to 



Walter Gyllenberg 



In other cases I have hesitated about entering observations of this kind in the cata- 

 logue, in particular as in many cases the observations show such an irregularity 

 that the estimation of the velocity of the centre of mass is quite hopeless. 



For several of those stars with variable radial velocity the observations are how- 

 ever numerous and so arranged that the amplitude comes forth with sufficient clear- 

 ness to give an acceptable value of the velocity of the binary system. In other 

 cases the stars have so small an amplitude, that a direct determination of the velo- 

 city of the centre of mass will be affected only by a small error. The velocities 

 were for these stars obtained by taking a mean between the highest and lowest 

 velocity observed. 



7. The stars for which in this manner it is possible, though with some un- 

 certainty, to obtain a value of the velocity of the centre of mass are all entered in 

 the catalogue. For all those stars I have however marked out the variation in 

 velocity and the uncertainty in the determination. There are in all 65 stars of 

 types B and A, having roughly determined velocities. These stars are all in- 

 cluded in the determination of the apex, but when the second moments are com- 

 puted 1 have rejected them, because their large errors may too much influence 

 the results. 



Doubtless there are amongst the stars noted to have constant velocities many 

 that are in reality variables and amongst them many which have probably very 

 large or very short periods. The observations obtainable are all made during the 

 last ten years. Most of them are observed during a very short time and for several 

 stars the velocities are computed from only a small number of observations. 



The catalogue contains no nebulae, but 5 stars of the spectral type Oe are included. 



For each star a card was prepared containing: the name or signification of 

 the star, its coordinates for 1900.0, its radial velocity and the proper motions in 

 right ascension and declination, the latter being taken from Boss' Preliminary cata- 

 logue. For the stars not found in this catalogue the proper motions were taken 

 from other sources. 



On the cards the spectral types and the magnitudes taken from the Revised 

 Harvard Photometry Annals, H. C. 0. No. 50 were also noted. 



The velocity in right ascension and declination are expressed in seconds of arc, 

 but concerning the velocity in the line of sight, I have given up the usual unity 

 — km per sec. — and accepted unities more convenient in Stellar Astronomy, 

 Siriorneter and Stellar year. These units, introduced by Charlier in his lectures, 

 have the following definitions: 



One Siriometer (Sm) = 10 6 the mean distance of the earth from the sun. 

 One Stellar year (St) = 10 6 usual years. 



The relations for transforming into the new units are the following: 

 1 km per sec. = O.2111 Sm per St. 

 1 Sm per St. = 4.7375 km per sec. 



