The HU Aqr planetary system hypothesis revisited

Kubicki, D.; Nasiroglu, I.; Nowak, G.; Gawroński, M.; Richichi, A.; Irawati, P.; Burwitz, V.; Rau, A.; Kanbach, G.; Żejmo, M.; Krzeszowski, K.; Dimitrov, D.; Słowikowska, A.; Goździewski, K.
Referencia bibliográfica

Monthly Notices of the Royal Astronomical Society, Volume 448, Issue 2, p.1118-1136

Fecha de publicación:
4
2015
Número de autores
14
Número de autores del IAC
1
Número de citas
36
Número de citas referidas
28
Descripción
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 two-planet system with an unconstrained outermost orbit. We present 22 new observations gathered between 2011 June and 2014 July with four instruments around the world. They reveal a systematic deviation of ˜60-120 s 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 two-planet configurations. A putative HU Aqr planetary system may be more complex, e.g. highly non-coplanar. Indeed, we found examples of three-planet configurations with the middle planet in a retrograde orbit, which are stable for at least 1 Gyr, 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.
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