On THE REALITY OF THE SUGGESTED PLANET IN THE Ν OCTANTIS SYSTEM

Eberle, J.; Cuntz, M.

doi:10.1088/2041-8205/721/2/l168

Cited by 49 publications

(63 citation statements)

References 20 publications

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“…A prograde orbit has no stability, and the binary-secondary scenario proposed by Morais & Correia (2012) appears to be unsupported by the available orbital solutions. Therefore the only recognizable astrophysical scenario continuing to be consistent with all available data is a retrograde planet (Ramm et al 2009;Eberle & Cuntz (2010). Thus, the reality of a planet in this unusually tight binary system's geometry (a bin < 3 AU, a pl /a bin ∼ 0.5) has more credibility and, for the time being, becomes that much more controversial.…”

Section: Discussionmentioning

confidence: 99%

“…The controversial geometry of ν Oct has been investigated with increasing depth beginning with Eberle & Cuntz (2010) and subsequently by Quarles, Cuntz & Musielak (2012) and Goździewski et al (2013). Goździewski et al explored the system in considerable detail and found that stable solutions consistent with the Ramm et al results existed but were confined to tiny regions of the phase space.…”

Section: Introductionmentioning

confidence: 99%

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Line-depth-ratio temperatures for the close binary ν Octantis: new evidence supporting the conjectured circumstellar retrograde planet

Ramm¹

2015

Monthly Notices of the Royal Astronomical Society

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We explore the possibly that either starspots or pulsations are the cause of a periodic radialvelocity signal (P ∼ 400 days) from the K-giant binary ν Octantis (P ∼ 1050 days, e ∼ 0.25), alternatively conjectured to have a retrograde planet. Our study is based on temperatures derived from 22 line-depth ratios (LDRs) for ν Oct and twenty calibration stars. Empirical evidence and stability modelling provide unexpected support for the planet since other standard explanations (starspots, pulsations and additional stellar masses) each have credibility problems. However, the proposed system presents formidable challenges to planet-formation and stability theories: it has by far the smallest stellar separation of any claimed planet-harbouring binary (a bin ∼ 2.6 AU) and an equally unbelievable separation ratio (a pl /a bin ∼ 0.5), hence the necessity that the circumstellar orbit be retrograde.The LDR analysis of 215 ν Oct spectra acquired between 2001-2007, from which the RV perturbation was first revealed, have no significant periodicity at any frequency. The LDRs recover the original 21 stellar temperatures with an average accuracy of 45 ± 25 K. The 215 ν Oct temperatures have a standard deviation of only 4.2 K. Assuming the host primary is not pulsating, the temperatures converted to magnitude differences strikingly mimic the very stable photometric Hipparcos observations 15 years previously, implying the long-term stability of the star and demonstrating a novel use of LDRs as a photometric gauge. Our results provide substantial new evidence that conventional starspots and pulsations are unlikely causes of the RV perturbation. The controversial system deserves continued attention, including with higher resolving-power spectra for bisector and LDR analyses.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Line-depth-ratio temperatures for the close binary ν Octantis: new evidence supporting the conjectured circumstellar retrograde planet

Ramm¹

2015

Monthly Notices of the Royal Astronomical Society

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“…apl 0.25abin (Holman & Wiegert 1999;Ramm et al 2009;Eberle & Cuntz 2010;Andrade-Ines et al 2016). However if the planet is in a retrograde orbit, as first suggested by Eberle & Cuntz (2010), the stability zone is wider (Jefferys 1974;Morais & Giuppone 2012), and places the conjectured orbit very near and perhaps within the boundary of stability. As extraordinary as the retrograde scenario may appear, since its very formation would also be challenged by strong dynamical interactions, the alternative standard explanations of instrumental or data reduction anomalies, starspots, pulsations or apsidal motion of the binary orbit are less supported by the observational evidence (Ramm et al 2009;Ramm 2015 5.81 ± 0.12 (6) T eff (K) 4 860 ± 40 (6) log g (cgs)…”

Section: Introductionmentioning

confidence: 83%

“…For a prograde orbit, models predict long-term stability should be limited to about half this distance i.e. apl 0.25abin (Holman & Wiegert 1999;Ramm et al 2009;Eberle & Cuntz 2010;Andrade-Ines et al 2016). However if the planet is in a retrograde orbit, as first suggested by Eberle & Cuntz (2010), the stability zone is wider (Jefferys 1974;Morais & Giuppone 2012), and places the conjectured orbit very near and perhaps within the boundary of stability.…”

Section: Introductionmentioning

confidence: 97%

The conjectured S-type retrograde planet in ν Octantis: more evidence including four years of iodine-cell radial velocities

Ramm

Nelson

Endl

et al. 2016

Mon. Not. R. Astron. Soc.

