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Title Productivity and impact of

Permalink https://escholarship.org/uc/item/3xb98207

Journal Publications of the Astronomical Society of the Pacific, 118(844)

ISSN 0004-6280

Authors Trimble, V Zaich, P

Publication Date 2006

DOI 10.1086/505182

License https://creativecommons.org/licenses/by/4.0/ 4.0

Peer reviewed

eScholarship.org Powered by the California Digital Library University of California Publications of the Astronomical Society of the Pacific, 118: 933–938, 2006 June ᭧ 2006. The Astronomical Society of the Pacific. All rights reserved. Printed in U.S.A.

Productivity and Impact of Radio Telescopes

Virginia Trimble1 and Paul Zaich2,3 Received 2005 October 18; accepted 2006 April 18; published 2006 June 14

ABSTRACT. In 2001, 836 papers appearing in 15 journals reported and/or analyzed data collected with ground- based radio, millimeter, and submillimeter telescopes, plus the HALCA, COBE,andSWAS satellites and a few balloon-borne detectors. More than 80 telescopes were represented, including 36 that were each responsible for five or more papers. These papers were cited 11,332 times in 2002, 2003, and 2004, for a mean rate of 13.56 citations per paper, or 4.52 citations per paper per year (sometimes called impact or impact factor, and compared to 5.40 citations per paper per year for optical papers in the same period and 6.42 for space-based papers). We examine here the distributions of papers, citations, and impact factors among subject areas and telescopes and make some comparisons with the 2100 optical and and 1200 space-based papers published and cited in the same years. The single largest item in the optical inventory was, naturally, the Hubble Space , with 16% of the papers and 19% of the citations. houses an even more dominant entity, the Very Large Array (VLA), responsible for 22% of the papers and 27% of the citations. The VLA is, therefore, proportionately even more influential in world radio astronomy than HST is in world optical astronomy. A third paper in this series looks at papers and citations in the area of infrared, X-ray, and -ray space- based astronomy and planetary missions. Of the “radio” papers, 149 were also optical papers and 76 were also “space” papers, in the sense of reporting or analyzing data in both bands. Their impact factors were 5.71 and 7.51 citations per paper per year, respectively, slightly above the averages for the individual bands. Thus, slightly more than half of observational astronomy is still optical astronomy, but multiwavelength papers are somewhat more influential than average. No radioϩoptical paper went completely uncited during the triennium.

1. INTRODUCTION reporting observational data from radio (including millimeter In 2005, we reported data concerning about 2100 papers, pub- and submillimeter) telescopes and from space facilities oper- lished in 18 journals, which had made use of data obtained with ating at infrared, X-ray, and gamma-ray wavelengths, using as ground-based optical and infrared telescopes plus the Hubble nearly as possible the same methods. Because ground-based (Trimble et al. 2005, hereafter Paper I). About radio and optical telescopes generally have lifetimes of many 250 telescopes were represented, including 25 with primary- years, data concerning them should be comparable. This cannot mirror diameters of 3 m or larger. In the next 2 years, 2002 be true for the space-based sample, because of the short life- and 2003, those papers were cited 24,334 times, for a mean times of missions. As far as we know, no similar ex- rate of 11.56 citations per paper, or 5.78 citations per paper amination of radio astronomy (or space-based) papers and ci- per year (sometimes called impact or impact factor). HST was tations has been carried out. Thus, no historical trends can be responsible for the single largest number of papers (346.3) and sought, and the present work is a sort of “first epoch” study, had a somewhat larger than average citation rate (13.71 cita- with the equivalent of proper motions to be determined 5–10 tions per paper). Keck was second, with 104.5 papers and 20.86 years into the future. In addition, the optical citation numbers citations per paper. Remarkably, telescopes with diameters less have been updated to represent the 3 years of 2002–2005. than 1 m contributed 107 papers, but only 5.02 citations per We present here the distributions of radio-observation papers paper. See Paper I for further details, including citation rates as a function of the telescope(s) used and subject matter, make as a function of subject matter, distribution of papers among some comparisons with the optical sample, and look very the journals, and details of the method adopted. briefly at the space-based sample (Trimble et al. 2006, hereafter In spring 2005, we decided to extend the analysis to papers Paper III).

