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Computing-Tabulating-Recording Company
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Computing-Tabulating-Recording Company
Industry
Business machines
Fate
Renamed
Successor
International Business Machines Corp. (IBM)
Founded
June 16, 1911; 107 years ago (1911-06-16)
Endicott, New York, U.S.[1]
Defunct
1924
Key people
Charles R. Flint (Founder, financier)
George W. Fairchild (Chairman)
Thomas J. Watson Sr. (President 1915-1924)
The Computing-Tabulating-Recording Company (CTR)[2] was a holding company of manufacturers of record-keeping and measuring systems subsequently known as IBM.
In 1911 financier and noted trust organizer, "Father of Trusts", Charles R. Flint amalgamated (via stock acquisition) four companies: The Tabulating Machine Company, International Time Recording Company, Computing Scale Company of America, and the Bundy Manufacturing Company; creating a fifth company - The Computing-Tabulating-Recording Company.[3][4] CTR was located in Endicott, New York [5] The amalgamated companies had 1,300 employees and manufactured a wide range of products, including employee time-keeping systems, weighing scales, automatic meat slicers, and punched card equipment.[6][7]
CTR was renamed International Business Machines (IBM) in 1924.[8]
The individual companies continued to operate using their established names until the businesses were integrated in 1933 and the holding company eliminated.[9][10]
Contents
1 Companies amalgamated
1.1 Tabulating Machine Company
1.2 Computing Scale Company of America
1.3 Bundy Manufacturing Company
1.4 International Time Recording Company
2 Amalgamation
3 Organization and leadership
3.1 Early Watson era
4 Watson's strategies
5 Organizational change and strategies
6 See also
7 Further reading
8 Notes and references
9 External links
Companies amalgamated[edit]
Tabulating Machine Company[edit]
Hollerith's plant in 1893.
Herman Hollerith initially did business under his own name, as The Hollerith Electric Tabulating System, specializing in punched card data processing equipment.[11] In 1896 he incorporated as the Tabulating Machine Company and in 1905 reincorporated as The Tabulating Machine Company.[12] Hollerith's series of patents on tabulating machine technology, first applied for in 1884, drew on his work at the U.S. Census Bureau from 1879 to 82. Hollerith was initially trying to reduce the time and complexity needed to tabulate the 1890 Census. His development of punched cards in 1886 set the industry standard for the next 80 years of tabulating and computing data input.[13]
In 1896 the Tabulating Machine Company leased some machines to a railway company[14] but quickly focused on the challenges of the largest statistical endeavor of its day – the 1900 US Census. After winning the government contract and completing the project, Hollerith was faced with the challenge of sustaining the company in non-Census years. He returned to targeting private businesses both in the United States and abroad, attempting to identify industry applications for his semiautomatic punching, tabulating and sorting machines.[15] Flint bought the business for $2.3 million (of which Hollerith got $1.2 million) in 1911.
Computing Scale Company of America[edit]
The Computing Scale Company of America was a holding company, organized in 1901 and amalgamating as subsidiary companies The Computing Scale Company, Dayton, Ohio; The Moneyweight Scale Company, Chicago, Illinois; The W.F. Simpson Company of Detroit, Michigan; and The Stimpson Computing Scale Company of Elkhart, Indiana.[16] In 1891, Edward Canby and Orange O. Ozias, two businessmen from Dayton, Ohio, purchased the patents for the newly invented computing scale and incorporated the Computing Scale Company for the production of commercial scales.[17][18][19][20]
Bundy Manufacturing Company[edit]
Main article: Bundy Manufacturing Company
Front cover of a January 1920 sales catalog showing clocks, scales and tabulating equipment)
The first time clock was invented on November 20, 1888, by Willard Bundy, a jeweler in Auburn, New York. A year later his brother, Harlow Bundy, organized the Bundy Manufacturing Company,[21] and began mass-producing time clocks.[22]
In 1900, Bundy Manufacturing sold its time recording business to a new company, the International Time Recording Company. Bundy Manufacturing went on to produce adding machines.
