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ABSTRACT We have developed an open-source pipeline for the analysis of Spitzer/IRAC channel 1 and 2 time-series photometry, incorporating some of the most popular decorrelation methods. We applied this pipeline to new phase curve observations of ultra-hot Jupiters MASCARA-1b and KELT-16b, and we performed the first comprehensive reanalysis of 15 phase curves. We find that MASCARA-1b and KELT-16b have phase offsets of $6^{+11}_{-11}~^{\circ }$W and $38^{+16}_{-15}~^{\circ }$W, dayside temperatures of $2952^{+100}_{-97}$  and $3070^{+160}_{-150}$ K, and nightside temperatures of $1300^{+340}_{-340}$ and $1900^{+430}_{-440}$ K, respectively. We confirm a strong correlation between dayside and irradiation temperatures with a shallower dependence for nightside temperature. We also find evidence that the normalized phase curve amplitude (peak-to-trough divided by eclipse depth) is correlated with stellar effective temperature. In addition, while our different models often retrieve similar parameters, significant differences occasionally arise between them, as well as between our preferred model and the literature values. Nevertheless, our preferred models are consistent with published phase offsets to within −8 ± 21 degrees (−1.6 ± 3.2 sigma), and normalized phase curve amplitudes are on average reproduced to within −0.01 ± 0.24 (−0.1 ± 1.6 sigma). Finally, we find that BLISS performs best in most cases, but not all; we therefore recommend future analyses consider numerous detector models to ensure an optimal fit and to assess model dependencies.

ABSTRACT We have developed an open-source pipeline for the analysis of Spitzer/IRAC channel 1 and 2 time-series photometry, incorporating some of the most popular decorrelation methods. We applied this pipeline to new phase curve observations of ultra-hot Jupiters MASCARA-1b and KELT-16b, and we performed the first comprehensive reanalysis of 15 phase curves. We find that MASCARA-1b and KELT-16b have phase offsets of $6^{+11}_{-11}~^{\circ }$W and $38^{+16}_{-15}~^{\circ }$W, dayside temperatures of $2952^{+100}_{-97}$  and $3070^{+160}_{-150}$ K, and nightside temperatures of $1300^{+340}_{-340}$ and $1900^{+430}_{-440}$ K, respectively. We confirm a strong correlation between dayside and irradiation temperatures with a shallower dependence for nightside temperature. We also find evidence that the normalized phase curve amplitude (peak-to-trough divided by eclipse depth) is correlated with stellar effective temperature. In addition, while our different models often retrieve similar parameters, significant differences occasionally arise between them, as well as between our preferred model and the literature values. Nevertheless, our preferred models are consistent with published phase offsets to within −8 ± 21 degrees (−1.6 ± 3.2 sigma), and normalized phase curve amplitudes are on average reproduced to within −0.01 ± 0.24 (−0.1 ± 1.6 sigma). Finally, we find that BLISS performs best in most cases, but not all; we therefore recommend future analyses consider numerous detector models to ensure an optimal fit and to assess model dependencies.

Although the final observations of the Spitzer Warm Mission are currentlyscheduled for March 2019, it can continue operations through the end of thedecade with no loss of photometric precision. As we will show, there is astrong science case for extending the current Warm Mission to December 2020.Spitzer has already made major impacts in the fields of exoplanets (includingmicrolensing events), characterizing near Earth objects, enhancing ourknowledge of nearby stars and brown dwarfs, understanding the properties andstructure of our Milky Way galaxy, and deep wide-field extragalactic surveys tostudy galaxy birth and evolution. By extending Spitzer through 2020, it cancontinue to make ground-breaking discoveries in those fields, and providecrucial support to the NASA flagship missions JWST and WFIRST, as well as theupcoming TESS mission, and it will complement ground-based observations by LSSTand the new large telescopes of the next decade. This scientific programaddresses NASA's Science Mission Directive's objectives in astrophysics, whichinclude discovering how the universe works, exploring how it began and evolved,and searching for life on planets around other stars.

