Orbital period changes of the nova-like cataclysmic variable AC Cancri: evidence of magnetic braking and an unseen companion

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. Astronomy and Astrophysics. vol. 466, No 2, p. 589-594. ISSN 0004-6361. 2007.

Basic information

• Original name: Orbital period changes of the nova-like cataclysmic variable AC Cancri: evidence of magnetic braking and an unseen companion
• Name in Czech: Změny orbitální periody nově podobné kataklyzmické proměnné hvězdy AC Cancri: důkaz magnetického brždění a neviditelné složky
• Authors: QIAN, Shengbang (156 China), Z.-B. DAI (156 China), J.-J. HE (156 China), J. Z. YUAN (156 China), F. Y. XIANG (156 China) and Miloslav ZEJDA (203 Czech Republic, guarantor).
• Edition: Astronomy and Astrophysics, 2007, 0004-6361.

Other information

• Original language: English
• Type of outcome: Article in a journal
• Field of Study: 10308 Astronomy
• Country of publisher: France
• Confidentiality degree: is not subject to a state or trade secret
• WWW: URL
• Impact factor: Impact factor: 4.259
• RIV identification code: RIV/00216224:14310/07:00029084
• Organization unit: Faculty of Science
• UT WoS: 000245686800021
• Keywords in English: nova; cataclysmic variables; eclipsing binaries;AC Cnc; evolution; mass loss
• Tags: AC Cnc, cataclysmic variables, Eclipsing Binaries, Evolution, mass loss, nova
• Tags: International impact, Reviewed

Abstract

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.

Abstract (in Czech)

Změny orbitální periody nově podobné kataklyzmické proměnné hvězdy AC Cancri: důkaz magnetického brždění a neviditelné složky

Links

• GA205/04/2063, research and development project: Name: Fotometrický výzkum zákrytových dvojhvězd

Investor: Czech Science Foundation