2. METHODS 1 Department of Physics and Astronomy, University of California, Irvine, As noted in Paper I, an analysis of this sort cannot be done 4129 Frederick Reimes Hall, Irvine, CA 92697-4575; and Las Cumbres Ob- servatory Global Telescope, Goleta, California. in real time. A facility must be debugged, significant numbers 2 5901 Sierra Bravo Road, Irvine, CA 92612. of observations accumulated, and papers written, refereed, and 3 Current address: P.O. Box 13844, Stanford, CA 94309. published. Only then can the papers be read and cited; and

933 934 TRIMBLE & ZAICH peak citation rates normally occur a year or two after publi- (85), PASJ (38), ApJS (23), Astronomy Reports (16), Icarus cation. Our data were collected from May to September 2005, (14), Nature (10), Science (8), J. Astrophys. . (8), PASP and it would thus have been possible to start over and use (4), Astronomy Letters (3), Ap&SS (1), and none in Astron. papers published in 2002 and cited in 2003 and 2004. The first Nachr., JRASC,orActa Astronomica. author simply quailed at the task. At a minimum of 3 minutes For each paper, the following information was recorded: per paper, examining 6000 papers, identifying the 4000 ob- name of first author, number of additional authors, volume and servational ones, and recording appropriate information about page number, total number of pages, subject, and identity of each takes more than 300 hr. Thus, what we have here is all all the telescopes contributing data to the paper, in the order the observational papers published in 2001 and citations to they were mentioned by the authors. Subjects were chosen from them from 2002 to 2004, compiled by the second author from the same list of about 25 used for the optical sample, although the Science Citation Index (SCI)/Web of Science. This appears a “radio first” approach might well have led to a somewhat to be somewhat more complete than the citation data in the different assortment. The largest number of individual tele- Astrophysics Data System, at least in the sense that fewer pa- scopes or dishes used in any one paper was 36, and at this pers turn up with no citations at all. point the decision was made to count the Very Long Baseline The radio situation is generally analogous to the optical one. Array (VLBA) and the European VLBI Network (EVN) as Some telescopes were just coming on line (including the new single entities and to accept that there would be a class of Green Bank Telescope), and others were probably past their “strays” that had contributed only small fractions of the data prime or no longer in existence, although data from them were to one or a few papers. For a few (but only a few) papers, it still being used (the Cambridge 3C survey at 178 MHz, to take was not possible to determine which telescopes were used. an extreme example). The numbers of papers from these classes These appear only in various totals. are likely to be smaller than their lifetime annual averages, but As in the optical case, the subject assignment was based on the citations per paper may be representative. In the optical what the authors said they had in mind. Observations of qua- case, Gemini, the Hobby-Eberly Telescope, and the Italian TNG sars, for instance, could have been aimed toward establishing (Telescopio Nazionale ) were just beginning operation, a more precise coordinate system (the “service” class), under- while the Mount Wilson 100 inch and the Byurakan 2 m were standing the core-jet structure (AGNs), or tracing out 21 cm no longer producing new data. absorption along the line of sight (very large scale structure or This time around, in April–May 2005, V. T. went page by cosmology). The service areas included catalogs, surveys, and page through the same issues of the same 18 journals (plus a instrument calibrations, as well as astrometry. few that had turned up since summer 2004) and identified all Again as in Paper I, all radio, millimeter, and submillimeter the papers that reported or analyzed data from any ground- telescopes contributing to the data in a given paper received based radio, millimeter, or submillimeter telescopes, plus the equal credit for the paper and for the citations to it, except that HALCA (Japanese interferometry), COBE ( back- citations were credited only in integers. Thus, the last-men- ground), and SWAS (submillimeter) satellites, and a few bal- tioned of seven telescopes contributing to a 13 citation paper loon-borne millimeter and submillimeter telescopes, like BOO- received credit for one citation, each of the others getting two. MERANG. P. Z. looked up all the citation numbers during This was not really very common. And optical, X-ray, or summer 2005. This is probably the place to confess that the gamma-ray telescopes contributing to the same papers were James Clerk Maxwell Telescope (JCMT) accidentally ended simply ignored, just as the radio ones were in Paper I. We up in the optical sample last time. It has been properly moved suspect that the gravest injustice done by this equal-credit sys- to submillimeter this time, and we were careful not to count tem is to HALCA, the Japanese VLBI satellite. It was typically its papers or citations twice! used in combination with two to very many ground-based tele- The rule, as in Paper I, was that it had to be possible to scopes, but because of the enormous increase in baseline it discern from the published paper itself which telescopes were made possible, it probably contributed more than 1/N of the involved. Thus, uses of the FIRST survey were credited to the weight to most results. Very Large Array (VLA), but papers that drew a sample of Which telescopes contributed to the 2001 literature, and active galactic nuclei (AGNs) from several catalogs and men- which to keep track of? In the end, the bean-counting approach tioned only the catalogs were not included. The resulting list won, and although 80 plus telescopes were mentioned at least consisted of 836 papers, 149 of which had also been in the once, we report only the 36 individual facilities that contributed previous, optical sample. For consistency, they and their ci- five or more papers, plus a number of collectivities. The un- tations were here credited entirely to the radio telescopes used, listed include some fairly well known places (like Hartebeest- since they had been credited entirely to the optical telescopes hoek) and others less so (like Qinghai). in Paper I. How accurate are the data? Several kinds of problems are The journals and paper yields were ApJ (205), A&A (in- possible. Rereading a paper, one sometimes finds some addi- cluding Letters, 195), MNRAS (116), ApJ Letters (110), AJ tional observational data (usually near the end!) from additional

