Hat-P-7: A Retrograde or Polar Orbit, and a Third Body

Winn, Joshua N.; Johnson, John Asher; Albrecht, S.; Howard, Andrew W.; Marcy, Geoffrey W.; Crossfield, Ian J. M.; Holman, Matthew J.

doi:10.1088/0004-637x/703/2/l99

Cited by 252 publications

(274 citation statements)

References 38 publications

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“…It is the prediction that the planet orbit must be retrograde with respect to the stellar orbits that makes the ν Oct planet so far unique. This geometry is fundamentally different from the growing list of transiting exoplanets which demonstrate, via the Rossiter-McLaughlin effect, that their orbits can also be retrograde, since the R-M effect can only determine anti-alignment of a planet orbit's axis with respect to the host star's rotation axis (the first such exoplanet being HAT-P-7b: Narita et al 2009;Winn et al 2009). …”

Section: Introductionmentioning

confidence: 72%

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: Introductionmentioning

confidence: 72%

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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“…HAT-P-6b is the seventh planet identified as having a retrograde orbit, after WASP-2b, 8b, 15b and 17b (Triaud et al 2010;Queloz et al 2010;Bayliss et al 2010) and HAT-P-7b and 14b (Winn et al 2009c(Winn et al , 2010aNarita et al 2009). Three planets also seem to have nearly polar orbits: CoRoT-1b (Pont et al 2010), WASP-1b (Simpson et al 2010), and HAT-P-11b (Winn et al 2010b;Hirano 2010b).…”

Section: Discussionmentioning

confidence: 99%

The retrograde orbit of the HAT-P-6b exoplanet

Hébrard

Ehrenreich

Bouchy

et al. 2011

A&A

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We observed the transit of the HAT-P-6b exoplanet across its host star with the SOPHIE spectrograph (OHP, France). The resulting stellar radial velocities display the Rossiter-McLaughlin anomaly and reveal a retrograde orbit: the planetary orbital spin and the stellar rotational spin point in approximately opposite directions. A fit to the anomaly measures a sky-projected angle λ = 166 • ± 10 • between these two spin axes. All seven known retrograde planets are hot Jupiters with masses M p < 3 M Jup . About two thirds of the planets in this mass range, however, are prograde and aligned (λ 0 • ). In contrast, most of the more massive planets (M p > 4 M Jup ) are prograde but misaligned. Different mechanisms may therefore be responsible for planetary obliquities above and below ∼3.5 M Jup .

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“…Some of the hot Jupiters appear to be in multiple systems but this appears unrelated to other parameters such as eccentricity or misalignment. Examples are: HD 80606 (Naef et al 2001), HD 189733 (Bakos et al 2006), Hat-P-1 (Bakos et al 2007), WASP-8 (Queloz et al 2010), Hat-P-7 (Winn et al 2009b), WASP-2, TrES-2 and TrES-4 (Daemgen et al 2009). …”

Section: Correlations Between Parametersmentioning

confidence: 99%

“…Since then, the misalignment of XO3b has been confirmed by Winn et al (2009c), and significant misalignments have been found for HD 80606b ) and WASP-14b (Johnson et al 2009). Moreover, retrograde orbital motion has been identified in HAT-P-7b (Winn et al 2009b;Narita et al 2009). Other systems show indications of misalignment but need confirmation.…”

Section: Introductionmentioning

confidence: 97%

Spin-orbit angle measurements for six southern transiting planets

Triaud

Cameron

Queloz

et al. 2010

A&A

418

435

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Context. Several competing scenarios for planetary-system formation and evolution seek to explain how hot Jupiters came to be so close to their parent stars. Most planetary parameters evolve with time, making it hard to distinguish between models. The obliquity of an orbit with respect to the stellar rotation axis is thought to be more stable than other parameters such as eccentricity. Most planets, to date, appear aligned with the stellar rotation axis; the few misaligned planets so far detected are massive (>2 M J ). Aims. Our goal is to measure the degree of alignment between planetary orbits and stellar spin axes, to search for potential correlations with eccentricity or other planetary parameters and to measure long term radial velocity variability indicating the presence of other bodies in the system. Methods. For transiting planets, the Rossiter-McLaughlin effect allows the measurement of the sky-projected angle β between the stellar rotation axis and a planet's orbital axis. Using the HARPS spectrograph, we observed the Rossiter-McLaughlin effect for six transiting hot Jupiters found by the WASP consortium. We combine these with long term radial velocity measurements obtained with CORALIE. We used a combined analysis of photometry and radial velocities, fitting model parameters with the Markov Chain Monte Carlo method. After obtaining β we attempt to statistically determine the distribution of the real spin-orbit angle ψ. Results. We found that three of our targets have β above 90 • : WASP-2b: β = 153 • +11 −15 , WASP-15b: β = 139.6 • +5.2 −4.3 and WASP17b: β = 148.5 • +5.1 −4.2 ; the other three (WASP-4b, WASP-5b and WASP-18b) have angles compatible with 0 • . We find no dependence between the misaligned angle and planet mass nor with any other planetary parameter. All six orbits are close to circular, with only one firm detection of eccentricity e = 0.00848 +0.00085 −0.00095 in WASP-18b. No long-term radial acceleration was detected for any of the targets. Combining all previous 20 measurements of β and our six and transforming them into a distribution of ψ we find that between about 45 and 85% of hot Jupiters have ψ > 30 • . Conclusions. Most hot Jupiters are misaligned, with a large variety of spin-orbit angles. We find observations and predictions using the Kozai mechanism match well. If these observational facts are confirmed in the future, we may then conclude that most hot Jupiters are formed from a dynamical and tidal origin without the necessity to use type I or II migration. At present, standard disc migration cannot explain the observations without invoking at least another additional process.

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Hat-P-7: A Retrograde or Polar Orbit, and a Third Body

Cited by 252 publications

References 38 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 retrograde orbit of the HAT-P-6b exoplanet

Spin-orbit angle measurements for six southern transiting planets

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