162 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1963 



Cepheids in the Large Magellanic Cloud, in red globular clusters. A 

 period-luminosity relation for these Cepheids has been established. 

 This research is helpful in determining the extragalactic distance 

 scale. 



Six of the Baker-Nunn cameras have been used since 1960 to photo- 

 graph flare stars in conjunction with radio-frequency measurements of 

 their radio emissions.^ The cooperating radio observatories are Jod- 

 rell Bank Experimental Station in England and the Commonwealth 

 Scientific and Industrial Research Organization at Sydney, Australia. 

 Leonard Solomon devised the photographic procedures used. The 

 one major flare observed this year correlates in time with a major burst 

 detected in the radio spectrum at Sydney. If these combined obser- 

 vations are significantly correlated, as they appear to be, they consti- 

 tute the first observations of radio energy from "normal" stellar 

 objects. Many minor flares (from previous years) correlate with 

 small bursts observed at Jodrell Bank. 



In collaboration with Prof. William Liller of Harvard, Dr. Gold- 

 berg has begun an observing program designed to search for evidence 

 of cyclic stellar activity similar to that connected with the solar sun- 

 spot cycle. They will conduct the search by monitoring the intensities 

 of the H and K emission lines of ionized calcium in the spectra of late- 

 type stars. They will look for both short-term changes, such as may 

 be produced by flares, and long-term cyclic variations. 



A star catalog ^ of gi'eat value to many astronomical enterprises has 

 been completed under the direction of Dr. Vies, Mr. Solomon, and Mrs. 

 Katherine Haramundanis. Initiated in 1959 under the Satellite 

 Tracking Program, the SAO Star Catalog was conceived as the com- 

 pilation of a large number of fundamental and differential catalogs 

 to cover the sky in a standard coordinate system. The project used 

 about 40 catalogs, providing data on approximately a quarter of a 

 million stars. Preparation of the Star Catalog involved investigations 

 of the details of the coordinate system and derivation of proper mo- 

 tions of each catalog. Comparisons of several catalogs were also 

 made in sky areas where the catalogs used did not provide adequate 

 information, usually for proper motions. The complete catalog is 

 stored on magnetic tape, while the publication of a book form is prog- 

 ressing. A set of star charts is to be produced from the Catalog in 

 Lambert-conformal projection, probably at two different scales. 



Stellar theory. — Theoretical studies of stellar atmospheres^" con- 

 tinued in several directions under Dr. IVliitney's supervision. Ex- 

 tensive calculations were performed concerning the structure of stellar 

 convection zones and the nature of the perturbations they produce in 

 stellar atmospheres. Investigations of the structure of shock fronts in 



See footnotes on p. 164. 



