LowOB...9..118A Altcode: 1983LowOB.167..118A; 1983IAUCo..62..118A
It is pointed out that a knowledge of the spectral types of
visual components is still basic to most intensive studies of
visual systems. There have been substantial improvements in speed,
accuracy, and reliability, since the discovery of the two-dimensional
Morgan-Keenan classification system about 40 years ago. Questions
regarding the reliability of the classification of stars are discussed,
taking into account the current accuracies of good-quality spectral
classification for typical stars. The presented values are less accurate
by a factor of six than the best photoelectric photometry.

---------------------------------------------------------
Title: Normal and abnormal binary frequencies.
Authors: Abt, H. A.
1983ARA&A..21..343A Altcode:
Recent data on duplicity and multiplicity for normal main sequence stars
and a variety of classes of stars that have abnormal frequencies are
discussed and compared. The occurrence of multiplicity among normal
stars is assessed and those classes of stars in which different
multiplicities have caused their spectroscopic or evolutionary
peculiarities are identified. It is shown that the correlations between
high or low duplicity and the consequent peculiarities are produced
by a variety of dynamical and astrophysical mechanisms.

---------------------------------------------------------
Title: A search for secondary lines in the visual spectra of 55
binaries.
Authors: Gomez, A. E.; Abt, H. A.
1982PASP...94..650G Altcode:
Using a CCD detector in the Kitt Peak coude spectrograph, a search was
made for secondary lines in the visual spectral region of single-lined
binaries. The lines were found in one-quarter of the 23 B2-B5 dwarfs
and 6 percent of the 32 F3-G2 dwarfs. In the cases of failures, there
are no contradictions between the earliest possible secondary spectral
types and the latest types allowed by the orbital mass functions.

---------------------------------------------------------
Title: Statistical Publication Histories of American Astronomers
Authors: Abt, Helmut A.
1982PASP...94..213A Altcode:
We have considered the 2988 papers published in 194580 in three American
journals by 115 astronomers who obtained Ph.D. `s in 194560. For the
entire sample there are peaks in publication rates at the times of
the Ph.D. award and 58 years later (tenure challenge?), and then,
surprisingly, a constant output until at least 25 years following
the Ph.D. Since some astronomers drop out of doing research, the
remainder must be increasing their annual publication rate. There was
a marked drop-out (9%) during the year of the Ph.D. award of people
doing astronomical research and then a constant drop of 1.5% per year
during the subsequent 21 years. If we divide the sample between the
13 astronomers who average more than ten 1000-word pages per author
per year and the 102 who average less, we find different publication
patterns. The more prolific astronomers show no peak outputs at
the times of the Ph.D. and tenure awards, but a generally steadily
increasing annual output until at least 27 years after the Ph.D.;
the less prolific astronomers show pronounced thesis and tenure
challenge peaks and then a constant output thereafter. The 11% of
prolific astronomers initially account for 30% of the pages published
and eventually for more than 65% of the annual total.

---------------------------------------------------------
Title: William C. Miller (1910-1981).
Authors: Abt, H. A.
1982AASPB..31....3A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Revised MK Spectral Atlas for Stars Earlier
than the Sun
Authors: Morgan, W. W.; Abt, H. A.; Tapscott, J. W.; Andrews, P. J.
1981Obs...101..217M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Editorial
Authors: Abt, H. A.
1981ApJ...249....1A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Some Trends in American Astronomical Publications
Authors: Abt, H. A.
1981PASP...93..269A Altcode:
We have studied the papers published in 1910, 1920,... 1980 in the
three principal American astronomical journals to derive the following
results: The total annual publication rate was relatively constant
until World War II, followed by a doubling time of 7.8 years and
with a recent slower rate. The average paper lengths, normalized to
the same page content, has tripled since 1940, with a much larger
increase in information. But the most surprising result is the
virtual disappearance of the very short papers (less than one page)
that accounted for one-third of the papers published earlier in the
century. While papers are becoming longer, authors are writing fewer
papers per person (by a factor of 0.6). The fraction of theoretical
papers has increased from 5% early in the century to a current 33%. The
strong tendency for single- author papers early in the century has been
replaced by a current average of double-author theoretical papers and
triple-author observational papers.

---------------------------------------------------------
Title: Long-Term Citation Histories of Astronomical Papers
Authors: Abt, H. A.
1981PASP...93..207A Altcode:
We studied the citation histories of 326 papers published in 1961 and
cited in the 18 subsequent years. On the average the citations reached
a maximum five years after publication, followed by a slow decline
such that 20 years after publication the citation rate is half the
maximum rate. Theoretical papers show the same rate of decline as
observational ones. Theoretical and observational papers are cited
with equal frequencies. The most frequently-cited papers are almost
invariably long ones, although only half of the long papers are cited
frequently. Frequently-cited papers have even a longer lifetime, namely
about 27 years to decline to half the maximum citation rate. Various
additional statistics and caveats to these conclusions are given.

---------------------------------------------------------
Title: Visual multiples. VII. MK classifications.
Authors: Abt, H. A.
1981ApJS...45..437A Altcode:
Classifications are given for 865 components of visual multiples; they
show no systematic differences from the MK system, and the random errors
are one subclass in type and two-thirds of a luminosity class. It is
found that at least 1% of the F-type IV and V stars are weak-lined,
32% of the A4-F1 IV and V stars are Am, and 5% of the A0-A3 IV and
V stars are early-type Am. Attention is called to the large fraction
(55%) of the A3-A9 III-V stars that are of luminosity classes III or
IV, unlike the percentage (16%) at neighboring types.

---------------------------------------------------------
Title: Some aspects of the spectroscopic behavior of the stars of
highest luminosity in the region of the Hertzsprung gap.
Authors: Morgan, W. W.; Keenan, P. C.; Abt, H. A.; Tapscott, J. W.
1981ApJ...243..894M Altcode:
The classification of the stars of highest luminosity in the spectral
range GO-KO is discussed. The method of pattern recognition is
applied to certain configurations of lines and blends in the region
λλ4100-48O0. One of the most sensitive of these patterns makes
possible the separation of the two brightest luminosity classes (zero,
0-Ia) from the general category of Ia stars in the range G8-K0;
this pattern should be usable on objective prism plates. The
two brightest luminosity classes (zero, 0-Ia) comprise stars probably
undergoing the most intense mass loss in the spectral interval F8-K0,
and those showing the most marked irregular spectral variations; this
latter characteristic makes difficult the assignment of accurate MK
spectral types. The most trustworthy morphological information seems
to be derivable from the approach in which spectrograms of several
of the super-supergiants are confronted with the F8-K2 fundamental
Ib standards. From such a confrontation, valid statements can be
made concerning the differential classification of members of the
super-supergiant group as well as their relationship to the Ib sequence.

---------------------------------------------------------
Title: Palomar Sky Survey Overlay Maps and Infrared Milky way Survey
Authors: Abt, H. A.
1981KPNON..18....4A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Visual multiples. VI. BET 1269, a system containing abnormal
stars.
Authors: Abt, H. A.
1980PASP...92..796A Altcode:
The primary star is reported by Mechler (1974) to be a metal-poor
light-variable while the secondary is reported to be normal. Recent
measures at the U.S. Naval Observatory tend to confirm the evidence
for a common proper motion. Both stars have constant radial velocities
but with means that differ by 5.0 km/s; it is not clear whether this
difference provides evidence against common space motions. The spectral
type of the primary is F0 IV with A3 V metallic lines, while that of
the secondary is F1 Vp(G-band strong). Thus both stars are abnormal
for reasons not known.

---------------------------------------------------------
Title: Are binaries concentrated toward the centers of open clusters?
Authors: Abt, H. A.
1980ApJ...241..275A Altcode:
The distances in the plane of the sky from the centers of eight
open clusters have been derived for 48 spectroscopic and visual
binaries and 113 constant-velocity stars. These show no evidence
for a concentration of binaries toward the center of young clusters
but indicate 2 sigma evidence for a binary concentration toward the
centers of old clusters or 2.4 sigma evidence from spectroscopic
binaries alone. The detailed radial distributions of binaries in old
clusters confirm this concentration, showing that the binaries near
the cluster centers are harder (or of shorter periods).

---------------------------------------------------------
Title: Visual multiples. V. Radial velocities of 160 systems.
Authors: Abt, H. A.; Sanwal, N. B.; Levy, S. G.
1980ApJS...43..549A Altcode:
937 radial velocities are listed from coude spectra of 160 visual
multiples with known visual orbital elements; these, plus the velocities
in paper of Roemer and Sanwal (1980), are discussed. Among the results
are (1) systems yielding spectroscopic elements with the visual period,
(2) systems probably showing velocity variations during the visual
period, (3) systems with short spectroscopic periods, some in addition
to detectable motion during the visual period, (4) systems showing no
variation in radial velocity during the visual period, either because
the components are similar in brightness or the periods are very long,
(5) systems with spectral lines too broad to allow the detection
of orbital motion, and (6) systems with insufficient data for any
conclusions to be drawn at present.

---------------------------------------------------------
Title: The Cost-Effectiveness in Terms of Publications and Citations
of Various Optical Telescopes at the Kitt-Peak
Authors: Abt, H. A.
1980PASP...92..249A Altcode:
This study is based upon (1) the 445 papers published in 197. 76 by
visiting and staff astronomers from observations with the two 0.44 ,
two 0.9-m, 1.3-m, and 2. 1-m telescopes at the Kitt Peak National
Observatory, (2) the 4179 references (citations) made in 197. 7S to
those papers, and (3) the relative annual operating costs for those
telescopes. The intermediate results are that the numbers of published
papers vary as the 1.1-power of the aperture, the numbers of citations
vary as the 1.5-power of the aperture, and the initial costs and annual
operating expenses vary as the 2.37- and 2.1-powers of the aperture,
respectively. These indicate that smaller telescopes, properly equipped,
are several times more productive of publications and citations than the
largest one at Kitt Peak National Observatory considered in this study,
the 2.1- m. Data are given on the average citation histories of papers
for the first five years after publication and on the frequencies of
highly- and little-cited papers from each telescope.

---------------------------------------------------------
Title: A small cluster near IC 1805.
Authors: Abt, H. A.; Perry, C. L.; Olsen, E. H.; Grauer, A. D.
1980PASP...92...60A Altcode:
A small group of stars near the edge of the IC 1805 (W4) H II region
has been studied partly for evidence of a physical association with
the nebula. The two brightest stars have pronounced shell spectra
and evidence of hydrogen emission lines. A B8 V star with weak Hg
lines, two normal B stars, and four fainter stars in the field were
studied. UBV, H-beta, and Stromgren four-color photometry of nine
stars yield a reddening of E(B - V) = 0.54 m, a distance of 485 pc,
and an age of not greater than 10 to the 7.4th yr. The two shell stars
and two normal B stars fall on the ZAMS but the Hg star is either a
multiple or foreground star and the three fainter stars are probably
background stars. The group is not associated with the more distant
(2200 pc) IC 1805.

---------------------------------------------------------
Title: Kitt Peak seeing
Authors: Abt, H. A.
1980PASP...92..103A Altcode:
The profiles of stellar images near the zenith are measured on 57 random
nights between 1975 and 1979, by employing a sequence of Coude slit
widths and an exposure meter that measures the profiles in one dimension
to an average internal standard error of plus or minus 0.06 arcsec. The
advantages and disadvantages of this method are discussed, together
with questions of seasonal variations in seeing for Kitt Peak. The
results are examined, and it is determined that directional (seeing)
differences occur due to local topography or to the wind direction.

---------------------------------------------------------
Title: The Cost-Effectiveness of Telescopes of Various Apertures
Authors: Abt, H.
1980oits.conf..609A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The frequencies of binaries on the main sequence.
Authors: Abt, H. A.
1979AJ.....84.1591A Altcode:
Available observational data on the frequencies of binaries along
the main sequence are reviewed for high and low masses, high- and
low-velocity stars, stars in clusters and in the field, and normal
and abnormal stars. Attention is given to normal solar-type dwarfs,
high-velocity dwarfs, binaries among B dwarfs, binary frequency
differences among clusters, binaries among cluster and field stars, and
binaries among such abnormal stars as common novae, U Gem stars, Am and
Ap stars, Be stars, Wolf-Rayet stars, and dMe stars. The data are shown
to imply that the binary characteristics of normal stars may not depend
sensitively on primary mass and that an inverse correlation exists
between duplicity and mean rotational velocity among cluster stars.

