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| Paper: |
Dark-Spot Activity on the Secondary as the Origin of Variable Mass Accretion in Cataclysmic Variables |
| Volume: |
482, 10th Pacific Rim Conference on Stellar Astrophysics |
| Page: |
171 |
| Authors: |
Qian, S.-B.; Zhu, L.-Y.; Lajús, E. F.; He, J.-J.; Liao, W.-P.; Zhao, E.-G.; Liu, L.; Yang, Y.-G. |
| Abstract: |
In magnetic CVs (polars), the magnetic fields of the white dwarfs
are strong enough to prevent materials from the main-sequence
companions for forming an accretion disc. Therefore, polars
especially eclipsing polars provide a good chance to study mass
accretion directly. In the past 4 years, we have monitored several
eclipsing polars (e.g., DP Leo and HU Aqr) by using the 2.4-m and
1.0-m telescopes in China and the 2.15-m telescope in Argentina.
Nearly 100 eclipse profiles were obtained. In this talk, apart from
the detection of a few giant planets orbiting polars, I will
summarize some other progresses of our research group at Yunnan
Observatories. Our results are as following: (1) the correlation
between the out-of-eclipse brightness variation and the change of
the eclipse profile suggests that both the accretion hot spot and
the accretion stream brighten and become faint instantaneously. This
is the direct evidence of variable mass transfer in a CV that is
also supported by the relation between the out-of-eclipse brightness
and the depth of eclipse. (2) We find the brightness state change is
correlated with the dark-spot activity near the L1 point. The low
state usually corresponds to the presence of a large spot at L1
point, while the dark spot disappear at a high state indicating that
it is the dark-spot activity caused the mass transfer in CVs. (3)
Magnetic activity cycles of the cool secondary did not correlate
with the brightness state change revealing the variable mass
accretion was not caused by magnetic activity cycles. |
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