2006 PASP, 118:933–938 RADIO TELESCOPES 935

TABLE 1 The Most Cited Radio Papers

Number of Citations Telescope(s) Journal Subject 298 ...... VLAϩoptical ApJ Letters GRBs 224 ...... MAXIMA ApJ Letters Cosmology 146 ...... MAXIMA ApJ Letters Cosmology 134 ...... JCMT,VLAϩoptical, and X-ray ApJ 120 ...... 1.2 m millimeter dishes at the Center for Astrophysics and ApJ ISM Cerro Tololo Inter-American Observatory 111 ...... VLAϩX-ray ApJ AGNs 91 ...... Westerbork Synthesis Radio Telescope MNRAS Galaxies 90 ...... VLAϩX-ray ApJ Letters Clusters of galaxies 85 ...... Parkes MNRAS Calibration 85 ...... JCMT ApJ Galaxies telescopes not caught the first time and not mentioned in the studies. The most cited radio papers appeared in only three abstract or methods sections. A possible final summary paper journals and concerned seven different subjects (four journals (to be submitted elsewhere) will correct the optical data in this and four subjects for the optical set). The 10 next most cited respect. Some subject assignments are a bit arbitrary, on the papers bring in some additional telescopes—the Institut de Ra- edge between young stellar objects (YSOs) and ordinary , dioastronomie Millime´trique (IRAM), BOOMERANG, Dwin- for instance. And there are occasional anomalies in the SCI geloo, the 30 m at Villa Elisa in Argentina, the Owens Valley database. About 10 papers (of the original 2100 of Paper I) Radio Observatory (OVRO), and the Multi-Element Radio- actually showed fewer citations when examined in summer linked Interferometer Network (MERLIN)—a couple more 2005 than they had the previous year. One paper’s citation subjects (, interstellar medium), and two additional jour- numbers had jumped from three in 2 years to 53 in 3 years nals (A&A and ApJS). and may have represented an injustice in Paper I to one small And some papers are never cited at all: 133 (6.3%) of the but well-used . Error bars of a few percent 2100 optical papers in the first 2 years, dropping to 63 (3.0%) should therefore be associated with all the numbers. with 3 years of citation data. The radio rate is very similar: 28 of 836 papers, or 3.3%, had no citations in the SCI database 3. RESULTS in the 3 years following 2001 publication. And none of the ϩ In Papers I and III, these were grouped under headings re- multiwavelength (radio optical) papers ended up completely ϩ flecting common misconceptions about the astronomical lit- uncited. There are also no zeros among the radio space papers, ϩ erature, and this section was originally structured the same way and only a very few among optical space papers. Perhaps it to facilitate comparisons of the results. In response to requests is just a matter of having two communities who might want from the referees, it has been reorganized, and some of the to mention the work. conclusions and predictions have been removed. Copies of the The radio zeros are not distributed uniformly over either the unexpurgated version are available from the first author and journals or the telescopes, and surprises are few. The mix of can be sent, on request, in plain brown wrappers. topics is much the same set of active galaxies, normal galaxies, interstellar material, and formation/YSOs that dominates 3.1. The Most and Least Cited Papers the cited papers, but the uncited appear more often in journals published in less prosperous countries, and they often report We had not expected radio astronomy to have any one tele- data collected at telescopes in difficult places (Russia, Maur- scope responsible for as large a fraction of the papers as HST itius, and India, for instance). But neither the high-profile jour- is in the case of optical data. Nor did we expect any one paper nals (ApJ, A&A, MNRAS) nor the most productive telescopes to stand out in quite the way that the HST Key Project deter- (VLA, BIMA, VLBA) are completely exempt. mination of the Hubble constant did (443 citations in 2 years; 632 citations in 3 years). The latter expectations proved to be 3.2. Trends correct, the former wrong (§ 3.4). The optical standout is Freed- man et al. (2001), which was miscited in Paper I. On this point, no information is available. Paper I noted that Table 1 lists the 10 most cited radio papers, giving the num- the most productive 3–5 m optical telescopes of a decade before bers of citations in 3 years, the telescopes used, the journals had all yielded fewer papers in the new compilation: not just of publication, and the subjects. Eight different telescopes were a smaller percent of the papers, but a smaller number, by 10%– involved (compared to 10 for the 10 most cited optical papers), 40% per telescope. In contrast, the large ground-based infrared and two papers are in both sets, highly cited multiwavelength telescopes had produced more papers and more citations in