---------------------------------------------------------
Title: The occurence of abnormal stars in open clusters.
Authors: Abt, H. A.
1979ApJ...230..485A Altcode:
The age dependence of the frequencies of various types of abnormal stars
in open clusters and associations is discussed. Spectra acquired at
dispersions of 39 A/mm and 129 A/mm were used to determine the spectral
types and luminosity classes of 661 stars in 14 open clusters and
associations. The frequencies of Ap(Si), Ap(Hg,Mn) and Ap(Sr,Cr) stars
are found to increase with age to a level about that of field stars,
while the rotational velocities of Ap(Si) and Ap(Hg,Mn) stars decrease
with time. Be stars in clusters exhibit a relatively constant frequency,
roughly equal to that of Be field stars. The frequencies of stars with
pronounced shell spectra are observed to remain constant with age,
while stars with unusually broad hydrogen lines (Vb stars) occur only
in the youngest clusters. The frequency of Am stars in clusters is not
significantly different from that of field stars, and does not seem to
depend on age, although rotational velocity is seen to decrease. It is
concluded that Ap or Am stars develop from stars of various rotational
speeds, with a subsequent decrease in rotational velocity.

---------------------------------------------------------
Title: Spectral types of stars with unusual photometric indices.
Authors: Abt, H. A.; Brodzik, D.; Schaefer, B.
1979PASP...91..176A Altcode:
The Kitt Peak 2.1-m Cassegrain spectrograph was used to obtain spectra
of 92 A5-G0 stars measured by Olsen in the Stromgren four-color system
and predicted to be abnormal in the sense of excessive reddening,
high luminosity, or abnormal composition. Of the five stars predicted
to be reddened B or A stars, four were indeed such while for the fifth
Olsen observed the blended components. Of twelve stars predicted to be
supergiants, one is a supergiant, four are giants, two are subgiants,
three are Ap stars, and two are Am stars. Thus photometrically predicted
supergiants are actually stars above main sequence in two out of three
cases but mostly much less luminous than expected. Of ten predicted
weak-lined stars, only two were found to be really so. Am stars were
well predicted, though detection is contaminated with Ap and luminous
stars. It is concluded that four-color photometry is useful in selecting
interesting stars, but is often unable to tell the specific type of
abnormality present.

---------------------------------------------------------
Title: Editorial
Authors: Abt, Helmut A.
1979ApJ...227..359A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Occurrence of Abnormal Stars in Open Clusters
Authors: Abt, Helmut
1979RA......9...95A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Forthcoming Morgan-Abt Spectral Atlas
Authors: Abt, H. A.
1979RA......9..477A Altcode: 1979IAUCo..47..477A
No abstract at ADS

---------------------------------------------------------
Title: Spectral types in Gurzadyan's clustering in Auriga.
Authors: Abt, H. A.
1978PASP...90..555A Altcode:
Spectral types of the 11 brightest stars in Gurzadyan's (1974)
clustering confirm that most of these are B stars. The conclusions
of Heiser et al. (1978) are confirmed that there are several groups
present: (1) a distant group at 1100 pc with 0.23 mag reddening and
three evolved stars; (2) an intermediate group at 630 pc with 0.06
mag reddening and lying mostly northeast of the distant group but with
some overlap; and (3) three foreground Am stars at 250-500 pc.

---------------------------------------------------------
Title: Editorial: Increased Costs
Authors: Abt, Helmut A.
1978ApJS...38...87A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Frequencies of Binaries on the Main Sequence
Authors: Abt, H. A.
1978BAAS...10Q.607A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectral types in the Ursa Major stream.
Authors: Levato, H.; Abt, H. A.
1978PASP...90..429L Altcode:
New spectral types are given for the 14 nucleus cluster stars and the
140 additional stars thought to be stream members. We found nine Ap and
eight Am stars, most of which had been previously known as abnormal. The
rotational velocities are consistent with the ideas that all the slow
rotators in the IV or V region have Am or Ap spectra but only half of
the early A-type slow rotators have obviously abnormal spectra. Key
words: open clusters-peculiar stars-spectral classification

---------------------------------------------------------
Title: Radial velocities of the cepheid X Cygni.
Authors: Abt, H. A.
1978PASP...90..309A Altcode:
A radial-velocity curve based on 17 coude spectra shows the following
results when compared with other velocities: (1) no variation in
mean velocity, implying no detectable companion; (2) no phase shifts
if a period of 16.3861 days is used, indicating a constant period;
(3) probably no variation in the shape of the velocity curve except
perhaps at phases 0.55-0.80. Strong lines show a greater expansion
by roughly one atmospheric scale height than moderate-strength lines,
but it is not clear whether they show a similar greater contraction.

---------------------------------------------------------
Title: Evidence for the duplicity of the anomalous cepheid Y Ophiuchi.
Authors: Abt, H. A.; Levy, S. G.
1978PASP...90..188A Altcode:
The mean velocity of this 17-day cepheid seems to show a variation
due to binary motion with a period of 2612 days. Orbital elements are
given. It is unlikely that the light of the companion is responsible
for the small ranges in light, color, and radial velocity of the
cepheid. Key words: cepheids-spectroscopic binaries

---------------------------------------------------------
Title: Spectral types in the Pleiades.
Authors: Abt, H. A.; Levato, H.
1978PASP...90..201A Altcode:
New spectral classification of 49 of the brightest stars in the Pleiades
shows the following peculiarities: (1) three Ap(Si) stars, of which one
is a member of a 2d46111 double4ined binary with an Am secondary, (2) an
Ap(Hg,Mn) star that may be a member of the cluster, (3) four Am stars,
of which two are only marginally abnormal, and (4) three shell spectra
that include the pronounced case of Pleione and two mild shell spectra
called "sn". The Ap + Am system should be checked for eclipses. Key
words: open clusters-peculiar stars-spectral classification

---------------------------------------------------------
Title: Binaries among B2 - B5 IV, V absorption and emission stars.
Authors: Abt, H. A.; Levy, S. G.
1978ApJS...36..241A Altcode:
Samples of 42 B2-B5 IV or V and 21 B2e-B5e IV or V stars are studied
on the basis of 20 coude spectra of each star for evidence of
spectroscopic binaries. Orbital elements are derived for eight newly
discovered binaries among the B stars and two among the Be stars,
orbital elements are confirmed or improved for four other systems,
and the apsidal motion of two stars is examined. The upper limit
in separation for common-proper-motion (CPM) pairs is investigated,
periods are estimated for three CPM systems with orbital elements,
and the statistics of the observed multiples is evaluated. It is shown
that there are 20 singles (51 percent), 14 doubles (36 percent), and
five triples (13 percent) in a reduced sample of 39 B stars, as well
as 15 singles (75 percent), four doubles (20 percent), and one triple
(5 percent) in a reduced sample of 20 Be stars. The B and Be stars are
found to differ in one major respect: there are no known Be binaries
in the sample with periods of less than about 100 days, but half the
B-star multiples have periods of less than 100 days. An assessment is
made of the number of binaries missed because their velocity variations
are small due to small orbital inclinations or small secondary masses.

---------------------------------------------------------
Title: The Occurrence of Peculiar Stars in Open Clusters
Authors: Abt, Helmut A.; Levato, Hugo
1978IAUS...80..155A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Revised MK Spectral Atlas for stars earlier than the sun
Authors: Morgan, W. W.; Abt, Helmut A.; Tapscott, J. W.
1978rmsa.book.....M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Binary Frequency Along the Main Sequence
Authors: Abt, H. A.
1978prpl.conf..323A Altcode: 1978IAUCo..52..323A; 1978ppsf.book..323A
Solar-type stars are considered, taking into account high-velocity
stars, low-velocity stars, and binaries and calcium emission. The
principal problem concerning binaries among the late A-type stars is
the occurrence of two subgroups, including the metallic-line (Am) stars
and the normal A stars. B-type stars are discussed along with O-type
stars, and M dwarfs. It is found that for most stars which are normal
in composition and lack pronounced emission lines, the frequency of
binaries is roughly the same and the binary characteristics do not seem
to depend strongly on type or primary mass. The short-period binaries
seem to be bifurcation doubles with secondary mass distributions that
decrease in frequency with decreasing secondary mass.

---------------------------------------------------------
Title: Spectral types in the Orion OB1 association.
Authors: Abt, H. A.; Levato, H.
1977PASP...89..797A Altcode:
Spectral types are derived for 152 stars in the Northwest, Belt, and
Outer Sword regions. The classifications show that the following are
present: (1) stars above the ZAMS in the O9B3 and the B7-A3 regions;
most of these have greater luminosities than class V or are double-lined
binaries or peculiar stars; (2) eleven Ap stars of which three are
Si rich, two are He rich, five are He poor, and one is Mg poor; (3)
four moderate Be stars; (4) only two stars with broad hydrogen lines
like the ones that are so prevalent in the Orion Nebula Cluster; (5)14
"sn" stars that have both sharp and broad He I lines, perhaps due to
tenuous shells; (6) one classical shell star; (7) several Sirius-type
Am stars, although most of the Am stars in the region are foreground
stars. Key words: associations-peculiar stars-spectral classification

---------------------------------------------------------
Title: Editorial Concerning Page Charges and Subscription Rates
Authors: Abt, Helmut A.
1977ApJS...35..127A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectral Types in the Open cluster NGC 2169
Authors: Abt, Helmut A.
1977PASP...89..646A Altcode:
Spectral classification of the eight brightest stars in the field
shows that six are cluster members and the earliest type is B2 III. The
cluster distance is 1500 :1: 2()0 pc and the mean reddening is . Key
words: open clusters-spectral classification

---------------------------------------------------------
Title: Editorial Concerning Page Charges and Subscription Rates
Authors: Abt, Helmut A.
1977ApJ...217....1A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectral types in the open cluster M34.
Authors: Abt, H. A.; Levato, H.
1977PASP...89..648A Altcode:
Spectral types for the 18 brightest members of M34 indicate the
following: one Hg-Mn Ap star, one pronounced Si-Cr-Sr Ap star,
one marginal Am star, a star with a weak shell spectrum, and five
suhgiants or giants. Key words: open clusters-peculiar A stars-spectral
classification

---------------------------------------------------------
Title: Spectral types in the open cluster NGC 6633.
Authors: Levato, H.; Abt, H. A.
1977PASP...89..274L Altcode:
Spectral types are given for the 26 brightest stars in the region of
NGC 6633. Only two of the giants are definitely cluster members. Two
apparent blue stragglers are present, as well as one extreme Ap star,
four marginal Am stars, and two stars with weak shell lines.

---------------------------------------------------------
Title: A search for a third star in the Cygnus X-1 system.
Authors: Abt, H. A.; Hintzen, P.; Levy, S. G.
1977ApJ...213..815A Altcode:
A search was made for a third low-mass star that might be the
origin of the X-rays, rather than the massive secondary star. From
radial-velocity measures of 86 moderate-dispersion spectra obtained
during three observing seasons, we found no evidence for a change in
velocity of HDE 226868 during intervals of days, months, or years. The
upper limit to the primary perturbation K1 &lt; 4 km 1 during days to
years suggests that a third star, if present, has roughly 1.5 . This
still admits the existence of a neutron star as a third body. Subject
headings: stars: binaries - X-rays: binaries

---------------------------------------------------------
Title: Multiplicity of Solar-Type Stars
Authors: Abt, H. A.
1977RMxAA...3...47A Altcode: 1977IAUCo..33...47A
A systematic search for binaries in a sample of 123 bright field stars
of types F3-G2 IV or V is described. Combination of the results for 25
newly discovered spectroscopic binaries with those of 21 spectroscopic,
23 visual, and 25 common-proper-motion pairs previously known brings
to 88 the total number of companions identified in the sample. The
distribution of the 88 periods shows a single maximum; the modian
period is 14 years. The frequencies of singles: doubles: triples:
quadruples are found to be 42: 46: 9: 2. Less than half of the stars
are thus observed to be single. Estimates of the completeness of this
search lead to a determination of the number of systems missed and to a
dotermination of their secondary masses. Analysis of the secondary-mass
distributions, observed and predicted from completeness estimates,
indicates the existence of two ,typos of binaries. For systems with
periods less than about 100 years, the distribution of secondaries
varies with the cube-root of tho secondary mass. These systems must be
tho result of fission. Two-thirds of their primaries have companions
of stellar mass. Extrapolation of the cube- root relation implies that
the remaining one-third of the primaries have non-stellar secondaries,
i.e., close companions whose masses are less than 0.07 solar masses. For
systems -with periods larger than roughly 100 years the distribution,
of secondaries follows that, given by the van Rhijn function. They must
be the result `of condensations contracted separately but are bound
gravitationally. Roughly three-fourths of all - primaries in the sample
ha,ve such distant companions, all of which are likely to be themselves
close fission-systems. single stars are raro among solar-type dwarfs. -
* Figures 1 and 2 have been reproduced fron Ap. J. Suppl. Se'r., 1976,
30, 273, published by the University of Chicago Press for the American
Astronomical Society.