In 1906 Harlow Bundy moved his business into a new three-story brick building in Endicott, New York.[23]
International Time Recording Company[edit]
In 1894, J. L. Willard and F. A. Frick of Rochester, New York, formed the Willard & Frick Manufacturing Company as the first time card recorder company in the world.[24]
In 1900 George W. Fairchild, an investor and director of the Bundy Manufacturing Company, led the formation in Jersey City, New Jersey,[25] of the International Time Recording Company (ITR) which consolidated the time recording business of Bundy with the Willard & Frick Manufacturing Co.[26] In 1901, the company was re-incorporated in Binghamton, New York. The same year, it acquired the Chicago Time-Register Co., the first autograph time recorder company in the world, and a manufacturer of key, card and autograph employee time recorders.[27]
In 1906, ITR relocated to Endicott, New York, where it had built a larger factory next to the new building of the Bundy Manufacturing Company. Before the CTR amalgamation, Harlow Bundy would be named ITR's Treasurer and General Manager.[16]
The first dial recorder was invented by Dr. Alexander Dey in 1888, and in 1907 ITR acquired the Del Ray Register Company.[28][29] In 1908, ITR acquired the Syracuse Time Recorder Company, a manufacturer of dial recorders.[30]
ITR's 1935 catalog lists a wide variety of clocks, from industrial timeclocks, recording clocks, and program clocks, to ornamental store-front clocks. It also lists the Series 970 Intercommunicating Telephone System.[31] Since 1907 or earlier ITR had published a magazine, Time, for employees and customers; in 1935 IBM renamed the magazine Think.[32]
Amalgamation[edit]
Charles Ranlett Flint had already created a number of successful consolidations, including creating industrial giant U.S. Rubber
Flint amalgamated the four companies into the new CTR holding company.[33][34][35] CTR had a bonded indebtedness of $6.5 million, three times its current assets, of which $4 million was borrowed from the Guaranty Trust Company.[36] Flint assigned it a value of $17.5 million, while its tangible assets only added up to $1 million. Flint stated that the various manufacturers produced similar but not identical products and that the
..."allied consolidation", instead of being dependent for earnings upon a single industry, would own three separate and distinct lines of business, so that in normal times the interest and sinking funds on its bonds could be earned by any one of these independent lines, while in abnormal times the consolidation would have three chances instead of one to meet its obligations and pay dividends.[37]
CTR's 1911 stock prospectus reported net earnings, from May 1, 1910 to April 30, 1911, of $950,000 for the four companies .[38]
Organization and leadership[edit]
CTR and the four amalgamated companies had 1,300 employees and offices and plants in Endicott and Binghamton, New York; Dayton, Ohio; Detroit, Michigan; Washington, D.C.; and Toronto, Ontario. CTR was located in Endicott.[1] The chairman was George Winthrop Fairchild, who, having been a member of Congress since 1906, was not expected to take an active part in management. When the first president left after just one month, however, Fairchild took over and ran CTR until 1912, when Frank N. Kandolf, formerly CEO of the International Time Recording subsidiary, took over. Flint was a member of the board of CTR (and later IBM) until his retirement in 1930.[7][39][40] Hollerith, then 51, joined the CTR board and served as a consulting engineer until he retired ten years later.[41]
Early Watson era[edit]
Thomas J. Watson
1917 Organizational Chart This style of chart, pyramids dividing into five parts, was required by Patterson. One of the many things Watson brought from NCR to CTR.[42]
Thomas J. Watson Sr., along with 29 other NCR officials, had been convicted in 1913 of various antitrust violations for their roles in a widespread National Cash Register scheme to run used cash register retailers out of business (see NCR Corporation § Expansion).[43] Watson's own extortionate writings were used as evidence against him. That lesson taught Watson to thereafter keep very little in writing. In 1914, having been fired from NCR Corporation and with a prison sentence threatening his future, Thomas J. Watson approached Flint, a leading financier, for assistance in finding a similar job. Despite his apparently perilous situation he was still very clear as to the type of job he wanted. He had already turned down a number of offers. He wanted control of the business for himself, and to be able to earn a share of the profits. Flint offered him CTR. Flint was, as described earlier, a great promoter of trusts and was presumably less worried about Watson's impending jail sentence. The other members of the CTR board were less sanguine, asking who was to run the company while he was in prison. As a result, they only gave him the title of general manager.[44] After Watson had been at CTR for 11 months, the Appeals Court ordered a retrial. Although he refused to sign a Consent Decree, a new trial never took place, and he was duly promoted by the board of CTR to the position of president. Among the many things Watson brought to CTR from NCR was the motto Think.[45]
Watson's strategies[edit]
Surprisingly, in view of his past record at NCR and his later colossal influence on IBM, Watson initially maintained a very low profile (almost tantamount to seeking obscurity) for the next decade until 1924, when the chairman George W. Fairchild died and he finally took over sole control.[46] For the whole of the previous decade, in some ways uncharacteristically, he consistently deferred to Flint, Fairchild and Hollerith.
