141 5935 142

- 24

- 26

- 90

- 3 0

- 37

34

3b

17" I 6" 48 4 0 3 1 24 ib 8 0 52 .l4 36 2 8 20 12

Fig. 3 . Short and long period variables in Scorpio-Ophiuchus.

The Ophiuchus-Scorpio group and the sur-

The community of distribution and relationship

Further comment on the distribution of these

rounding region are charted in Fig. 3 .

of some kind are obvious.

variables is unnecessary at present.

Observatorio Nacional Argentino, Cordoba, 1932 July 16.

C. D. Perrine.

Dependence of stellar variability on region of sky. By C. D. Perrzize. It has not been suspected heretofore that the a m o u n t

of variability depended upon the region of sky in which the variable was located, except in so far perhaps as the preference of the 6 Cephei stars for the Milky Way may be interpreted as such. The finding of the preference of the very short periods for the extra-galactic regions and the casual observation that in some regions there were numbers of very small variations and in others an apparent preponderance of larger amplitude suggested further examination.

There are now sufficient stars with known ranges of variability to give confidence in a conclusion drawn from them.

Several facts must be taken into account - the regions must be fairly limited in size and yet contain a sufficient number of stars; a distinction must be made between photographic and visual magnitudes; and the periods should be noted. Only periods less than 90 days were used.

A difference was suspected between the constellations Carina and Sagittarius and they were examined first. The former contained 81 stars with p h o t o g r a p h i c magnitudes sufficiently accurate to serve, 56 of which had periods deter- mined. There are also 6 stars with visual m a g n i t u d e , all with periods.

Sagittarius contained 138 stars with photographic magnitudes, 18 with periods assigned. There were also I I stars with v isua l magnitudes.

The propriety of using stars with unknown periods may be questioned. As the great majority of such stars show small changes of brightness together with their galactic affinities and the greater probability of discovery of short periods, justifies the assumption that the great majority are of periods shorter than 90 days assumed as the upper limit. In order to test the matter, however, the stars with periods were also classified separately.

These show slightly smaller amplitudes as was to be expected, but fully justify the assumption that comparatively few are of large amplitude due to long period. The results are given in the following Table I .

These results, visual as well as photographic, show a larger variation in the Sagittarius than in the Carina region.

The individual values show as much consistency as is to be expected under the circumstances and clearly indicate a diffe- rence between the two regions.

T a b l e I .

S h o r t Per iod V a r i a b i l i t y i n t h e Constel la t ions S a g i t t a r i u s a n d C a r i n a .

~~ I1 Photographic j j Visual Constellation -

No. Of 1 period Stars I No'of Period I Am

Sagittarius 138 1 I rms1 I 1 l 18 j 18do 1.56 I

1 5 1 6.7? 1.44 lip-- 1 Mean 1.60 1.601 1

Carina I 1.14 7.4 I 0.98

1 Mean 1.06

, 26 j ':::4 1 . 2 7

6 i 4.7l)I 1 . 1 7

I 1 0.45 1 1 . 5 Ophiuchus / / 7 , 1.44 1

l ) Rejecting periods over 5od

The numbers of stars with visual determinations are small and by themselves would mean little. But in connection with the much more numerous photographic results, they furnish very satisfactory confirmation. For not only do the visual results show the difference between the two regions, but they show approximately the same relation between visual and photographic results as is known to exist. The ratio usually used is 1.50. The results in Table I give 1.38 and 1.25

respectively for Sagittarius and Carina. As the individual determinations are by many different

observers there seems no reason to suspect any form of syste- matic error affecting the two regions differently. The 6 Cephei stars and Algol stars were not classified separately because of the small numbers in some of the groups. Any difference in the amplitudes of these stars should be neutralized, however, by the fact that there are more Algol stars in the Carina group where the average is smaller than in the Sagittarius group where the amplitude is large.

'43

Die Gesellschaft fur ZeitmeBkunde und Uhrentechnik e. V. hat im vergangenen Jahre den dritten Wettbewerb fur eine wissenschaftliche Arbeit von Wert aus dein Gebiete dcr Zeitmellkunde und Uhrentechnik ausgeschrieben, der init 5ooRM dotiert ist und a u f den in dicser Zcitschrift (245.295) hingewiesen wurde. Ein festes Thenla war nicht vorge-

I44

schrieben, sondern jedcr konnte sich clas Thema, das er bearbeiten will, selbst auswahlen. Es sci daran erinnert, dalJ Arbeiten fur diesen Wettbewerb bis sphtestens 3 1 . Mlrz tl. J. in einer fur den Druck geeigneten Form bei der Ge- sellschaft fur Zeitmenkunde und Uhrentechnik c . V., Berlin SW 68, Neuenhurgerstr. 8 , eingereicht scin mussen.

As a further test the considerable number of very short period stars in the nearby constellation of Ophiuchus were compared with the stars of similar period in Carinn. The few stars of longer period in Ophiuchus were also included. Both these groups, visual as well as photographic, agree satisfactorily with the stars in Sagittarius and differ in conse- quence just as definitely from those of the Carina region.

In this connection may be pointed out the fact of ii

preference which led to the examination of the Ophiuchus stars. In this region is a small, compact and numerous group of 1/2 day stars with comparatively few of longer periods, whereas in the ( ' ~ i n a region just the reverse is true - -- there

are but few stars of ' I 2 day periods but a large number of stars with periods of several days.

There appears thus to be the curious condition that whatever cause produces stellar variability, produces more short periods in the region where the variations are g r e a t e s t . I n other words conditions producing large amplitudes are favorable to the formation of very s h o r t periods and conditions producing smaller amplitudes arc favorable to the production of periods of several days.

'The desirability of a much more extended investigation of this subject including the underlying ciiusc is indicated.

Cordoba, I 93 I Nov. 30. C'. 1). Z't~YYLlIZ.

Zurn Ableben von L. Hufnagel.

I n h a l t zu Nr. 5935. C D P C Y ~ L ~ K . O n thc cause underlying v:triable radial vdocities. i' D PWJVZC. Rclationship Ixtwcen 3 Ccphci type variations of light and vclocity. 137. - - - L' D. P c i w ~ z c . 1)istrilJutlon of thc 3 Ccphci stars in tht . sky 1 3 9 . - C'.D. Pfcn-me. 1)cpendrncc of stellar variability on region of 5ky 141. . - F. K@ziisky. %urn .4l)lrl>cn von L. Zfu/nagr/. 143. - Preisnussc.hrei~t.i~. 143. - G Nrujmvz. P l a n c ~ t c n l ~ c n r i i x ~ i i ~ ~ ~ , 143.

129: -~

. - .- .- ... . . ~~. - Ccschloisen 1931 h h r , 7. Herausgeber: H. K a b o I d . Expedition: Kie l , Moltkestr. 80. Postscheck-Kooto Nr. 6n38 Hamburg 1 1 .

Druck <on C. Sehaidt. Inhabw G o r p Ohem, Kie l .