---------------------------------------------------------
Title: The spectroscopic binary HR 1300.
Authors: Abt, H. A.; Levy, S. G.
1977PASP...89..185A Altcode:
HR 1300 consists of two indistinguishable Am stars in 3.65866-day
orbits. Key words: metallic-line stars - spectroscopic binaries

---------------------------------------------------------
Title: The companions of sunlike stars.
Authors: Abt, H. A.
1977SciAm.236d..96A Altcode: 1977SciAm.236...96A
Searches for binary systems more likely to encompass planets sustaining
some form of (intelligent) life are outlined and statistical analysis
applied to a sample of 123 primaries is sketched. Periods of rotation,
relative Doppler shifts, orbital speeds, orbit plane, positions on
line of sight, perturbations if and when detectable, and reasons why
many pairs are likley to escape detection are considered. Sunlike
stars, visual doubles, astrometric doubles, spectroscopic binaries,
eclipsing binaries, close and wide binaries, and bifurcation doubles
(of near-equal mass) formed from rapidly rotating protostars are
explained. The apparent distribution of evolved secondaries (67%
normal stars, 20% planets from bodies of mass less than 0.01 solar
mass, 15% nonluminous dwarfs), a Van Rhijn distribution, is cited,
and uncertainties are noted.

---------------------------------------------------------
Title: Spectral types in the Coma Berenices cluster.
Authors: Abt, H. A.; Levato, H.
1977PASP...89...29A Altcode:
This open cluster has the following abnormal stars, many of which were
discovered by Weaver: (1) six Am stars of various degrees of extremity,
(2) two Ap stars of the Sr-Cr type, (3) one extreme shell spectrum (14
Com), and (4) a composite spectrum (12 Com). Key words: open clusters -
spectral classification

---------------------------------------------------------
Title: Addendum: MK Morphology of a Group of AM Stars
Authors: Abt, Helmut A.; Morgan, W. W.
1976ApJ...209..961A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectral types in the Orion nebula cluster.
Authors: Levato, H.; Abt, H. A.
1976PASP...88..712L Altcode:
MK spectral types of 26 of the brightest cluster members show (1)
nine stars with broad hydrogen-line cores, (2) two Am stars, of
which one is in the region of the pre-main-sequence stars, (3) two
stars with weak K lines similar to ones found in NGC 6475 and M 39,
(4) three shell stars, of which one has hydrogen emission, (5) two
composite spectra, and (6) no evolved (luminosity class IV or brighter)
stars or Ap stars. Key words: open clusters - spectral classification

---------------------------------------------------------
Title: The Frequency of Binaries Among Absorption and Emission B2-B5
IV or V Stars.
Authors: Abt, H. A.; Levy, S. G.
1976BAAS....8Q.521A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Visual multiples. III. ADS 11745 (beta Lyrae group).
Authors: Abt, H. A.; Levy, S. G.
1976AJ.....81..659A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The cause of the light variation in the metallic-line star
HR 976.
Authors: Abt, H. A.; Levy, S. G.
1976PASP...88..487A Altcode:
HR 976 has the largest light variation among six Am variables discovered
by Wiuzer. New orbital elements show the same relationship between
velocity and light curves that one finds among ellipsoidal variables,
and the light range is reasonable for the observed period. This probable
identification of the light variation as an ellipsoidal effect makes
it likely, but not certain, that the other Am light variables are also
ellipsoidal variables. Key words: ellipsoidal variable - metallic-line
stars - spectroscopic binary

---------------------------------------------------------
Title: Visual multiples. II. The gamma Velorum group.
Authors: Abt, H. A.; Landolt, A. U.; Levy, S. G.; Mochnacki, S.
1976AJ.....81..541A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectral types in the open cluster M39.
Authors: Abt, H. A.; Levato, H.
1976PASP...88..222A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Radial-velocity measurements of the lunar-occultation binary
HR 2013
Authors: Griffin, R. F.; Abt, H. A.
1976Obs....96...54G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: MK morphology of a group of Am stars.
Authors: Abt, H. A.; Morgan, W. W.
1976ApJ...205..446A Altcode:
Among the "classical" metallic-line stars (Roman et al.), some of those
showing the greatest difference between K-line type and metallic-line
type are found to have markedly brighter luminosity classes in the
violet than in the blue spectral region: in the range AA3850-4l00,
the luminosity classes range from Ib to III; in the region of the G
band, the luminosity classes are usually IV and V. The most striking
example of this phenomenon is HD 103877, where the blue metallic-line
type is F5 IV and the violet type is F5 Ib. Subject headings: stars:
metallic-line - stars: spectral classification

---------------------------------------------------------
Title: Spectral types in the Lacerta OB1 association.
Authors: Levato, H.; Abt, H. A.
1976PASP...88..141L Altcode:
Spectral types are given for 31 members and 11 probable nonmembers of
the association. The members include four evolved stars (luminosity
classes IV and III), one double-lined binary, and three shell stars,
all of which are right of the main-sequence band. The remaining three
Be stars and one peculiar star fall within the main-sequence band. Key
words: associations - peculiar stars - spectral classification

---------------------------------------------------------
Title: Multiplicity among solar-type stars.
Authors: Abt, H. A.; Levy, S. G.
1976ApJS...30..273A Altcode:
The paper presents results of a search for spectroscopic binaries among
135 bright field stars of types F3 - G2 IV or V. Orbital elements for
25 newly discovered spectroscopic binaries are derived from radial
velocities measured in 20 coude spectra for each star, and velocity
curves are also computed for each of these binaries. It is found
that the ratios of observed singles:doubles:triples:quadruples among
the 135 program stars are 42:46:9:2. The 88 computed and estimated
periods show a relatively smooth distribution with a single maximum
and a median period of 14 years. It is tentatively suggested that the
discovered binaries show no pronounced grouping tendency in age or
evolutionary state. The number of binaries not revealed is estimated,
the secondary masses for both the observed and undetected binaries are
determined statistically, and it is concluded that the short-period
binaries are fission systems while the long-period systems are those
in which pairs of protostars contracted separately. On the average,
the multiple systems are found to be 0.22 magnitude brighter than the
primaries alone.

---------------------------------------------------------
Title: Spectral types in the open cluster IC 4665.
Authors: Abt, H. A.; Levato, H.
1975PASP...87..849A Altcode:
Spectral types for 18 bright cluster members have been derived from
spectra of several dispersions. Among the peculiar spectra are (1)
two B6 Vp stars with enhanced C ii, (2) one Hg-Mn Ap star, (3) a
shell star, and (4) a classical Am star. Key words: open clusters -
peculiar stars - spectral classification

---------------------------------------------------------
Title: Announcement from the Editor
Authors: Abt, H.
1975ApJ...202..562A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectral types in the open cluster NGC 6475.
Authors: Abt, H. A.
1975PASP...87..417A Altcode:
Spectral classification of 27 of the brightest cluster members shows
(1) an earliest type of B5 IV, (2) a hot Am or Sirius-type star, (3)
three Ap stars of the Si or Si-Cr kind, all with weak Ca II K lines,
(4) two additional stars with weak K lines, and (5) one "classical"
Am star. It is noticed that among the eight spectroscopic binaries in
this cluster, the ones with broad lines have normal K-line strengths
whereas nearly all of those with sharp lines have weak K lines. Key
words: Ap stars - open clusters - Spectral classification

---------------------------------------------------------
Title: The Binary Frequency Among Solar-Type Stars.
Authors: Abt, H. A.; Levy, S. G.
1975BAAS....7..268A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotational velocities of marginal metallic-line stars.
Authors: Abt, H. A.
1975ApJ...195..405A Altcode:
Projected rotational velocities are estimated for the 44 marginal
metallic-line stars (Am:) listed by Cowley et al. These rotational
velocities are slightly larger than for the more pronounced Am
stars. The frequency distribution of equatorial rotational velocities
of Am: stars shows little overlap with that of normal A5-A9 IV, V
stars, and the overlap can be explained by differences in spectral
classification. Thus rotation velocity will determine whether a star
will have a normal (A5-A9) or abnormal (Am or Am:) spectrum, but will
not determine whether the abnormality will be marked (Am) or marginal
(Am:). Analysis of published data on binaries indicates that the Am:
stars have the same high frequency of short-period binaries as do the Am
stars and that in both cases the low rotational velocities are caused
mostly by tendencies toward synchronous rotation in binaries. Subject
headings: binaries - metallic-line stars - rotation, stellar

---------------------------------------------------------
Title: Spectral Types of M Dwarf Stars
Authors: Joy, Alfred H.; Abt, Helmut A.
1974ApJS...28....1J Altcode:
Spectral types on a uniform system based on primarily TiO band
strengths are given for 426 M dwarf stars. It is found that the
frequency of emission-line stars increases steadily from 5 percent
among the early M's through 50 percent at M4.5 to 100 percent for M5.5
and later. The absolute magnitudes of emission-line (dMe) and normal
(dM) dwarfs average the same within 0.07 mag at a given spectral
type. A new calibration of absolute magnitudes, based on trigonometric
parallaxes, is given. The measured width of the main-sequence band
can be accounted for mostly in terms of the errors in classification,
parallaxes, and photometry and to some duplicity; the cosmic dispersion
is less than 0.3 mag. The R - 1 colors of dMe stars are larger by 0.08
1 0.02(p.e.) mag than for dM stars, although the B - V colors do not
show this effect. Subject headings: late-type stars - luminosities -
spectral classification

---------------------------------------------------------
Title: The Ellipsoidal System BD +56°2190
Authors: Burke, Edward W., Jr.; Abt, Helmut A.
1974PASP...86..677B Altcode:
BD + is found to be a variable with a range of , a sinusodial light
curve, and a period 0f0d5713698 It is also found to be a spectroscopic
binary with the same period. The variable linewidths indicate that
the system is an unresolved double4ined nearly-contact binary seen
at an inclination of about 4O . The light variation is probably due
to ellipsoidal distortions of the stars, rather than to eclipses. Key
words: spectroscopic binary - variable star

---------------------------------------------------------
Title: Reinvestigation of certain long-period A-type binaries.
Authors: Abt, H. A.; Levy, S. G.
1974ApJ...188..291A Altcode:
The published orbital elements of 16 normal late A-type stars have
been reinvestigated with new radial velocities. For small-amplitude
systems, we do not confirm the published orbital elements that were
derived by combining velocities from various observatories. New
or confirmed elements are given for several systems. There is no
longer any convincing evidence for secondary stars (or black holes)
having masses greater than those of their primaries. We continue to
find no short-period (&lt;300 days) binaries, such as are common
among the Am stars, in this sample of normal late A-type stars,
although a few nearly-contact systems outside this sample need further
investigation. Subject headings: binaries - early-type stars

---------------------------------------------------------
Title: Period Variation of the Cepheid Zeta Geminorum
Authors: Abt, Helmut A.; Levy, Saul G.
1974ApJ...188L..75A Altcode:
In anticipation of the coming lunar occultations of Gem on 1974
March 4 and 31, we derive a new ephemeris based on 70 years of
radial-velocity measurements. The phases at the two occultations
are predicted to be 0.96 and 0.65 phases, respectively, after light
maximum. The period decreases at a steady rate of per year, which is
4 times the evolutionary rate for a 7 9) Cepheid in the fundamental
mode. However, it is also possible that the period decrease is due to
a light-time effect in a long-period (&gt;225 years) binary having a
low-mass secondary. Subject headings: Cepheids and W Virginis stars -
lunar occultation - stars, individual - stellar evolution

---------------------------------------------------------
Title: Visual multiples. I. ADS 7251
Authors: Abt, Helmut A.; Levy, Saul G.
1973AJ.....78.1093A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Catalog of Individual Radial Velocities, 12^{h}-24^{h},
Measured by Astronomers of the Mount Wilson Observatory
Authors: Abt, Helmut A.
1973ApJS...26..365A Altcode:
This is the second part of a compilation of the times of observation
and individual radial velocities that formed the basis for the mean
velocities obtained at the Mount Wilson Observatory and published in
Wilson's General Catalogue of Stellar Radial Velocities. This part
contains nearly 12,000 velocity measures made prior to 1952 of 3700
stars. Subject heading: radial velocities

