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Post Info TOPIC: WASP-43b
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Title: The Atmospheric Circulation of the Hot Jupiter WASP-43b: Comparing Three-Dimensional Models to Spectrophotometric Data
Author: Tiffany Kataria, Adam P. Showman, Jonathan J. Fortney, Kevin B. Stevenson, Michael R. Line, Laura Kreidberg, Jacob L. Bean, Jean-Michel Désert

The hot Jupiter WASP-43b has now joined the ranks of transiting hot Jupiters HD 189733b and HD 209458b as an exoplanet with a large array of observational constraints on its atmospheric properties. Because WASP-43b receives a similar stellar flux as HD 209458b but has a rotation rate 4 times faster and a much higher gravity, studying WASP-43b serves as a test of the effect of rotation rate and gravity on the circulation when stellar irradiation is held approximately constant. Here we present 3D atmospheric circulation models of WASP-43b using the SPARC/MITgcm, a coupled radiation and circulation model, exploring the effects of composition, metallicity, and frictional drag. We find that the circulation regime of WASP-43b is not unlike other hot Jupiters, with equatorial superrotation that yields an eastward-shifted hotspot and large day-night temperature variations (~600 K at photospheric pressures). We then compare our model results to observations from Stevenson et al. which utilize HST/WFC3 to collect spectrophotometric phase curve measurements of WASP-43b from 1.12-1.65 microns. Our results show the 5x solar model lightcurve provides a good match to the data, with a phase offset of peak flux and planet/star flux ratio that is similar to observations; however, the model nightside appears to be brighter. Nevertheless, our 5x solar model provides an excellent match to the WFC3 dayside emission spectrum. This is a major success, as the result is a natural outcome of the 3D dynamics with no model tuning, and differs significantly from 1D models that can generally only match observations when appropriately tuned. In sum, these results demonstrate that 3D circulation models can provide important insights in interpreting exoplanet atmospheric observations, even at high spectral resolution, and highlight the potential for future observations with HST, JWST and other next-generation telescopes.

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Blobrana


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Hubble Maps the Temperature and Water Vapour on an Extreme Exoplanet

A team of scientists using NASA's Hubble Space Telescope have made the most detailed global map yet of the glow from a planet orbiting another star, revealing secrets of air temperatures and water.
The map provides information about temperatures at different layers of the world's atmosphere and traces the amount and distribution of water vapour on the planet. The findings have ramifications for the understanding of atmospheric dynamics and the formation of giant planets like Jupiter.
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Blobrana


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Title: Spitzer observations of the thermal emission from WASP-43b
Author: Jasmina Blecic, Joseph Harrington, Nikku Madhusudhan, Kevin B. Stevenson, Ryan A. Hardy, Patricio E. Cubillos, Matthew Hardin, Sarah Nymeyer, David R. Anderson, Coel Hellier, Alexis M. S. Smith, Andrew Collier Cameron

WASP-43b is one of the closest-orbiting hot Jupiters, with a semimajor axis of a = 0.01526 +/- 0.00018 AU and a period of only 0.81 days. However, it orbits one of the coolest stars with a hot Jupiter (Tstar = 4520 +/- 120 K), giving the planet a modest equilibrium temperature of Teq = 1440 +/- 40 K, assuming zero Bond albedo and uniform planetary energy redistribution. The eclipse depths and brightness temperatures from our jointly fit model are 0.347% +/- 0.013% and 1670 +/- 23 K at 3.6 {\mu}m and 0.382% +/- 0.015% and 1514 +/- 25 K at 4.5 {\mu}m. The eclipse timings improved the estimate of the orbital period, P, by a factor of three (P = 0.81347436 +/- 1.4*10-7 days) and put an upper limit on the eccentricity (e = 0.010+0.010 -0.007). We use our Spitzer eclipse depths along with four previously reported ground-based photometric observations in the near-infrared to constrain the atmospheric properties of WASP-43b. The data rule out a strong thermal inversion in the dayside atmosphere of WASP-43b. Model atmospheres with no thermal inversions and fiducial oxygen-rich compositions are able to explain all the available data. However, a wide range of metallicities and C/O ratios can explain the data. The data suggest low day-night energy redistribution in the planet, consistent with previous studies, with a nominal upper limit of about 35% for the fraction of energy incident on the dayside that is redistributed to the nightside.

