科研之友
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摘要
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 HJD(mid) = 2 454 104.7086(2) 0.3358706(5) x 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 K(2) = 181 /- 3 km s(-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 M(sec) = 0.26-0.29 M(circle dot), while the mass of the white dwarf is most likely M(wd) = 0.46-0.48 M(circle dot). From an empirical mass-radius relation we estimate the radius of the red dwarf to be in the range 0.28-0.31 R(circle dot), whereas we get R(wd) = 0.016-0.018 R(circle dot) from a theoretical mass-radius realation. Finally we discuss the spectral energy distribution and the likely evolutionary state of SDSS1212-0123.
- 出版日期2009-2
