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SDSSJ212531.92-010745.9 - the first definite PG1159 close binary system

T. Nagel·S. Schuh·D. -J. Kusterer·T. Stahn·S. D. Hügelmeyer·S. Dreizler·B. T. Gänsicke·M. R. Schreiber
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Abstract

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.

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T. Nagel, S. Schuh, D. -J. Kusterer, T. Stahn, S. D. Hügelmeyer, S. Dreizler, B. T. Gänsicke, M. R. Schreiber. 2006-01-23. SDSSJ212531.92-010745.9 - the first definite PG1159 close binary system. https://doi.org/10.1051/0004-6361%3A200600009

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