A SEARCH FOR THE TRANSIT OF HD 168443b: IMPROVED ORBITAL PARAMETERS AND PHOTOMETRY

Raymond

2014

ApJ

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Since exoplanets were detected using the radial velocity method, they have revealed a diverse distribution of orbital configurations. Amongst these are planets in highly eccentric orbits (e > 0.5). Most of these systems consist of a single planet but several have been found to also contain a longer period planet in a near-circular orbit. Here we use the latest Keplerian orbital solutions to investigate four known systems which exhibit this extreme eccentricity diversity; HD 37605, HD 74156, HD 163607, and HD 168443. We place limits on the presence of additional planets in these systems based on the radial velocity residuals. We show that the two known planets in each system exchange angular momentum through secular oscillations of their eccentricities. We calculate the amplitude and timescale for these eccentricity oscillations and associated periastron precession. We further demonstrate the effect of mutual orbital inclinations on the amplitude of high-frequency eccentricity oscillations. Finally, we discuss the implications of these oscillations in the context of possible origin scenarios for unequal eccentricities.

Section: The Hd 168443 Systemmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Orbital Dynamics of Multi-Planet Systems With Eccentricity Diversity

Raymond

2014

ApJ

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“…The two known planets of the HD 168443 system were discovered by Marcy et al (1999Marcy et al ( , 2001. The orbital parameters were further refined by Pilyavsky et al (2011) along with photometric observations which excluded transits for the inner planet. The revised parameters of Pilyavsky et al (2011) also confirmed a long-term trend in the RV data which indicated the presence of a long-period companion.…”

Section: Limits To Stellar/planetary Companionsmentioning

confidence: 99%

“…The orbital parameters were further refined by Pilyavsky et al (2011) along with photometric observations which excluded transits for the inner planet. The revised parameters of Pilyavsky et al (2011) also confirmed a long-term trend in the RV data which indicated the presence of a long-period companion. The DSSI results shown in Section 5 are sensitive out to a separation of 52.4 AU.…”

Section: Limits To Stellar/planetary Companionsmentioning

confidence: 99%

Limits on Stellar Companions to Exoplanet Host Stars With Eccentric Planets

Howell

Horch

et al. 2014

ApJ

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Though there are now many hundreds of confirmed exoplanets known, the binarity of exoplanet host stars is not well understood. This is particularly true of host stars which harbor a giant planet in a highly eccentric orbit since these are more likely to have had a dramatic dynamical history which transferred angular momentum to the planet. Here we present observations of four exoplanet host stars which utilize the excellent resolving power of the Differential Speckle Survey Instrument (DSSI) on the Gemini North telescope. Two of the stars are giants and two are dwarfs. Each star is host to a giant planet with an orbital eccentricity > 0.5 and whose radial velocity data contain a trend in the residuals to the Keplerian orbit fit. These observations rule out stellar companions 4-8 magnitudes fainter than the host star at passbands of 692 nm and 880 nm. The resolution and field-of-view of the instrument result in exclusion radii of 0.05-1.4 ′′ which excludes stellar companions within several AU of the host star in most cases. We further provide new radial velocities for the HD 4203 system which confirm that the linear trend previously observed in the residuals is due to an additional planet. These results place dynamical constraints on the source of the planet's eccentricities, constraints on additional planetary companions, and informs the known distribution of multiplicity amongst exoplanet host stars.

“…The combination of RV data with transit data from the K2 mission by Chakraborty et al (2018) produced an exceptionally strong constraint on the time of periastron passage for EPIC 211945201b. In the case of HD 168443b, targeted RV observations during periastron by the Transit Ephemeris Refinement and Monitoring Survey (TERMS), combined with a long time baseline, yielded very small uncertainties on the time of periastron passage (Pilyavsky et al 2011). In general, the calculations presented here demonstrate the need for further RV observations to reacquire the planetary location.…”

Section: Exoplanet Orbital Ephemeridesmentioning

confidence: 76%

Maximum Angular Separation Epochs for Exoplanet Imaging Observations

Meshkat

Turnbull

2018

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Direct imaging of exoplanets presents both significant challenges and significant gains. The advantages primarily lie in receiving emitted and, with future instruments, reflected photons at phase angles not accessible by other techniques, enabling the potential for atmospheric studies and the detection of rotation and surface features. The challenges are numerous and include coronagraph development and achieving the necessary contrast ratio. Here, we address the specific challenge of determining epochs of maximum angular separation for the star and planet. We compute orbital ephemerides for known transiting and radial velocity planets, taking Keplerian orbital elements into account. We provide analytical expressions for angular star-planet separation as a function of the true anomaly, including the locations of minimum and maximum. These expressions are used to calculate uncertainties for maximum angular separation as a function of time for the known exoplanets, and we provide strategies for improving ephemerides with application to proposed and planned imaging missions.