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Title: Ground-based detections of thermal emission from the dense hot Jupiter WASP-43b in H and Ks-bands
Authors: Wei Wang (1), Roy van Boekel (2), Nikku Madhusudhan (3), Guo Chen (4), Gang Zhao (1), Thomas Henning (2) ((1) Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, (2) Max Planck Institute for Astronomy, (3) Yale University (4) Purple Mountain Observatory, Chinese Academy of Sciences)

We report new detections of thermal emission from the transiting hot Jupiter WASP-43b in the H and Ks-bands as observed at secondary eclipses. The observations were made with the WIRCam instrument on the CFHT. We obtained a secondary eclipse depth of 0.103_{-0.017}^{+0.017}% and 0.194_{-0.029}^{+0.029}% in the H and Ks-bands, respectively. The Ks band depth is consistent with previous measurement in the narrow band centered at 2.09µm by Gillon et al. (2012). Our eclipse depths in both bands are consistent with a blackbody spectrum with a temperature of ~1850 K, slightly higher than the dayside equilibrium temperature without day-night energy redistribution. Based on theoretical models of the dayside atmosphere of WASP-43b, our data constrain the day-night energy redistribution in the planet to be \lesssim 15-25%, depending on the metal content in the atmosphere. Combined with energy balance arguments our data suggest that a strong temperature inversion is unlikely in the dayside atmosphere of WASP-43b. However, a weak inversion cannot be strictly ruled out at the current time. Future observations are required to place detailed constraints on the chemical composition of the atmosphere.

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Title: The TRAPPIST survey of southern transiting planets. I. Thirty eclipses of the ultra-short period planet WASP-43 b
Authors: M. Gillon, A. H. M. J. Triaud, J. J. Fortney, B.-O. Demory, E. Jehin, M. Lendl, P. Magain, P. Kabath, D. Queloz, R. Alonso, D. R. Anderson, A. Collier Cameron, A. Fumel, L. Hebb, C. Hellier, A. Lanotte, P. F. L. Maxted, N. Mowlavi, B. Smalley

We present twenty-three transit light curves and seven occultation light curves for the ultra-short period planet WASP-43 b, in addition to eight new measurements of the radial velocity of the star. Thanks to this extensive data set, we improve significantly the parameters of the system. Notably, the largely improved precision on the stellar density (2.41±0.08 rho_sun) combined with constraining the age to be younger than a Hubble time allows us to break the degeneracy of the stellar solution mentioned in the discovery paper. The resulting stellar mass and size are 0.717±0.025 solar masses and 0.667±0.011 Solar radii. Our deduced physical parameters for the planet are 2.034±0.052 Jupiter masses and 1.036±0.019 Jupiter radii. Taking into account its level of irradiation, the high density of the planet favours an old age and a massive core. Our deduced orbital eccentricity, 0.0035(-0.0025,+0.0060), is consistent with a fully circularised orbit. We detect the emission of the planet at 2.09 microns at better than 11-sigma, the deduced occultation depth being 1560±140 ppm. Our detection of the occultation at 1.19 microns is marginal (790±320 ppm) and more observations are needed to confirm it. We place a 3-sigma upper limit of 850 ppm on the depth of the occultation at ~0.9 microns. Together, these results strongly favour a poor redistribution of the heat to the night-side of the planet, and marginally favour a model with no day-side temperature inversion.

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Title: WASP-43b: The closest-orbiting hot Jupiter
Authors: Coel Hellier (Keele), D.R. Anderson, A. Collier Cameron, M. Gillon, E. Jehin, M. Lendl, P.F.L. Maxted, F. Pepe, D. Pollacco, D. Queloz, D. Segransan, B. Smalley, A.M.S. Smith, J. Southworth, A.H.M.J. Triaud, S. Udry, R.G. West

We report the discovery of WASP-43b, a hot Jupiter transiting a K7V star every 0.81 d. At 0.6-Msun the host star has the lowest mass of any star hosting a hot Jupiter. It also shows a 15.6-d rotation period. The planet has a mass of 1.8 Mjup, a radius of 0.9 Rjup, and with a semi-major axis of only 0.014 AU has the smallest orbital distance of any known hot Jupiter. The discovery of such a planet around a K7V star shows that planets with apparently short remaining lifetimes owing to tidal decay of the orbit are also found around stars with deep convection zones.

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