Planetary Phase Variations of the 55 Cancri System

Kane, Stephen R.; Gelino, Dawn; Ciardi, David R.; Dragomir, Diana; Braun, Kaspar von

doi:10.1088/0004-637x/740/2/61

Cited by 14 publications

(12 citation statements)

References 38 publications

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“…Kane et al (2011) showed that, at visible wavelengths, the modulation due to planet "b" may not be negligible compared with that of planet e, depending of course on the respective albedos of planets e and "b". Characterizing the properties of planet e by orbital photometry thus requires the ability to distinguish between the two components, which is an additional challenge.…”

Section: Discussionmentioning

confidence: 99%

Tidal dissipation and eccentricity pumping: Implications for the depth of the secondary eclipse of 55 Cancri e

Bolmont

Selsis

Raymond

et al. 2013

A&A

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Aims. We use the super Earth 55 Cnc e as a case study to address an observable effect of tidal heating. This transiting short-period planet belongs to a compact multiple system with massive planets. We investigate whether planet-planet interactions can force the eccentricity of this planet to a level affecting the eclipse depth observed with Spitzer. Methods. Using the constant time lag tidal model, we first calculate the observed planet flux as a function of albedo and eccentricity, for different tidal dissipation constants and for two extreme cases: a planet with no heat redistribution and a planet with full heat redistribution. We derive the values of albedo and eccentricity that match the observed transit depth. We then perform N-body simulations of the planetary system including tides and general relativity to follow the evolution of the eccentricity of planet e. We compare the range of eccentricities given by the simulations with the eccentricities required to alter the eclipse depth. Results. Using our nominal value for the dissipation constant and the most recent estimates of the orbital elements and masses of the 55 Cnc planets, we find that the eccentricity of planet e can be large enough to contribute at a measurable level to the thermal emission measured with Spitzer. This affects the constraints on the albedo of the planet, which can be as high as 0.9 (instead of 0.55 when ignoring tidal heating). We also derive a maximum value for the eccentricity of planet e directly from the eclipse depth: e < 0.015 assuming Earth's dissipation constant. Conclusions. Transiting exoplanets in multiple planet systems -like 55 Cancri -are exceptional targets for testing tidal models because their tidal luminosity may be observable. Future multi-wavelengths observations of eclipse depth and phase curves (for instance with EChO and JWST) should allow us to better resolve the temperature map of these planets and break the degeneracy between albedo and tidal heating that remains for single band observations. In addition, an accurate determination of the eccentricity will make it possible to constrain the dissipation rate of the planet and to probe its internal structure.

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Section: Discussionmentioning

confidence: 99%

Tidal dissipation and eccentricity pumping: Implications for the depth of the secondary eclipse of 55 Cancri e

Bolmont

Selsis

Raymond

et al. 2013

A&A

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“…Winn et al (2011) and Demory et al (2011) both independently report the photometric detection of a transit of 55 Cnc e. In addition, Kane et al (2011) calculate combinations of expected planetary brightness variations with phase, for which knowledge of planetary radius is useful.…”

Section: The Transiting Super-earth 55 Cnc Ementioning

confidence: 99%

55 Cancri: Stellar Astrophysical Parameters, a Planet in the Habitable Zone, and Implications for the Radius of a Transiting Super-Earth

