Browsing by Subject "secondary eclipse"

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The Hot-Jupiter Kepler-17b: Discovery, Obliquity from Stroboscopic Starspots, and Atmospheric Characterization
(2011-11) Desert, Jean-Michel; Charbonneau, David; Demory, Brice-Olivier; Ballard, Sarah; Carter, Joshua A.; Fortney, Jonathan J.; Cochran, William D.; Endl, Michael; Quinn, Samuel N.; Isaacson, Howard T.; Fressin, Francois; Buchhave, Lars A.; Latham, David W.; Knutson, Heather A.; Bryson, Stephen T.; Torres, Guillermo; Rowe, Jason F.; Batalha, Natalie M.; Borucki, William J.; Brown, Timothy M.; Caldwell, Douglas A.; Christiansen, Jessie L.; Deming, Drake; Fabrycky, Daniel C.; Ford, Eric B.; Gilliland, Ronald L.; Gillon, Michael; Haas, Michael R.; Jenkins, Jon M.; Kinemuchi, Karen; Koch, David; Lissauer, Jack J.; Lucas, Philip; Mullally, Fergal; MacQueen, Phillip J.; Marcy, Geoffrey W.; Sasselov, Dimitar D.; Seager, Sara; Still, Martin; Tenenbaum, Peter; Uddin, Kamal; Winn, Joshua N.; Cochran, William D.; Endl, Michael; MacQueen, Phillip J.
This paper reports the discovery and characterization of the transiting hot giant exoplanet Kepler-17b. The planet has an orbital period of 1.486 days, and radial velocity measurements from the Hobby-Eberly Telescope show a Doppler signal of 419.5(-15.6)(+13.3) m s(-1). From a transit-based estimate of the host star's mean density, combined with an estimate of the stellar effective temperature T-eff = 5630 +/- 100 from high-resolution spectra, we infer a stellar host mass of 1.06 +/- 0.07 M-circle dot and a stellar radius of 1.02 +/- 0.03 R-circle dot. We estimate the planet mass and radius to be M-P = 2.45 +/- 0.11 M-J and R-P = 1.31 +/- 0.02 R-J. The host star is active, with dark spots that are frequently occulted by the planet. The continuous monitoring of the star reveals a stellar rotation period of 11.89 days, eight times the planet's orbital period; this period ratio produces stroboscopic effects on the occulted starspots. The temporal pattern of these spot-crossing events shows that the planet's orbit is prograde and the star's obliquity is smaller than 15 degrees. We detected planetary occultations of Kepler-17b with both the Kepler and Spitzer Space Telescopes. We use these observations to constrain the eccentricity, e, and find that it is consistent with a circular orbit (e < 0.011). The brightness temperatures of the planet's infrared bandpasses are T-3.6 mu m = 1880 +/- 100 K and T-4.5 mu m = 1770 +/- 150 K. We measure the optical geometric albedo A(g) in the Kepler bandpass and find A(g) = 0.10 +/- 0.02. The observations are best described by atmospheric models for which most of the incident energy is re-radiated away from the day side.
Kepler-10 c: a 2.2 Earth Radius Transiting Planet in a Multiple System
(2011-11) Fressin, Francois; Torres, Guillermo; Desert, Jean-Michel; Charbonneau, David; Batalha, Natalie M.; Fortney, Jonathan J.; Rowe, Jason F.; Allen, Christopher; Borucki, William J.; Brown, Timothy M.; Bryson, Stephen T.; Ciardi, David R.; Cochran, William D.; Deming, Drake; Dunham, Edward W.; Fabrycky, Daniel C.; Gautier, Thomas N., III; Gilliland, Ronald L.; Henze, Christopher E.; Holman, Matthew J.; Howell, Steve B.; Jenkins, Jon M.; Kinemuchi, Karen; Knutson, Heather; Koch, David G.; Latham, David W.; Lissauer, Jack J.; Marcy, Geoffrey W.; Ragozzine, Darin; Sasselov, Dimitar D.; Still, Martin; Tenenbaum, Peter; Uddin, Kamal; Cochran, William D.
The Kepler mission has recently announced the discovery of Kepler-10 b, the smallest exoplanet discovered to date and the first rocky planet found by the spacecraft. A second, 45 day period transit-like signal present in the photometry from the first eight months of data could not be confirmed as being caused by a planet at the time of that announcement. Here we apply the light curve modeling technique known as BLENDER to explore the possibility that the signal might be due to an astrophysical false positive (blend). To aid in this analysis we report the observation of two transits with the Spitzer Space Telescope at 4.5 mu m. When combined, they yield a transit depth of 344 +/- 85 ppm that is consistent with the depth in the Kepler passband (376 +/- 9 ppm, ignoring limb darkening), which rules out blends with an eclipsing binary of a significantly different color than the target. Using these observations along with other constraints from high-resolution imaging and spectroscopy, we are able to exclude the vast majority of possible false positives. We assess the likelihood of the remaining blends, and arrive conservatively at a false alarm rate of 1.6 x 10(-5) that is small enough to validate the candidate as a planet (designated Kepler-10 c) with a very high level of confidence. The radius of this object is measured to be R-p = 2.227(-0.057)(+ 0.052) R-circle plus (in which the error includes the uncertainty in the stellar properties), but currently available radial-velocity measurements only place an upper limit on its mass of about 20 M-circle plus. Kepler-10 c represents another example (with Kepler-9 d and Kepler-11 g) of statistical "validation" of a transiting exoplanet, as opposed to the usual "confirmation" that can take place when the Doppler signal is detected or transit timing variations are measured. It is anticipated that many of Kepler's smaller candidates will receive a similar treatment since dynamical confirmation may be difficult or impractical with the sensitivity of current instrumentation.
