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Post common envelope binaries from SDSS. IV, SDSS J121258.25–012310.1, a new eclipsing system
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Gomez-Moran, A. Nebot, Schwope, A. D. (Axel D.), Schreiber, Matthias R., Gaensicke, B. T. (Boris T.), Pyrzas, S., Schwarz, R. (Robert), Southworth, J. (John), Kohnert, J., Vogel, J., Krumpe, M. and Rodriguez-Gil, P. (2009) Post common envelope binaries from SDSS. IV, SDSS J121258.25–012310.1, a new eclipsing system. Astronomy & Astrophysics, Vol.495 (No.2). pp. 561-569. doi:10.1051/0004-6361:200811244 ISSN 0004-6361.
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Official URL: http://dx.doi.org/10.1051/0004-6361:200811244
Abstract
From optical photometry we show that SDSS J121258.25–012310.1 is a new eclipsing, post common-envelope binary with an orbital period of 8.06 h and an eclipse length of 23 min. We observed the object over 11 nights in different bands and determined the ephemeris of the eclipse to HJDmid = 2 454 104.7086(2) + 0.3358706(5) × E, where numbers in parenthesis indicate the uncertainties in the last digit. The depth of the eclipse is 2.85 ± 0.17 mag in the V band, 1.82 ± 0.08 mag in the R band and 0.52 ± 0.02 mag in the
I band. From spectroscopic observations we measured the semi-amplitude of the radial velocity K2 = 181±3 kms−1 for the secondary star. The stellar and binary parameters of the system were constrained from a) fitting the SDSS composite spectrum of the binary,b) using a K-band luminosty-mass relation for the secondary star, and c) from detailed analyses of the eclipse light curve. The white
dwarf has an effective temperature of 17 700±300 K, and its surface gravity is log g = 7.53±0.2. We estimate that the spectral type of the red dwarf is M4±1 and the distance to the system is 230±20 parsec. The mass of the secondary star is estimated to be in the range Msec = 0.26−0.29 M , while the mass of the white dwarf is most likely Mwd = 0.46−0.48 M. From an empirical mass-radius relation we estimate the radius of the red dwarf to be in the range 0.28−0.31 R , whereas we get Rwd = 0.016−0.018 R from a theoretical
mass-radius realation. Finally we discuss the spectral energy distribution and the likely evolutionary state of SDSS1212–0123.
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