We examine the secondary eclipse of the exoplanet HAT-P-1b using the IRAC instrument on board the... more We examine the secondary eclipse of the exoplanet HAT-P-1b using the IRAC instrument on board the Spitzer Space Telescope. This planet is close to the boundary between the pM and pL classes of hot Jupiters, which makes it an important test case for theoretical models of temperature inversions in the atmospheres of this type of gas giants. Our analysis shows secondary eclipse depths for HAT-P-1b, as a fraction of the stellar flux, to be: 0.075% +/- 0.008% (3.6 micron), 0.128% +/- 0.022% (4.5 micron), 0.183% +/- 0.031% (5.8 micron) and 0.230% +/- 0.034% (8.0 micron). These values can be produced, within errors, by a 1500K black body, or alternatively by a hot Jupiter with a small temperature inversion in its atmosphere. In both cases, the planet must radiate a significant amount of the energy received from the star through its day side, which suggests that little energy is redistributed through atmospheric circulation to be emitted through the night side of the planet. It has been suggested that this planet is inflated through tidal dissipation, based on its large radius and non-zero eccentricity allowed by the radial velocity data. By timing the secondary transit, we are able to determine that the orbit is very close to circular. The leading author was funded by the NASA Astrobiology Institute SUIA program.
ABSTRACT Stevenson et al. (2010, Nature 464, 1161-1164) made the surprising discovery of a lack o... more ABSTRACT Stevenson et al. (2010, Nature 464, 1161-1164) made the surprising discovery of a lack of methane (CH4) and abundant carbon monoxide (CO) on the cool exoplanet GJ 436b. This was based on a nondetection at 4.5 microns (CO band), a strong detection at 3.6 microns (CH4 band), and a weak signal at 8.0 microns (CH4 band). At GJ 436b's equilibrium temperature of 770 K, CH4 is thermochemically favored over CO. We present a second cool exoplanet that also features a detection at 3.6 microns and a nondetection at 4.5 microns, suggesting strong CO absorption. The transiting extrasolar planet WASP-29b was discovered by the Wide Angle Search for Planets by Hellier et al. (2010, ApJL 723, L60-L63). WASP-29b is a hot Saturn with a equilibrium temperature of 980 K. It orbits a K4 dwarf star every 3.922 days at a distance of 0.0457 AU. We analyze lightcurves from two Spitzer 3.6 micron secondary eclipses taken in August 2010 and January 2011, and one Spitzer 4.5 micron secondary eclipse taken in January 2011. We detect no eclipse in the 4.5 micron observation. This mirrors the results of Stevenson et al. for GJ 436b and suggests that WASP-29b may also have abundant CO. We strongly detect eclipses in the 3.6 micron observations, which provide timing constraints for all three observations. The lack of an 8.0 micron observation prevents us from confirming a lack of methane. K-band observations would help to address its abundance. These observations are part of the Spitzer Exoplanet Target of Opportunity program. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA, which provided support for this work.
ABSTRACT Stevenson et al. (2010, Nature 464, 1161-1164) made the surprising discovery of a lack o... more ABSTRACT Stevenson et al. (2010, Nature 464, 1161-1164) made the surprising discovery of a lack of methane (CH4) and abundant carbon monoxide (CO) on the cool exoplanet GJ 436b. This was based on a nondetection at 4.5 microns (CO band), a strong detection at 3.6 microns (CH4 band), and a weak signal at 8.0 microns (CH4 band). At GJ 436b's equilibrium temperature of 770 K, CH4 is thermochemically favored over CO. We present a second cool exoplanet that also features a detection at 3.6 microns and a nondetection at 4.5 microns, suggesting strong CO absorption. The transiting extrasolar planet WASP-29b was discovered by the Wide Angle Search for Planets by Hellier et al. (2010, ApJL 723, L60-L63). WASP-29b is a hot Saturn with a equilibrium temperature of 980 K. It orbits a K4 dwarf star every 3.922 days at a distance of 0.0457 AU. We analyze lightcurves from two Spitzer 3.6 micron secondary eclipses taken in August 2010 and January 2011, and one Spitzer 4.5 micron secondary eclipse taken in January 2011. We detect no eclipse in the 4.5 micron observation. This mirrors the results of Stevenson et al. for GJ 436b and suggests that WASP-29b may also have abundant CO. We strongly detect eclipses in the 3.6 micron observations, which provide timing constraints for all three observations. The lack of an 8.0 micron observation prevents us from confirming a lack of methane. K-band observations would help to address its abundance. These observations are part of the Spitzer Exoplanet Target of Opportunity program. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA, which provided support for this work.
