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ABSTRACT We present EXOFAST, a fast, robust suite of routines written in IDL that is designed to fit exoplanetary transits and radial velocity variations simultaneously or separately and characterize the parameter uncertainties and covariances with a differential evolution Markov chain Monte Carlo method. We describe how our code incorporates both data sets to derive simultaneously stellar parameters along with the transit and RV parameters, resulting in more self-consistent results on an example fit of the discovery data of HAT-P-3b that is well-mixed in under 5 minutes on a standard desktop computer. We describe in detail how our code works and outline ways in which the code can be extended to include additional effects or generalized for the characterization of other data sets-including non-planetary data sets. We discuss the pros and cons of several common ways to parameterize eccentricity, highlight a subtle mistake in the implementation of MCMC that could bias the inferred eccentricity of intrinsically circular orbits to significantly non-zero results, discuss a problem with IDL's built-in random number generator in its application to large MCMC fits, and derive a method to analytically fit the linear and quadratic limb darkening coefficients of a planetary transit. Finally, we explain how we achieved improved accuracy and over a factor of 100 improvement in the execution time of the transit model calculation. Our entire source code, along with an easy-to-use online interface for several basic features of our transit and radial velocity fitting, are available online at http://astroutils.astronomy.ohio-state.edu/exofast.

Over 40% of Sun-like stars are bound in binary or multistar systems. Stellar remnants in edge-on binary systems can gravitationally magnify their companions, as predicted 40 years ago. By using data from the Kepler spacecraft, we report the detection of such a \"self-lensing\" system, in which a 5-hour pulse of 0.1% amplitude occurs every orbital period. The white dwarf stellar remnant and its Sun-like companion orbit one another every 88.18 days, a long period for a white dwarf–eclipsing binary. By modeling the pulse as gravitational magnification (microlensing) along with Kepler's laws and stellar models, we constrain the mass of the white dwarf to be ∼63% of the mass of our Sun. Further study of this system, and any others discovered like it, will help to constrain the physics of white dwarfs and binary star evolution.

We report the detection of Kepler-47, a system consisting of two planets orbiting around an eclipsing pair of stars. The inner and outer planets have radii 3.0 and 4.6 times that of Earth, respectively. The binary star consists of a Sun-like star and a companion roughly one-third its size, orbiting each other every 7.45 days. With an orbital period of 49.5 days, 18 transits of the inner planet have been observed, allowing a detailed characterization of its orbit and those of the stars. The outer planet's orbital period is 303.2 days, and although the planet is not Earth-like, it resides within the classical \"habitable zone,\" where liquid water could exist on an Earth-like planet. With its two known planets, Kepler-47 establishes that close binary stars can host complete planetary systems.

'Hot Jupiters' just got hotter 'Hot Jupiter' extrasolar planets are close to their parent stars, so are likely to be tidally locked (like the Earth and Moon), with permanent day and night sides. That raises the question of whether the atmosphere is able to transport energy from the day side to the night side. Infrared data from the Spitzer Space Telescope have now answered that question for the extrasolar planet HD 189733b. Night and day temperatures are similar, around 950–1,200 K, indicating that energy from the irradiated side is efficiently redistributed throughout the atmosphere. A paper going live online this week reports observations of the atmosphere of the extra-solar plant HD 149026b. It’s a very hot Jupiter, the hottest planet known, at about 2,300 K. This matches predictions for a planet where each patch of surface area instantaneously re-emits all absorbed light as a blackbody. ‘Hot Jupiter’ extrasolar planets are expected to be tidally locked because they are close (<0.05 astronomical units, where 1  au is the average Sun–Earth distance) to their parent stars, resulting in permanent daysides and nightsides. By observing systems where the planet and star periodically eclipse each other, several groups have been able to estimate the temperatures of the daysides of these planets 1 , 2 , 3 . A key question is whether the atmosphere is able to transport the energy incident upon the dayside to the nightside, which will determine the temperature at different points on the planet’s surface. Here we report observations of HD 189733, the closest of these eclipsing planetary systems 4 , 5 , 6 , over half an orbital period, from which we can construct a ‘map’ of the distribution of temperatures. We detected the increase in brightness as the dayside of the planet rotated into view. We estimate a minimum brightness temperature of 973 ± 33 K and a maximum brightness temperature of 1,212 ± 11 K at a wavelength of 8 μm, indicating that energy from the irradiated dayside is efficiently redistributed throughout the atmosphere, in contrast to a recent claim for another hot Jupiter 7 . Our data indicate that the peak hemisphere-integrated brightness occurs 16 ± 6° before opposition, corresponding to a hotspot shifted east of the substellar point. The secondary eclipse (when the planet moves behind the star) occurs 120 ± 24 s later than predicted, which may indicate a slightly eccentric orbit.

