Bibcode
Nebot Gómez-Morán, A.; Schwope, A. D.; Schreiber, M. R.; Gänsicke, B. T.; Pyrzas, S.; Schwarz, R.; Southworth, J.; Kohnert, J.; Vogel, J.; Krumpe, M.; Rodríguez-Gil, P.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 495, Issue 2, 2009, pp.561-569
Fecha de publicación:
2
2009
Revista
Número de citas
36
Número de citas referidas
31
Descripción
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 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_&sun; , while the mass of the white dwarf
is most likely M_wd= 0.46-0.48 M_&sun;. From an empirical mass-radius
relation we estimate the radius of the red dwarf to be in the range
0.28-0.31 R_&sun; , whereas we get R_wd= 0.016-0.018 R_&sun; from a
theoretical mass-radius realation. Finally we discuss the spectral
energy distribution and the likely evolutionary state of SDSS1212-0123.
This paper includes data gathered with the 6.5 m Magellan Telescopes
located at Las Campanas Observatory, Chile.
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