The dayside of HD 149026b is near the edge of detectability by the Spitzer Space Telescope. We re... more The dayside of HD 149026b is near the edge of detectability by the Spitzer Space Telescope. We report on 11 secondary-eclipse events at 3.6, 4.5, 3 × 5.8, 4 × 8.0, and 2 × 16 μm plus three primary-transit events at 8.0 μm. The eclipse depths from jointly fit models at each wavelength are 0.040% ± 0.003% at 3.6 μm, 0.034% ± 0.006% at 4.5 μm, 0.044% ± 0.010% at 5.8 μm, 0.052% ± 0.006% at 8.0 μm, and 0.085% ± 0.032% at 16 μm. Multiple observations at the longer wavelengths improved eclipse-depth signal-to-noise ratios by up to a factor of two and improved estimates of the planet-to-star radius ratio (Rp /R sstarf = 0.0518 ± 0.0006). We also identify no significant deviations from a circular orbit and, using this model, report an improved period of 2.8758916 ± 0.0000014 days. Chemical-equilibrium models find no indication of a temperature inversion in the dayside atmosphere of HD 149026b. Our best-fit model favors large amounts of CO and CO2, moderate heat redistribution (f = 0.5), and a strongly enhanced metallicity. These analyses use BiLinearly-Interpolated Subpixel Sensitivity (BLISS) mapping, a new technique to model two position-dependent systematics (intrapixel variability and pixelation) by mapping the pixel surface at high resolution. BLISS mapping outperforms previous methods in both speed and goodness of fit. We also present an orthogonalization technique for linearly correlated parameters that accelerates the convergence of Markov chains that employ the Metropolis random walk sampler. The electronic supplement contains light-curve files.
The Spitzer Exoplanet Target of Opportunity program observes secondary eclipses, when the planet ... more The Spitzer Exoplanet Target of Opportunity program observes secondary eclipses, when the planet passes behind its parent star, to provide direct measurements of emitted planetary flux, thus constraining atmospheric models. Here we present dayside atmospheric constraints of two exoplanets using a total of 16 secondary eclipse observations at six different infrared wavelengths. The first exoplanet is HD 149026b which transits its large, relatively hot G0 parent star at a distance of only 0.042 AU. The Saturn-sized planet's high average density suggests that most of its mass must be in its large, 80 Earth-mass icy/rocky core. The second planet, GJ 436b, is a hot Neptune that orbits a small, M-dwarf star and is currently Earth's nearest transiting exoplanet at a distance of only 33 ly. We also present a new technique that models Spitzer's position-dependent sensitivity effect using a high resolution, bilinearly-interpolated subpixel sensitivity map. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA, which provided support for this work.
WASP-12b is one of the largets planets yet discovered, with an inflated radius of 1.79 Rjup. It a... more WASP-12b is one of the largets planets yet discovered, with an inflated radius of 1.79 Rjup. It also lies in very close proximity to its G-type star, with a semi-major axis of 0.0229 AU and orbital period of only 1.09 days. It is one of the hottest exoplanets discovered to date as well, with an equilibrium temperature of 2516 K for zero albedo and uniform redistribution of incident flux. We observed four secondary eclipses of the WASP-12b using Spitzer's Infrared Array Camera (IRAC), which yielded six separate eclipse lightcurves over the IRAC wavelengths (2x3.6, 2x4.5, 5.8, and 8.0 mum). From these observations, we are able to constrain the planet's orbital and atmospheric properties, such as eccentricity, atmospheric composition, and thermal structure. The secondary eclipse photometry is presented along with our analysis. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA, which provided support for this work.
