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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 and 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}. 2007, vol.~466, No~2, p.~589-594. ISSN~0004-6361.
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