ORBITAL PHASE VARIATIONS OF THE ECCENTRIC GIANT PLANET HAT-P-2b

By N. Lewis, H. Knutson, A. Showman, N. Cowan, Gregory Laughlin, Adam Burrows, D. Deming, J. Crepp, K. Mighell, E. Agol and 12 more. 2013

144 citations recorded by the source corpus.

We present the first secondary eclipse and phase curve observations for the highly eccentric hot Jupiter HAT-P-2b in the 3.6, 4.5, 5.8, and 8.0 μm bands of the Spitzer Space Telescope. The 3.6 and 4.5 μm data sets span an entire orbital period of HAT-P-2b (P = 5.6334729 d), making them the longest continuous phase curve observations obtained to date and the first full-orbit observations of a planet with an eccentricity exceeding 0.2. We present an improved non-parametric method for removing the intrapixel sensitivity variations in Spitzer data at 3.6 and 4.5 μm that robustly maps position-dependent flux variations. We find that the peak in planetary flux occurs at 4.39 ± 0.28, 5.84 ± 0.39, and 4.68 ± 0.37 hr after periapse passage with corresponding maxima in the planet/star flux ratio of 0.1138% ± 0.0089%, 0.1162% ± 0.0080%, and 0.1888% ± 0.0072% in the 3.6, 4.5, and 8.0 μm bands, respectively. Our measured secondary eclipse depths of 0.0996% ± 0.0072%, 0.1031% ± 0.0061%, , and 0.1392% ± 0.0095% in the 3.6, 4.5, 5.8, and 8.0 μm bands, respectively, indicate that the planet cools significantly from its peak temperature before we measure the dayside flux during secondary eclipse. We compare our measured secondary eclipse depths to the predictions from a one-dimensional radiative transfer model, which suggests the possible presence of a transient day side inversion in HAT-P-2b's atmosphere near periapse. We also derive improved estimates for the system parameters, including its mass, radius, and orbital ephemeris. Our simultaneous fit to the transit, secondary eclipse, and radial velocity data allows us to determine the eccentricity (e = 0.50910 ± 0.00048) and argument of periapse (ω = 188.°09 ± 0.°39) of HAT-P-2b's orbit with a greater precision than has been achieved for any other eccentric extrasolar planet. We also find evidence for a long-term linear trend in the radial velocity data. This trend suggests the presence of another substellar companion in the HAT-P-2 system, which could have caused HAT-P-2b to migrate inward to its present-day orbit via the Kozai mechanism.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/b9fe811326a662d6d3ed27de7b021757e6356a11

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In Astronomy and Astrophysics

1. N. Madhusudhan
2. Jon Fortney
3. A. Showman
4. D. Deming
5. D. Charbonneau
6. D. Sing
7. H. Knutson
8. M. Line

Citations in the corpus

• SPITZER SECONDARY ECLIPSES OF THE DENSE, MODESTLY-IRRADIATED, GIANT EXOPLANET HAT-P- 20 b ?> USING PIXEL-LEVEL DECORRELATION (2014, methodology): “…such as Bi-Linear Interpolated Sub- pixel Sensitivity (BLISS) mapping (Stevenson et al. 2012), and novel variants such as a spatial weighting-function approach (Ballard et al. 2010; Cowan et al. 2012), and modifications thereof (Lewis et al. 2013; Zellem et al. 2014; Lanotte et al. 2014).”
• THE INFLUENCE OF NONUNIFORM CLOUD COVER ON TRANSIT TRANSMISSION SPECTRA (2015, background): “This eastward shift in temperature was first predicted by Showman and Guillot (2002) and since observed in a a number of hot Jupiter’s (Knutson et al. 2007;2009;2012; Crossfield et al. 2010; Cowan et al. 2012; Lewis et al. 2013; Stevenson et al. 2014).”
• INFERENCE OF INHOMOGENEOUS CLOUDS IN AN EXOPLANET ATMOSPHERE (2013, methodology): “In a second step, we apply the noise-pixel variable aperture technique (Lewis et al. 2013) to all AORs.”
• ATMOSPHERIC HEAT REDISTRIBUTION ON HOT JUPITERS (2013, unknown): “We also exclude planets on highly eccentric orbits such as HD 80606b (Laughlin et al. 2009) andHAT-P-2b (Lewis et al. 2013).”
• HST hot-Jupiter transmission spectral survey: detection of potassium in WASP-31b along with a cloud deck and Rayleigh scattering (2014, methodology): “…using alternative methods such as fitting a two-dimensional Gaussian function to the stellar image, previous experiences with warm Spitzer photometry showed that the flux-weighted centroiding method is either equivalent or superior (Beerer et al. 2011; Knutson et al. 2012; Lewis et al. 2013).”
• SPITZER PHASE CURVE CONSTRAINTS FOR WASP-43b AT 3.6 AND 4.5 μm (2016, methodology): “Similar formulations have been used to model other exoplanet phase curves (e.g. Cowan & Agol 2008; Knutson et al. 2012; Lewis et al. 2013; Stevenson et al. 2014).”
• SPITZER OBSERVATIONS CONFIRM AND RESCUE THE HABITABLE-ZONE SUPER-EARTH K2-18b FOR FUTURE CHARACTERIZATION (2016, methodology): “…aperture, our extraction includes estimating and subtracting the sky background, calculating the flux-weighted centroid position of the star on the array, and then calculating the total flux within circular apertures (Knutson et al. 2012; Lewis et al. 2013; Todorov et al. 2013; Kammer et al. 2015).”
• The Apparently Decaying Orbit of WASP-12b (2017, methodology): “In the second scheme, we tried 11 apertures for which the radius was allowed to vary at each time step, based on the procedure described in Appendix A of Lewis et al. (2013).”
• FRIENDS OF HOT JUPITERS. I. A RADIAL VELOCITY SEARCH FOR MASSIVE, LONG-PERIOD COMPANIONS TO CLOSE-IN GAS GIANT PLANETS (2013, background): “…remaining fourteen systems with evidence for an outer companion, eight have previously been reported in the published literature including: HATP-2 (Lewis et al. 2013), HAT-P-4 (Winn et al. 2011), HAT-P-7 (Winn et al. 2009b), HAT-P-13 (Bakos et al. 13 2009b; Winn et al. 2010a), HAT-P-17 (Howard et…”