2006 PASP, 118:933–938 936 TRIMBLE & ZAICH

TABLE 2 Citation Rates by Topic and Comparison with Optical Numbers

Radio Radio Percentage of Percentage of Topic Citations Papers C/P Radio Papers Optical Papers Optical C/P Cosmology ...... 1037 37 28.02 0.044 0.051 42.24 Clusters of galaxies ...... 534 22 16.69 0.038 0.040 14.81 GRBs ...... 463 9 51.54 0.011 0.012 30.10 AGNs ...... 1944 148 13.36 0.177 0.098 16.56 Galaxies ...... 2021 144 14.03 0.172 0.147 23.02 ...... 285 22 12.95 0.026 0.008 29.81 ISM ...... 1897 174 10.90 0.208 0.066 10.44 SNe/SNR ...... 306 36 8.50 0.043 0.021 15.75 NS/BH/XRB/PSR ...... 1109 73 15.19 0.087 0.021 14.43 YSO/star formation ...... 775 53 14.62 0.063 0.041 14.57 Stars/clusters/BDs ...... 389 43 9.05 0.051 0.250 12.24 PNe/WDs ...... 87 7 12.43 0.008 0.035 11.22 Binary stars/CVs ...... 37 6 6.17 0.007 0.108 7.38 ...... 205 23 8.91 0.028 0.051 11.03 Exoplanets/SETI ...... 65 4 16.25 0.005 0.018 28.48 Service (surveys, catalogs, calibrations, astrometry) 178 25 7.12 0.030 0.016 24.95 Totals ...... 11,332 836 13.56 1.000 1.000 16.18

2001–2003 than they had in 1990–1993. Possible reasons were seen in some very different data compilations, centered around suggested, and a prediction or two made. We are not aware of individual astronomers rather than facilities (Trimble 1985). any previous survey of papers and citations from radio, mil- We have been assured by a number of colleagues that this limeter, and submillimeter telescopes with which the present is really just a matter of community size. Lots of astronomers data could be compared. working on, say, active galaxies means lots of citations per That is not to say that such a survey could not exist. It would paper. But the numbers in Table 2 strongly suggest that size is currently be very difficult to assemble the set of papers pub- not the whole story. Gamma-ray bursts and exoplanets appear lished in 2011 and cited in 2012–2014, but there is nothing to in very few, but very highly cited, papers, while the largest prevent one of us (or even one of you) from going back and radio subdiscipline, the interstellar medium, consists of papers looking at the radio papers from 1991 and their subsequent cited, on average, less often than the whole field (10.9 vs. 16.2 citation rates. The number of papers would probably be only citations per paper). about 500. 3.4. Distribution by Facility 3.3. Distribution by Subject Matter Table 3, at long last, reveals the numbers of papers, citations, Table 2 shows the numbers of papers and citations to them, and citations per paper for the 36 ground-based radio telescopes divided by subdiscipline, and using the same subject headings (including millimeter and submillimeter facilities), balloon- as in Paper I, except that several topics that appeal to optical borne detectors, and space missions that contributed at least astronomers are so rarely studied in the radio regime that we five papers each (in our equal-credit-to-all-telescopes in a paper merged a few of them in the table. These include star clusters, rubric), plus groups that include the other 44 less productive brown dwarfs, white dwarfs, and all sorts of binary stars. Not telescopes (grouped as “other European” and so forth). The surprisingly, interstellar material, active galaxies, and star for- ordering is, first, interferometers and their component dishes mation are larger presences in the radio literature than in the when used separately, plus other single radio dishes and arrays, optical. second, facilities used primarily for cosmology and study of On average, optical papers are cited more often than radio the cosmic microwave background, and third, millimeter and papers. (The numbers in Table 2 reflect 3 years of citations, submillimeter devices. Each is referred to by the name found not 2 as in Paper I). High-profile topics in one tend to be high- most often in the papers read for this project (frequently a profile in the other (cosmology, gamma-ray bursts, extrasolar- location), occasionally abbreviated to fit in the column. system ), and similarly for some low-profile ones (binary Much can be said about the potential unfairness of such stars, system). Supernovae and their remnants and the numbers. Green Bank (NRAO) was in the process of com- Milky Way garner more citations per paper at optical wave- missioning a new dish to replace the one that had collapsed, lengths than radio, and there are a few other differences. Most and several other facilities were just coming on line, had already of the numbers are not statistically significant in the last digit, fallen from space, or experienced various other indignities. And but the large differences among subjects are real and can been it is probable that HALCA contributed more strength to the