The TRAPPIST-1 system contains seven roughly Earth-sized planets locked in a multiresonant orbital configuration 1 , 2 , which has enabled precise measurements of the planets’ masses and constrained their compositions 3 . Here we use the system’s fragile orbital structure to place robust upper limits on the planets’ bombardment histories. We use N -body simulations to show how perturbations from additional objects can break the multiresonant configuration by either triggering dynamical instability or simply removing the planets from resonance. The planets cannot have interacted with more than ~5% of one Earth mass ( M ⊕ ) in planetesimals—or a single rogue planet more massive than Earth’s Moon—without disrupting their resonant orbital structure. This implies an upper limit of 10 −4 M ⊕ to 10 −2   M ⊕ of late accretion on each planet since the dispersal of the system’s gaseous disk. This is comparable to (or less than) the late accretion on Earth after the Moon-forming impact 4 , 5 , and demonstrates that the growth of the TRAPPIST-1 planets was complete in just a few million years, roughly an order of magnitude faster than that of the Earth 6 , 7 . Our results imply that any large water reservoirs on the TRAPPIST-1 planets must have been incorporated during their formation in the gaseous disk. The resonant chain of the TRAPPIST-1 planets is dynamically fragile, as small perturbations during its lifetime would have disrupted it. N -body simulations show that the system could not have interacted with more than 0.05 Earth masses of material after its formation. Thus, any water in the planets must come from the planets’ original accretion.

We present an IDL graphical user-interface-driven software package designed for the analysis of exoplanet transit light curves. The Transit Analysis Package (TAP) software uses Markov Chain Monte Carlo (MCMC) techniques to fit light curves using the analytic model of Mandal and Agol (2002). The package incorporates a wavelet-based likelihood function developed by Carter and Winn (2009), which allows the MCMC to assess parameter uncertainties more robustly than classic χ2 methods by parameterizing uncorrelated “white” and correlated “red” noise. The software is able to simultaneously analyze multiple transits observed in different conditions (instrument, filter, weather, etc.). The graphical interface allows for the simple execution and interpretation of Bayesian MCMC analysis tailored to a user’s specific data set and has been thoroughly tested on ground-based and Kepler photometry. This paper describes the software release and provides applications to new and existing data. Reanalysis of ground-based observations of TrES-1b, WASP-4b, and WASP-10b (Winn et al., 2007, 2009; Johnson et al., 2009; resp.) and space-based Kepler 4b–8b (Kipping and Bakos 2010) show good agreement between TAP and those publications. We also present new multi-filter light curves of WASP-10b and we find excellent agreement with previously published values for a smaller radius.

The search for habitable planets like Earth around other stars fulfills an ancient imperative to understand our origins and place in the cosmos. The past decade has seen the discovery of hundreds of planets, but nearly all are gas giants like Jupiter and Saturn. Recent advances in instrumentation and new missions are extending searches to planets the size of Earth but closer to their host stars. There are several possible ways such planets could form, and future observations will soon test those theories. Many of these planets we discover may be quite unlike Earth in their surface temperature and composition, but their study will nonetheless inform us about the process of planet formation and the frequency of Earth-like planets around other stars.