The nearby extrasolar planet GJ 436b-which has been labelled as a 'hot Neptune'-reveals i... more The nearby extrasolar planet GJ 436b-which has been labelled as a 'hot Neptune'-reveals itself by the dimming of light as it crosses in front of and behind its parent star as seen from Earth. Respectively known as the primary transit and secondary eclipse, the former constrains the planet's radius and mass, and the latter constrains the planet's temperature and, with measurements at multiple wavelengths, its atmospheric composition. Previous work using transmission spectroscopy failed to detect the 1.4-mum water vapour band, leaving the planet's atmospheric composition poorly constrained. Here we report the detection of planetary thermal emission from the dayside of GJ 436b at multiple infrared wavelengths during the secondary eclipse. The best-fit compositional models contain a high CO abundance and a substantial methane (CH(4)) deficiency relative to thermochemical equilibrium models for the predicted hydrogen-dominated atmosphere. Moreover, we report the prese...
The Spitzer Exoplanet Target-of-Opportunity program has observed the secondary eclipses of severa... more The Spitzer Exoplanet Target-of-Opportunity program has observed the secondary eclipses of several planets in suspected eccentric orbits around their host stars. The midpoint time determined from each observation can be combined with radial velocity (RV) and transit data to provide improved sets of orbital parameters for a given exoplanet. The orbital phase of the midpoint can be used to establish lower limits on the eccentricity (particularly on ecosomega, where e is eccentricity and omega is the argument of periastron) that are independent of RV data. Multiple midpoints can be used to detect parameter variation. We present results for WASP-12b (e < 0.06), WASP-14b (e 0.087), WASP-18b (e 0.0088), GJ 436b (e 0.1368), and HAT-P-13b; discussion of techniques of joint orbital modeling, including methods of detecting apsidal motion; dynamical implications for selected systems; and the role of amateur observers as sources of exoplanet data. Spitzer is operated by the Jet Propulsion La...
The Saturn-sized exoplanet HD 149026b transits a large, relatively hot parent star at a distance ... more The Saturn-sized exoplanet HD 149026b transits a large, relatively hot parent star at a distance of only 0.042 AU. The planet's high average density suggests that most of HD 149026b's mass must be in it's large, icy/rocky core. Using the Spitzer Space Telescope to observe the system during secondary eclipse, previous authors report contradicting eclipse depths at 8.0 mum. We re-analyze these data, combine the results with two new observations at 8.0 mum, and use additional observations in other Spitzer channels to present constraints on the atmospheric composition of HD 149026b. We also present a new technique that models Spitzer's position-dependent (intrapixel) sensitivity effect to a high degree of precision. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA, which provided support for this work.
The transiting exoplanet WASP-18b was discovered in 2008 by the Wide Angle Search for Planets (WA... more The transiting exoplanet WASP-18b was discovered in 2008 by the Wide Angle Search for Planets (WASP) project. The Spitzer Exoplanet Target of Opportunity Program observed secondary eclipses of WASP-18b using Spitzer's Infrared Array Camera (IRAC) in the 3.6 micron and 5.8 micron bands on 2008 December 20, and in the 4.5 micron and 8.0 micron bands on 2008 December 24. We present a pressure-temperature profile, eclipse depths and brightness temperatures of WASP-18b, which is one of the hottest planets yet discovered, as hot as an M-dwarf star. These observations are part of the Spitzer Exoplanet Target of Opportunity program, which observes eclipses and transits of new exoplanets. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA, which provided support for this work.
The dayside of HD 149026b is near the edge of detectability by the Spitzer Space Telescope. We re... more The dayside of HD 149026b is near the edge of detectability by the Spitzer Space Telescope. We report on eleven secondary-eclipse events at 3.6, 4.5, 3 x 5.8, 4 x 8.0, and 2 x 16 microns plus three primary-transit events at 8.0 microns. The eclipse depths from jointly-fit models at each wavelength are 0.040 +/- 0.003% at 3.6 microns, 0.034 +/- 0.006% at 4.5 microns, 0.044 +/- 0.010% at 5.8 microns, 0.052 +/- 0.006% at 8.0 microns, and 0.085 +/- 0.032% at 16 microns. Multiple observations at the longer wavelengths improved eclipse-depth signal-to-noise ratios by up to a factor of two and improved estimates of the planet-to-star radius ratio (Rp/Rs = 0.0518 +/- 0.0006). We also identify no significant deviations from a circular orbit and, using this model, report an improved period of 2.8758916 +/- 0.0000014 days. Chemical-equilibrium models find no indication of a temperature inversion in the dayside atmosphere of HD 149026b. Our best-fit model favors large amounts of CO and CO2, mod...