---------------------------------------------------------
Title: Editorial on Growth of the Astrophysical Journal
Authors: Abt, Helmut A.
1973ApJ...185..737A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A spectroscopic study of the open cluster M39.
Authors: Abt, H. A.; Sanders, W. L.
1973ApJ...186..177A Altcode:
M39 is found to be intermediate among open clusters in its mean stellar
rotational velocity and its frequency of binaries. A study of the
15 brightest members yielded orbital elements for four spectroscopic
binaries; one other star has double lines. For six well-studied clusters
there is a welldefined inverse correlation between mean rotational
velocity and frequency of binaries with periods less than about 10 days;
if longer-period binary motion is also effective in reducing rotational
velocities, then the results imply preferential inclinations for some
clusters. Subject headings: binaries - open clusters - rotation, stellar

---------------------------------------------------------
Title: Editorial
Authors: Abt, Helmut A.
1973ApJ...184L..45A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Supergiant binaries in the h and chi Persei association.
Authors: Abt, H. A.; Levy, S. G.
1973ApJ...184..167A Altcode:
A study of 23 supergiants in Per OB1 showed the existence of three
spectroscopic binaries for which orbital elements are derived and
three possible additional binaries. The resultant binary frequency
of at least 15 percent is similar to that of field supergiants
and Cepheids. No binaries with periods less than 32 days in length
were found, implying that the known supergiant X-ray sources of much
shorter periods are probably rarely found systems. Subject headings:
associations - binaries - luminous stars

---------------------------------------------------------
Title: Rotation and shell spectra among A-type dwarfs.
Authors: Abt, H. A.; Moyd, K. I.
1973ApJ...182..809A Altcode:
Rotational velocities for 66 metallic-line and 123 normal A5-A9 IV or
V stars are given and used to determine the frequency distributions
of equatorial rotational velocities. Those distributions have only a
1.3 percent overlap, which is probably due to a small contamination
of the two samples. If so, then the rotational velocity is a necessary
and sufficient parameter to determine whether, within certain spectral
type and age ranges, a star will have a well-developed metallic-line
or normal spectrum. Among the 35 most rapidly rotating normal stars,
eight were found to have shell spectra. Most of the shell stars
occur during or just after the overall stellar contraction when the
stars have depleted most of their core hydrogen; one shell star has
apparently recently contracted to the main sequence. These shell stars
seem to be the A-type counterparts of the Be stars. Subject headings:
circumstellar shells - metallic-line stars - rotation, stellar

---------------------------------------------------------
Title: On the metallicity of the main-sequence stars in M67.
Authors: Morgan, W. W.; Abt, H. A.
1973AJ.....78..386M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Introductory Remarks on Spectroscopic Parameters
Authors: Abt, H. A.
1973JRASC..67...73A Altcode: 1973IAUCo..18...73A
No abstract at ADS

---------------------------------------------------------
Title: The Binary Frequency for AP Stars
Authors: Abt, Helmut A.; Snowden, Michael S.
1973ApJS...25..137A Altcode:
A search was made with coude' spectra of the 62 brightest northern Ap
stars for spectroscopic binaries. Orbital elements are given for seven
newly discovered binaries. The binary frequency of 40 percent for 15
Hg-Mn stars is roughly normal, but the frequency of 20 percent for
45 Si and Sr-Cr-Eu stars is significantly low. The deficiency cannot
be explained by the occurrence of low- mass (1 .( . I o) companions
or preferred orbital inclinations. Synchronization of rotational and
orbital motions occurs for the few systems with orbital periods less
than 6.0 days, but rarely for longer periods. Thus the low rotational
velocities of Ap stars do not seem to be due to tidal interactions
in binaries. The frequency of visual binaries seems to be normal for
all three subgroups of Ap stars. We conclude that for those Ap stars
(Si and Sr-Cr-Eu groups) having strong external magnetic fields,
the formation of binaries with separations of 10 -10 km is inhibited,
but not for the non-magnetic Hg-Mn stars or for any Ap stars in systems
with separations of x 1011 km. The evidence for the occurrence of very
low-mass ( 0.01 o) companions or short-term (30- minute) nonrandom
radial-velocity fluctuations is very weak. Subject headings: binaries -
peculiar A stars - visual double or multiple stars

---------------------------------------------------------
Title: Editorial
Authors: Abt, Helmut A.
1973ApJ...179..679A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Catalog of individual radial velocities, 12h - 24h, measured
by astronomers of the Mount Wilson Observatory
Authors: Abt, Helmut A.
1973cirv.book.....A Altcode: 1973QB1.A88n234v26.
No abstract at ADS

---------------------------------------------------------
Title: A. H. Joy (1882 - 1973)
Authors: Abt, H. A.
1973Mercu...2....9A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotational Velocities of AP Stars
Authors: Abt, Helmut A.; Chaffee, Frederic H.; Suffolk, Graham
1972ApJ...175..779A Altcode:
Projected rotational velocities were measured on coude' spectra for
essentially all the northern bright Ap stars. Differences in these
rotational velocities between subgroups are found to be marginal, except
that Guthrie's discovery of a deficiency of very narrow-lined Si stars
is confirmed. Ap stars have onequarter the mean projected rotational
velocity of normal stars of the same types and luminosities, hut it
is likely that a low rotatinnal velocity is an insufficient criterion
to produce a peculiar spectrum. Ap stars cannot be explained simply by
an aspect effect. A comparison of projected rotational velocities with
equatorial rotational velocities computed from periods of variations
in light, magnetic field, or spectrum leads to evidence for random
orientations of rotational axes.

---------------------------------------------------------
Title: Radial Velocity of RR Lyrae Variable RW Ari
Authors: Abt, H. A.; Wisniewski, W. Z.
1972IBVS..697....1A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The H-R Diagram of the Open Cluster IC 2602
Authors: Abt, H. A.; Morgan, W. W.
1972ApJ...174L.131A Altcode:
Revised spectral types have been determined for Whiteoak's cluster
members of types A0 and earlier. The resulting H-R diagram shows a
rather narrow main sequence and a previously known silicon star, HD
92664; the spectrum of the latter shows well-marked absorption lines
over the excitation range from C II x4267 to Sr ii X4077. The most
remarkable feature of the cluster is the spectrum of its brightest star,
0 Car: lines of N rn are abnormally strong, while C iii is abnormally
weak; these characteristics suggest membership in a peculiar spectral
category described by Walborn.

---------------------------------------------------------
Title: Editorial.
Authors: Abt, Helmut A.
1972ApJ...172..527A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Radial velocities of 65 early-type stars.
Authors: Abt, H. A.; Levy, S. G.; Gandet, T. L.
1972AJ.....77..138A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectroscopic Binaries in the Open Cluster NGC 2516.
Authors: Abt, Helmut A.; Levy, Saul G.
1972ApJ...172..355A Altcode: 1972ApJ...171..355A
A limited study of the radial velocities of the 16 brightest early-type
stars in NGC 2516 yields approximate periods for six binaries. Tidal
interaction in that number of binaries is insufficient to explain
the low mean rotational velocity obtained for the cluster stars, but
allowance for the additional Ap stars, in which decreased rotation by
magnetic braking may have occurred, does account for the low rotational
velocities.

---------------------------------------------------------
Title: IC 4665, a Cluster of Binaries
Authors: Abt, Helmut A.; Bolton, C. T.; Levy, Saul G.
1972ApJ...171..259A Altcode:
Radial velocities of the 19 brightest stars in this open cluster show
that all but one are spectroscopic binaries. Orbital elements are
derived for 13 systems, and one additional one is double-lined. It
is suggested that the low mean rotational velocity for stars in
this cluster is due to its reduction by tidal interactions in binary
systems, although in most of the systems with periods greater than 6
days the rotational motion has not yet attained synchronization with
the orbital motion.

---------------------------------------------------------
Title: The spectral classification of the F stars of intermediate
luminosity.
Authors: Morgan, W. W.; Abt, H. A.
1972AJ.....77...35M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Bibliography of stellar radial velocities
Authors: Abt, Helmut A.; Biggs, Eleanor S.
1972bsrv.book.....A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Radial Velocity of 60 Serpentis
Authors: Abt, Helmut A.; Levy, Saul G.
1971PASP...83..687A Altcode:
Coude' measures of this K0 III star do not confirm the published
evidence that it is a single-lined spectroscopic binary with a period
of three days. Key words: spectroscopic binary - radial velocity

---------------------------------------------------------
Title: Rotational Velocities in Short-Period A-Type Binaries
Authors: Abt, Helmut A.; Hudson, Katherine I.
1971ApJ...163..333A Altcode:
Although a low rotational velocity is a necessary condition for a star
to have a metallicAine (Am) spectrum, is it a sufficient condition? This
study of rotational velocities of stars in binaries with periods less
than 5 days shows that (1) most, but not all, late A-type stars rotate
synchronously, and the remainder rotate too rapidly; (2) there is an
overlap in equatorial rotational velocities of normal and Am stars which
indicates that a given rotational velocity is sometimes insufficient
to determine whether a star should have a normal or an abnormal
spectrum. The additional distinguishing parameter does not appear to
be the star's age, the angle at which the star is viewed, or previous
history of mass exchange, although it could be a combination of these.

---------------------------------------------------------
Title: Rotational Velocities in the Orion Nebula Cluster
Authors: Abt, Helmut A.; Muncaster, George W.; Thompson, Laird A.
1970AJ.....75.1095A Altcode:
Rotational velocities for 26 stars in the Orion Nebula cluster show: (i)
the unusually low mean rotational velocity for the early B stars that
is a characteristic of the Orion association, (11) higher rotational
velocities for the middle and late B stars than in the association, and
(ill) very high rotational velocities among A stars relative to similar
field stars. it is not known whether the high rotational velocities
are a peculiarity of the Orion stars or a characteristic of all B-
and A-type stars that have recently arrived on the main sequence.

---------------------------------------------------------
Title: Rotational velocities in the Ursa Major group.
Authors: Geary, J. C.; Abt, H. A.
1970AJ.....75..718G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Mean Velocities of Binaries in the Perseus Arm
Authors: Abt, Helmut A.; Jennings, Mark; Lee, Paul D.; Villere,
Karen R.
1970ApJ...161..477A Altcode:
Orbital elements are given for eleven faint binaries in the Perseus
arm near 100 . The mean gamma velocity is marginally larger (4.6 +
2.2 km sec-1) than for twenty-six constant-velocity stars in the same
region. It is concluded that not only is the mean radial velocity of
single stars similar to that of neutral hydrogen gas in their vicinity,
but the velocities of spectroscopic binaries are also roughly similar if
those velocities are derived from measures of absorption4ine wings. It
is still possible that measurements of line cores for closely spaced
binaries may lead to velocities that are systematically too large.

---------------------------------------------------------
Title: The Metal-Deficient Binary HR 8899
Authors: Abt, Helmut A.; Lee, Paul D.; Perry, Charles L.
1970PASP...82..716A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectra of the Cepheid HR 8157
Authors: Abt, Helmut A.; Levy, Saul G.
1970PASP...82..334A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Frequency of Spectroscopic Binaries in NGC 6475
Authors: Abt, Helmut A.; Levy, Saul G.; Baylor, Lynn A.; Hayward,
Robert R.; Jewsbury, Clifford P.; Snell, Charles M.
1970ApJ...159..919A Altcode:
This cluster is known to have unusually low projected rotational
velocities among its B stars, in contrast to the Pleiades, a cluster
of the same age, which has unusually high rotational velocities. In
NGC 6475 eight of the nineteen brightest main-sequence stars are found
to be short-period spectroscopic binaries; orbital elements are given
for these. This frequency is high relative to that for field stars and
especially high relative to that for the Pleiades, among whosc B stars
no short-period binaries were found. It is concluded that low rotational
velocities are probably caused primarily by tidal interactions in
binary systems and that open clusters differ significantly in their
binary frequencies.

---------------------------------------------------------
Title: Photometry and radial velocities of W Serpentis.
Authors: Abt, H. A.; Golson, J. C.
1970IBSH...16...35A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Catalog of Indidual Radial Velocities, 0h-12h, Measured by
Astronomers of the Mount Wilson Observatory
Authors: Abt, Helmut A.
1970ApJS...19..387A Altcode:
For those stars for which ouly undated mean velocities have been
published by Mount Wilson astronomers, the individual velocities,
times of observation, and other pertinent data are given. Included
in this catalog are approximately 11000 velocities of 3500 stars,
observed and measured between 1909 and 1951.