IBM song books with Think signs in several languages and punched cards.
In the meantime he took personal charge of 400 demoralized and poorly-supervised salesmen. His stated objective was to produce a sales force in the NCR mold, as well as advanced machines that would be superior to any of the competitors' machines. In a series of small meetings he presented his 'competitive proposition' to the sales force. Despite the aggressive-sounding title, right from these beginnings there was as much emphasis on the ethics and philosophies of the business as there was on sales techniques. In particular he stressed sincerity, integrity and loyalty, saying that they should do nothing that could be construed as 'unfair competition' and should conduct themselves in an 'honest, fair and square way' -- something which would be radical even today. Musical events, even IBM songs, were introduced to improve and maintain employee morale.[47]
The other philosophies that motivated CTR and IBM for the next three-quarters of a century were also evident. The company motto was to be 'We sell and deliver service'; CTR was to be in the business of genuinely assisting its customers. Watson strongly believed that when a sale was made both sides came out ahead.
Organizational change and strategies[edit]
CTR was a company with three separate elements:
- Computing Scale interested Watson the least and the largest element of this (Dayton Scale) was eventually sold off in 1933, to Hobart Manufacturing. After the sale the company, to Watson's chagrin, began making money.[48]
- Time Recording was at first the main revenue earner, and was used by Watson as a vehicle for diversification, though none of these was great success.
- The tabulating business most interested Watson, perhaps because it was closest to his NCR experience. This was where he directed much of his attention and by the early 1930s this had indeed become the largest piece of CTR.[49]
In 1920s, while still under Fairchild's domination, Watson focused on achieving a significant degree of growth. Revenue grew from $4.2 million in 1914, when he took over, to the peak of $16 million in 1920. The price of this, however, was a precarious cash position. In 1921, sales fell to $10.6 million and Watson faced a cash-flow crisis. Once again CTR was to be funded, and rescued, by Guaranty Trust. Watson was forced to cut costs across the board, including reducing R & D and laying off employees. He never again allowed his cash position to fall so low. He subsequently maintained a policy of low dividends, high revenues, and careful cost controls. He adopted very conservative accounting principles.[citation needed]
Hollerith, beginning with the 1890 census, had rented his machines so that his company could provide the maintenance necessary to assure reliable operation.[50] Watson recognized other benefits including the idea that renting equipment was inherently more stable, since the income continued when equipment orders would otherwise have dried up. Less obviously, it forced sales personnel, aware that they might lose the rental, to maintain regular contact with customers, thus ensuring — even as early as the 1930s — that customer relationships were well-managed. This approach became central to IBM's activities.
Thereafter, Watson deliberately lagged on the introduction of new products, though but not on research. Even after competitors launched new products he still waited until the market was ripe for large scale development. Watson recognized the importance of sound R&D, appointing James W. Bryce in 1922 to manage this (moving him from its Time Recording Division, which he had joined in 1915). However, Watson continued to be personally involved R&D, not least through his insistence on rigorous standards.