The James Webb Space Telescope will revolutionize transiting exoplanetatmospheric science due to its capability for continuous, long-durationobservations and its larger collecting area, spectral coverage, and spectralresolution compared to existing space-based facilities. However, it is unclearprecisely how well JWST will perform and which of its myriad instruments andobserving modes will be best suited for transiting exoplanet studies. In thisarticle, we describe a prefatory JWST Early Release Science (ERS) program thatfocuses on testing specific observing modes to quickly give the community thedata and experience it needs to plan more efficient and successful futuretransiting exoplanet characterization programs. We propose a multi-prongedapproach wherein one aspect of the program focuses on observing transits of asingle target with all of the recommended observing modes to identify andunderstand potential systematics, compare transmission spectra at overlappingand neighboring wavelength regions, confirm throughputs, and determine overallperformances. In our search for transiting exoplanets that are well suited toachieving these goals, we identify 12 objects (dubbed "community targets") thatmeet our defined criteria. Currently, the most favorable target is WASP-62bbecause of its large predicted signal size, relatively bright host star, andlocation in JWST's continuous viewing zone. Since most of the community targetsdo not have well-characterized atmospheres, we recommend initiating preparatoryobserving programs to determine the presence of obscuring clouds/hazes withintheir atmospheres. Measurable spectroscopic features are needed to establishthe optimal resolution and wavelength regions for exoplanet characterization.Other initiatives from our proposed ERS program include testing the instrumentbrightness limits and performing phase-curve observations.(Abridged)

The James Webb Space Telescope will revolutionize transiting exoplanetatmospheric science due to its capability for continuous, long-durationobservations and its larger collecting area, spectral coverage, and spectralresolution compared to existing space-based facilities. However, it is unclearprecisely how well JWST will perform and which of its myriad instruments andobserving modes will be best suited for transiting exoplanet studies. In thisarticle, we describe a prefatory JWST Early Release Science (ERS) program thatfocuses on testing specific observing modes to quickly give the community thedata and experience it needs to plan more efficient and successful futuretransiting exoplanet characterization programs. We propose a multi-prongedapproach wherein one aspect of the program focuses on observing transits of asingle target with all of the recommended observing modes to identify andunderstand potential systematics, compare transmission spectra at overlappingand neighboring wavelength regions, confirm throughputs, and determine overallperformances. In our search for transiting exoplanets that are well suited toachieving these goals, we identify 12 objects (dubbed "community targets") thatmeet our defined criteria. Currently, the most favorable target is WASP-62bbecause of its large predicted signal size, relatively bright host star, andlocation in JWST's continuous viewing zone. Since most of the community targetsdo not have well-characterized atmospheres, we recommend initiating preparatoryobserving programs to determine the presence of obscuring clouds/hazes withintheir atmospheres. Measurable spectroscopic features are needed to establishthe optimal resolution and wavelength regions for exoplanet characterization.Other initiatives from our proposed ERS program include testing the instrumentbrightness limits and performing phase-curve observations.(Abridged)

We analyze full-orbit phase curve observations of the transiting hot JupitersWASP-19b and HAT-P-7b at 3.6 and 4.5 $\mu$m obtained using the Spitzer SpaceTelescope. For WASP-19b, we measure secondary eclipse depths of $0.485\%\pm0.024\%$ and $0.584\%\pm 0.029\%$ at 3.6 and 4.5 $\mu$m, which are consistentwith a single blackbody with effective temperature $2372 \pm 60$ K. Themeasured 3.6 and 4.5 $\mu$m secondary eclipse depths for HAT-P-7b are$0.156\%\pm 0.009\%$ and $0.190\%\pm 0.006\%$, which are well-described by asingle blackbody with effective temperature $2667\pm 57$ K. Comparing the phasecurves to the predictions of one-dimensional and three-dimensional atmosphericmodels, we find that WASP-19b's dayside emission is consistent with a modelatmosphere with no dayside thermal inversion and moderately efficient day-nightcirculation. We also detect an eastward-shifted hotspot, suggesting thepresence of a superrotating equatorial jet. In contrast, HAT-P-7b's daysideemission suggests a dayside thermal inversion and relatively inefficientday-night circulation; no hotspot shift is detected. For both planets, thesesame models do not agree with the measured nightside emission. Thediscrepancies in the model-data comparisons for WASP-19b might be explained byhigh-altitude silicate clouds on the nightside and/or high atmosphericmetallicity, while the very low 3.6 $\mu$m nightside planetary brightness forHAT-P-7b may be indicative of an enhanced global C/O ratio. We compute Bondalbedos of 0 ($