2006 PASP, 118:933–938 RADIO TELESCOPES 937

TABLE 3 tained by countries with a long tradition of radio astronomy, Papers and Citations Attributable to Radio, Millimeter, tend to do best. Second, the VLA dominated world radio as- and Submillimeter Telescopes and Satellites tronomy early in this century by an even wider margin than Facility Citations Papers C/P HST dominated optical astronomy. The VLA was responsible for 22% of the papers published in 2001 and 27% of the tri- Interferometers, Parts Used Separately, and Single Dishes ennium citations, compared to 16% of the papers and 19% of HALCA satellite ...... 26 3.4 7.65 the optical citations for HST. VLBI unspecified ...... 38 5.1 7.45 VLBAϩcomponent dishes ...... 482 38.25 10.01 Another point to be noted is that most of the millimeter and VLA ...... 3003 181.4 16.55 submillimeter facilities rank above average in citations per pa- MERLIN ...... 194 18.6 10.43 per. An exception is the 12 m in Arizona, formerly owned and Australia Telescope Compact Array ...... 525 46.8 11.22 operated by NRAO, then closed down, and then reopened under Parkes ...... 786 38.3 20.52 different management, much of this during the time when data Other AustraliaϩDeep Space Network ...... 94 11.4 8.25 Arecibo ...... 366 28.0 13.07 for 2001 publications would have been being collected. The European VLBI Network ...... 106 12.2 8.69 James Clerk Maxwell Telescope and IRAM facilities are re- Jodrell Bank (several) ...... 112 10.5 10.67 sponsible for a sizable numbers of papers, while US observing Westerbork ...... 181 14.1 12.84 at shorter wavelengths was largely in the hands of universi- Effelsberg ...... 183 21.0 8.71 ties—Caltech (OVRO), the Five College Radio Astronomy Ob- Puschina ...... 24 7.0 3.43 RATAN-600 ...... 6 6.0 1.00 servatory of Massachusetts (FCRAO, recently closed), and the Nanc¸ay ...... 41 6.2 6.62 Berkeley-Illinois-Maryland consortium (BIMA). OVRO and Other European ...... 115 17.4 56.61 BIMA were very nearly equal in both numbers of papers and Giant Metrewave Radio Telescope ...... 40 6.0 6.67 citation rates, support for the wisdom of their ongoing unifi- Ooty ...... 10 6.0 1.67 cation of dishes, budgets, and programs. With the coming of Other Asian ...... 26 9.4 2.77 Green Bank (several) ...... 118 8.9 13.26 ALMA (the Atacama Large Millimeter Array, an international Dominion Radio Astrophysical Observatory ...... 60 8.0 7.50 collaboration), US involvement in this wave band will move Other Western Hemisphere ...... 53 6.3 8.41 back into public hands. Used Primarily for Cosmology and CMB Studies COBE ...... 227 14.6 15.55 4. CONCLUSIONS BOOMERANG ...... 136 5.6 24.29 MAXIMA ...... 456 5.6 81.43 In 2001, 836 papers published in 15 refereed journals re- 3C, 6C, 7C surveys ...... 134 6.8 19.71 ported or analyzed data from radio, submillimeter, and milli- Other cosmological horns, balloons, etc...... 223 12.4 17.98 meter telescopes on the ground, in the air, or in space. These Millimeter and Submillimeter Facilities were cited 11,332 times in 2002–2004 in journals that form SWAS ...... 120 8.3 14.46 part of the Science Citation Index/Web of Science database, JCMT ...... 988 46.9 21.07 for an average of 13.56 citations per paper, or 4.52 citations NRAO 12 m ...... 189 16.5 11.45 per paper per year (a bit smaller than the optical number for IRAM 30 m ...... 467 31.6 14.78 the same periods, 5.40 citations per paper per year; the space IRAM interferometer ...... 212 10.75 19.72 average is 6.42). Caltech Submillimeter Observatory ...... 128 9.4 13.62 Five College Radio Astronomy Observatory ...... 164 10.3 15.92 Some topics included many more highly cited papers than Owens Valley Radio Observatory ...... 282 21.1 13.36 others, cosmology, gamma-ray bursts, and exoplanets being Berkeley-Illinois-Maryland Association ...... 302 23.3 13.02 popular in all wave bands. No one radio paper outweighed all Swedish-ESO Submillimetre Telescope ...... 169 20.0 8.45 the rest, in the way that the HST Key Project determination of Heinrich Hertz Telescope ...... 37 5.0 7.40 the Hubble constant did among the optical papers, but the Very Antarctic submillimeter ...... 40 5.3 7.55 Nagoya 4 m ...... 84 16.1 5.52 Large Array dominated radio astronomy even more thoroughly Nobeyama 45 m ...... 128 19.2 6.62 than the did optical astronomy. No Nobeyama interferometer ...... 34 6.8 5.00 multiwavelength paper went completely uncited, and the multi- Other millimeter/submillimeter ...... 260 18.1 14.36 wavelength averages are a bit higher than those in any one wave band. projects in which it was used than is apparent from giving it Although there seem to be no previous studies of radio as- equal credit with other participating telescopes, because it con- tronomy papers with which this can be compared, it is tempting tributed the longest baselines. Papers and citations have, how- to suggest trends that might appear in the future, based on ever, been apportioned in the same way, so that the relatively optical data and on overviews such as the decadal reports. All low rate of citations per paper for HALCA is real. 4 m class optical telescopes have become less productive since With all due reservations, one can nevertheless conclude the deployment of several 8 m mirrors, and one might expect several things. First, telescopes on well-supported sites, main- ALMA to have a similar effect on smaller short-wavelength

