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Double cyclic variations in orbital period of the eclipsing cataclysmic variable EX Dra
HAN, Zhong-tao - Personal Name
QIAN, Sheng-bang - Personal Name
VOLOSHINA, Irina - Personal Name
ZHU, Li-Ying - Personal Name
EX Dra is a long-period eclipsing dwarf nova
with ∼ 2–3 mag amplitude outbursts. This star has been
monitored photometrically from November, 2009 to March,
2016 and 29 new mid-eclipse times were obtained. By us-
ing new data together with the published data, the best fit to
the O − C curve indicate that the orbital period of EX Dra
have an upward parabolic change while undergoing double-
cyclic variations with the periods of 21.4 and 3.99 years,
respectively. The upward parabolic change reveals a long-
term increase at a rate of Ṗ = +7.46 × 10 −11 s s −1 . The
evolutionary theory of cataclysmic variables (CVs) predicts
that, as a CV evolves, the orbital period should be decreas-
ing rather than increasing. Secular increase can be explained
as the mass transfer between the secondary and primary or
may be just an observed part of a longer cyclic change.
Most plausible explanation for the double-cyclic variations
is a pair of light travel-time effect via the presence of two
companions. Their masses are determined to be M A sin i A =
29.3(±0.6)M J up and M B sin i B = 50.8(±0.2)M J up . When
the two companions are coplanar to the orbital plane of the
central eclipsing pair, their masses would match to brown
dwarfs.
with ∼ 2–3 mag amplitude outbursts. This star has been
monitored photometrically from November, 2009 to March,
2016 and 29 new mid-eclipse times were obtained. By us-
ing new data together with the published data, the best fit to
the O − C curve indicate that the orbital period of EX Dra
have an upward parabolic change while undergoing double-
cyclic variations with the periods of 21.4 and 3.99 years,
respectively. The upward parabolic change reveals a long-
term increase at a rate of Ṗ = +7.46 × 10 −11 s s −1 . The
evolutionary theory of cataclysmic variables (CVs) predicts
that, as a CV evolves, the orbital period should be decreas-
ing rather than increasing. Secular increase can be explained
as the mass transfer between the secondary and primary or
may be just an observed part of a longer cyclic change.
Most plausible explanation for the double-cyclic variations
is a pair of light travel-time effect via the presence of two
companions. Their masses are determined to be M A sin i A =
29.3(±0.6)M J up and M B sin i B = 50.8(±0.2)M J up . When
the two companions are coplanar to the orbital plane of the
central eclipsing pair, their masses would match to brown
dwarfs.
Availability
| EB00000003923K | Available | ||
| EB00000003924K | Available | ||
| EB00000003925K | Available |
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Statement of Responsibility
Zhong-tao Han 1,2,3 · Sheng-bang Qian 1,2,3 · Irina Voloshina 4 · Li-Ying Zhu 1,2,3
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