"Watson had never liked the clumsy hyphenated title of the CTR" and chose to replace it with the more expansive title International Business Machines.[51] First as a name for a 1917 Canadian subsidiary, then as a line in advertisements. For example, the McClures magazine, v53, May 1921, ran a full page ad with the following tag at the bottom:
     International Time Recording Company of New York Subsidiary of Computing-Tabulating-Recording Company, New York Makers of International Business Machines

Patterson died in 1922 and Fairchild died December 31, 1924. On February 5, 1924, Watson submitted an application to list International Business Machines (IBM) on the New York stock Exchange, and (the name) C-T-R disappeared[52] Watson began to mold the company in his own image and for the next quarter of a century, until he was 75, took it to new levels of success.[53] He celebrated his new status with the first Quarter Century Club. Even though CTR had only been going for 13 years, he based qualification on the subsidiary companies. The holding company itself disappeared in 1933 after most of the subsidiaries had been merged into one company, IBM.[54]
See also[edit]
History of IBM
History of computing hardware
Time clock
Further reading[edit]
For more on Punched card history, technology, see: Unit record equipment#Further reading
For IBM see: IBM#Further reading and History of IBM#Further reading
Aswad, Ed; Meredith, Suzanne M. (2005). IBM in Endicott. Arcadia.
Engelbourg, Saul (1954). International Business Machines: A Business History (Ph.D.). Columbia University. p. 385. Reprinted by Arno Press, 1976, from the best available copy. Some text is illegible.
IBM Archives: Reference / FAQ / Predecessor Companies.
IBM Archives: CTR product ad (1911).
Notes and references[edit]
^ Jump up to: a b Certificate of Incorporation of Computing-Tabulating-Recording-Co, 14th day of June 1911
Jump up ^ IBM Archives: Computing-Tabulating-Recording Company (1911–1924).
Jump up ^ NY Times June 10, 1911 Tabulating Concerns Unite: Flint & Co. Bring Four Together with $19,000,000 capital
Jump up ^ Flint uses allied consolidation. See Flint, Memories of an Active Life, Putnam's, 1923, p. 312.
Jump up ^ Certificate of Incorporation of Computing-Tabulating-Recording-Co ... Fifth. The location of the principal business office is to be in the Town of Endicott, County of Broome, and State of New York.
Jump up ^ [1]
^ Jump up to: a b Campbell-Kelly, Martin; Aspray, William (2004). Computer: A history of the information machine (2nd ed.). Boulder, Colo.: Westview Press. pp. 37–39. ISBN 978-0-8133-4264-1.
Jump up ^ IBM Archives
Jump up ^ For example, the last page of The Inventory Simplified, published in 1923, stated "The Tabulating Machine Company - Division of - International Business Machines Corporation.
Jump up ^ Rodgers, Williams (1969). Think. Stein and Day. p. 83.
Jump up ^ Austrian, 1982, p. 153.
Jump up ^ Engelbourg, 1954, p. 52.
Jump up ^ Officemuseum.com – early Hollerith history, with good photographs of period equipment
Jump up ^ Austrian, Geoffrey D.; Herman Hollerith: Forgotten Giant of Information Processing Columbia University Press NY NY ISBN 0-231-05146-8, p. 138.
Jump up ^ Brooks, Frederick P.; Iverson, Kenneth E. (1963). Automatic Data Processing. Wiley. p. 94 "semiautomatic".
^ Jump up to: a b Bennett, Frank P.; Company (17 June 1911). United States Investor. 22, Part 2. p. 1298 (26).
Jump up ^ IBM Archives: Computing Scale Company.
Jump up ^ IBM Archives: Computing Scale Company scale.
Jump up ^ IBM Archives: Dayton Computing Scale.
Jump up ^ IBM Archives: Dayton meat choppers.
Jump up ^ "IBM Archives: Bundy Manufacturing Co". www-03.ibm.com. 23 January 2003.
Jump up ^ IBM Archives: George W. Fairchild.
Jump up ^ North Street, Endicott.