2006 PASP, 118:933–938 938 TRIMBLE & ZAICH facilities. The highly cited topics will probably become more of papers per radio telescope will necessarily come down so and the less-cited topics still more obscure, because of the further. tendency of funding to follow the crowd. We hope to come back in a decade or so and “do the The authors are grateful to Major and Colonel Jim numbers” again, but it is perhaps worth noting now that a single Deshafy of the US Air Force Reserve, who, by remarkable study in which all papers and citations are divided among all chance, brought them together. We are indebted to James Ul- the observing facilities used, no matter what the wavelength, vestad for authorizing, and to NRAO for providing, the page may not have the expected effect. The total numbers of papers charges. The National Radio Astronomy Observatory is a fa- and citations of course stay the same; they are simply more cility of the National Science Foundation, operated under a widely spread. Thus, the total number of papers for each and cooperative agreement by Associated Universities, Inc. Among every telescope ever used in multiwavelength studies will come the colleagues who read and commented on the first draft of down, although citations per paper will not change. Because, this study, special thanks to Richard Hills and Richard Wie- for instance, the 149 radioϩoptical papers make up 18% of lebinski for thoughtful insights and for catching some errors the radio total but only 7% of the optical total, the numbers that had eluded us.

REFERENCES

Freedman, W. L., et al. 2001, ApJ, 553, 47 Trimble, V., Zaich, P., & Bosler, T. 2005, PASP 117, 111 (Paper I) Trimble, V. 1985, QJRAS, 26, 40 ———. 2006, PASP, 118, 651 (Paper III)

2006 PASP, 118:933–938