Author name code: abt ADS astronomy entries on 2022-09-14 author:"Abt, Helmut A." OR author:"Abt, Arthur" ------------------------------------------------------------------------ Title: The Lifetimes of Astronomical Papers and the Completeness of the ADS Authors: Abt, Helmut A. Bibcode: 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. Title: Lifetime Data on Astronomical Papers and Citations Authors: Abt, Helmut A. Bibcode: 2019RNAAS...3...93A Altcode: 2019RNAAS...3g..93A No abstract at ADS Title: VizieR Online Data Catalog: The evolutionary status of GK subgiants (Abt, 2019) Authors: Abt, H. A. Bibcode: 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 & 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). Title: The Evolutionary Status of GK Subgiants Authors: Abt, Helmut A. Bibcode: 2019AJ....157..177A Altcode: Snowden & 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. Title: Publication Changes during the IAU History Authors: Abt, Helmut A. Bibcode: 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. Title: Principles of Editing Authors: Abt, Helmut A. Bibcode: 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. Title: Spectroscopic Orbits for Late-type Stars. II Authors: Fekel, Francis C.; Willmarth, Daryl W.; Abt, Helmut A.; Pourbaix, Dimitri Bibcode: 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. Title: The life and times of Aden and Marjorie Meinel; a biography Authors: Breckinridge, James B.; Abt, Helmut Bibcode: 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. Title: What Fraction of Papers in Astronomy and Physics Are Not Cited in 40 Years? Authors: Abt, Helmut A. Bibcode: 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. Title: An earlier explosion date for the Crab Nebula supernova Authors: Abt, Helmut A.; Fountain, John W. Bibcode: 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. Title: The Most Productive Years of Average Astronomers Authors: Abt, Helmut A. Bibcode: 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. Title: VizieR Online Data Catalog: Shape parameters for 154 Galactic open clusters (Zhai+, 2017) Authors: Zhai, M.; Abt, H.; Zhao, G.; Li, C. Bibcode: 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). 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. Bibcode: 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). Title: What Happens to Am Stars After They Leave the Main Sequence? Authors: Abt, Helmut A. Bibcode: 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 < 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. Title: Citations and Team Sizes Authors: Abt, Helmut A. Bibcode: 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&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&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. Title: The Shape Evolution of Galactic Open Clusters from Observations Under Galactic External Forces Authors: Zhai, Meng; Abt, Helmut; Zhao, Gang; Li, Chengdong Bibcode: 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. 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. Bibcode: 2016yCat..51520046W Altcode: The radial velocities used here are mainly from four sources: those obtained during the aforementioned work of Abt & Willmarth 2006 (Cat. J/ApJS/162/207), an earlier survey of solar-type stars (1986-1990, Julian Days 2546708-2550885) reported in Abt & 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 & 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 & Willmarth (1992ASPC...32...82A) employed the same equipment, except the "B" grating was used yielding approximately half the resolution used in Abt & Willmarth 2006 (Cat. J/ApJS/162/207). Subsequent observations obtained by DW used either the "A" grating as in Abt & 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). Title: At What Ages Did Astronomers Write Their Most Important Papers? Authors: Abt, Helmut A. Bibcode: 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. Title: Spectroscopic Orbits for 15 Late-type Stars Authors: Willmarth, Daryl W.; Fekel, Francis C.; Abt, Helmut A.; Pourbaix, Dimitri Bibcode: 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. Title: Hot Gaseous Stellar Disks Avoid Regions of Low Interstellar Densities Authors: Abt, Helmut A. Bibcode: 2015PASP..127.1218A Altcode: No abstract at ADS Title: VizieR Online Data Catalog: Bibliography of stellar radial velocities (Abt+ 1972) Authors: Abt, H. A.; Biggs, E. S. Bibcode: 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). Title: The Lifetimes of Astronomers Authors: Abt, Helmut A. Bibcode: 2015PASP..127..713A Altcode: No abstract at ADS Title: The Research Use of Astronomical Monographs Authors: Abt, Helmut A. Bibcode: 2014PASP..126..409A Altcode: No abstract at ADS Title: Joy, Alfred Harrison Authors: Abt, Helmut A. Bibcode: 2014bea..book.1142A Altcode: No abstract at ADS Title: Mayall, Nicholas Ulrich Authors: Abt, Helmut A. Bibcode: 2014bea..book.1426A Altcode: No abstract at ADS Title: Bohlin, Karl Petrus Teodor Authors: Abt, Helmut A. Bibcode: 2014bea..book..256A Altcode: No abstract at ADS Title: Scientific Efficiency of Ground-based Telescopes Authors: Abt, Helmut A. Bibcode: 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 >7 m average 1.29 more citations than those with an aperture of 2 to <4 m, this represents a small return for a factor of four difference in operating costs. Among the 17 papers that have received >=100 citations in 3+ years, only half come from the large (>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. Title: The h- and a-Indexes in Astronomy Authors: Abt, Helmut A. Bibcode: 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. Title: The age of the local interstellar bubble Authors: Abt, Helmut A. Bibcode: 2012AIPC.1452....9A Altcode: No abstract at ADS Title: The Discovered Exoplanets Have The Same Orbital Elements As Stellar Systems Authors: Abt, Helmut A. Bibcode: 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</u>

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. Title: The Age of the Local Interstellar Bubble Authors: Abt, H. A. Bibcode: 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). Title: The Nature of the Exoplanets Authors: Abt, Helmut A. Bibcode: 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. Title: The Age of the Local Interstellar Bubble Authors: Abt, Helmut A. Bibcode: 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 & 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. Title: The Tonantzintla Search for High Luminosity Stars Authors: Abt, H. A. Bibcode: 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. Title: Symposium Summary Authors: Abt, H. A. Bibcode: 2011RMxAC..39..117A Altcode: No abstract at ADS Title: Astronomical Publication Rates in the US, UK, and Europe Authors: Abt, Helmut A. Bibcode: 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. Title: The Origin of the Exoplanets Authors: Abt, Helmut A. Bibcode: 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] < -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. Bibcode: 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. Bibcode: 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. Bibcode: 2009PASP..121.1307A Altcode: No abstract at ADS Title: Reviewing and Revision Times for The Astrophysical Journal Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 < ω < 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. Bibcode: 2009AJ....138...28A Altcode: I wondered why there are still slowly rotating (V < 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. Bibcode: 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. Bibcode: 2009PASP..121..544A Altcode: I looked at statistically large samples of references in the Astrophysical Journal and Astronomy & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2008PASP..120..715A Altcode: Furenlid & 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 <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. Bibcode: 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. Bibcode: 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] < -0.30) observed by Latham et al. and Goldberg et al., (2) 42 blue metal-poor binaries discovered by Preston & Sneden, (3) all 145 known FG dwarf binaries with [Fe/H] > -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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2007ASPC..362...92A Altcode: No abstract at ADS Title: Editor's Forum Authors: Abt, Helmut A. Bibcode: 2007fpca.conf..239A Altcode: No abstract at ADS Title: Changing Sources for Research Literature Authors: Abt, Helmut A. Bibcode: 2007fpca.conf..177A Altcode: Including material published previously, I considered all the references listed in the January issues of Astronomy & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & 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. Bibcode: 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 Bibcode: 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. Bibcode: 2005BAAS...37.1540A Altcode: No abstract at ADS Title: Observed Orbital Eccentricities Authors: Abt, Helmut A. Bibcode: 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 Bibcode: 2005BAAS...37..551A Altcode: No abstract at ADS Title: Erratum: ``Spectral Classification of Stars in A Supplement to the Bright Star Catalogue'' (ApJS, 155, 175 [2004]) Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 2005coas.conf....2A Altcode: No abstract at ADS Title: Peer Reviewing Authors: Abt, Helmut A. Bibcode: 2005coas.conf...19A Altcode: No abstract at ADS Title: The Formation of Planets Authors: Abt, H. A. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2004RMxAC..21...37A Altcode: 2004IAUCo.191...37A Two previous studies of the secondary mass function in spectroscopic binaries by Abt & Levy (1976) and by Duquennoy & 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 >500 AU fits a van Rhijn function, as was shown previously by Abt and Levy. Title: Dedication to Arcadio Poveda Authors: Abt, H. A. Bibcode: 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. Bibcode: 2004yCat.3106....0A Altcode: The spectral types listed here represent about one-third of a program of MK classification of all the Northern (Dec>-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&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. Bibcode: 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. Bibcode: 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. Bibcode: 2004BAAS...36..948A Altcode: No abstract at ADS Title: Evidence for an Interstellar Origin of Stellar Shells Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 2003ASSL..296..197A Altcode: 2003osa4.book..197A No abstract at ADS Title: Foreword Authors: Abt, H. A. Bibcode: 2003ASSL..290D...7A Altcode: 2003asco.bookD...7A No abstract at ADS Title: Scientific Impact of Small Telescopes Authors: Abt, Helmut A. Bibcode: 2003ASSL..287...55A Altcode: 2003fst1.book...55A No abstract at ADS Title: Changes in Astronomical Publications During the 20th Century Authors: Abt, H. A. Bibcode: 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. Bibcode: 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 Bibcode: 2003gafe.conf..123A Altcode: No abstract at ADS Title: Rotational velocities of B stars Authors: Abt, Helmut A.; Levato, Hugo; Grosso, Monica Bibcode: 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 <4, the conservation of angular momentum is by rigid-body rotation but for factors >4, it is in shells. (4) In binaries the primaries have synchronized rotational and orbital motions for periods <2.4 days. For the A stars studied by Abt & Morrell the limit is 5.0 days. (5) In binaries the orbits are circularized for periods <1.5 days and for A star <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 Bibcode: 2003gafe.conf...47A Altcode: No abstract at ADS Title: The Production and Distribution Times for Conference Proceedings Authors: Abt, Helmut A. Bibcode: 2002BAAS...34.1354A Altcode: No abstract at ADS Title: How to write a good astronomical paper Authors: Abt, Helmut A. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 2002RMxAC..14..111A Altcode: No abstract at ADS Title: The Productivity of Ground-Based Optical Telescopes of Various Apertures Authors: Abt, H. A. Bibcode: 2001AAS...19914501A Altcode: 2001BAAS...33.1524A We scanned the papers published in the first quarter of 1996 in A&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 <4 meters. Then we counted citations since 1996 to those papers and found that 75% of the citations were to those papers from telescopes <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 <4 meters in aperture. These numbers tell us that the bulk of our astronomical papers and of the most important results come from telescopes <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 Bibcode: 2001BAAS...33..935A Altcode: No abstract at ADS Title: Are Stellar Rotational Axes Distributed Randomly? Authors: Abt, Helmut A. Bibcode: 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 & Renson compiled rotational periods from the literature and Abt & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2000ApJ...544..933A Altcode: As noted by Abt & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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, & 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 & 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. Bibcode: 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. Bibcode: 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 > 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& 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. Bibcode: 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. Bibcode: 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. Bibcode: 2000AcHA...10..232S Altcode: No abstract at ADS Title: Do Important Papers Produce High Citation Counts? Authors: Abt, H. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1999aasf.book..176A Altcode: No abstract at ADS Title: Electronic publication in 1997. Authors: Abt, H. A. Bibcode: 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. Bibcode: 1998ApJ...499..525A Altcode: No abstract at ADS Title: Is the Astronomical Literature Still Expanding Exponentially? Authors: Abt, Helmut A. Bibcode: 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&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. Bibcode: 1998ASPC..138....3A Altcode: 1998stas.conf....3A No abstract at ADS Title: Access to Journals Authors: Abt, H. A. Bibcode: 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 Bibcode: 1997ApJ...487..365A Altcode: At any one time, approximately one-quarter of the most rapidly rotating normal A-type dwarfs (V sin i >= 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. Bibcode: 1997ASPC..130..117A Altcode: 1997rdbs.conf..117A No abstract at ADS Title: Access to Journals Authors: Abt, H. A. Bibcode: 1997IAUJD..20E..31A Altcode: No abstract at ADS Title: The Maximum Ages of Trapezium Systems Authors: Abt, H. A.; Corbally, C. J. Bibcode: 1997ASSL..223..127A Altcode: 1997vdsf.conf..127A No abstract at ADS Title: How Long Are Astronomical Papers Remembered? Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 1996ApJ...466..603A Altcode: No abstract at ADS Title: Announcement: faster publication times for electronic manuscripts and other changes. Authors: Abt, Helmut A. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1996ASPC...90..105A Altcode: 1996oedb.conf..105A No abstract at ADS Title: Some Statistical Highlights of the Astrophysical Journal Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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&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. Bibcode: 1994ApJ...430..445A Altcode: No abstract at ADS Title: Institutional Productivities 1993 Authors: Abt, H. A. Bibcode: 1994PASP..106..107A Altcode: No abstract at ADS Title: MK Spectra of the Bright A-Type Stars Authors: Abt, H. A. Bibcode: 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. Bibcode: 1994IAUTA..22..239A Altcode: No abstract at ADS Title: Obituary: Goro Ishida, 1924-1992 Authors: Abt, Helmut A. Bibcode: 1993BAAS...25.1497A Altcode: No abstract at ADS Title: Institutional Productivities Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 1993ApJ...406..359A Altcode: No abstract at ADS Title: CCD Observations of Possible Trapezium Systems Authors: Abt, H. A.; Corbally, C. J. Bibcode: 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. Bibcode: 1993ASPC...44..384A Altcode: 1993IAUCo.138..384A; 1993pvnp.conf..384A No abstract at ADS Title: Announcement - Proposed Cd-Rom Series Authors: Abt, H. A. Bibcode: 1993ApJ...402....1A Altcode: No abstract at ADS Title: Astronomical Publications Authors: Abt, H. A. Bibcode: 1993ASPC...38..466A Altcode: 1993nfbs.proc..466A No abstract at ADS Title: The Astrophysical Journal Videotapes Authors: Abt, H. A. Bibcode: 1992ApJ...393....1A Altcode: No abstract at ADS Title: Spectroscopic Binaries in the alpha Persei Cluster Authors: Morrell, Nidia; Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1992dpas.conf...47A Altcode: No abstract at ADS Title: Closing Comments Authors: Abt, H. A. Bibcode: 1992dpas.conf..223A Altcode: No abstract at ADS Title: A noteworthy occasion Authors: Abt, H. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1991Sci...251.1408A Altcode: No abstract at ADS Title: Publication Practices in Various Sciences Authors: Abt, H. A. Bibcode: 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. Bibcode: 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. Bibcode: 1991ApJ...366..341A Altcode: No abstract at ADS Title: Spectroscopic Binaries in the Orion Nebula Cluster Authors: Abt, Helmut A.; Wang, Ruyou; Cardona, Octavio Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1990ApJ...357....1A Altcode: No abstract at ADS Title: Refereed Conference Papers - Editorial Authors: Abt, H. A. Bibcode: 1990ApJ...354....1A Altcode: No abstract at ADS Title: Trends Toward Internationalization in Astronomical Literature Authors: Abt, Helmut A. Bibcode: 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&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. Bibcode: 1989ApJ...346....1A Altcode: No abstract at ADS Title: Journal Referencing Authors: Abt, Helmut A.; Liu, Jinming Bibcode: 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. Bibcode: 1989HiA.....8.....M Altcode: No abstract at ADS Title: The Future of Astronomical Literature Authors: Abt, H. A. Bibcode: 1989lisa.conf...37A Altcode: 1989IAUCo.110...37A No abstract at ADS Title: Growth Rates in Various Fields of Astronomy Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 1988ApJ...328L...1A Altcode: No abstract at ADS Title: What Happens to Rejected Astronomical Papers? Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 1988PASP..100..156A Altcode: No abstract at ADS Title: Interacting Am binaries. Authors: Abt, H. A. Bibcode: 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. Bibcode: 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, <R>, and mean paper lengths,

, expressed in normalized 1000-word pages; it is <R> 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 < 8.0 km s-1 are undetected, as well as all broad-lined systems with K1 < 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1986BAAS...18..681W Altcode: No abstract at ADS Title: An Assessment of Research done at the National Optical Observatories Authors: Abt, H. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1984mpsc.conf..340A Altcode: No abstract at ADS Title: The Occurence of Peculiar Stars in Clusters and Visual Systems Authors: Abt, H. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1981Obs...101..217M Altcode: No abstract at ADS Title: Editorial Authors: Abt, H. A. Bibcode: 1981ApJ...249....1A Altcode: No abstract at ADS Title: Some Trends in American Astronomical Publications Authors: Abt, H. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1981KPNON..18....4A Altcode: No abstract at ADS Title: Visual multiples. VI. BET 1269, a system containing abnormal stars. Authors: Abt, H. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1980oits.conf..609A Altcode: No abstract at ADS Title: The frequencies of binaries on the main sequence. Authors: Abt, H. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1979ApJ...227..359A Altcode: No abstract at ADS Title: The Occurrence of Abnormal Stars in Open Clusters Authors: Abt, Helmut Bibcode: 1979RA......9...95A Altcode: No abstract at ADS Title: The Forthcoming Morgan-Abt Spectral Atlas Authors: Abt, H. A. Bibcode: 1979RA......9..477A Altcode: 1979IAUCo..47..477A No abstract at ADS Title: Spectral types in Gurzadyan's clustering in Auriga. Authors: Abt, H. A. Bibcode: 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. Bibcode: 1978ApJS...38...87A Altcode: No abstract at ADS Title: The Frequencies of Binaries on the Main Sequence Authors: Abt, H. A. Bibcode: 1978BAAS...10Q.607A Altcode: No abstract at ADS Title: Spectral types in the Ursa Major stream. Authors: Levato, H.; Abt, H. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 1978rmsa.book.....M Altcode: No abstract at ADS Title: The Binary Frequency Along the Main Sequence Authors: Abt, H. A. Bibcode: 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. Bibcode: 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. Bibcode: 1977ApJS...35..127A Altcode: No abstract at ADS Title: Spectral Types in the Open cluster NGC 2169 Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 1977ApJ...217....1A Altcode: No abstract at ADS Title: Spectral types in the open cluster M34. Authors: Abt, H. A.; Levato, H. Bibcode: 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. Bibcode: 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. Bibcode: 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 < 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1976ApJ...209..961A Altcode: No abstract at ADS Title: Spectral types in the Orion nebula cluster. Authors: Levato, H.; Abt, H. A. Bibcode: 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. Bibcode: 1976BAAS....8Q.521A Altcode: No abstract at ADS Title: Visual multiples. III. ADS 11745 (beta Lyrae group). Authors: Abt, H. A.; Levy, S. G. Bibcode: 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. Bibcode: 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. Bibcode: 1976AJ.....81..541A Altcode: No abstract at ADS Title: Spectral types in the open cluster M39. Authors: Abt, H. A.; Levato, H. Bibcode: 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. Bibcode: 1976Obs....96...54G Altcode: No abstract at ADS Title: MK morphology of a group of Am stars. Authors: Abt, H. A.; Morgan, W. W. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1975ApJ...202..562A Altcode: No abstract at ADS Title: Spectral types in the open cluster NGC 6475. Authors: Abt, H. A. Bibcode: 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. Bibcode: 1975BAAS....7..268A Altcode: No abstract at ADS Title: Rotational velocities of marginal metallic-line stars. Authors: Abt, H. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 (<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. Bibcode: 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 (>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. Bibcode: 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. Bibcode: 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. Bibcode: 1973ApJ...185..737A Altcode: No abstract at ADS Title: A spectroscopic study of the open cluster M39. Authors: Abt, H. A.; Sanders, W. L. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1973AJ.....78..386M Altcode: No abstract at ADS Title: Introductory Remarks on Spectroscopic Parameters Authors: Abt, H. A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1973cirv.book.....A Altcode: 1973QB1.A88n234v26. No abstract at ADS Title: A. H. Joy (1882 - 1973) Authors: Abt, H. A. Bibcode: 1973Mercu...2....9A Altcode: No abstract at ADS Title: Rotational Velocities of AP Stars Authors: Abt, Helmut A.; Chaffee, Frederic H.; Suffolk, Graham Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1972AJ.....77..138A Altcode: No abstract at ADS Title: Spectroscopic Binaries in the Open Cluster NGC 2516. Authors: Abt, Helmut A.; Levy, Saul G. Bibcode: 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. Bibcode: 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. Bibcode: 1972AJ.....77...35M Altcode: No abstract at ADS Title: Bibliography of stellar radial velocities Authors: Abt, Helmut A.; Biggs, Eleanor S. Bibcode: 1972bsrv.book.....A Altcode: No abstract at ADS Title: The Radial Velocity of 60 Serpentis Authors: Abt, Helmut A.; Levy, Saul G. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1970PASP...82..716A Altcode: No abstract at ADS Title: Spectra of the Cepheid HR 8157 Authors: Abt, Helmut A.; Levy, Saul G. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1969AJ.....74.1153A Altcode: No abstract at ADS Title: Spectral Classification of A-Type Spectroscopic Binaries Authors: Abt, Helmut A.; Bidelman, William P. Bibcode: 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. Bibcode: 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. Bibcode: 1969AJ.....74..908A Altcode: No abstract at ADS Title: The H-R diagram of NGC 2516. Authors: Abt, H. A.; Morgan, W. W. Bibcode: 1969AJ.....74..813A Altcode: No abstract at ADS Title: Accuracies of Radial-Velocity Measurements Authors: Abt, Helmut A.; Smith, Gregory H. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1969BAAS....1..164A Altcode: No abstract at ADS Title: Introductory Remarks Authors: Abt, Helmut A. Bibcode: 1969BAAS....1..141A Altcode: No abstract at ADS Title: Radial velocity of the stars Authors: Abt, H. A. Bibcode: 1969stas.conf...99A Altcode: No abstract at ADS Title: Research Possibilities with Moderate Dispersion Authors: Abt, Helmut A. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 1968aald.book.....A Altcode: No abstract at ADS Title: Frequency of Spectroscopic Binaries among High-Velocity Stars. Authors: Abt, Helmut A.; Levy, Saul G. Bibcode: 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 (<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 Bibcode: 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< 100 km/sec) normal stars in the range B7-AO and no rapidly rotating (V> 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. Bibcode: 1967PASP...79..197A Altcode: No abstract at ADS Title: Rotational Velocities of Stars in IC 4665 Authors: Abt, Helmut A.; Chaffee, Frederic H. Bibcode: 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. Bibcode: 1967IAUS...30...55A Altcode: No abstract at ADS Title: Duplicity and Rotation Among Am, Ap, and A Stars Authors: Abt, Helmut A. Bibcode: 1967mrs..conf..173A Altcode: No abstract at ADS Title: Recent Work on Radial Velocities in Nearby Clusters Authors: Abt, H. A. Bibcode: 1967IAUS...30..159A Altcode: No abstract at ADS Title: Rotational Velocities in the Galactic Cluster IC 4465 Authors: Abt, H. A.; Chaffee, F. H. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1966AJ.....71Q.377A Altcode: The nearby Cepheids and those in the Small Magellanic Cloud have very different light amplitud&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. Bibcode: 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. Bibcode: 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. Bibcode: 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 < 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. Bibcode: 1965PASP...77..367A Altcode: No abstract at ADS Title: The Frequency of Binaries among Normal A-Type Stars. Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1964ApJ...140.1641A Altcode: No abstract at ADS Title: The Galactic Cluster IC 4665. Authors: Abt, Helmut A.; Snowden, Michael S. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1963paa..book..119A Altcode: No abstract at ADS Title: Interstellar Absorption in the North Equatorial Polar Region. Authors: Abt, Helmut A.; Golson, John C. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1961ApJ...134.1013A Altcode: No abstract at ADS Title: Radial Velocities of Three Metallic-Line Stars. Authors: Abt, Helmut A. Bibcode: 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 Bibcode: 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&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&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&ld and Bo~hmVitense) account for their peculiar spectra. Title: The Frequency of Binaries among Metalmc-Line Stars. Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 1960PASP...72..348A Altcode: No abstract at ADS Title: The Spectra of Two High-Lattitude Supergiants. Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1959ApJ...130.1021A Altcode: No abstract at ADS Title: Wesselink's Method and Shock Waves in RR Lyrae. Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 1959PASP...71..345A Altcode: No abstract at ADS Title: Photoelectric Photometry of an Outburst of SS Cygni. Authors: Grant, Golden; Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 1958PASP...70..414A Altcode: No abstract at ADS Title: A Spectroscopic Binary in the Pleiades. Authors: Abt, Helmut A. Bibcode: 1958ApJ...128..139A Altcode: No abstract at ADS Title: Line Broadening in High-Luminosity Stars. II. Less Luminous Supergiants. Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 1955PASP...67..412T Altcode: No abstract at ADS Title: Spectroscopic Observations of the Cluster-Type Variable VZ CANCRI. Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 1955ApJ...122..199A Altcode: No abstract at ADS Title: Studies of RV Tauri Stars. I. U Monocerotis Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 1954PASP...66..171A Altcode: No abstract at ADS Title: Abstract: An Analysis of W Virginis. Authors: Abt, Helmut A. Bibcode: 1954ApJ...119..469A Altcode: No abstract at ADS Title: The Luminosity of the Cepheid Y Ophiuchi Authors: Abt, Helmut A. Bibcode: 1954PASP...66...65A Altcode: No abstract at ADS Title: An Analysis of W Virginis. Authors: Abt, Helmut A. Bibcode: 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. Bibcode: 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. Bibcode: 1953PASP...65..274A Altcode: No abstract at ADS Title: An analysis of W Virginis. Authors: Abt, Arthur Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 1951PASP...63..236A Altcode: No abstract at ADS