Jump up ^ IBM Archives: 1894.
Jump up ^ "American Machinist". 23 (14). American Machinist Press. 19 April 1900: 45.
Jump up ^ IBM Archives: 1900.
Jump up ^ IBM Archives: 1901.
Jump up ^ IBM Archives: 1880.
Jump up ^ IBM Archives: 1907.
Jump up ^ IBM Archives: 1908.
Jump up ^ "International Time Recording Catalog, 1935" (PDF).
Jump up ^ Aswad (2005) p. 18.
Jump up ^ Flint, Charles R. (1923). Memories of an Active Life: Men, and Ships, and Sealing Wax. G.P. Putnam's Sons. p. 312.
Jump up ^ Since the 1960s or earlier, IBM has described its formation as a merger of three companies: The Tabulating Machine Company (1880s origin in Washington, DC), the International Time Recording Company (ITR; 1900, Endicott), and the Computing Scale Company of America (1901, Dayton, Ohio). (Austrian, 1982, p. 312.) (Belden, 1961) (IBM Archives). However there was no merger, it was an amalgamation, and an amalgamation of four, not three, companies. The 1911 CTR stock prospectus states that the Bundy Manufacturing Company was also included. While ITR had acquired its time recording business in 1900, Bundy had remained a separate entity producing an adding machine and other wares (see Early Office Museum)
Jump up ^ "IBM Archives: Computing-Tabulating-Recording Company (1911-1924)".
Jump up ^ Flint (1923), p. 312-313.
Jump up ^ Flint (1923), p. 312.
Jump up ^ Bennett, Frank P.; Company (17 June 1911). United States Investor. 22, Part 2. p. 1298 (26).
Jump up ^ "IBM Archives: Charles R. Flint".
Jump up ^ IBM Archives: 1910s.
Jump up ^ O'Connor, J.J.; Robertson, E.F. "Herman Hollerith". The MacTutor History of Mathematics Archive. School of Mathematics and Statistics, University of St Andrews, Scotland. Retrieved 2 Feb 2014.
Jump up ^ Crowther, Samuel (undated). John H. Paterson - The Romance of Business, Geoffrey Bliss
Jump up ^ Austrian, 1982, p. 329.
Jump up ^ IBM Archives: Thomas J. Watson, Sr. CTR's general manager, in 1914.
Jump up ^ IBM Archives: Thomas Watson Comments on Think.
Jump up ^ IBM Archives: Thomas Watson & George Fairchild.
Jump up ^ IBM Archives: IBM Music On a happy note.
Jump up ^ Pugh, Emerson W., Building IBM, MIT, 1995, p. 28.
Jump up ^ Belden, 1962, p. 107.
Jump up ^ Austrian, G.D. (1982). Herman Hollerith: The Forgotten Giant of Information Processing. Columbia. p. 53. ISBN 0-231-05146-8.
Jump up ^ Belden, 1962, p. 125.
Jump up ^ Maney, Kevin (2003) The Maverick and His Machine, Wiley, p. 89.
Jump up ^ Rodgers, Think, p. 82-83
Jump up ^ Rodgers, Think, p. 83.
External links[edit]
IBM Archives: History of the Time Equipment Division and its Products
Early Office Museum: Punched Card Tabulating Machines
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RR Lyrae variable
From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is about the star type. For the prototype of the star type, see RR Lyrae.
The RR Lyrae variable stars fall in a particular area on a Hertzsprung–Russell diagram of color versus brightness.
RR Lyrae variables are periodic variable stars, commonly found in globular clusters. They are used as standard candles to measure (extra)galactic distances, as a part of the cosmic distance ladder. This class of variable star is named after the prototype and brightest example, RR Lyrae.
RR Lyraes are pulsating horizontal branch aging stars of spectral class A or F, with a mass of around half the Sun's. They are thought to have previously shed mass during the Red-giant branch phase, and consequently, they were once stars with similar or slightly less mass than the Sun, around 0.8 solar masses.
