The HU Aqr planetary system hypothesis revisited

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.Comment: 18 pages, 16 figures, 4 tables, accepted to Monthly Notices of the Royal Astronomical Society (MNRAS

Very fast photometric observations of the intermediate polar V2069 Cygni

4th High Time Resolution Astrophysics - The Era of Extremely Large Telescopes, HTRA 2010 --5 May 2010 through 7 May 2010 -- --We present fast timing photometric observations of the intermediate polar V2069 Cygni (RX J2123.7+4217) using the Optical Timing Analyzer (OPTIMA) at the Skinakas Observatory 1.3 m telescope. OPTIMA is a single-photon counting aperture photo-polarimeter with the timing accuracy of about 4 microseconds and absolute (GPS) tagging of photon arrival-times. The optical (450-950 nm) light curve of V2069 Cygni was measured with sub-second resolution during July 2009 and revealed a double-peaked pulsation with 743.385 (±0.250) s period. A similar doublepeaked modulation was found in simultaneous soft X-ray observations with the Swift satellite. We suggest that the 743.385 (±0.250) s period represents the spin of the white dwarf accretor. In the Porb-Pspin diagram of all IPs, V2069 Cyg is rather an indistinct member of this population. It has however a rather low spin to orbit ratio of 0.027.Erzincan Üniversitesi: PERG05-GA-2009-249168 FNP HOM/2009/11B MKTD-CT-2006-042722 MTKD-CT-2006-039965A. Slowikowska acknowledges support from the grant N203 387737 of the Polish Ministry of Science and Higher Education, as well as the grant FNP HOM/2009/11B and the EU grant PERG05-GA-2009-249168. I. Nasiroglu acknowledges support from the EU FP6 Transfer of Knowledge Project "Astrophysics of Neutron Stars" (MKTD-CT-2006-042722). G. Kanbach acknowledges support from the EU FP6 Transfer of Knowledge Project ASTROCENTER (MTKD-CT-2006-039965) and the kind hospitality of the Skinakas team at UoC. We thank Arne Rau for discussions on this paper

Very fast photometric and X-ray observations of the intermediate polar V2069 Cygni (RX J2123.7+4217)

We present fast timing photometric observations of the intermediate polar V2069 Cygni (RX J2123.7+4217) using the Optical Timing Analyzer (OPTIMA) at the 1.3 m telescope of Skinakas Observatory. The optical (450-950 nm) light curve of V2069 Cygni was measured with sub-second resolution for the first time during July 2009 and revealed a double-peaked pulsation with a period of 743.38 +0.25. A similar double-peaked modulation was found in the simultaneous Swift satellite observations. We suggest that this period represents the spin of the white dwarf accretor. Moreover, we present the results from a detailed analysis of the XMM-Newton observation that also shows a double-peaked modulation, however shifted in phase, with 742.35 +0.23 s period. The X-ray spectra obtained from the XMM-Newton EPIC (European Photon Imaging Camera) instruments were modelled by a plasma emission and a soft black body component with a partial covering photo-electric absorption model with covering fraction of 0.65. An additional Gaussian emission line at 6.385 keV with an equivalent width of 243 eV is required to account for fluorescent emission from neutral iron. The iron fluorescence (~6.4 keV) and FeXXVI lines (~6.95 keV) are clearly resolved in the EPIC spectra. In the Porb-Pspin diagram of IPs, V2069 Cyg shows a low spin to orbit ratio of ~0.0276 in comparison with ~0.1 for other intermediate polars.Comment: 11 pages, 18 figures, 4 table

Very fast photometric and X-ray observations of the intermediate polar V2069 Cygni (RX J2123.7+4217)

We present fast timing photometric observations of the intermediate polar V2069 Cygni (RX J2123.7+4217) using the Optical Timing Analyzer (OPTIMA) at the 1.3-m telescope of Skinakas Observatory. The optical (450-950 nm) light curve of V2069 Cygni was measured with sub-second resolution for the first time during 2009 July and revealed a double-peaked pulsation with a period of 743.38 ± 0.25s. A similar double-peaked modulation was found in the simultaneous Swift satellite observations. We suggest that this period represents the spin of the white dwarf accretor. Moreover, we present results from a detailed analysis of the XMM-Newton observation, which also shows a double-peaked modulation, however shifted in phase, with a period of 742.35 ± 0.23s. The X-ray spectra obtained from the XMM-Newton European Photon Imaging Camera (EPIC) instruments were modelled by a plasma emission and a soft blackbody component with a partial covering photoelectric absorption model with a covering fraction of 0.65. An additional Gaussian emission line at 6.385keV with an equivalent width of 243eV is required to account for fluorescent emission from neutral iron. The iron fluorescence (~6.4keV) and Fexxvi lines (~6.95keV) are clearly resolved in the EPIC spectra. In the P orb-P spin diagram of intermediate polars, V2069 Cyg shows a low spin-to-orbit ratio of ~0.0276 in comparison with ~0.1 for other intermediate polars. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS

The orbital ephemeris of HU Aquarii observed with OPTIMA. Are there two giant planets in orbit?