---------------------------------------------------------
Title: Stellar Rotation in Open Clusters (review Paper)
Authors: Abt, H. A.
1970stro.coll..193A Altcode: 1970IAUCo...4..193A
No abstract at ADS

---------------------------------------------------------
Title: Rotational velocities in NGC 2516.
Authors: Abt, H. A.; Clements, A. E.; Doose, L. R.; Harris, D. H.
1969AJ.....74.1153A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectral Classification of A-Type Spectroscopic Binaries
Authors: Abt, Helmut A.; Bidelman, William P.
1969ApJ...158.1091A Altcode:
MR spectral types have been determined or are quoted for ninety-eight of
101 known spectroscopic binaries with primaries in the range A2-F3. Half
of these stars are metallic-line (Am) stars; most of the remainder are
outside the domain (approximately A4-F1 IV, V) of the Am stars. The
remaining nine normal stars in the domain have periods of either less
than 2.5 or more than about 100 days. It is con- cluded that all stars
in the range A4-F1, IV, V that are primaries of binaries with periods
of approximate- ly 2.3-100 days have metallic-line spectra

---------------------------------------------------------
Title: The Spectroscopic Binary HD 206874
Authors: Fisk, Robert S.; Abt, Helmut A.
1969PASP...81..692F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The frequency of spectroscopic binaries among high-velocity
dwarf stars.
Authors: Abt, H. A.; Levy, S. G.
1969AJ.....74..908A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The H-R diagram of NGC 2516.
Authors: Abt, H. A.; Morgan, W. W.
1969AJ.....74..813A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Accuracies of Radial-Velocity Measurements
Authors: Abt, Helmut A.; Smith, Gregory H.
1969PASP...81..332A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: 12 Cam., Calcium emission in giant binaries.
Authors: Abt, Helmut A.; Dukes, Robert J.; Weaver, W. Bruce
1969ApJ...157..717A Altcode:
Bidelman predicted that 12 Cam is a spectroscopic binary because it
shows the strong calcium emis- sion that is evidently characteristic
of giant binaries of short period. This prediction is confirmed, and
orbital elements are derived. The strong calcium emission (1) does not
originate near the secondary star, (2) varies slowly with time but
not in phase in the eccentric orbit, and (3) does not significantly
interfere with the Wilson-Bappu correlation of chromospheric emission
width with luminosity

---------------------------------------------------------
Title: The Spectroscopic Binary 66 Andromedae
Authors: Abt, Helmut A.; Levy, Saul G.
1969PASP...81..280A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotational Velocities in the Open Cluster NGC 6475 (M7)
Authors: Abt, Helmut A.; Jewsbury, Clifford P.
1969ApJ...156..983A Altcode:
The cluster NGC 6475 (M7) is found to have the following distinctive
characteristics: (1) a very low mean rotational velocity among its
B6-B9.5 stars; (2) several Ap stars; (3) an unusually high mean
rotational velocity among its A1-A3 stars; (4) a possible separation
between sharp- and broad-lined stars in its H-R diagra

---------------------------------------------------------
Title: Summary
Authors: Abt, Helmut A.
1969BAAS....1..164A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Introductory Remarks
Authors: Abt, Helmut A.
1969BAAS....1..141A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Radial velocity of the stars
Authors: Abt, H. A.
1969stas.conf...99A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Research Possibilities with Moderate Dispersion
Authors: Abt, Helmut A.
1968PASP...80..637A Altcode:
RESEARCH POSSIBILITIES WITH MODERATE DISPERSION HELMUT A. ABT Kitt
Peak National Observatoryf Tucson, Arizona Received October 10, 1968

---------------------------------------------------------
Title: The Mass and Other Characteristics of the Magnetic Star
HD 98088
Authors: Abt, Helmut A.; Conti, Peter S.; Deutsch, Armin J.;
Wallerstein, George
1968ApJ...153..177A Altcode:
This system is a double-lined spectroscopic binary involving an Ap
primary and having an orbital period of 5d905, which is also the period
of the magnetic variation and rotation. The system is not an eclipsing
one, but it is sufficiently inclined that the minimum mass of the Ap
star is 9J~ sin3 I = 1.70 9Qo. The Ap star has hydrogen lines as in an
A3 V star. From line ratios, it is concluded that the secondary is 1.2
mag fainter, or an A8 V star. Assuming a normal mass for the latter,
we find an inclination of 67° and a primary mass of 2.2 9J1o. Such a
mass is identical with that of a normal star at that location on the
main sequence. This strongly suggests that the Ap star is on the main
sequence for the first time. The spectrum variation is described and
shows two maxima for some elements, with a phasing that is consist-
ent with the characteristics of the eccentric orbit. The problem of
synchronism between rotation and orbital motion for an eccentric orbit
is discussed

---------------------------------------------------------
Title: Award of the Bruce Gold Medal to Professor Willem J. Luyten
Authors: Abt, Helmut A.
1968PASP...80..247A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: An Atlas of low-dispersion grating stellar spectra
Authors: Abt, Helmut A.; Meinel, A. B.; Morgan W. W.; Tapscott I. W.
1968aald.book.....A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Frequency of Spectroscopic Binaries among High-Velocity Stars.
Authors: Abt, Helmut A.; Levy, Saul G.
1968AJS....73R.161A Altcode:
The frequency of spectroscopic binaries among high- velocity F- and
G-type dwarfs is considered on the basis of 622 moderate-dispersion
spectra of 69 stars. Following Str6mgren, we have divided these stars
into five groups of progressive line weakening; these groups also show
progressively increasing space motion relative to the local standard
of rest. A literature search among low-velocity F8-G2 dwarfs shows a
frequency of short-period (&lt;100 days) binaries of 15% and, among
these, a median period of 10 days. In comparison, among the high-
velocity stars no binary periods less than 40 days were found; the
frequency of short-period binaries for the two groups of most nearly
normal stars is roughly 7% and for the three groups of most abnormal
stars is 0%. We conclude that spectroscopic binaries are rare among
high-velocity stars and decrease in frequency with both increasing
space motion and decreasing orbital period. The latter result seems
consistent with results by Partridge, who found the same binary
frequency for visual (long-period) binaries of high and low velocity.

---------------------------------------------------------
Title: Rotational Velocities of AP Stars.
Authors: Abt, Helmut A.; Chaffee, Frederic H.; Suffolk, Graham
1967AJ.....72R.783A Altcode:
Rotational velocities have been obtained from coude spectra for the
63 brightest Ap stars; these velocities average 22% of those of the
normal stars, using hyrodgen-line spectral types. it is shown that
the idea that Ap stars are normal stars seen pole on is incompatible
with the frequency distributions of rotational velocities. Assuming,
therefore, random orientations of axes for both normal main-sequence
and Ap stars, we find that there are no slowly rotating (V&lt; 100
km/sec) normal stars in the range B7-AO and no rapidly rotating (V&gt;
150 km/sec) Ap stars. Again assuming random orientations of axes,
we find no serious inconsistencies between rotational periods and the
periods of 16 spectrum variables, magnetic variables, and short-period
spectroscopic binaries. Copyright 1967 by the ~

---------------------------------------------------------
Title: Award of the Bruce Gold Medal to Professor Ludwig Biermann
Authors: Abt, Helmut A.
1967PASP...79..197A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotational Velocities of Stars in IC 4665
Authors: Abt, Helmut A.; Chaffee, Frederic H.
1967ApJ...148..459A Altcode:
The B4-B7 V stars in the open cluster IC 4665 have an extremely small
mean rotational velocity compared with the Pleiades or field stars,
while the mean rotational velocities of the B8-A3 V stars are the
same as for the Pleiades. It is suggested that tidal interactions in
binary systems, which are frequent in IC 4665 but not in the Pleiades,
cause the low mean rotational velocities in the former cluster.

---------------------------------------------------------
Title: Two Radial Velocity Catalogues
Authors: Abt, H. A.
1967IAUS...30...55A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Duplicity and Rotation Among Am, Ap, and A Stars
Authors: Abt, Helmut A.
1967mrs..conf..173A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Recent Work on Radial Velocities in Nearby Clusters
Authors: Abt, H. A.
1967IAUS...30..159A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotational Velocities in the Galactic Cluster IC 4465
Authors: Abt, H. A.; Chaffee, F. H.
1966PASP...78Q.438A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Atmospheric Characteristics of a Cepheid of Unusually Large
Light Amplitude: TV Camelopardalis
Authors: Abt, Helmut A.; Osmer, Patrick S.; Kraft, Robert P.
1966ApJ...145..479A Altcode:
The nearby Cepheids and those in the Small Magellanic Cloud have
very different light-amplitude- period relations. TV Cam is a distant
galactic short-period Cepheid of large light amplitude that seems to
be like those in the SMC. Since its spectrum has weak lines, it was
previously suggested that its composition may be low in metals and the
composition, in some unspecified way, causes unusual light and color
amplitudes. The present analysis shows that the metal abundance is
normal to within a factor of about 2, and that the cause of the weak
lines is a low turbulent velocity.

---------------------------------------------------------
Title: Mass of a magnetic star.
Authors: Abt, H. A.; Conti, P. S.; Deutsch, A. J.; Wallerstein, G.
1966AJ.....71Q.843A Altcode: 1966AJ.....71..843A
No abstract at ADS

---------------------------------------------------------
Title: Atmospheric Characteristics of a Cepheid of Unusually Large
Light Amplitude.
Authors: Abt, Helmut A.; Osmer, Patrick S.; Kraft, Robert P.
1966AJ.....71Q.377A Altcode:
The nearby Cepheids and those in the Small Magellanic Cloud have very
different light amplitud&amp;period relations. TV Camelopardalis is
a distant galactic short-period Cepheid of large light amplitude that
seems to be like those in the SMC. Since its spectrum has weak lines,
it was previously suggested that its composition may be low in metals
and that the composition, in some unspecified way, causes unusual light
and color amplitudes. The present analysis shows that the metallic
abundance is normal to within a factor of about 2, and that the cause
of the weak lines is a low turbulent velocity.

---------------------------------------------------------
Title: On the separation by Balmer-line photometry of high and low
luminosity stars having H-alpha in emission.
Authors: Abt, H. A.; Golson, J. C.
1966ApJ...143..306A Altcode:
Among the early-type stars found in objective-prism surveys to have
lla in emission, the majority are dwarf Be stars but about 10 per cent
are normal Ia supergiants, whose absolute magnitudes are about = -
7. This paper describes a search for an efficient method of separating
these two groups. It is found that, with photoelectric measures using
narrow-band filters centered on Ha and H , it is possible to separate
from a mixed sample about two-thirds of the Be stars and two-thirds
of the supergiants.

---------------------------------------------------------
Title: The metallic-line stars
Authors: Abt, Helmut A.
1966VA......8...75A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Frequency of Spectroscopic Binaries in the Pleiades.
Authors: Abt, Helmut A.; Barnes, Ronnie C.; Biggs, Eleanor S.; Osmer,
Patrick S.
1965ApJ...142.1604A Altcode:
From 585 radial-velocity measures of the forty-seven brightest Pleiades
stars and from measures published previously, orbital elements are
derived for five newly discovered spectroscopic binaries. Among
the thirteen stars no short-period (P &lt; 100 days) binaries were
found, and it is suggested that the unusually rapid rotational
velocities in these stars are due to an absence of tidal interaction
in close binaries. Among the twenty B9.S V-A3 V stars the frequency
of short-period binaries seems normal and the rotational velocities
are normal compared to similar field stars. Among the fourteen A4 V-A9
V stars no good examples of metallic4ine (Am) stars are known and no
short-period binaries have been found. It is suggested that, since Am
stars are generally members of close binary systems and the Pleiades
has none in that spectral range, the cluster will never have Am stars.

---------------------------------------------------------
Title: Spectrographic Measures of the Eclipsing System BH Virginis
Authors: Abt, Helmut A.
1965PASP...77..367A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Frequency of Binaries among Normal A-Type Stars.
Authors: Abt, Helmut A.
1965ApJS...11..429A Altcode:
In a previous paper it was learned all metallic-line (Am) stars are
members of spectroscopic binaries and that the period distribution of
these is normal, e.g., the most frequent period is about 4 days. The
present is a study of the frequency of spectroscopic binaries among
the normal stars that occupy the same region (A4-F2 IV, V) of the H-R
diagram as do the Am stars. In a sample of fifty-five stars, seventeen
were found to have variable velocities and orbital elements are given
for fifteen of these. Surprisingly, all seventeen binaries have periods
greater than 100 days; there seem to be no short-period binaries among
the normal A-t e stars. The equatorial rotational velocities of the
normal A-type stars are invariably large (5() 250 km sec) while those
of the Am stars are small (() 100 km/sec). It is suggested that tidal
interaction, particularly during the slower evolutionary contracting
phase, causes members of relatively close binary systems (periods 100
days) to have small rotational velocities while single stars or members
of widely spaced binaries have large rotational velocities. It is then
suggested that the primary problem is to explain why rapidly rotating
stars have spectra that are characteristic of normal compositions
while slowly rotating stars have abnormal spectra.