The period of pulsation and absolute magnitude of RR Lyraes makes them good standard candles for relatively nearby targets, especially within the Milky Way and Local Group. Beyond the Milky Way they are difficult to detect due to their low luminosity. They are extensively used in globular cluster studies, and also used to study chemical properties of older stars.
Contents
[hide]
1 Discovery and recognition
2 Classification
3 Distribution
4 Properties
5 Period-luminosity relationships
6 Recent developments
7 References
8 External links
Discovery and recognition[edit]
H-R diagram for globular cluster M5, with the horizontal branch marked in yellow and known RR Lyrae stars in green
In surveys of globular clusters, these "cluster-type" variables were being rapidly identified in the mid-1890s, especially by E. C. Pickering.
Probably the first star of definitely RR Lyrae type found outside a cluster was U Leporis, discovered by J. Kapteyn in 1890.
The prototype star RR Lyrae was discovered prior to 1899 by Williamina Fleming, and reported by Pickering in 1900 as "indistinguishable from cluster-type variables".
From 1915 to the 1930s, the RR Lyraes became increasingly accepted as a class of star distinct from the classical Cepheids, due to their shorter periods, differing locations within the galaxy, and chemical differences. RR Lyrae variables are metal-poor, Population II stars.[1]
RR Lyraes have proven difficult to observe in external galaxies because of their intrinsic faintness. (In fact, Walter Baade's failure to find them in the Andromeda galaxy led him to suspect that the galaxy was much farther away than predicted, to reconsider the calibration of Cepheid variables, and to propose the concept of stellar populations.[1]) Using the Canada-France-Hawaii Telescope in the 1980s, Pritchet & van den Bergh found RR Lyraes in Andromeda's galactic halo[2] and, more recently, in its globular clusters.[3]
Classification[edit]
The RR Lyrae stars are conventionally divided into three main types,[1] following classification by S.I. Bailey based on the shape of the stars' brightness curves:
RRab variables are the most common, making up 91% of all observed RR Lyrae, and display the steep rises in brightness typical of RR Lyrae
RRc are less common, making up 9% of observed RR Lyrae, and have shorter periods and more sinusoidal variation
RRd are rare, making up between <1% and 30%[4] of RR Lyrae in a system, and are double-mode pulsators, unlike RRab and RRc
Distribution[edit]
RR Lyrae stars were formerly called "cluster variables" because of their strong (but not exclusive) association with globular clusters; conversely, over 80% of all variables known in globular clusters are RR Lyraes.[5] RR Lyrae stars are found at all galactic latitudes, as opposed to classical Cepheids, which are strongly associated with the galactic plane.
Several times as many RR Lyraes are known as all Cepheids combined; in the 1980s, about 1900 were known in globular clusters. Some estimates have about 85000 in the Milky Way.[1]
Though binary star systems are common for typical stars, RR Lyrae are very rarely observed in pairs.[6]
Properties[edit]
RR Lyrae stars pulse in a manner similar to Cepheid variables, but the nature and histories of these stars is thought to be rather different. Like all variables on the Cepheid instability strip, pulsations are caused by the κ-mechanism, when the opacity of ionised helium varies with its temperature.