4th High Time Resolution Astrophysics - The Era of Extremely Large Telescopes, HTRA 2010 --5 May 2010 through 7 May 2010 -- --HU Aqr is an eclipsing CV system hosting a highly magnetic white dwarf orbited by a M4V dwarf with a period of about 125 min. Its orbital ephemeris has been followed with precision since 1993. Regular OPTIMA observations of eclipses of HU Aqr since 1999 can be used to follow the secular changes of the binary orbit. We report new modeling of the orbital ephemeris including recent 2008/2009 observations and find that a model including a linear and quadratic term as well as two sinusoidal oscillatory terms provides the best fit to the observed eclipses. We propose that the sinusoidal variations can be explained by the presence of two giant planets in orbit around HU Aqr.MTKD-CT-2006-042722, MTKD-CT-2006-039965 PERG05-GA-2009-249168 Fundacja na rzecz Nauki Polskiej: HOM/2009/11BA. Slowikowska acknowledges financial support from the Foundation for Polish Science grant HOM/2009/11B and the Marie Curie European Reintegration Grant PERG05-GA-2009-249168. I. Nasiroglu acknowledges support from the EU FP6 Transfer of Knowledge Project ’Astrophysics of Neutron Stars’ (MTKD-CT-2006-042722). G. Kanbach acknowledges support from the EU FP6 Transfer of Knowledge Project ’ASTROCENTER’ (MTKD-CT-2006-039965) and the kind hospitality of the Skinakas team at UoC. We thank Arne Rau for discussions on this paper

On the HU aquarii planetary system hypothesis

In this paper, we investigate the eclipse timing of the polar binary HUAquarii that has been observed for almost two decades. Recently, Qian et al. attributed large (O-C) deviations between the eclipse ephemeris and observations to a compact system of two massive Jovian companions. We improve the Keplerian, kinematic model of the light travel time effect and re-analyse the whole currently available data set. We add almost 60 new, yet unpublished, mostly precision light curves obtained using the time high-resolution photopolarimeter Optical Timing Analyzer (OPTIMA), as well as photometric observations performed at the Monitoring Network of Telescopes/North, Physics Innovations Robotic Astronomical Telescope Explorer and Carlos Sánchez Telescope. We determine new mid-egress times with a mean uncertainty at the level of 1s or better. We claim that because the observations that currently exist in the literature are non-homogeneous with respect to spectral windows (ultraviolet, X-ray, visual and polarimetric mode) and the reported mid-egress measurements errors, they may introduce systematics that affect orbital fits. Indeed, we find that the published data, when taken literally, cannot be explained by any unique solution. Many qualitatively different and best-fit two-planet configurations, including self-consistent, Newtonian N-body solutions may be able to explain the data. However, using high-resolution, precision OPTIMA light curves, we find that the (O-C) deviations are best explained by the presence of a single circumbinary companion orbiting at a distance of ~4.5au with a small eccentricity and having ~7 Jupiter masses. This object could be the next circumbinary planet detected from the ground, similar to the announced companions around close binaries HWVir, NNSer, UZFor, DPLeo, FSAur or SZHer, and planets of this type around Kepler-16, Kepler-34 and Kepler-35. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS

Probing transit timing variations of three hot Jupiters: HATP-36b, HATP-56b, and WASP-52b

We report the results of new transit observations for the three hot Jupiter-like planets, HATP-36b, HATP-56b, and WASP-52b, respectively. Transit timing variations (TTVs) are presented for these systems based on observations that span the period 2016-2020. The data were collected with the 0.6-m telescope at Adiyaman University (ADYU60, Turkey) and the 1.0 m telescope at TÜBCrossed D signTAK National Observatory (TUG, Turkey). Global fits were performed to the combined light curves for each system along with the corresponding radial velocity (RV) data taken from the literature. The extracted parameters (for all three systems) are found to be consistent with the values from previous studies. Through fits to the combined mid-Transit times data from our observations and the data available in the literature, an updated linear ephemeris is obtained for each system. Although a number of potential outliers are noted in the respective O-C diagrams, the majority of the data are consistent within the 3σ confidence level implying a lack of convincing evidence for the existence of additional objects in the systems studied