Lichtkurve und Dimensionsbestimmung des Bedeckungssystems W Delphini

Abstract

Cuiiiplete light curves in B and V of this semi-detached system observed 1964 in Sicily are given. The primary minimum has been found to be strongly asymmetric whilst i t was symmetric in the years near 19.I t is shown that a gas stream suggested already by STRUVE from spectroscopic obscrvations may account for the photometric peculiarities like the observed ones, if the enlightening of the bright component by particles of the gas stream hitting this star will be considered. From the light curves photometric solutions arc calculated and compared with earlier ones. It is shown that the effect of dissimilarity of the shapes of the components may strongly influence the calculated value of the ratio of radii.

UBV photometry of the ring in SW Cygni

“…The protuberance might furthermore be a common occurrence in Algollike binaries. The photometric peculiarities manifested in the light curves of U Cephei (Miczaika 1953) and W Delphini (Walter 1970), to mention two examples, are remarkably similar to those in the B and V light curves of SW Cyg: one sees the depressed descending branch, the gradual increase in brightness from midprimary eclipse to third contact, and the dips outside eclipse. Moreover, Miczaika has succeeded in representing the asymmetries in his blue and yellow light curves of U Cep with a model which also has a protuberance situated on the leading hemisphere of the hot star.…”

“…Kopal (1959) has claimed that the subgiant does not fill its lobe because the mass ratio required for the contact configuration implies a mass for the hot star which violates the mass-luminosity relation for main-sequence stars, in the sense that the mass is too large. But recently Walter (1971) has argued that the amplitude of the radial velocity curve is probably enlarged by the action of the gas stream and that hence the value of the mass function determined by Struve (1946) of q = 0.25 to the mass ratio.…”

“…Unfortunately Struve's spectrograms of SW Cyg did not reach very far into the ultraviolet, so except for Hß and Hô the emission from the envelope has not been observed spectroscopically. Walter (1971) explained the asymmetries, etc., in his light curve of SW Cyg in terms of scattering by the gas stream. We find his data can be interpreted in an alternate way: in terms of our envelope-protuberance model.…”

“…With the 1969 data, which did not cover the falling branch, we used the tracing paper method. In order to avoid the asymmetry, apparent in Figure 1 of Walter (1971), we have made the comparison at a light level a few tenths of a magnitude above minimum. The last time was determined by the observers at Hamburg and kindly communicated to us by Herczeg (1972) in advance of publication.…”

“…It is understood now that this emission is produced by circumstellar matter in the binary system. Recently Walter (1971) has published an excellent light curve in B and V which reveals various asymmetries and other photometric complications.…”