RR Lyraes are old, relatively low mass, Population II stars, in common with W Virginis and BL Herculis variables, the type II Cepheids. Classical Cepheid variables are higher mass population I stars. RR Lyrae variables are much more common than Cepheids, but also much less luminous. The average absolute magnitude of an RR Lyrae star is about +0.75, only 40 or 50 times brighter than our Sun.[7] Their period is shorter, typically less than one day, sometimes ranging down to seven hours. Some RRab stars, including RR Lyrae itself, exhibit the Blazhko effect in which there is a conspicuous phase and amplitude modulation.[8]
Period-luminosity relationships[edit]
Unlike Cepheid variables, RR Lyrae variables do not follow a strict period-luminosity relationship at visual wavelengths, although they do in the infrared K band.[9] They are normally analysed using a period-colour-relationship, for example using a Wesenheit function. In this way, they can be used as standard candles for distance measurements although there are difficulties with the effects of metallicity, faintness, and blending. The effect of blending can impact RR Lyrae variables sampled near the cores of globular clusters, which are so dense that in low-resolution observations multiple (unresolved) stars may appear as a single target. Thus the brightness measured for that seemingly single star (e.g., an RR Lyrae variable) is erroneously too bright, given those unresolved stars contributed to the brightness determined. Consequently, the computed distance is wrong, and certain researchers have argued that the blending effect can introduce a systematic uncertainty into the cosmic distance ladder, and may bias the estimated age of the Universe and the Hubble constant.[10][11][12]
Recent developments[edit]
The Hubble Space Telescope has identified several RR Lyrae candidates in globular clusters of the Andromeda galaxy[13] and has measured the distance to the prototype star RR Lyrae.[14]
The Kepler space telescope provided extended coverage of a single field with accurate photometric data. RR Lyrae itself was in Kepler field of view.[15]
The Gaia mission is expected to greatly improve knowledge of RR Lyraes by providing homogeneous spectrographic information of a large population of such stars.[16]
References[edit]
^ Jump up to: a b c d Smith, Horace A., RR Lyrae Stars, Cambridge (2004)
Jump up ^ Pritchet, Christopher J.; Van Den Bergh, Sidney (1987). "Observations of RR Lyrae stars in the halo of M31". Astrophysical Journal. 316: 517. Bibcode:1987ApJ...316..517P. doi:10.1086/165223.
Jump up ^ Clementini, G.; Federici, L.; Corsi, C.; Cacciari, C.; Bellazzini, M.; Smith, H. A. (2001). "RR Lyrae Variables in the Globular Clusters of M31: A First Detection of Likely Candidates". The Astrophysical Journal. 559 (2): L109. arXiv:astro-ph/0108418  . Bibcode:2001ApJ...559L.109C. doi:10.1086/323973.
Jump up ^ Christensen-Dalsgaard, J.; Balona, L. A.; Garrido, R.; Suárez, J.C. (Oct 20, 2012). "Stellar Pulsations: Impact of New Instrumentation and New Insights". Astrophysics and Space Science Proceedings. ISBN 9783642296307. Retrieved 17 October 2014.
Jump up ^ Clement, Christine M.; Muzzin, Adam; Dufton, Quentin; Ponnampalam, Thivya; Wang, John; Burford, Jay; Richardson, Alan; Rosebery, Tara; Rowe, Jason; Hogg, Helen Sawyer (2001). "Variable Stars in Galactic Globular Clusters". The Astronomical Journal. 122 (5): 2587. arXiv:astro-ph/0108024  . Bibcode:2001AJ....122.2587C. doi:10.1086/323719.
Jump up ^ Hajdu, G.; Catelan, M.; Jurcsik, J.; Dékány, I.; Drake, A.J.; Marquette, B. (2015). "New RR Lyrae variables in binary systems". Monthly Notices of the Royal Astronomical Society. 449 (1): L113–L117. arXiv:1502.01318  . Bibcode:2015MNRAS.449L.113H. doi:10.1093/mnrasl/slv024.
Jump up ^ Layden, A. C.; Hanson, Robert B.; Hawley, Suzanne L.; Klemola, Arnold R.; Hanley, Christopher J. (August 1996). "The Absolute Magnitude and Kinematics of RR Lyrae Stars via Statistical Parallax". Astron. J. 112: 2110–2131. arXiv:astro-ph/9608108  . Bibcode:1996AJ....112.2110L. doi:10.1086/118167.
Jump up ^ Szabó, R.; Kolláth, Z.; Molnár, L.; Kolenberg, K.; Kurtz, D. W.; Bryson, S. T.; Benkő, J. M.; Christensen-Dalsgaard, J.; Kjeldsen, H.; Borucki, W. J.; Koch, D.; Twicken, J. D.; Chadid, M.; Di Criscienzo, M.; Jeon, Y.-B.; Moskalik, P.; Nemec, J. M.; Nuspl, J. (2010). "Does Kepler unveil the mystery of the Blazhko effect? First detection of period doubling in Kepler Blazhko RR Lyrae stars". Monthly Notices of the Royal Astronomical Society. 409 (3): 1244. arXiv:1007.3404  . Bibcode:2010MNRAS.409.1244S. doi:10.1111/j.1365-2966.2010.17386.x.
