EC 10246-2707: a new eclipsing sdB + M dwarf binary⋆
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Date
2013
Journal Title
Journal ISSN
Volume Title
Publisher
OUP
Abstract
We announce the discovery of a new eclipsing hot subdwarf B + M dwarf binary,
EC 10246-2707, and present multi-colour photometric and spectroscopic observations
of this system. Similar to other HW Vir-type binaries, the light curve shows both
primary and secondary eclipses, along with a strong reflection effect from the M dwarf;
no intrinsic light contribution is detected from the cool companion. The orbital period
is 0.118 507 993 6 ± 0.000 000 000 9 days, or about three hours. Analysis of our time-
series spectroscopy reveals a velocity semi-amplitude of K1 = 71.6 ± 1.7 km s−1 for
the sdB and best-fitting atmospheric parameters of Teff = 28900 ± 500 K, log g =
5.64 ± 0.06, and log N(He)/N(H) = -2.5 ± 0.2. Although we cannot claim a unique
solution from modeling the light curve, the best–fitting model has an sdB mass of 0.45
M⊙ and a cool companion mass of 0.12 M⊙. These results are roughly consistent with
a canonical–mass sdB and M dwarf separated by a ∼ 0.84 R⊙. We find no evidence of
pulsations in the light curve and limit the amplitude of rapid photometric oscillations
to < 0.08%. Using 15 years of eclipse timings, we construct an O-C diagram but find
no statistically significant period changes; we rule out | ˙P | > 7.2×10−12. If EC 10246-
2707 evolves into a cataclysmic variable, its period should fall below the famous CV
period gap.
Description
Keywords
Stars, Subdwarfs, Variables, Individual, EC 10246-2707
Citation
Barlow, B.N. et al. (2013). EC 10246-2707: a new eclipsing sdB + M dwarf binary*. Monthly Notices of the Royal Astronomical Society, 430(1): 22 - 31