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The archival spectrum of SDSSJ212531.92-010745.9 shows not only the typical signature of a PG1159 star, but also indicates the presence of a companion. Our aim was the proof of the binary nature ofthis object and the determination of its orbital period.We performed time-series photometry of SDSSJ212531.92-010745.9. We observed the object during 10 nights, spread over one month, with the Tuebingen 80cm and the Goettingen 50cm telescopes. We fitted the observed light curve with a sine and simulated the light curve of this system with the nightfall program. Furthermore, we compared the spectrum of SDSSJ212531.92-010745.9 with NLTE models, the results of which also constrain the light curve solution. An orbital period of 6.95616(33)h with an amplitude of 0.354(3)mag is derived from our observations. A pulsation period could not be detected. For the PG1159 star we found, as preliminary results from comparison with our NLTE models, Teff about 90000K, log g about 7.60, and the abundance ratio C/He = 0.05 by number fraction. For the companion we obtained with a mean radius of 0.4 +/- 0.1 Rsol, a mass of 0.4 +/- 0.1 Msol, and a temperature of 8200K on the irradiated side, good agreement between the observed light curve and the nightfall simulation, but we do not regard those values as final.
Methods to measure masses of PG1159 stars in order to test evolutionary scenarios are currently based on spectroscopic masses or asteroseismological mass determinations. One recently discovered PG1159 star in a close binary system may finally allow t
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BD And is a fairly bright (V = 10.8), active and close (P = 0.9258 days) eclipsing binary. The cyclic variability of the apparent orbital period as well as third light in the light curves indicate the presence of an additional late-type component. Th
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