---------------------------------------------------------
Title: The Frequency of Spectroscopic Binaries in the Pleiades
Authors: Abt, H. A.
1965PASP...77..121A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Filter Transmission Effects on Photoelectric Measures of
Rotationally Broadened Hβ Line Strenghts.
Authors: Abt, Helmut A.; Osmer, Patrick S.
1965ApJ...141..949A Altcode:
It has been suggested that the observed dependence on line width
of H line strengths measured photoelectrically through narrow
interference filters is due simply to a redistribution of the light
within the peaked-filter pass band, rather than to actual differences in
equivalent widths of H lines between broad- and sharp-lined stars. This
possibility has been investigated with computed rotationally broadened
H profiles and filter transmission-curves. It is concluded that this
filter effect is not significant for of about 30-A half-width, such as
those now being used; the filter effect, however, is present for the
15-A filters originally used, but it is not large enough to explain
entirely the observed dependence of line strengths on line widths.

---------------------------------------------------------
Title: The Frequency of Spectroscopic Binaries in the Plejades.
Authors: Abt, Helmut A.; Barnes, Ronnie C.; Biggs, Eleanor S.; Osmer,
Patrick S.
1965AJ.....70R.317A Altcode:
As a cluster the Pleiades has several distinctive characteristics. One
is the unusually large rotational velocities among its B stars,
whereas its early A stars have rotational velocities that are normal
for their types. A second is the absence of metallic-line stars; this
lack has been attributed by others to the cluster's small age. These
characteristics seem to be correlated with the unusual binary
frequencies reported here. At Kitt Peak nearly 600 spectra of 63 and
128 A/mm dispersion have been obtained of the 46 brightest stars in the
Pleiades. The resulting radial velocities indicate that none of the 13
B~B9 stars show evidence of being members of closely spaced binaries
with periods less than 100 days, whereas Petrie has shown that among
field B stars approximately half are found to be in such systems. It is
suggested that in the absence of close binaries tidal interaction has
not been effective in slowing the rotation. In contrast, the rotational
velocities of the 14 early A stars in the Pleiades are normal, as is
the frequency of closely spaced binaries. Among the Pleiades A4-A9 stars
the velocity ranges are small, which is characteristic of normal stars
of such types in contrast to the metallic-line stars among which large
velocity ranges are frequent. This absence of close binaries will not
change with time and indicates that not only now, but at no time in
the future, will the Pleiades have metallic-line stars.

---------------------------------------------------------
Title: Erratum: Colors and Variability of Magnetic Stars.
Authors: Abt, Helmut A.
1964ApJ...140.1641A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Galactic Cluster IC 4665.
Authors: Abt, Helmut A.; Snowden, Michael S.
1964ApJ...139.1139A Altcode:
his cluster contains about thirty-five visual members with spectral
types from B4 V to F0 V. Star ts in the cluster region and in a
nearby control region indicate that there are no fainter members
[hat the late-type giant stars in the cluster region are probably not
members. Radial velocities by uthors and by Trumpler show an unusually
high fraction of spectroscopic binaries. The rotational ities by Deutsch
for cluster members are low for their spectral types. These three
properties (short . sequence, high binary frequency, and low rotational
velocities) are the reverse of the characteristics e Pleiades.

---------------------------------------------------------
Title: Stellar Radial Velocities in the Perseus Arm.
Authors: Abt, Helmut A.; Bautz, Laura P.
1963ApJ...138.1002A Altcode:
Published stellar radial velocities for early-type stars in the Persens
Arm, froni the vicinity of it and Persei q10 = t3O , yield a mean that
is algebraically larger by 7.4 km/sec than the 21-cm velocity of the
neutral hydrogen in the same region. To investigate this discrepancy,
velocities have been obtained for forty-five stars in a more-distant
section of the Perseus Arm at l - 100 . Twenty- four of these stars
seem to have constant radial velocities, and their mean velocity
agrees with the 21-cm velocity for the same region. The mean velocity
from three observations of each of the twenty- one variable-velocity
stars exceeds that from the constant-velocity stars by 15.6 + 3.7
(p.e.) km/sec. An explanation for this difference, involving the
effect of gaseous streams on the observed stellar radial velocities,
is proposed. If the velocities of the constant- and variable-velocity
stars are averaged together, the mean exceeds the 21-cm velocity by
8.7 km/sec, which is similar to the result for the remainder of the
Perseus Arm. It is therefore suggested that the mean velocities of
many spectroscopic binaries involving early-type supergiants or giants
may be systematically too large and would therefore be mireliable for
galactic-structure studies.

---------------------------------------------------------
Title: Stellar Radial Velocities in the Perseus Arm.
Authors: Abt, Helmut A.
1963AJ.....68R.271A Altcode:
Published stellar radial velocities it tl e viciiiit of h and Persei (1"
1300), yield a meai that is algebraically larger by 7.4 l m$sec than the
21-cm velocities of the neutral hydrogen in the center of that arm. To
investigate this discrepancy, velocities have been obtained for 45 stars
in a more distant section of the Perseus Arm at lIT - 1000. Twenty-
four of these stars seem to have constant radial velocities and their
mean velocity agrees well with the 21-cm velocity for the center of the
arm. However, the mean velocity from three observations of each of the
21 variable-velocity stars exceeds that from the constant-velocity stars
by 15.6+3.7 (p.e.) km/sec. An explanation for this difference, involving
the effect of gaseous streams on the observed stellar radial velocities,
is proposed. If the velocities of the constant and variable-velocity
stars are averaged together, the mean exceeds the 21-cm velocity for
the center of the arm by 8.7 km/sec, which is similar to the result for
the h and x Persei region. It is therefore suggested that the velocities
of many OB-type spectroscopic binaries may be systematically too large
and may be unreliable for galactic-structure studies.

---------------------------------------------------------
Title: The Multiple System 1 Geminorum.
Authors: Abt, Helmut A.; Kallarakal, Varkey V.
1963ApJ...138..140A Altcode:
This visual double-star system has a small separation (0'.'2) and a
composite spectrum. The brighter component is of class K0 iii, while
the fainter is G8 iii, iV and is a 9.66-day, single-lined spectroscopic
binary. Orbital elements are derived both for this spectroscopic binary
and for the visual pair (11.00 years). The observed radial velocities
are consistent with these orbital elements.

---------------------------------------------------------
Title: A Discussion of Spectral Classification.
Authors: Abt, Helmut A.
1963ApJS....8...99A Altcode:
A conference was held to consider aspects of current interest
in the field of spectral classification. The motivation for the
discussion was current work on a new atlas of stellar spectra, based
on grating-dispersion spectrograms that include the ultraviolet
spectral region. The work on this atlas has raised fundamental,
as well as detailed, questions about spectral classification. Under
discussion during the first session of the conference were the most
sultable spectral resolutions and dispersions for various types of
stars; the usefulness of the ultraviolet, red, and infrared regions
for spectral classification; the construction and contents of the new
atlas; useful new luminosity and spectral-type discriminants; and the
philosophy of spectral classification. The second session was devoted
to the characteristics, advantages, limitations, and future prospects of
photoelectric photometry with filters of narrow- and intermediate-width
spectral transmissions and comparisons of this technique with visual
spectral classification and spectrographicphotoelectric techniques. In
the third session many projects involving spectral classification
were stated and discussed; these projects included the compilation
and dispersal of data, the need for additional standards, and numerous
classes of stars that have not been adequately subclassified.

---------------------------------------------------------
Title: Intrinsic Variable Stars
Authors: Abt, Helmut A.
1963paa..book..119A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Interstellar Absorption in the North Equatorial Polar Region.
Authors: Abt, Helmut A.; Golson, John C.
1962ApJ...136..363A Altcode:
The interstellar reddening to moderately distant stars in the region
north of declination +80 has been measured to obtain an independent
determination of the reddening of NGC 188 U, B, V photometry and
spectral types yielded an average color excess, EB-v, of 0 09 mag
for 27 stars at a mean distance of 580 parsecs. This is in excellent
agreement with previous results on the north polar region by Keenan
and Babcock Mter an uncertain extrapolation to outside the galaxy,
the reddening becomes 0 14 mag., which is somewhat less than the 0 19
mag predicted from galaxy counts However, the measured reddening shows
a large amount of scatter, even for stars that are close together The
resulting uncertain determination of the reddening of NGC 188 does
not contradict Sandage's value.

---------------------------------------------------------
Title: Stellar Rotation in Galactic Clusters.
Authors: Abt, Helmut A.; Hunter, James H., Jr.
1962ApJ...136..381A Altcode:
Rotational velocities are derived for the brighter stars in the
I Lacerta and I Orion associations and the a Persei and Pleiades
clusters. These, as well as published data on four other clusters,
show that each group has a distinctive dependence of mean rotational
velocity on luminosity. For field stars the irregularities in the
dependence of mean rotational velocity on luminosity and its dips at B2
and A2 are seen as being due to large admixtures of stars from certain
groups which have distinctive rotational velocities, such as the Ursa
Major stream and the Cassiopeia-Taurus stars There is evidence in four
groups for a strong inverse correlation between binary frequency and
mean rotational velocity.

---------------------------------------------------------
Title: Colors and Variability of Magnetic Stars.
Authors: Abt, Helmut A.; Golson, John C.
1962ApJ...136...35A Altcode:
An average of 5.4 U, B, V observations has been obtained at random times
during a 2-year interval for 70 Ap magnetic stars. The mean colors agree
with those of normal dwarfs and giants but for those that are about 0 2
spectral classes earlier (among the B8p-A2p stars). Mter observational
inaccuracies are allowed for, it is found that all magnetic stars are
slightly variable in visual light and in B - V and U - B colors. The
mean dispersions from the mean are 0.039, 0.017, and 0023 mag. in V,
B - V, and U - B, respectively. There is no correlation between the
amounts of variability in magnitude and in color, although there
is a correlation between the dispersions in the two colors. There
are no correlations between the photometric dispersions and the (1)
magnetic-field strengths, (2) predominant sign or regularity of the
magnetic-field variations, (3) spectral peculiarities, (4) mean colors,
or (S) line widths.

---------------------------------------------------------
Title: Rotational Velocities in Galactic Clusters.
Authors: Abt, Helmut A.
1962AJ.....67Q.267A Altcode:
Axial rotational velocities of stars in four galactic clusters and
associations have been determined from McDonald Observatory coude'
spectrograms of 18 A7mm. Those measured were 23 B6-AI Pleiades stars,
21 B3-A1 a Persei cluster stars, 39 O9.5-B5 I Orion stars, and 26 O9-B3
I Lacerta stars. The relation between mean rotational velocity and
spectral type differs from group to group by statistically significant
amounts and from that for field stars. For instance, in agreement with
Struve and Smith, we find that the B stars in the Pleiades rotate about
50% faster than field B stars but the A-type Pleiades stars rotate
about 50% slower than field stars. The O9.5-B3 stars in I Orion rotate
20% less rapidly than similar field stars (in approximate agreement
with McN amara 5 results) but the B5 stars rotate more rapidly than
field B5 stars. It appears that although the dependence of angular
momentum on mass (or spectral type) differs between groups, the total
angular momentum per unit mass may be the same for all groups. Also,
the apparent dips at B2 and A2 in the rotational velocity dependence
on spectral type among field stars may be explained in terms of large
admixtures in the sample of stars from certain groups with unusual
rotational velocities. There is preliminary evidence of a strong inverse
correlation between mean rotational velocity and binary frequency.

---------------------------------------------------------
Title: Non-Periodic Spectroscopic Changes in Beta Lyrae.
Authors: Abt, Helmut A.
1962ApJ...135..424A Altcode:
The spectroscopic observations taken during the international Lyrae
campaign of 1959 are discussed. These show no evidence for the effect
of a third body on the velocity of the primary star or changes in the
shape of its orbit. Accompanying the differences in light of up to 005
mag. between two successive eclipses are differences in the strengths
and velocities of the helium lines formed in the expanding shell around
the primary star. In general, the shell lines are stronger during cycles
when the shell absorbs more continuous light near primary minimum,
although instantaneously this correlation does not seem to be valid.