The orbital phase of the midpoint of an extrasolar planet&amp;amp;#39;s secondary eclipse is ... more The orbital phase of the midpoint of an extrasolar planet&amp;amp;#39;s secondary eclipse is determined solely by the orbital parameters eccentricity (e) and argument of periapsis (omega). Consequently, a precise measurement of the phase imposes a tight, but non-unique, constraint on these two parameters, which can be combined with other methods, such as radial velocity measurements, to estimate their values. By
Exoplanet WASP-12b has a period of 1.09 days and is close enough to its G0 star that, if eccentri... more Exoplanet WASP-12b has a period of 1.09 days and is close enough to its G0 star that, if eccentric, its orbital precession period of a few decades could be measureable in just a few years with high-precsion secondary eclipse measurements. We observed four secondary eclipses of WASP-12b with the Spitzer Space Telescope separated by several years. Combined with ground-based transit
The nearby exoplanet GJ 436b is a hot Neptune with an equilibrium temperature of approximately 70... more The nearby exoplanet GJ 436b is a hot Neptune with an equilibrium temperature of approximately 700K, assuming uniform redistribution and 0.3 Bond albedo. This eccentric exoplanet is the only known transiting hot Neptune and the only known transiting M dwarf companion. The Spitzer Exoplanet Target of Opportunity program observes secondary eclipses, where the planet passes behind the star, to provide
WASP-14b belongs to a class of highly irradiated hot Jupiters (Teq = 1866 K) with a mass of 7.3 \... more WASP-14b belongs to a class of highly irradiated hot Jupiters (Teq = 1866 K) with a mass of 7.3 \pm 0.5 MJ and a radius of 1.28 \pm 0.08 RJ . With a mean density of 4.6 gcm-3, this transiting planet is one of the densest known to date (Joshi et al. 2009), for planets with periods less than 3
We examine the secondary eclipse of the exoplanet HAT-P-1b using the IRAC instrument on board the... more We examine the secondary eclipse of the exoplanet HAT-P-1b using the IRAC instrument on board the Spitzer Space Telescope. This planet is close to the boundary between the pM and pL classes of hot Jupiters, which makes it an important test case for theoretical models of temperature inversions in the atmospheres of this type of gas giants. Our analysis shows secondary eclipse depths for HAT-P-1b, as a fraction of the stellar flux, to be: 0.075% +/- 0.008% (3.6 micron), 0.128% +/- 0.022% (4.5 micron), 0.183% +/- 0.031% (5.8 micron) and 0.230% +/- 0.034% (8.0 micron). These values can be produced, within errors, by a 1500K black body, or alternatively by a hot Jupiter with a small temperature inversion in its atmosphere. In both cases, the planet must radiate a significant amount of the energy received from the star through its day side, which suggests that little energy is redistributed through atmospheric circulation to be emitted through the night side of the planet. It has been suggested that this planet is inflated through tidal dissipation, based on its large radius and non-zero eccentricity allowed by the radial velocity data. By timing the secondary transit, we are able to determine that the orbit is very close to circular. The leading author was funded by the NASA Astrobiology Institute SUIA program.
