THE HU Aqr O-C DIAGRAM TREND CHANGE: ARE THERE STILL ANY CIRCUMBINARY PLANETS?

JOURNAL OF OCCULTATION AND ECLIPSE (JOE); ISSN 2522-7955; No. 5, 2018

A. Slowikowska¹, I. Nasiroglu², K. Gozdziewski³, K. Krzeszowski⁴, M. Zejmo⁵, P Irawati⁶, D. Buckley⁷, D. Dimitrov⁸ and H. Er⁹

¹Torun Centre for Astronomy, Nicolaus Copernicus University in Torun, Poland, aga@umk.pl

²Astronomy and Astrophysics Dep., Ataturk University, Turkey, inasir@atauni.edu.tr

³Torun Centre for Astronomy, Nicolaus Copernicus University in Torun, Poland, k.gozdziewski@umk.pl

⁴Janusz Gil Institute of Astronomy, University of Zielona Góra, Poland, chriss@astro.ia.uz.zgora.pl

⁵Janusz Gil Institute of Astronomy, University of Zielona Góra, Poland, michalzejmo@gmail.com

⁶National Astronomical Research Institute of Thailand, Thailand, puji.irawati@gmail.com

⁷South African Astronomical Observatory, Cape Town, South Africa, dibnob@saao.ac.za

⁸Institute of Astronomy, Bulgarian Academy of Sciences, Sofia, Bulgaria, dinko@astro.bas.bg

⁹Astronomy and Astrophysics Dep., Ataturk University, Turkey, huseyin.er@atauni.edu.tr

Abstract

We investigate the HU Aqr binary eclipse timing to verify if the third-body solutions proposed by Gozdziewski et al. (2015) and in earlier papers are still valid. We aim to test whether the variability seen in (O–C) diagram is due to the presence of one or more circumbinary low-mass companions based on our the most recent and more precise measurements of the mid-egress times. The (O-C) variability can be interpreted as the light time travel effect. With the addition of new observations, we extended the data set presented in Gozdziewski et al. (2015) by approximately three years.Our recent observations indicate a sudden reversing of the previously, long-term decaying (O–C), that took place between May and August 2016. Since none of the previous eclipse ephemeris hold, it reinforces still an unclear hypothesis that the (O-C) variability has not the third-body origin. Moreover, the unusual change of the (O–C) diagram provides a convincing argument for frequent, regular and continuous observations of the HU Aqr - like binaries.

Keywords: Eclipse timing – HU Aqr – Stability of circumbinary planets