We analyze full-orbit phase curve observations of the transiting hot JupitersWASP-19b and HAT-P-7b at 3.6 and 4.5 $\mu$m obtained using the Spitzer SpaceTelescope. For WASP-19b, we measure secondary eclipse depths of $0.485\%\pm0.024\%$ and $0.584\%\pm 0.029\%$ at 3.6 and 4.5 $\mu$m, which are consistentwith a single blackbody with effective temperature $2372 \pm 60$ K. Themeasured 3.6 and 4.5 $\mu$m secondary eclipse depths for HAT-P-7b are$0.156\%\pm 0.009\%$ and $0.190\%\pm 0.006\%$, which are well-described by asingle blackbody with effective temperature $2667\pm 57$ K. Comparing the phasecurves to the predictions of one-dimensional and three-dimensional atmosphericmodels, we find that WASP-19b's dayside emission is consistent with a modelatmosphere with no dayside thermal inversion and moderately efficient day-nightcirculation. We also detect an eastward-shifted hotspot, suggesting thepresence of a superrotating equatorial jet. In contrast, HAT-P-7b's daysideemission suggests a dayside thermal inversion and relatively inefficientday-night circulation; no hotspot shift is detected. For both planets, thesesame models do not agree with the measured nightside emission. Thediscrepancies in the model-data comparisons for WASP-19b might be explained byhigh-altitude silicate clouds on the nightside and/or high atmosphericmetallicity, while the very low 3.6 $\mu$m nightside planetary brightness forHAT-P-7b may be indicative of an enhanced global C/O ratio. We compute Bondalbedos of 0 ($

We present full-orbit phase curve observations of the eccentric (e ∼ 0.08) transiting hot Jupiter WASP-14b obtained in the 3.6 and 4.5 μm bands using the Spitzer Space Telescope. We use two different methods for removing the intrapixel sensitivity effect and compare their efficacy in decoupling the instrumental noise. Our measured secondary eclipse depths of 0.1882% ± 0.0048% and 0.2247% ± 0.0086% at 3.6 and 4.5 μm, respectively, are both consistent with a blackbody temperature of 2402 ± 35 K. We place a 2σ upper limit on the nightside flux at 3.6 μm and find it to be 9% ± 1% of the dayside flux, corresponding to a brightness temperature of 1079 K. At 4.5 μm, the minimum planet flux is 30% ± 5% of the maximum flux, corresponding to a brightness temperature of 1380 ± 65 K. We compare our measured phase curves to the predictions of one-dimensional radiative transfer and three-dimensional general circulation models. We find that WASP-14b's measured dayside emission is consistent with a model atmosphere with equilibrium chemistry and a moderate temperature inversion. These same models tend to overpredict the nightside emission at 3.6 μm, while underpredicting the nightside emission at 4.5 μm. We propose that this discrepancy might be explained by an enhanced global C/O ratio. In addition, we find that the phase curves of WASP-14b (7.8 MJup) are consistent with a much lower albedo than those of other Jovian mass planets with thermal phase curve measurements, suggesting that it may be emitting detectable heat from the deep atmosphere or interior processes.

In this work we present Spitzer 3.6 and 4.5 μm secondary eclipse observations of five new cool ( K) transiting gas giant planets: HAT-P-19b, WASP-6b, WASP-10b, WASP-39b, and WASP-67b. We compare our measured eclipse depths to the predictions of a suite of atmosphere models and to eclipse depths for planets with previously published observations in order to constrain the temperature- and mass-dependent properties of gas giant planet atmospheres. We find that the dayside emission spectra of planets less massive than Jupiter require models with efficient circulation of energy to the night side and/or increased albedos, while those with masses greater than that of Jupiter are consistently best-matched by models with inefficient circulation and low albedos. At these relatively low temperatures we expect the atmospheric CH4/CO ratio to vary as a function of metallicity, and we therefore use our observations of these planets to constrain their atmospheric metallicities. We find that the most massive planets have dayside emission spectra that are best-matched by solar metallicity atmosphere models, but we are not able to place strong constraints on metallicities of the smaller planets in our sample. Interestingly, we find that the ratio of the 3.6 and 4.5 μm brightness temperatures for these cool transiting planets is independent of planet temperature, and instead exhibits a tentative correlation with planet mass. If this trend can be confirmed, it would suggest that the shape of these planets' emission spectra depends primarily on their masses, consistent with the hypothesis that lower-mass planets are more likely to have metal-rich atmospheres.