ABSTRACT Stevenson et al. (2010, Nature 464, 1161-1164) made the surprising discovery of a lack o... more ABSTRACT Stevenson et al. (2010, Nature 464, 1161-1164) made the surprising discovery of a lack of methane (CH4) and abundant carbon monoxide (CO) on the cool exoplanet GJ 436b. This was based on a nondetection at 4.5 microns (CO band), a strong detection at 3.6 microns (CH4 band), and a weak signal at 8.0 microns (CH4 band). At GJ 436b&#39;s equilibrium temperature of 770 K, CH4 is thermochemically favored over CO. We present a second cool exoplanet that also features a detection at 3.6 microns and a nondetection at 4.5 microns, suggesting strong CO absorption. The transiting extrasolar planet WASP-29b was discovered by the Wide Angle Search for Planets by Hellier et al. (2010, ApJL 723, L60-L63). WASP-29b is a hot Saturn with a equilibrium temperature of 980 K. It orbits a K4 dwarf star every 3.922 days at a distance of 0.0457 AU. We analyze lightcurves from two Spitzer 3.6 micron secondary eclipses taken in August 2010 and January 2011, and one Spitzer 4.5 micron secondary eclipse taken in January 2011. We detect no eclipse in the 4.5 micron observation. This mirrors the results of Stevenson et al. for GJ 436b and suggests that WASP-29b may also have abundant CO. We strongly detect eclipses in the 3.6 micron observations, which provide timing constraints for all three observations. The lack of an 8.0 micron observation prevents us from confirming a lack of methane. K-band observations would help to address its abundance. These observations are part of the Spitzer Exoplanet Target of Opportunity program. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA, which provided support for this work.
ABSTRACT Stevenson et al. (2010, Nature 464, 1161-1164) made the surprising discovery of a lack o... more ABSTRACT Stevenson et al. (2010, Nature 464, 1161-1164) made the surprising discovery of a lack of methane (CH4) and abundant carbon monoxide (CO) on the cool exoplanet GJ 436b. This was based on a nondetection at 4.5 microns (CO band), a strong detection at 3.6 microns (CH4 band), and a weak signal at 8.0 microns (CH4 band). At GJ 436b&#39;s equilibrium temperature of 770 K, CH4 is thermochemically favored over CO. We present a second cool exoplanet that also features a detection at 3.6 microns and a nondetection at 4.5 microns, suggesting strong CO absorption. The transiting extrasolar planet WASP-29b was discovered by the Wide Angle Search for Planets by Hellier et al. (2010, ApJL 723, L60-L63). WASP-29b is a hot Saturn with a equilibrium temperature of 980 K. It orbits a K4 dwarf star every 3.922 days at a distance of 0.0457 AU. We analyze lightcurves from two Spitzer 3.6 micron secondary eclipses taken in August 2010 and January 2011, and one Spitzer 4.5 micron secondary eclipse taken in January 2011. We detect no eclipse in the 4.5 micron observation. This mirrors the results of Stevenson et al. for GJ 436b and suggests that WASP-29b may also have abundant CO. We strongly detect eclipses in the 3.6 micron observations, which provide timing constraints for all three observations. The lack of an 8.0 micron observation prevents us from confirming a lack of methane. K-band observations would help to address its abundance. These observations are part of the Spitzer Exoplanet Target of Opportunity program. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA, which provided support for this work.
The dayside of HD 149026b is near the edge of detectability by the Spitzer Space Telescope. We re... more The dayside of HD 149026b is near the edge of detectability by the Spitzer Space Telescope. We report on 11 secondary-eclipse events at 3.6, 4.5, 3 × 5.8, 4 × 8.0, and 2 × 16 μm plus three primary-transit events at 8.0 μm. The eclipse depths from jointly fit models at each wavelength are 0.040% ± 0.003% at 3.6 μm, 0.034% ± 0.006% at 4.5 μm, 0.044% ± 0.010% at 5.8 μm, 0.052% ± 0.006% at 8.0 μm, and 0.085% ± 0.032% at 16 μm. Multiple observations at the longer wavelengths improved eclipse-depth signal-to-noise ratios by up to a factor of two and improved estimates of the planet-to-star radius ratio (Rp /R sstarf = 0.0518 ± 0.0006). We also identify no significant deviations from a circular orbit and, using this model, report an improved period of 2.8758916 ± 0.0000014 days. Chemical-equilibrium models find no indication of a temperature inversion in the dayside atmosphere of HD 149026b. Our best-fit model favors large amounts of CO and CO2, moderate heat redistribution (f = 0.5), and a strongly enhanced metallicity. These analyses use BiLinearly-Interpolated Subpixel Sensitivity (BLISS) mapping, a new technique to model two position-dependent systematics (intrapixel variability and pixelation) by mapping the pixel surface at high resolution. BLISS mapping outperforms previous methods in both speed and goodness of fit. We also present an orthogonalization technique for linearly correlated parameters that accelerates the convergence of Markov chains that employ the Metropolis random walk sampler. The electronic supplement contains light-curve files.