---------------------------------------------------------
Title: The Visual Multiple System Containing Beta Lyrae.
Authors: Abt, Helmut A.; Jeffers, Hamilton M.; Gibson, James; Sandage,
Allan R.
1962ApJ...135..429A Altcode:
Beta Lyrae is a member of the visual multiple system ADS 1174S and has
five companions which range in magnitude from 7.2 to 15 2. Previous
and new astrometric measures of the three brightest companions (B,
E, and F) yield motions that are probably consistent with physical
association with Lyrae. Spectroscopic measures of these three
companions show that one of them (E) is probably not a member. Another
companion (B) is a spectroscopic binary, for which orbital elements are
derived. Photoelectric measures show that the two faintest companions (C
and D) are not physically associated with p Lyrae From the association
of companions B and F with p Lyrae we derive a reddening, EB-v,
of 0065 mag., a distance modulus of 7.1 mag., and a luminosity, Mv,
for p Lyrae of -39. This leads to a secondary mass for p Lyrae that
is greater than that of the primary.

---------------------------------------------------------
Title: Observations of the Variable Star Tau Cygni.
Authors: Abt, Helmut A.
1961ApJ...134.1013A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Radial Velocities of Three Metallic-Line Stars.
Authors: Abt, Helmut A.
1961ApJ...133..910A Altcode:
Orbital elements are derived for the double-lined spectroscopic binary
ND 12881 and the single-lined mary 51 Sagittarii; II Virginis is found
to be constant in velocity.

---------------------------------------------------------
Title: The Frequency of Binaries among A-Type Stars.
Authors: Abt, Helmut
1961AJ.....66Q.277A Altcode:
Previously it was reported that an investigation of a random sample
of 25 metallic-line (Am) stars showed that 88% gave evidence of
binary motion. After a reasonable allowance for undetected binaries we
concluded that all Am stars are members of spectroscopic binaries. This
is a preliminary report on the binary frequency among the normal
field stars in the same region of the color-magnitude diagram as
the Am stars. A sample of 57 such stars (A4-F2 V, IV) was observed
repeatedly with the McDonald 82-inch coude' and Mount Wilson 60-inch
Cassegrain spectrographs. Complete measurements on 24 stars yielded nine
spectroscopic binaries, indicating a frequency of at least 35%. However,
surprisingly all nine binaries have periods greater than too days; also
none of the remaining 33 incompletely measured stars have large velocity
variations. Therefore it appears that all stars in this region of the
color- magnitude diagram that are members of binaries with periods less
than too days have abnormal spectra while the single stars have normal
spectra. The way in which duplicity affects the spectral appearance is
probably through its effect on the rotational velocity. There are no
rapidly rotating Am stars or slowly rotating normal ones. Perhaps rapid
rotation inhibits the magnetic fields which, in turn, may (according to
Uns&amp;ld and Bo~hmVitense) account for their peculiar spectra. % gave
evidence of binary motion. After a reasonable allowance for undetected
binaries we concluded that all Am stars are members of spectroscopic
binaries. This is a preliminary report on the binary frequency among the
normal field stars in the same region of the color-magnitude diagram
as the Am stars. A sample of 57 such stars (A4-F2 V, IV) was observed
repeatedly with the McDonald 82-inch coude' and Mount Wilson 60-inch
Cassegrain spectrographs. Complete measurements on 24 stars yielded nine
spectroscopic binaries, indicating a frequency of at least 35%. However,
surprisingly all nine binaries have periods greater than too days; also
none of the remaining 33 incompletely measured stars have large velocity
variations. Therefore it appears that all stars in this region of the
color- magnitude diagram that are members of binaries with periods less
than too days have abnormal spectra while the single stars have normal
spectra. The way in which duplicity affects the spectral appearance is
probably through its effect on the rotational velocity. There are no
rapidly rotating Am stars or slowly rotating normal ones. Perhaps rapid
rotation inhibits the magnetic fields which, in turn, may (according to
Uns&amp;ld and Bo~hmVitense) account for their peculiar spectra. % gave
evidence of binary motion. After a reasonable allowance for undetected
binaries we concluded that all Am stars are members of spectroscopic
binaries. This is a preliminary report on the binary frequency among the
normal field stars in the same region of the color-magnitude diagram
as the Am stars. A sample of 57 such stars (A4-F2 V, IV) was observed
repeatedly with the McDonald 82-inch coude' and Mount Wilson 60-inch
Cassegrain spectrographs. Complete measurements on 24 stars yielded nine
spectroscopic binaries, indicating a frequency of at least 35%. However,
surprisingly all nine binaries have periods greater than too days; also
none of the remaining 33 incompletely measured stars have large velocity
variations. Therefore it appears that all stars in this region of the
color- magnitude diagram that are members of binaries with periods less
than too days have abnormal spectra while the single stars have normal
spectra. The way in which duplicity affects the spectral appearance is
probably through its effect on the rotational velocity. There are no
rapidly rotating Am stars or slowly rotating normal ones. Perhaps rapid
rotation inhibits the magnetic fields which, in turn, may (according
to Uns&amp;ld and Bo~hmVitense) account for their peculiar spectra.

---------------------------------------------------------
Title: The Frequency of Binaries among Metalmc-Line Stars.
Authors: Abt, Helmut A.
1961ApJS....6...37A Altcode:
The question of what fraction of the metallic-line (Am) stars are
spectroscopic binaries is treated by an intensive study of a random
sample of 25 such stars. It is found that only 3 of these have constant
velocities. Of the remaining 22, orbital elements are now known for
18 and periods (only) for 2 more. Estimates of the fraction of the
binaries which would be undetectable because their velocity amplitudes
are too small easily account for the 3 onstant-velocity stars, and
it is concluded that 100 per cent of the Am stars are spectroscopic
binanes. There is nothing obviously unusual about the secondary stars
such as to suggest that they are causing the abnormal appearance
of the spectra of the Am stars. The composite nature of these stars
does not seem to account for their location about 0.7 mag. above the
main sequence in a color-absolute-magnitude diagram. There is a rough
correlation between the discrepancy in spectral-type classification from
various criteria and the ultraviolet deficiency shown by essentially all
Am stars. On the supposition that in close binaries the axes of rotation
and revolution should be approximately parallel, we can determine that
the low projected rotational velocities (about one-third normal) of Am
stars are not due to a selective aspect effect. However, in the close
binaries the rotational velocities have been modified to synchronize
with the orbital motion: in binaries with periods less than 1.8 days
the rotation is increased, and in ones with slightly larger periods
(1.8 .5 days) it is slowed down. Two stars (32 Vir and u Oph) have
mass functions or mass ratios which indicate that their primaries or
secondaries violate the mass-luminosity relation for stars near the main
sequence. Furthermore, these two stars have line strengths that vary
with phase, indicating gaseous streams, although both are far from being
close binaries. Orbital elements are given for eleven new binaries.

---------------------------------------------------------
Title: The Visual Multiple-star System Containing β Lyrae
Authors: Abt, Helmut A.
1960PASP...72..348A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Spectra of Two High-Lattitude Supergiants.
Authors: Abt, Helmut A.
1960ApJ...131...99A Altcode:
The high4atitude F-type Ia supergiants 89 Herculis and HD 161796 are
found to have under- abundances, relative to iron, of some of the
moderately heavy metals. All the measured elements which were formed
by the capture of slow neutrons are underabundant by factors of 2-16;
furthermore, the width of the iron peak is narrower. These abundances
do not seem to have an explanation in terms of an excessive second
ionization of these elements. These stars have electron pressures such
as to suggest luminosities at least as high as that of 4) Cassiopeiae
(M = - 8.8). Their distances above the galactic plane are 2.6 and 6.3
kpc. To arrive at these heights in their predicted lifetimes after an
origin in the plane would require extremely high vertical velocities
(550 and 1350 km/sec). It seems more likely that these stars originated
in interstellar clouds far above the plane and re ect the present
composition in these clouds.

---------------------------------------------------------
Title: The 1.3-DAY Variable BL Herculis.
Authors: Abt, A.; Hardie, Rober H.
1960ApJ...131..155A Altcode:
BL Herculis was investigated photometrically and spectroscopically
in anticipation that it might be a field star similar to the
globular-cluster variables of the same period This star is similar to
RR Lyrae in that it has (1) a hump on the light-curves during rising
light, primarily at shorter wave lengths; (2) a large loop in the U -
B, B - V plane; (3) hydrogen emission lines at mid-rising light; and
(4) a radialvelocity variation that is larger for the Balmer lines
than for the metallic lines. It is assumed that, as seems true in the
case of RR Lyrae, the explanation for the first three effects is the
presence of radiation from the hot region behind an outward-moving
shock wave. Wesselink's method, after correction of the light-curves
for this radiation, gives a mean Mpg = - 0.1. This is in agreement with
the luminosities of globular-cluster variables of similar periods,
particularly if they are corrected for a possible lower luminosity
for the RR Lyrae stars BL Herculis does not have a weak-lined spectrum.

---------------------------------------------------------
Title: Light and Color Measures of Magnetic Stars.
Authors: Abt, Helmut A.; Golson, John C.
1960AJ.....65R.481A Altcode:
A program is under way to obtain photoelectric photometry on the UB V
system of nearly all the known peculiar A-type stars, using the 16-
and 36-inch reflectors on Kitt Peak. The purpose of the project
is to locate these stars in a U-B, B-V diagram and to determine
which ones are variable in light and color. It has been found that
except for the silicon-rich stars, the peculiar A-type stars fall on
the main-sequence line in the U-B, B-V plane and show about as much
scatter as do normal A-type stars. The silicon-rich stars, however, show
considerable ultraviolet and blue excesses; these cannot be attributed
to interstellar reddening or intrinsic variability. Among 17 stars
measured at least three times, about 60% seem to be variable in light,
about 35% show a detectable variation in B-V color, and only about 10%
show a detectable variation in U-B color. %.

---------------------------------------------------------
Title: A New Radial-Velocity for the Cepheid SU Cassiopeiae.
Authors: Abt, Helmut A.
1959ApJ...130.1021A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Wesselink's Method and Shock Waves in RR Lyrae.
Authors: Abt, Helmut A.
1959ApJ...130..824A Altcode:
Wesselink's method for obtaining the luminosity of a pulsating
star from photometric and spectroscopic observations is found to be
unsuccessful if the total expansion is only of the order of magnitude
of the atmospheric scale height or less. In RR Lyrae, whose expansion
is relatively large, further difliculties are encountered which are
attributed to the presence during rising light of radiation from the
hot emitting layer behind an outward-moving shock front. The shock-wave
model successfully accounts for the observed ultraviolet excess, the
hydrogen emission lines, the double absorption lines, the difficulty
with Wesselink's method, and the hump at mid-rising light.

---------------------------------------------------------
Title: The Cepheid Binary FF Aquilae.
Authors: Abt, Helmut A.
1959ApJ...130..769A Altcode:
This 4.47-day cepheid shows a slow variation in mean velocity which is
interpreted as being due to binary motion. Orbital elements for this
1435-day binary are derived. The cause of the scarcity of binaries
(about 2 per cent) among cepheids is discussed.

---------------------------------------------------------
Title: The Visual Companion of RW Tauri
Authors: Abt, Helmut A.; van Biesbroeck, G.
1959PASP...71..345A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Photoelectric Photometry of an Outburst of SS Cygni.
Authors: Grant, Golden; Abt, Helmut A.
1959ApJ...129..323G Altcode:
U, B, V photometry was obtained during a 3-mag. outburst of SS
Cygni. The colors agree with those of old novae and other nova-like
variables by Walker except during the rapid rising branch of the
lightcurve. An attempt is made to correct the colors for the presence
of the dG5 companion. If we assume that the deviation of the variable
from the main-sequence curve in the color-color diagram is due to
interstellar and circumstellar absorption, then the colors of the
variable are constant throughout the outburst except for an ultraviolet
deficiency of 43 mag. during rising light.

---------------------------------------------------------
Title: Photoelectric Observations of the 1955-1956 Eclipse of Zeta
Aurigae.
Authors: Grant, Gordon; Abt, Helmut A.
1959ApJ...129..320G Altcode:
U, B, V observations are given for ingress of the 1955-1956 eclipse. The
colors and magnitudes of the component stars have been determined. These
show the secondary to be of spectral type B7 V, which leads to Mv =
-2.2 for the K4 II star.