Jump up ^ Catelan, M.; Pritzl, Barton J.; Smith, Horace A. (2004). "The RR Lyrae Period-Luminosity Relation. I. Theoretical Calibration". The Astrophysical Journal Supplement Series. 154 (2): 633. arXiv:astro-ph/0406067  . Bibcode:2004ApJS..154..633C. doi:10.1086/422916.
Jump up ^ Majaess, D.; Turner, D.; Gieren, W.; Lane, D. (2012). "The Impact of Contaminated RR Lyrae/Globular Cluster Photometry on the Distance Scale". The Astrophysical Journal Letters. 752: L10. arXiv:1205.0255  . Bibcode:2012ApJ...752L..10M. doi:10.1088/2041-8205/752/1/L10.
Jump up ^ Lee, Jae-Woo; López-Morales, Mercedes; Hong, Kyeongsoo; Kang, Young-Woon; Pohl, Brian L.; Walker, Alistair (2014). "Toward a Better Understanding of the Distance Scale from RR Lyrae Variable Stars: A Case Study for the Inner Halo Globular Cluster NGC 6723". The Astrophysical Journal Supplement. 210: 6. arXiv:1311.2054  . Bibcode:2014ApJS..210....6L. doi:10.1088/0067-0049/210/1/6.
Jump up ^ Neeley, J. R.; Marengo, M.; Bono, G.; Braga, V. F.; Dall'Ora, M.; Stetson, P. B.; Buonanno, R.; Ferraro, I.; Freedman, W. L.; Iannicola, G.; Madore, B. F.; Matsunaga, N.; Monson, A.; Persson, S. E.; Scowcroft, V.; Seibert, M. (2015). "On the Distance of the Globular Cluster M4 (NGC 6121) Using RR Lyrae Stars. II. Mid-infrared Period-luminosity Relations". The Astrophysical Journal. 808: 11. arXiv:1505.07858  . Bibcode:2015ApJ...808...11N. doi:10.1088/0004-637X/808/1/11.
Jump up ^ Clementini, G.; Federici, L.; Corsi, C.; Cacciari, C.; Bellazzini, M.; Smith, H. A. (2001). "RR Lyrae Variables in the Globular Clusters of M31: A First Detection of Likely Candidates". The Astrophysical Journal. 559 (2): L109. arXiv:astro-ph/0108418  . Bibcode:2001ApJ...559L.109C. doi:10.1086/323973.
Jump up ^ Benedict, G. Fritz; et al. (January 2002). "Astrometry with the Hubble Space Telescope: A Parallax of the Fundamental Distance Calibrator RR Lyrae". The Astronomical Journal. 123 (1): 473–484. arXiv:astro-ph/0110271  . Bibcode:2002AJ....123..473B. doi:10.1086/338087.
Jump up ^ Kinemuchi, Karen (2011). "RR Lyrae Research with the Kepler Mission". RR Lyrae Stars: 74. arXiv:1107.0297  . Bibcode:2011rrls.conf...74K.
Jump up ^ Bono, G. (2003). "The Cepheid and RR Lyrae instability strip with GAIA". GAIA Spectroscopy: Science and Technology. 298: 245. Bibcode:2003ASPC..298..245B.
External links[edit]
APOD M3: Inconstant Star Cluster four-frame animation of RR Lyrae variables in globular cluster M3
Animation of RR Lyrae-Variables in globular cluster M15
Animation with the variable stars RR Lyrae in the center area of the globular cluster M15
RR Lyrae stars
AAVSO Variable Star of the Season - RR Lyrae
OGLE Atlas of Variable Star Light Curves - RR Lyrae stars
[hide]
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