The Spitzer Exoplanet Target of Opportunity program observes secondary eclipses, when the planet ... more The Spitzer Exoplanet Target of Opportunity program observes secondary eclipses, when the planet passes behind its parent star, to provide direct measurements of emitted planetary flux, thus constraining atmospheric models. Here we present dayside atmospheric constraints of two exoplanets using a total of 16 secondary eclipse observations at six different infrared wavelengths. The first exoplanet is HD 149026b which transits its large, relatively hot G0 parent star at a distance of only 0.042 AU. The Saturn-sized planet's high average density suggests that most of its mass must be in its large, 80 Earth-mass icy/rocky core. The second planet, GJ 436b, is a hot Neptune that orbits a small, M-dwarf star and is currently Earth's nearest transiting exoplanet at a distance of only 33 ly. We also present a new technique that models Spitzer's position-dependent sensitivity effect using a high resolution, bilinearly-interpolated subpixel sensitivity map. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA, which provided support for this work.
WASP-12b is one of the largets planets yet discovered, with an inflated radius of 1.79 Rjup. It a... more WASP-12b is one of the largets planets yet discovered, with an inflated radius of 1.79 Rjup. It also lies in very close proximity to its G-type star, with a semi-major axis of 0.0229 AU and orbital period of only 1.09 days. It is one of the hottest exoplanets discovered to date as well, with an equilibrium temperature of 2516 K for zero albedo and uniform redistribution of incident flux. We observed four secondary eclipses of the WASP-12b using Spitzer's Infrared Array Camera (IRAC), which yielded six separate eclipse lightcurves over the IRAC wavelengths (2x3.6, 2x4.5, 5.8, and 8.0 mum). From these observations, we are able to constrain the planet's orbital and atmospheric properties, such as eccentricity, atmospheric composition, and thermal structure. The secondary eclipse photometry is presented along with our analysis. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA, which provided support for this work.
The nearby extrasolar planet GJ 436b-which has been labelled as a 'hot Neptune'-reveals i... more The nearby extrasolar planet GJ 436b-which has been labelled as a 'hot Neptune'-reveals itself by the dimming of light as it crosses in front of and behind its parent star as seen from Earth. Respectively known as the primary transit and secondary eclipse, the former constrains the planet's radius and mass, and the latter constrains the planet's temperature and, with measurements at multiple wavelengths, its atmospheric composition. Previous work using transmission spectroscopy failed to detect the 1.4-mum water vapour band, leaving the planet's atmospheric composition poorly constrained. Here we report the detection of planetary thermal emission from the dayside of GJ 436b at multiple infrared wavelengths during the secondary eclipse. The best-fit compositional models contain a high CO abundance and a substantial methane (CH(4)) deficiency relative to thermochemical equilibrium models for the predicted hydrogen-dominated atmosphere. Moreover, we report the prese...
The Spitzer Exoplanet Target-of-Opportunity program has observed the secondary eclipses of severa... more The Spitzer Exoplanet Target-of-Opportunity program has observed the secondary eclipses of several planets in suspected eccentric orbits around their host stars. The midpoint time determined from each observation can be combined with radial velocity (RV) and transit data to provide improved sets of orbital parameters for a given exoplanet. The orbital phase of the midpoint can be used to establish lower limits on the eccentricity (particularly on ecosomega, where e is eccentricity and omega is the argument of periastron) that are independent of RV data. Multiple midpoints can be used to detect parameter variation. We present results for WASP-12b (e < 0.06), WASP-14b (e 0.087), WASP-18b (e 0.0088), GJ 436b (e 0.1368), and HAT-P-13b; discussion of techniques of joint orbital modeling, including methods of detecting apsidal motion; dynamical implications for selected systems; and the role of amateur observers as sources of exoplanet data. Spitzer is operated by the Jet Propulsion La...
The Saturn-sized exoplanet HD 149026b transits a large, relatively hot parent star at a distance ... more The Saturn-sized exoplanet HD 149026b transits a large, relatively hot parent star at a distance of only 0.042 AU. The planet's high average density suggests that most of HD 149026b's mass must be in it's large, icy/rocky core. Using the Spitzer Space Telescope to observe the system during secondary eclipse, previous authors report contradicting eclipse depths at 8.0 mum. We re-analyze these data, combine the results with two new observations at 8.0 mum, and use additional observations in other Spitzer channels to present constraints on the atmospheric composition of HD 149026b. We also present a new technique that models Spitzer's position-dependent (intrapixel) sensitivity effect to a high degree of precision. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA, which provided support for this work.