Seven rocky planets orbit the nearby dwarf star TRAPPIST-1, providing a unique opportunity to search for atmospheres on small planets outside the Solar System 1 . Thanks to the recent launch of the James Webb Space Telescope (JWST), possible atmospheric constituents such as carbon dioxide (CO 2 ) are now detectable 2 , 3 . Recent JWST observations of the innermost planet TRAPPIST-1 b showed that it is most probably a bare rock without any CO 2 in its atmosphere 4 . Here we report the detection of thermal emission from the dayside of TRAPPIST-1 c with the Mid-Infrared Instrument (MIRI) on JWST at 15 µm. We measure a planet-to-star flux ratio of f p / f ⁎  = 421 ± 94 parts per million (ppm), which corresponds to an inferred dayside brightness temperature of 380 ± 31 K. This high dayside temperature disfavours a thick, CO 2 -rich atmosphere on the planet. The data rule out cloud-free O 2 /CO 2 mixtures with surface pressures ranging from 10 bar (with 10 ppm CO 2 ) to 0.1 bar (pure CO 2 ). A Venus-analogue atmosphere with sulfuric acid clouds is also disfavoured at 2.6 σ confidence. Thinner atmospheres or bare-rock surfaces are consistent with our measured planet-to-star flux ratio. The absence of a thick, CO 2 -rich atmosphere on TRAPPIST-1 c suggests a relatively volatile-poor formation history, with less than 9.5 − 2.3 + 7.5 Earth oceans of water. If all planets in the system formed in the same way, this would indicate a limited reservoir of volatiles for the potentially habitable planets in the system. The detection of thermal emission from the rocky exoplanet TRAPPIST-1 c using the Mid-Infrared Instrument on the James Webb Space Telescope reveals a dayside brightness temperature that disfavours a thick, CO 2 -rich atmosphere.

Last year, three Earth-sized planets were discovered to be orbiting the nearby Jupiter-sized star TRAPPIST-1; now, follow-up photometric observations from the ground and from space show that there are at least seven Earth-sized planets in this star system, and that they might be the right temperature to harbour liquid water on their surfaces. Seven Earth-like planets around a nearby dwarf star Michaël Gillon et al . report the results of a photometric monitoring campaign of the star TRAPPIST-1 from the ground and space. They reveal that at least seven planets with sizes and masses similar to Earth revolve around this Jupiter-sized star. These planets all have equilibrium temperatures low enough to make it possible for liquid water to exist on their surfaces. One aim of modern astronomy is to detect temperate, Earth-like exoplanets that are well suited for atmospheric characterization. Recently, three Earth-sized planets were detected that transit (that is, pass in front of) a star with a mass just eight per cent that of the Sun, located 12 parsecs away 1 . The transiting configuration of these planets, combined with the Jupiter-like size of their host star—named TRAPPIST-1—makes possible in-depth studies of their atmospheric properties with present-day and future astronomical facilities 1 , 2 , 3 . Here we report the results of a photometric monitoring campaign of that star from the ground and space. Our observations reveal that at least seven planets with sizes and masses similar to those of Earth revolve around TRAPPIST-1. The six inner planets form a near-resonant chain, such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.1 and 12.35 days) are near-ratios of small integers. This architecture suggests that the planets formed farther from the star and migrated inwards 4 , 5 . Moreover, the seven planets have equilibrium temperatures low enough to make possible the presence of liquid water on their surfaces 6 , 7 , 8 .

We present the detection of five planets—Kepler-62b, c, d, e, and f—of size 1.31, 0.54, 1.95, 1.61 and 1.41 Earth radii (R ⊕ ), orbiting a K2V star at periods of 5.7, 12.4, 18.2, 122.4, and 267.3 days, respectively. The outermost planets, Kepler-62e and -62f, are super-Earth-size (1.25 R ⊕ < planet radius < 2.0 R ⊕ ) planets in the habitable zone of their host star, respectively receiving 1.2 ± 0.2 times and 0.41 ± 0.05 times the solar flux at Earth's orbit. Theoretical models of Kepler-62e and -62f for a stellar age of ~7 billion years suggest that both planets could be solid, either with a rocky composition or composed of mostly solid water in their bulk.