A circumbinary planet in orbit around the short-period white dwarf eclipsing binary RR Cae

Authors

  • S.-B. Qian,

    Corresponding author
    1. National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, PO Box 110, 650011 Kunming, China
    2. Key Laboratory of the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, PO Box 110, 650011 Kunming, China
    3. Graduate University of the Chinese Academy of Sciences, 19A Yuquanlu, Sijingshang Block, 100049 Beijing, China
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  • L. Liu,

    1. National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, PO Box 110, 650011 Kunming, China
    2. Key Laboratory of the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, PO Box 110, 650011 Kunming, China
    3. Graduate University of the Chinese Academy of Sciences, 19A Yuquanlu, Sijingshang Block, 100049 Beijing, China
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  • L.-Y. Zhu,

    1. National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, PO Box 110, 650011 Kunming, China
    2. Key Laboratory of the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, PO Box 110, 650011 Kunming, China
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  • Z.-B. Dai,

    1. National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, PO Box 110, 650011 Kunming, China
    2. Key Laboratory of the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, PO Box 110, 650011 Kunming, China
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  • E. Fernández Lajús,

    1. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, 1900 La Plata, Buenos Aires, Argentina
    2. Instituto de Astrofisica de La Plata (CCT La Plata – CONICET/UNLP), Paseo del Bosque s/n, La Plata, BA, B1900FWA, Argentina
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  • G. L. Baume

    1. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, 1900 La Plata, Buenos Aires, Argentina
    2. Instituto de Astrofisica de La Plata (CCT La Plata – CONICET/UNLP), Paseo del Bosque s/n, La Plata, BA, B1900FWA, Argentina
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E-mail: qsb@ynao.ac.cn

ABSTRACT

By using six newly determined mid-eclipse times together with those collected from the literature, we have found that the observed minus calculated (O−C) curve of RR Cae shows a cyclic change with a period of 11.9 yr and an amplitude of 14.3 s while it undergoes an upward parabolic variation [revealing a long-term period increase at a rate of inline image]. The cyclic change was analysed for the light-travel-time effect that arises from the gravitational influence of a third companion. The mass of the third body was determined to be M3sin i′= 4.2(± 0.4) MJup, suggesting that it is a circumbinary giant planet when its orbital inclination is larger than 17bsl000646. The orbital separation of the circumbinary planet from the central eclipsing binary is about 5.3(± 0.6) au. The period increase is opposite to the changes caused by angular momentum loss via magnetic braking or/and gravitational radiation; and it cannot be explained by the mass transfer between both components because of its detached configuration. These indicate that the observed upward parabolic change is only a part of a long-period (longer than 26.3 yr) cyclic variation, which may reveal the presence of another giant circumbinary planet in a wide orbit.

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