The transiting exoplanet WASP-18b was discovered in 2008 by the Wide Angle Search for Planets (WA... more The transiting exoplanet WASP-18b was discovered in 2008 by the Wide Angle Search for Planets (WASP) project. The Spitzer Exoplanet Target of Opportunity Program observed secondary eclipses of WASP-18b using Spitzer's Infrared Array Camera (IRAC) in the 3.6 micron and 5.8 micron bands on 2008 December 20, and in the 4.5 micron and 8.0 micron bands on 2008 December 24. We present a pressure-temperature profile, eclipse depths and brightness temperatures of WASP-18b, which is one of the hottest planets yet discovered, as hot as an M-dwarf star. These observations are part of the Spitzer Exoplanet Target of Opportunity program, which observes eclipses and transits of new exoplanets. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA, which provided support for this work.
The dayside of HD 149026b is near the edge of detectability by the Spitzer Space Telescope. We re... more The dayside of HD 149026b is near the edge of detectability by the Spitzer Space Telescope. We report on eleven secondary-eclipse events at 3.6, 4.5, 3 x 5.8, 4 x 8.0, and 2 x 16 microns plus three primary-transit events at 8.0 microns. The eclipse depths from jointly-fit models at each wavelength are 0.040 +/- 0.003% at 3.6 microns, 0.034 +/- 0.006% at 4.5 microns, 0.044 +/- 0.010% at 5.8 microns, 0.052 +/- 0.006% at 8.0 microns, and 0.085 +/- 0.032% at 16 microns. Multiple observations at the longer wavelengths improved eclipse-depth signal-to-noise ratios by up to a factor of two and improved estimates of the planet-to-star radius ratio (Rp/Rs = 0.0518 +/- 0.0006). We also identify no significant deviations from a circular orbit and, using this model, report an improved period of 2.8758916 +/- 0.0000014 days. Chemical-equilibrium models find no indication of a temperature inversion in the dayside atmosphere of HD 149026b. Our best-fit model favors large amounts of CO and CO2, mod...
The orbital phase of the midpoint of an extrasolar planet&amp;amp;#39;s secondary eclipse is ... more The orbital phase of the midpoint of an extrasolar planet&amp;amp;#39;s secondary eclipse is determined solely by the orbital parameters eccentricity (e) and argument of periapsis (omega). Consequently, a precise measurement of the phase imposes a tight, but non-unique, constraint on these two parameters, which can be combined with other methods, such as radial velocity measurements, to estimate their values. By
Exoplanet WASP-12b has a period of 1.09 days and is close enough to its G0 star that, if eccentri... more Exoplanet WASP-12b has a period of 1.09 days and is close enough to its G0 star that, if eccentric, its orbital precession period of a few decades could be measureable in just a few years with high-precsion secondary eclipse measurements. We observed four secondary eclipses of WASP-12b with the Spitzer Space Telescope separated by several years. Combined with ground-based transit
The nearby exoplanet GJ 436b is a hot Neptune with an equilibrium temperature of approximately 70... more The nearby exoplanet GJ 436b is a hot Neptune with an equilibrium temperature of approximately 700K, assuming uniform redistribution and 0.3 Bond albedo. This eccentric exoplanet is the only known transiting hot Neptune and the only known transiting M dwarf companion. The Spitzer Exoplanet Target of Opportunity program observes secondary eclipses, where the planet passes behind the star, to provide
WASP-14b belongs to a class of highly irradiated hot Jupiters (Teq = 1866 K) with a mass of 7.3 \... more WASP-14b belongs to a class of highly irradiated hot Jupiters (Teq = 1866 K) with a mass of 7.3 \pm 0.5 MJ and a radius of 1.28 \pm 0.08 RJ . With a mean density of 4.6 gcm-3, this transiting planet is one of the densest known to date (Joshi et al. 2009), for planets with periods less than 3
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