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Released ABSTRACTWe report 1212 radial-velocity (RV) measurements obtained in the years 2009-2013 using an iodine cell for the spectroscopic binary ν Octantis (K1III/IV). This system (a bin ∼ 2.6 au, P ∼ 1050 days) is conjectured to have a Jovian planet with a semi-major axis half that of the binary host. The extreme geometry only permits long-term stability if the planet is in a retrograde orbit. Whilst the reality of the planet (P ∼ 415 days) remains uncertain, other scenarios (stellar variability or apsidal motion caused by a yet unobserved third star) continue to appear substantially less credible based on CCF bisectors, line-depth ratios and many other independent details. If this evidence is validated but the planet is disproved, the claims of other planets using RVs will be seriously challenged.We also describe a significant revision to the previously published RVs and the full set of 1437 RVs now encompasses nearly 13 years. The sensitive orbital dynamics allow us to constrain the 3D architecture with a broad prior probability distribution on the mutual inclination, which with posterior samples obtained from an N -body Markov chain Monte Carlo is found to be 152 • .5± 0.7 0.6 . None of these samples are dynamically stable beyond 10 6 years. However, a grid search around the best-fitting solution finds a region that has many models stable for 10 7 years, and includes one model within 1-sigma that is stable for at least 10 8 years. The planet's exceptional nature demands robust independent verification and makes the theoretical understanding of its formation a worthy challenge.

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“…Another example for significantly increased stability limits for retrograde orbits has been given by Eberle & Cuntz (2010b). They pursued a theoretical investigation of a previous observational finding about the ν Octantis binary system (Ramm et al 2009) that indicates the possible existence of a Jupiter-mass planet, although the planet appears to be located outside the zone of orbital stability.…”

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confidence: 99%

On the Possibility of Habitable Moons in the System of HD 23079: Results from Orbital Stability Studies

Cuntz

Quarles

Eberle

et al. 2013

Publ. Astron. Soc. Aust.

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The aim of our study is to investigate the possibility of habitable moons orbiting the giant planet HD 23079b, a Jupitermass planet, which follows a low-eccentricity orbit in the outer region of HD 23079's habitable zone. We show that HD 23079b is able to host habitable moons in prograde and retrograde orbits, as expected, noting that the outer stability limit for retrograde orbits is increased by nearly 90% compared with that of prograde orbits, a result consistent with previous generalised studies. For the targeted parameter space, it was found that the outer stability limit for habitable moons varies between 0.05236 and 0.06955 AU (prograde orbits) and between 0.1023 and 0.1190 AU (retrograde orbits), depending on the orbital parameters of the Jupiter-type planet if a minimum mass is assumed. These intervals correspond to 0.306 and 0.345 (prograde orbits) and 0.583 and 0.611 (retrograde orbits) of the planet's Hill radius. Larger stability limits are obtained if an increased value for the planetary mass m p is considered; they are consistent with the theoretically deduced relationship of m 1/3 p . Finally, we compare our results with the statistical formulae of Domingos, Winter, & Yokoyama, indicating both concurrence and limitations.

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On THE REALITY OF THE SUGGESTED PLANET IN THE Ν OCTANTIS SYSTEM

Cited by 49 publications

References 20 publications

Line-depth-ratio temperatures for the close binary ν Octantis: new evidence supporting the conjectured circumstellar retrograde planet

Line-depth-ratio temperatures for the close binary ν Octantis: new evidence supporting the conjectured circumstellar retrograde planet

The conjectured S-type retrograde planet in ν Octantis: more evidence including four years of iodine-cell radial velocities

On the Possibility of Habitable Moons in the System of HD 23079: Results from Orbital Stability Studies

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