Braun

Boyajian

Brummelaar

et al. 2011

ApJ

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129

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The bright star 55 Cancri is known to host five planets, including a transiting super-Earth. The study presented here yields directly determined values for 55 Cnc's stellar astrophysical parameters based on improved interferometry: R = 0.943 ± 0.010 R , T EFF = 5196 ± 24 K. We use isochrone fitting to determine 55 Cnc's age to be 10.2 ± 2.5 Gyr, implying a stellar mass of 0.905 ± 0.015 M . Our analysis of the location and extent of the system's habitable zone (HZ; 0.67-1.32 AU) shows that planet f, with period ∼260 days and M sin i = 0.155 M Jupiter , spends the majority of the duration of its elliptical orbit in the circumstellar HZ. Though planet f is too massive to harbor liquid water on any planetary surface, we elaborate on the potential of alternative low-mass objects in planet f's vicinity: a large moon and a low-mass planet on a dynamically stable orbit within the HZ. Finally, our direct value for 55 Cancri's stellar radius allows for a model-independent calculation of the physical diameter of the transiting super-Earth 55 Cnc e (∼2.05 ± 0.15 R ⊕ ), which, depending on the planetary mass assumed, implies a bulk density of 0.76 ρ ⊕ or 1.07 ρ ⊕ .

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“…The detection of the exoplanet emission spectra was also possible through high-resolution spectroscopy (Brogi et al 2012;Rodler et al 2012;de Kok et al 2014). The measurement of phase variations relies on the detection of the flux variation along the planet's orbit as it alternately presents its day and night hemisphere to us (e.g., Knutson et al 2009;Kane et al 2011). These techniques represent the current front line of exoplanet characterization and are limited only by flux measurement precision that they impose as a result of the low planet-star flux ratio (e.g., in the most favorable cases, for a Jupiter sized planet with a 3 day period orbit F Planet /F Star ≈ 10 −4 in the visible and F Planet /F Star ≈ 10 −3 in the IR).…”

Section: Introductionmentioning

confidence: 99%

Evidence for a spectroscopic direct detection of reflected light from 51 Pegasi b

Martins

Santos

Figueira

et al. 2015

A&A

133

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Context. The detection of reflected light from an exoplanet is a difficult technical challenge at optical wavelengths. Even though this signal is expected to replicate the stellar signal, not only is it several orders of magnitude fainter, but it is also hidden among the stellar noise. Aims. We apply a variant of the cross-correlation technique to HARPS observations of 51 Peg to detect the reflected signal from planet 51 Peg b. Methods. Our method makes use of the cross-correlation function (CCF) of a binary mask with high-resolution spectra to amplify the minute planetary signal that is present in the spectra by a factor proportional to the number of spectral lines when performing the cross correlation. The resulting cross-correlation functions are then normalized by a stellar template to remove the stellar signal. Carefully selected sections of the resulting normalized CCFs are stacked to increase the planetary signal further. The recovered signal allows probing several of the planetary properties, including its real mass and albedo. Results. We detect evidence for the reflected signal from planet 51 Peg b at a significance of 3σ noise . The detection of the signal permits us to infer a real mass of 0.46 +0.06 −0.01 M Jup (assuming a stellar mass of 1.04 M Sun ) for the planet and an orbital inclination of 80 +10 −19 degrees. The analysis of the data also allows us to infer a tentative value for the (radius-dependent) geometric albedo of the planet. The results suggest that 51Peg b may be an inflated hot Jupiter with a high albedo (e.g., an albedo of 0.5 yields a radius of 1.9 ± 0.3 R Jup for a signal amplitude of 6.0 ± 0.4 × 10 −5 ). Conclusions. We confirm that the method we perfected can be used to retrieve an exoplanet's reflected signal, even with current observing facilities. The advent of next generation of instruments (e.g. VLT-ESO/ESPRESSO) and observing facilities (e.g. a new generation of ELT telescopes) will yield new opportunities for this type of technique to probe deeper into exoplanets and their atmospheres.

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Planetary Phase Variations of the 55 Cancri System

Cited by 14 publications

References 38 publications

Tidal dissipation and eccentricity pumping: Implications for the depth of the secondary eclipse of 55 Cancri e

Tidal dissipation and eccentricity pumping: Implications for the depth of the secondary eclipse of 55 Cancri e

55 Cancri: Stellar Astrophysical Parameters, a Planet in the Habitable Zone, and Implications for the Radius of a Transiting Super-Earth

Evidence for a spectroscopic direct detection of reflected light from 51 Pegasi b

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