Nagel, T., Schuh, S., Kusterer, D.-J., Stahn, T., Hügelmeyer, S. D., Dreizler, S., Gänsicke, B. T. (Boris T.) and Schreiber, Matthias R.. (2006) SDSS J212531.92–010745.9 : the first definite PG 1159 close binary system. Astronomy & Astrophysics, Vol.448 (No.2). L25-L28. ISSN 0004-6361

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Abstract

Aims. The archival spectrum of SDSS J212531.92−010745.9 shows not only the typical signature of a PG 1159 star, but also indicates the presence of a companion. Our aim was the proof of the binary nature of this object and the determination of its orbital period. Methods. We performed time-series photometry of SDSS J212531.92−010745.9. We observed the object during 10 nights, spread over one month, with the Tübingen 80 cm and the Göttingen 50 cm 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 SDSS J212531.92−010745.9 with NLTE models, the results of which also constrain the light curve solution. Results. 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 PG 1159 star we found, as preliminary results from comparison with our NLTE models, T eff ∼ 90 000 K, log g ∼ 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 R, a mass of 0.4 ± 0.1 M, and a temperature of 8200 K on the irradiated side, good agreement between the observed light curve and the nightfall simulation, but we do not regard those values as final.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Double stars, White dwarf stars, Asymptotic giant branch stars
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Date:	March 2006
Volume:	Vol.448
Number:	No.2
Page Range:	L25-L28
Identification Number:	10.1051/0004-6361:200600009
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	Particle Physics and Astronomy Research Council (Great Britain) (PPARC)
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URI:	http://wrap.warwick.ac.uk/id/eprint/3569

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