60r6

Note on SSCygni Variables.

Wie mir die I. G. Farbenindustrie Aktiengesellschaft mitgeteilt hat, ist fur die Agfa Superpanplatte von der Emnl- sion F I 123 ab die Sensibilisierung geandert worden. Die neue Sensibilisierung hat den Charakter der in meinem Aufsatz als Vcrsuchsemulsion bezeichneten Plattensorte Pan 1494. Die Superpanplatte hat von der genannten Eyulsionsnummer ab

Studying some problems of stellar variability I had a chance to look over critically the existing data on the variables usually quoted as belonging to SS Cygni (U Geminorpm) group. As a by-product of this work a revised list of these variables was compiled, which may be of use to thosc inte- rested in these peculiar objects. Only undoubtful SS Cygni variables are included in this list. There arc 1 2 more objects assigned to SS Cygni group in the recent Prager's Catalogue. probably sqme of them really belong to this type. Only 5 vad- ables of the list are under permanent observations, our infor- mation on the others being rather unsatisfactory.

eine hohere Allgemeinempfindlichkeit und geringere Grun- lucke, reicht aber nicht mehr so weit in den roten Spektral- bereich hinein. Fur die Aufnahme der H,-Linie ist die Super- panplatte infolgedessen jetzt kaum noch brauchbar.

Kiel, 7934 MEirZ ~ J. Sto66e.

RX And UV Per T Z o SS Aur CZ Ori AW Getn U ))

SU UMa Z Cam X Leo TW Vir AY Lyh

UU Aql

RU Peg

EY CYg

ss CYg

L B

- 21 - 4

+ I 5 '+ I + 21 + 24 + 34 + 33 + 46 + 55 + I 7

-

+ 2 - 20 - 8 - 36

Max.

1om6 I2:4 12.4 10. j 11.8 13.0 9.3 11.5 10.6

11.8 12.5

12.0

11.0

11.0

8.4 10.2

2m8 >3.6

2.9 4.2 4.4

>4.2 5.3 3.9 2.6 3.1

>q.o >2.0

4.5 5.8 3.7 2.9

- Mean :ycle C _- 14d

64

= 0 7

23 24

22

104

0.59

0.14

0.13 0.17 0.52

0.23

0.33

Some interesting conclusions can be drawn from this list Though every SS Cygni variable exhibits characteristics of its own (Z Cam. phenomenon, perturbed cycles, the amount of regularity in the succession of sharp and flat maxima), it is difficult to find such a division into Mira like and 6 Cephei like variables as it was suggested by some authors.

The last column kontains the values of TIC the ratio of the duration of the outburst to that of the mean cycle, as calculated by L.jaccAiu (Pub]. Bologna Obseivatory 2, 1929)

2 5 6

for those variables for which rt definite mean cycle can be determined. I f one compares the TIC values with the maxi- mum ranges A an undoubtful correlation between both variates can be found, small values of TIC corresponding to large A . This correlation is not contradicted by the variables, for which only the lower limit of C is known. I t appears as if the physical causes, which are responsible for the variability, require more time (in parts of the mean cycle) to rpreparec more violent outbursts. This remark can have some bearing on Nova problem. It can be shown that the Nova like variable T Pyxidis, which strickingly resembles SS Cygni, roughly fit the above correlation between the range and TIC. If classical Novae obey this correlation, their mean cycle should be longer than 300 years.

The apparent distribution of SS Cygni variables is rather remarkable. Our revised list supports early F. de Roy's intimation to the effect that SS Cygni variables contrary to Ndvat tend to avoid the hemisphere containing galactic centre, preferring the anticentre hemisphere, The distribution in galactic latitudes is very significant. Only five out of 16 vari- ables are located in latitudes (IO', the variables being more numerous in the higher latitudes. On the other hand only two variables of the group are brighter than I O ~ at maximum. This seems to indicate that these variables cannot be luminous, their absolute magnitude at maximum hardly exceeding oM. At minimum light they are almost certainly dwarfish. There are some reasons to think that their normal luminosities are rather low. This remark is especially significant with respect to the brighter variables (SS Aurigae, SS Cygni and U Gemi- norum) which show early spectra with broad lines and are whitish at maxima as well as at minima.

Though the questions of terminology are of minor importance, it seems proper to point out that some authors call this group after U Geminorum, and others after SS Cygni. From historical point of view the former variable has some privilege. However if no other reasons can be offered, U Gemi- norum, as the most regular of these irregular variables, seems to be less representative than SS Cygni.

Poulkovo, 1934 Jan. 5. B. P. Geraszmovzt

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241. - K. ReinmutL, M. MiindZer. Photographische Aufnahmen von Kleinen Planeten in Heidelberg. 251. - G. R. Micaaiku. Beobachtungen von X Persei auf Babelsberger uberwachungsplatten. 253. - R. Pruger. Berichtigungen. 253. - B. P. Geraszmovzc'. Note on SS Cygni Variables. 255. - -7. Stobbe. Bemerkung. 255. - Anzeige. 255. . _ _ _ ~ ... ~

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