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@article{772276,
author = {Qian, Shengbang and Dai, Z.andB. and He, J.andJ. and Yuan, J. Z. and Xiang, F. Y. and Zejda, Miloslav},
article_number = {2},
keywords = {nova; cataclysmic variables; eclipsing binaries;AC Cnc; evolution; mass loss},
language = {eng},
issn = {0004-6361},
journal = {Astronomy and Astrophysics},
title = {Orbital period changes of the nova-like cataclysmic variable AC Cancri: evidence of magnetic braking and an unseen companion},
url = {http://adsabs.harvard.edu/abs/2007A%26A...466..589Q},
volume = {466},
year = {2007}
}
TY - JOUR
ID - 772276
AU - Qian, Shengbang - Dai, Z.-B. - He, J.-J. - Yuan, J. Z. - Xiang, F. Y. - Zejda, Miloslav
PY - 2007
TI - Orbital period changes of the nova-like cataclysmic variable AC Cancri: evidence of magnetic braking and an unseen companion
JF - Astronomy and Astrophysics
VL - 466
IS - 2
SP - 589-594
EP - 589-594
SN - 00046361
KW - nova
KW - cataclysmic variables
KW - eclipsing binaries;AC Cnc
KW - evolution
KW - mass loss
UR - http://adsabs.harvard.edu/abs/2007A%26A...466..589Q
N2 - Aims.The source AC Cnc is a nova-like cataclysmic variable containing a white-dwarf primary with a mass of 0.76 Mo and a K2-type secondary with a mass of 0.77 Mo. We intend to study its period changes and search for evidence of magnetic braking and unseen third body. Methods: The period changes were investigated based on the analysis of the O-C curve, which is formed by one new eclipse time together with the others compiled from the literature. Results: A cyclic change with a period of 16.2 yr was found to be superimposed on a long-term period decrease at a rate of dot{P}=-1.24(0.44).{10-8} days/year. Conclusions: It is shown that the mechanism of magnetic activity-driven changes in the quadrupole momentum of the secondary star (Applegate's mechanism) does not explain it easily. This period oscillation was plausibly interpreted by a light-travel time effect caused by the presence of a cool M-type dwarf companion (M_3<0.097 Mo) in a long orbit (16.2 yr) around the binary. Since the masses of both components are nearly the same, the mass transfer from the lobe-filling secondary to the primary is not efficient to cause the continuous period decrease. It may be strong evidence of an enhanced magnetic stellar wind from the K2-type component. If the Alfén radius of the cool secondary is the same as that of the Sun (i.e., RA = 15 Ro), the mass-loss rate should be dot{M_2}=-1.65.{10-10} Mo/year. By using the enhanced mass loss proposed by Tout and Eggleton (1988), the mass-loss rate should be dot{M_2}=-1.18.{10-9} Mo/year. In this case, the Alfén radius is determined to be RA = 5.2 Ro. However, the long-term decrease of the period may be only a part of a long-period (<100 yr) oscillation caused by the presence of an additional body. To check the conclusions, new precise times of light minimum will be required.
ER -
QIAN, Shengbang, Z.-B. DAI, J.-J. HE, J. Z. YUAN, F. Y. XIANG a Miloslav ZEJDA. Orbital period changes of the nova-like cataclysmic variable AC Cancri: evidence of magnetic braking and an unseen companion. \textit{Astronomy and Astrophysics}. roč.~466, č.~2, s.~589-594. ISSN~0004-6361. 2007.
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