200 CARNEGIE INSTITUTION OF WASHINGTON. 



Apart from these two major investigations on radial velocities, reference 

 may be made to the following results obtained in this department of work 

 during the year: 



(1) The radial velocities of 192 additional stars have been obtained from 

 three or more spectrograms. 



(2) A special series of observations has been carried out on the stars in 

 the cluster of Prsesepe. In a total of 34 stars observed, 26 are found from 

 their velocities to belong to the moving cluster, 3 do not belong, and 5 

 are spectroscopic binaries. The radial velocity of the cluster as determined 

 from these 26 stars is +33 km. 



(3) Observations of a number of the fainter variables of the cluster type 

 show that the remarkably large dispersion in radial velocity previously found 

 among stars of this class is present in an even greater degree among its fainter 

 members. Two stars of this character, VX Herculis and RZ Lyrse, show 

 radial velocities of —375 and —280 km. respectively, with probably only a 

 moderate variation. 



(4) Several spectroscopic binaries are under investigation by Sanford. For 

 two of these, Lalande 13792 and A. Oe 12584, orbits have been computed and 

 published. Preliminary orbits have been found for four others. From 

 these results and those derived previously, Sanford finds that the evidence 

 indicates shorter periods and smaller eccentricities for dwarf spectroscopic 

 binaries than for giants of the same spectral type. 



(5) Sanford has completed the determination of the radial velocities of 30 

 stars of the R type of spectrum from a total of about 80 spectrograms. All 

 of these have been measured by two different methods, and intercomparisons 

 show that no serious systematic error appears to exist. The range in velocity 

 among these stars is extraordinarily great, one star in the list showing a 

 velocity of —380 km. For this reason, in spite of the comparatively small 

 amount of material, a study of the space-motions of these stars will be of 

 interest in its bearing on the asymmetry of the velocity distribution of stars 

 of rapid motion. 



(6) Spectroscopic observations of both components of the unique double 

 star X Ophiuchi have been secured by Merrill, which lead to a reliable value 

 of +0.3 for the absolute magnitude of the variable component when at 

 maximum of light. The importance of this determination lies in the fact 

 that this component is a typical long-period variable, and that the absolute 

 magnitudes of such objects have been derived hitherto only by statistical 

 methods. The apparent radial velocity of the variable (spectral class M6e) 

 is found from the absorption lines to be —70.6 km. and from the emission 

 lines —83.4 km. The velocity of the other component, a giant star of class 

 KO, is —70.8 km., showing that the absorption lines of the variable yield 

 essentially the true radial motion, while the emission lines at maximum are 

 displaced toward shorter wave-lengths by an unknown cause. A systematic 

 variation in the displacements of the bright lines, depending on the light 

 phase, has been detected. 



(7) Humason has continued the determination of the radial velocities 

 of the stars in the Selected Areas with the Cassegrain spectrographs. Spec- 

 trograms have been obtained of 98 stars, and the velocities of 62 of these have 

 been measured on three or more negatives. 



