• DOI:10.1093/mnras/stu2728
• Corpus ID: 119192454

The HU Aqr planetary system hypothesis revisited

@article{Godziewski2014TheHA,
  title={The HU Aqr planetary system hypothesis revisited},
  author={Krzysztof Goździewski and Aga Słowikowska and Dinko P. Dimitrov and Krzysztof Krzeszowski and Michal Zejmo and G.Kanbach and Vadim Burwitz and Arne Rau and P. Irawati and Andrea Richichi and Marcin P. Gawroński and Grzegorz Nowak and Ilham Nasiroglu and Dominik J{\'o}zef Kubicki},
  journal={Monthly Notices of the Royal Astronomical Society},
  year={2014},
  volume={448},
  pages={1118-1136}
}

• K. Goździewski, A. Słowikowska, +11 authors D. Kubicki
• Published 18 December 2014
• Physics, Geology
• Monthly Notices of the Royal Astronomical Society

We study the mid-egress eclipse timing data gathered for the cataclysmic binary HU Aquarii during the years 1993-2014. The (O-C) residuals were previously attributed to a single ~7 Jupiter mass companion in ~5 au orbit or to a stable 2-planet system with an unconstrained outermost orbit. We present 22 new observations gathered between June, 2011 and July, 2014 with four instruments around the world. They reveal a systematic deviation of ~60 - 120 seconds from the older ephemeris. We re-analyse the whole set of the timing data available. Our results provide an erratum to the previous HU Aqr planetary models, indicating that the hypothesis for a third and fourth body in this system is uncertain. The dynamical stability criterion and a particular geometry of orbits rule out coplanar 2-planet configurations. A putative HU Aqr planetary system may be more complex, e.g., highly non-coplanar. Indeed, we found examples of 3-planet configurations with the middle planet in a retrograde orbit, which are stable for at least 1Gyr, and consistent with the observations. The (O-C) may be also driven by oscillations of the gravitational quadrupole moment of the secondary, as predicted by the Lanza et al. modification of the Applegate mechanism. Further systematic, long-term monitoring of HU Aqr is required to interpret the (O-C) residuals.