Animal Models

Kreidberg, Jordan A.

doi:10.1007/978-3-540-76341-3_16

Cited by 2 publications

(2 citation statements)

References 189 publications

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“…We compute the transit light curve f (t i ) using the Batman implementation (Kreidberg 2015) of the Equations derived in Mandel & Agol (2002). The transit parameters fitted in our Spitzer analysis are the planet-tostar radius ratio R P /R * , the mid-transit time T C , and the impact parameter b.…”

Section: Transit Modelmentioning

confidence: 99%

SPITZER OBSERVATIONS CONFIRM AND RESCUE THE HABITABLE-ZONE SUPER-EARTH K2-18b FOR FUTURE CHARACTERIZATION

Benneke

Werner

Petigura

et al. 2017

ApJ

127

121

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The recent detections of two transit events attributed to the super-Earth candidate K2-18b have provided the unprecedented prospect of spectroscopically studying a habitable-zone planet outside the solar system. Orbiting a nearby M2.5 dwarf and receiving virtually the same stellar insolation as Earth, K2-18b would be a prime candidate for the first detailed atmospheric characterization of a habitable-zone exoplanet using the Hubble Space Telescope (HST)and James Webb Space Telescope ( JWST). Here, we report the detection of a third transit of K2-18b near the predicted transit time using the Spitzer Space Telescope. The Spitzer detection demonstrates the periodic nature of the two transit events discovered by K2, confirming that K2-18 is indeed orbited by a super-Earth in a 33 day orbit, ruling out the alternative scenario of two similarly sized, long-period planets transiting only once within the 75 day Kepler Space Telescope (K2) observation. We also find, however, that the transit event detected by Spitzer occurred 1.85 hr ( s 7 ) before the predicted transit time. Our joint analysis of the Spitzer and K2 photometry reveals that this early occurrence of the transit is not caused by transit timing variations, but the result of an inaccurate ephemeris due to a previously undetected data anomaly in the K2 photometry. We refit the ephemeris and find that K2-18b would have been lost for future atmospheric characterizations with HST and JWST if we had not secured its ephemeris shortly after the discovery. We caution that immediate follow-up observations as presented here will also be critical for confirming and securing future planets discovered by the Transiting Exoplanet Survey Satellite (TESS), in particular if only two transit events are covered by the relatively short 27-day TESS campaigns.

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Section: Transit Modelmentioning

confidence: 99%

SPITZER OBSERVATIONS CONFIRM AND RESCUE THE HABITABLE-ZONE SUPER-EARTH K2-18b FOR FUTURE CHARACTERIZATION

Benneke

Werner

Petigura

et al. 2017

ApJ

127

121

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“…The package can be used to calculate limb darkening coefficients and their uncertainties for freely defined passbands prior to the modelling, or it can be directly integrated into the modelling code. LDTK can also be used to generate limb darkening profile samples directly, bypassing the need to use simple limb darkening models if the modelling approach allows for the use of arbitrary limb darkening profiles (such as the BATMAN transit modelling code, Kreidberg 2015). This can be useful when the features that are not well captured by the simple limb darkening models, such as the very edge of the star, are important.…”

Section: Discussionmentioning

confidence: 99%

ldtk: Limb Darkening Toolkit

Parviainen¹,

Aigrain²

2015

Mon. Not. R. Astron. Soc.

248

187

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We present a Python package LDTK that automates the calculation of custom stellar limb darkening (LD) profiles and model-specific limb darkening coefficients (LDC) using the library of PHOENIX-generated specific intensity spectra by Husser et al. (2013). The aim of the package is to facilitate analyses requiring custom generated limb darkening profiles, such as the studies of exoplanet transits-especially transmission spectroscopy, where the transit modelling is carried out for custom narrow passbands-eclipsing binaries (EBs), interferometry, and microlensing events. First, LDTK can be used to compute custom limb darkening profiles with uncertainties propagated from the uncertainties in the stellar parameter estimates. Second, LDTK can be used to estimate the limb-darkening-model specific coefficients with uncertainties for the most common limb-darkening models. Third, LDTK can be directly integrated into the log posterior computation of any pre-existing modelling code with minimal modifications. The last approach can be used to constrain the LD model parameter space directly by the LD profile, allowing for the marginalization over the LD parameter space without the need to approximate the constraint from the LD profile using a prior. Where µ = √ 1 − z 2 = cos γ, z is the normalized distance from the centre of the stellar disk, and γ is the foreshortening angle.

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Animal Models

Cited by 2 publications

References 189 publications

SPITZER OBSERVATIONS CONFIRM AND RESCUE THE HABITABLE-ZONE SUPER-EARTH K2-18b FOR FUTURE CHARACTERIZATION

SPITZER OBSERVATIONS CONFIRM AND RESCUE THE HABITABLE-ZONE SUPER-EARTH K2-18b FOR FUTURE CHARACTERIZATION

ldtk: Limb Darkening Toolkit

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