We report secondary eclipse photometry of the hot Jupiter XO-3b in the 4.5 μm band taken with the Infrared Array Camera on the Spitzer Space Telescope. We measure individual eclipse depths and center of eclipse times for a total of 12 secondary eclipses. We fit these data simultaneously with two transits observed in the same band in order to obtain a global best-fit secondary eclipse depth of 0.1580% ± 0.0036% and a center of eclipse phase of 0.67004 ± 0.00013. We assess the relative magnitude of variations in the dayside brightness of the planet by measuring the size of the residuals during ingress and egress from fitting the combined eclipse light curve with a uniform disk model and place an upper limit of 0.05%. The new secondary eclipse observations extend the total baseline from one and a half years to nearly three years, allowing us to place an upper limit on the periastron precession rate of 2.9 × 10-3 deg day-1 - the tightest constraint to date on the periastron precession rate of a hot Jupiter. We use the new transit observations to calculate improved estimates for the system properties, including an updated orbital ephemeris. We also use the large number of secondary eclipses to obtain the most stringent limits to date on the orbit-to-orbit variability of an eccentric hot Jupiter and demonstrate the consistency of multiple-epoch Spitzer observations.

The hot Jupiter HD 209458b is particularly amenable to detailed study as it is among the brightest transiting exoplanet systems currently known (V-mag = 7.65; K-mag = 6.308) and has a large planet-to-star contrast ratio. HD 209458b is predicted to be in synchronous rotation about its host star with a hot spot that is shifted eastward of the substellar point by superrotating equatorial winds. Here we present the first full-orbit observations of HD 209458b, in which its 4.5 μm emission was recorded with Spitzer/IRAC. Our study revises the previous 4.5 μm measurement of HD 209458b's secondary eclipse emission downward by 35% to , changing our interpretation of the properties of its dayside atmosphere. We find that the hot spot on the planet's dayside is shifted eastward of the substellar point by 40.°9 ± 6.°0, in agreement with circulation models predicting equatorial superrotation. HD 209458b's dayside (T bright = 1499 ± 15 K) and nightside (T bright = 972 ± 44 K) emission indicate a day-to-night brightness temperature contrast smaller than that observed for more highly irradiated exoplanets, suggesting that the day-to-night temperature contrast may be partially a function of the incident stellar radiation. The observed phase curve shape deviates modestly from global circulation model predictions potentially due to disequilibrium chemistry or deficiencies in the current hot CH4 line lists used in these models. Observations of the phase curve at additional wavelengths are needed in order to determine the possible presence and spatial extent of a dayside temperature inversion, as well as to improve our overall understanding of this planet's atmospheric circulation. © 2014. The American Astronomical Society. All rights reserved..

We have obtained the first time-resolved, disk-integrated observations of Earth's poles with the Deep Impact spacecraft as part of the EPOXI mission of opportunity. These data mimic what we will see when we point next-generation space telescopes at nearby exoplanets. We use principal component analysis (PCA) and rotational light curve inversion to characterize color inhomogeneities and map their spatial distribution from these unusual vantage points, as a complement to the equatorial views presented by Cowan etal. in 2009. We also perform the samePCA on a suite of simulated rotational multi-band light curves from NASA's Virtual Planetary Laboratory three-dimensional spectral Earth model. This numerical experiment allows us to understand what sorts of surface featuresPCA can robustly identify. We find that the EPOXI polar observations have similar broadband colors as the equatorial Earth, but with 20%-30% greater apparent albedo. This is because the polar observations are most sensitive to mid-latitudes, which tend to be more cloudy than the equatorial latitudes emphasized by the original EPOXI Earth observations. The cloudiness of the mid-latitudes also manifests itself in the form of increased variability at short wavelengths in the polar observations and as a dominant gray eigencolor in the south polar observation. We construct a simple reflectance model for a snowball Earth. By construction, our model has a higher Bond albedo than the modern Earth; its surface albedo is so high that Rayleigh scattering does not noticeably affect its spectrum. The rotational color variations occur at short wavelengths due to the large contrast between glacier ice and bare land in those wavebands. Thus, we find that both the broadband colors and diurnal color variations of such a planet would be easily distinguishable from the modern-day Earth, regardless of viewing angle. © 2011. The American Astronomical Society. All rights reserved.