Kepler-18B, C, and D: A System of Three Planets Confirmed by Transit Timing Variations, Light Curve Validation, Warm-Spitzer Photometry, and Radial Velocity Measurements
(2011-11) Cochran, William D.; Fabrycky, Daniel C.; Torres, Guillermo; Fressin, Francois; Desert, Jean-Michel; Ragozzine, Darin; Sasselov, Dimitar; Fortney, Jonathan J.; Rowe, Jason F.; Brugamyer, Erik J.; Bryson, Stephen T.; Carter, Joshua A.; Ciardi, David R.; Howell, Steve B.; Steffen, Jason H.; Borucki, William J.; Koch, David G.; Winn, Joshua N.; Welsh, William F.; Uddin, Kamal; Tenenbaum, Peter; Still, M.; Seager, Sara; Quinn, Samuel N.; Mullally, F.; Miller, Neil; Marcy, Geoffrey W.; MacQueen, Phillip J.; Lucas, Phillip; Lissauer, Jack J.; Latham, David W.; Knutson, Heather; Kinemuchi, K.; Johnson, John A.; Jenkins, Jon M.; Isaacson, Howard; Howard, Andrew; Horch, Elliott; Holman, Matthew J.; Henze, Christopher E.; Haas, Michael R.; Gilliland, Ronald L.; Gautier, Thomas N., III; Ford, Eric B.; Fischer, Debra A.; Everett, Mark; Endl, Michael; Demory, Brice-Oliver; Deming, Drake; Charbonneau, David; Caldwell, Douglas; Buchhave, Lars; Brown, Timothy M.; Batalha, Natalie; Cochran, William D.; MacQueen, Phillip J.
We report the detection of three transiting planets around a Sun-like star, which we designate Kepler-18. The transit signals were detected in photometric data from the Kepler satellite, and were confirmed to arise from planets using a combination of large transit-timing variations (TTVs), radial velocity variations, Warm-Spitzer observations, and statistical analysis of false-positive probabilities. The Kepler-18 star has a mass of 0.97M(circle dot), a radius of 1.1R(circle dot), an effective temperature of 5345 K, and an iron abundance of [Fe/H] = +0.19. The planets have orbital periods of approximately 3.5, 7.6, and 14.9 days. The innermost planet "b" is a "super-Earth" with a mass of 6.9 +/- 3.4M(circle plus), a radius of 2.00 +/- 0.10R(circle plus), and a mean density of 4.9 +/- 2.4 g cm(3). The two outer planets "c" and "d" are both low-density Neptune-mass planets. Kepler-18c has a mass of 17.3 +/- 1.9 M-circle plus, a radius of 5.49 +/- 0.26R(circle plus), and a mean density of 0.59 +/- 0.07 g cm(3), while Kepler-18d has a mass of 16.4 +/- 1.4 M-circle plus, a radius of 6.98 +/- 0.33 R-circle plus and a mean density of 0.27 +/- 0.03 g cm(.)(3) Kepler-18c and Kepler-18d have orbital periods near a 2:1 mean-motion resonance, leading to large and readily detected TTVs.
Non-Detection Of L-Band Line Emission From The Exoplanet HD189733B
(2011-02) Mandell, Avi M.; Deming, L. Drake; Blake, Geoffrey A.; Knutson, Heather A.; Mumma, Michael J.; Villanueva, Geronimo L.; Salyk, Colette; Salyk, Colette
We attempt to confirm bright non-local thermodynamic equilibrium (non-LTE) emission from the exoplanet HD 189733b at 3.25 mu m, as recently reported by Swain et al. based on observations at low spectral resolving power (lambda/delta lambda approximate to 30). Non-LTE emission lines from gas in an exoplanet atmosphere will not be significantly broadened by collisions, so the measured emission intensity per resolution element must be substantially brighter when observed at high spectral resolving power. We observed the planet before, during, and after a secondary eclipse event at a resolving power lambda/delta lambda = 27, 000 using the NIRSPEC spectrometer on the Keck II telescope. Our spectra cover a spectral window near the peak found by Swain et al., and we compare emission cases that could account for the magnitude and wavelength dependence of the Swain et al. result with our final spectral residuals. To model the expected line emission, we use a general non-equilibrium formulation to synthesize emission features from all plausible molecules that emit in this spectral region. In every case, we detect no line emission to a high degree of confidence. After considering possible explanations for the Swain et al. results and the disparity with our own data, we conclude that an astrophysical source for the putative non-LTE emission is unlikely. We note that the wavelength dependence of the signal seen by Swain et al. closely matches the 2 nu(2) band of water vapor at 300 K, and we suggest that an imperfect correction for telluric water is the source of the feature claimed by Swain et al.