---------------------------------------------------------
Title: A New 16-Inch Reflector at Yerkes Observatory
Authors: Abt, Helmut A.; Hiltner, W. A.
1958PASP...70..414A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Spectroscopic Binary in the Pleiades.
Authors: Abt, Helmut A.
1958ApJ...128..139A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Line Broadening in High-Luminosity Stars. II. Less Luminous
Supergiants.
Authors: Abt, Helmut A.
1958ApJ...127..658A Altcode:
Several types of line broadening are considered for Ib supergiants
Macroturbulence, in at least one likely form, gives profiles that are
indistinguishable from rotational profiles. A magnetic field of 3800
gauss produces no broadening of X 4508 Fe ii but causes an apparent
abundance increase of 38 per cent. Rotationally broadened profiles fit
the observed ones and lead to a mean projected rotational velocity of
17 km/sec If conservation of angular momentum occurs, the rotational
velocities are in accord with the evolution of Ib supergiants from
early B dwarfs, provided that supergiants do not rotate as rigid bodies
The rotational-velocity distributions of the recovered and present B
dwarfs agree in maximum, mean, and general form. On the other hand,
if conservation of angular momentum does not occur due to mass loss,
this mass would not be readily apparent. We are not able to choose
between these two pos -ibilities.

---------------------------------------------------------
Title: Line Broadening in High-Luminosity Stars. I. Bright Giants.
Authors: Abt, Helmut A.
1957ApJ...126..503A Altcode:
Line profiles have been obtained from high-dispersion spectra of a
random sample of ten A- and F-type bright giants. These profiles match
very well ones computed with the Doppler velocity from curves of growth
combined with various amounts of rotation. The mean projected rotational
velocity of 26 km/sec is in good agreement with that predicted from
B stars and the Sandage-Schwarzschild evolutionary tracks, provided
that the bright giants do not rotate as rigid bodies.

---------------------------------------------------------
Title: A Description of Certain Galactic Nebulosities. II.
Authors: Abt, Helmut A.; Morgan, W. W.; Strömgren, Bengt
1957ApJ...126..322A Altcode:
A description summary is given for the large nearby emission nebulosity
discovered by Gum in VelaPuppis; the plates were obtained with an
S4nch F/t Schmidt camera

---------------------------------------------------------
Title: The Variability of Supergiants.
Authors: Abt, Helmut A.
1957ApJ...126..138A Altcode:
Eight A- and F-type Ia supergiants, selected effectively at random,
were all found to be variable in radial valocity. The variability is
semiregular in the manner of the M-type semiregular stars. Periods
derived from these eight stars and from published observations of
similar stars show that they are functions of luminosity and spectral
type. Several pieces of evidence suggest that the variability is due
to pulsation. Values of the pulsation quantity, P(p/p0)1/2, where o
is the mean solar density, are approximately constant for both early-
and late-type semiregular supergiants and are equal within a factor of
2 to the value for the classical cepheids. A survey of variables in the
upper part of the H-R diagram suggests that probably all stars brighter
than M,, = +1 and to the right of the main sequence are variable. The
values of the pulsation quantity for all these classes of variables
differ from those for the classical cepheids by factors of only 2 or 3,
except possibly in the case of the M giants.

---------------------------------------------------------
Title: "Distortions" in the Light-Variation of the Spectroscopic
Binary HD 22124
Authors: Thomsen, Ivan L.; Abt, Helmut A.; Kron, Gerald E.
1955PASP...67..412T Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Spectroscopic Observations of the Cluster-Type Variable
VZ CANCRI.
Authors: Abt, Helmut A.
1955ApJ...122..390A Altcode:
The radial velocities obtained from ninety-two spectrograms of VZ
Cancri show variations with both periods (4ht7 and t7ht2 found by
Fitch from light-observations. The phase shift of mid-rising light
with the long-period variation is reflected by a similar phase
shift in the radial velocities. Mid-decreasing velocity occurs at
mid-rising light. Maximum velocity range occurs at the same phase of
the long-period variation as does maximum light-range. The range of 39.6
km/sec in the mean velocity-curve is consistent with expectations from
three other short-period variables. The spectrum is of luminosity class
III and varies between A7-A9 at light-maxima and F1-F2 at light-minima.

---------------------------------------------------------
Title: The Spectrum of Nova Sagittarii 1954.1.
Authors: Abt, Helmut A.
1955ApJ...122..199A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Studies of RV Tauri Stars. I. U Monocerotis
Authors: Abt, Helmut A.
1955ApJ...122...72A Altcode:
High-dispersion spectrograms of the low-velocity RV Tauri star U
Monocerotis have been obtained regularly for 62' months, or for more
than four light-minima. The results from these plates are compared with
a few photoelectric observations and an A.A V S 0. light-curve. The
spectrograms show that the radial-velocity-curve has a discontinuity
at each light-maximum Displacements of the atmosphere, computed from
the radial-velocity-curve, are as large as 55 X 106 km; they are large
during cycles of deep light-minima and small during cycles of shallow
minima Curves of growth have been constructed from line intensities
on 17 spectrograms, including some with double absorption lines. Large
apparent abundance changes during times of single lines are attributed
to a variable continuous opacity within the regions of line formation
Ionization temperatures computed with numerical values of the variable
continuous opacity are probably in agreement with other determinations
of the temperature. Within their probable errors, the rates of change
of ionization temperature and of electron pressure with displacement
are independent of cycle or direction of motion.

---------------------------------------------------------
Title: The Atmosphere of AN RV Tauri Variable
Authors: Abt, Helmut A.
1955stat.conf..158A Altcode: 1954stat.conf..158A
No abstract at ADS

---------------------------------------------------------
Title: V 367 Cygni : an Eclipsing Binary with a Shell Spectrum
Authors: Abt, Helmut A.
1954PASP...66..171A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Abstract: An Analysis of W Virginis.
Authors: Abt, Helmut A.
1954ApJ...119..469A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Luminosity of the Cepheid Y Ophiuchi
Authors: Abt, Helmut A.
1954PASP...66...65A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: An Analysis of W Virginis.
Authors: Abt, Helmut A.
1954ApJS....1...63A Altcode:
A study has been made of the population II cepheid, W Virginis,
from high-dispersion spectra obtained by Sanford and Abt and from
photoelectric colors and magnitudes obtained by Whitford and Code,
Eggen, and Gordon and Kron. The radial velocity-curve by Sanford has
been integrated for three different choices of a velocfty, each giving
a total displacement of the order of 35 X 106 krn. Layers of gas rise
and fall in about twice the period of light-variation. During nearly
half the period two layers of gas can be seen, one rising while the
other is falling. Hydrogen emission lines are formed in the lower
layer when it is first seen to rise. The light- and color-curves have
been used to obtain relative radII. A comparison with displacements
from the radial gives a maximum radius that is smaller than the total
displacement of the atmosphere. Curves of growth were constructed for
17 of the plates. Excitation temperatures for Fe I and for lines of
high excitation potential of Mg n show that when two layers are seen,
their temperatures differ by ()o . Ionization temperatures calculated
from the degree of ionization of Fe I and the continuous opacity
agree with the effective temperatures from the colors and with the
Mg II excitation temperatures. Relative to Fe, Ba and Ca have normal
abundances, but the Sr and Sc abundances are small by factors of 5 and
3, respectively. Several lines of evidence indicate that the layers of
gas are geometrically thin and transparent. A model of a shock wave
traveling through an extended atmosphere was found to give too much
material between the compressed regions following the shock fronts
and too high temperatures. A model of shells of gas thrown off at
maximum expansion of the photosphere explains the failure of Baade's
method for finding the total radius. If these shells have to coffi4e,
they cannot be uniform but must consist of many condensations.

---------------------------------------------------------
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: Radial Velocity and Spectrum of HD 98088
Authors: Abt, Helmut A.
1953PASP...65..274A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: An analysis of W Virginis.
Authors: Abt, Arthur
1952AJ.....57..158A Altcode:
W Virgin is is believed to be a typical population II Cepheid. A
study of this star was therefore made to provide a comparison with
the classical Cepheids. The data consist of a photoelectric light
curve by Kron and Gordon, a photoelectric color curve by Whitford
and Code, and spectra of dispersion 10 Amm by Sanford and Abt. The
radial velocity curve, derived by R. F. Sanford, is discontinuous. Just
before maximicrons light a set of weak absorption lines appears at -95
kmsec. These lines quickly strengthen with time and move longward. Then
they fade and disappear with a velocity of -40 km$sec just after the
next light maximum. So for several days around maximum light two sets
of weak absorption lines are present. The radial velocity curve was
integrated over time to obtain displacements. These show a symmetrical
expansion and contraction with a total displacement of 36 million
kilometers, or 50 solar radii. The displacement curve, however, shows
an overlap of cycles such that when the upper part of the atmosphere is
contracting, the lower part is expanding. The curve suggests that the
period of pulsation is twice the period of light variation and the time
between pulses is just one-half the duration of one pulse. The colors
were used to derive effective temperatures and bolometric corrections
to the light curve. From these we obtained relative radii, which show a
radius change by a factor of at least three. However, when the relative
radii curve was fitted to the displacement curve to get the scale of
the changes, a maximum radius less than the total displacement was
derived. The method fails probably because the continuous and line
spectra are formed predominantly in parts of an extended atmosphere
that have different motions. Curves of growth indicate that during
phases of double lines the excitation temperatures for the shortward
components, which are formed lower in the atmosphere, are 8000 to 10000
hotter than those for the longward components. The electron pressure
reaches a minimum at maxi- *Of papers presented at the Joint Meeting
of the Americaii Astronomical Society and the Astronomical Society
of the Pacific, Victoria, B. C., June 25-28, 1952. t Submitted as
partial fulfillment of the requirements for Ph.D. at the California
Institute of Technology. μm expansion. ionization temperatures were
calculated. The various determinations of the temperature at any one
phase indicate too large a range for a normal stellar atmosphere;
in an extended atmosphere the temperature gradient could be large
enough to give the observed temperature range'. The star shows a large
spectrum-color difference. The ionization temperatures indicate a range
in spectral types from Fo to F8, while the colors correspond to F4 to
K2. The largest difference occurs at maximum expansion. The classical
Cepheids show no such differences; an unreddened one of the same
period would have a spectral type range of F7 to G9. The spectrumcolor
difference for W Virginis may be due to an extended atmosphere or to
the impossibility of using the color-effective temperature relation of
population I stars for population II giants. Moitnt W?lson and Palomar
Observatories, Carnegie Institution of Washington, and Calsfornia
Institute of Technology.

---------------------------------------------------------
Title: Hyperfine Structure in the Solar Spectrum
Authors: Abt, Arthur
1952ApJ...115..199A Altcode:
The hyperfine structure of certain lines can be detected in the
solar spectrum as reproduced in the Utrecht atlas; it can contribute
appreciably to the width of the lines. The agreement between the
predicted and observed half-widths and profiles of lines with hyperfine
structure broadening is good. Solar lines with wide hyperfine structure
patterns show a wave-length shift toward the weak end of the pattern
as compared to the laboratory wave length. Hyperfine broadened lines
fall on a different curve of growth, characterized by a larger Doppler
velocity and a smaller damping constant. A resum of the elements most
affected by hyperfine broadening is given.

---------------------------------------------------------
Title: An analysis of the variable star, W Virginis
Authors: Abt, Helmut A.
1952PhDT........13A Altcode: 1952PhDT.........1A
W Virginis is a 17-day variable star which is considered to be the
prototype of population II Cepheids. An analysis of the physical
conditions in W Virginis during its cyclic variations has been made from
the following data: High dispersion (10 [...]/mm.) Coude plates were
measured for radial velocities (by R.F.Sanford) and lines intensities
which yielded curves of growth. Also used were a light curve in one
color (Gordon and Kron) and colors (Whitford and Code).The observations
indicate an expansion of about 36x10[superscript 6] km. and then
a subsequent contraction. The first indication of a new expansion
wave is the appearance of hydrogen emission lines, formed deep in the
atmosphere. Later the outward-moving region of gas produces absorption
lines like that of an F-type star. These gain in strength until maximum
expansion. This is also a time of minimum electron pressure and nearly
minimum temperature. During the contraction the electron pressure,
temperature, and opacity rapidly increase. Also just after maximum
expansion the appearance of a new set of hydrogen emission lines from
deep in the atmosphere indicates the start of a new outward-moving
wave. There is a time of several days during which absorption lines
are seen from the two masses of gas: the one falling downward and the
other moving upward. As the spectral features of the downward-moving
region fade, those of the upward-moving region increase toward maximum
strength. Data derived from the two simultaneous sets of absorption
lines indicate very different conditions in the two regions.It was found
that relative radii derived from light and color curves could not be
compared with displacements derived from the radial velocity curve,
because, perhaps, the regions predominantly forming the continuous
and line spectra have different motions. The extremely red colors and
the large apparent temperature gradient, both particularly at maximum
expansion, may be due to the presence of an extended atmosphere.

---------------------------------------------------------
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: Hyperfine Structure in the Solar Spectrum
Authors: Abt, Arthur
1951PASP...63..236A Altcode:
No abstract at ADS