Homogeneous studies of transiting extrasolar planets – I. Light-curve analyses

By J. Southworth. 2008

301 citations recorded by the source corpus.

I present a homogeneous analysis of the transit light curves of 14 well-observed transiting extrasolar planets. The light curves are modelled using jktebop, random errors are measured using Monte Carlo simulations and the effects of correlated noise are included using a residual-permutation algorithm. The importance of stellar limb darkening on the light-curve solutions and parameter uncertainties is investigated using five different limb darkening laws and including different numbers of coefficients as fitted parameters. The linear limb darkening law cannot adequately fit the Hubble Space Telescope (HST) photometry of HD 209458, but the other four laws give very similar results to each other for all transit light curves. In most cases fixing the limb darkening coefficients at theoretically predicted values does not bias the results, but does cause the error estimates to be too small. The available theoretical limb darkening coefficients clearly disagree with empirical values measured from the HST light curves of HD 209458; limb darkening must be included as fitted parameters when analysing high-quality light curves. In most cases the results of my analysis agree with the values found by other authors, but the uncertainties I find can be significantly larger (by factors of up to 3). Despite these greater uncertainty estimates, the analyses of sets of independent light curves for both HD 189733 and HD 209458 lead to results which do not agree with each other. This discrepancy is worst for the ratio of the radii (6.7 sigma for HD 189733 and 3.7 sigma for HD 209458), which depends primarily on the depth of the transit. It is therefore not due to the analysis method but is present in the light curves. These underlying systematic errors cannot be detected from the reduced data alone unless at least three independent light curves are available for an individual planetary system. The surface gravities of transiting extrasolar planets are known to be correlated with their orbital periods. New surface gravity values, calculated from the light-curve results and the stellar spectroscopic orbits, show that this correlation is still present. New high-precision light curves are needed for HD 149026, OGLE-TR-10, OGLE-TR-56, OGLE-TR-132 and GJ 436, and new radial velocity curves for the XO-1, WASP-1, WASP-2 and the OGLE (Optical Gravitational Lensing Experiment) planetary systems.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/20412a10560550bb6ca60829b470f5b58b7e9dd1

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In Astronomy and Astrophysics

1. Jon Fortney
2. D. Charbonneau
3. J. Southworth
4. J. Winn
5. N. Madhusudhan
6. A. Showman
7. D. Deming
8. H. Knutson

In Instrumentation

1. J. Southworth
2. Jon Fortney
3. D. Charbonneau
4. J. Winn
5. J. Johnson
6. D. Sing
7. H. Knutson
8. A. Showman

Citations in the corpus

• SOPHIE velocimetry of Kepler transit candidates XVII. The physical properties of giant exoplanets within 400 days of period (2015, methodology): “We used the JKTEBOP code (Southworth 2008) assuming the limb darkening coefficients from Claret & Bloemen (2011) to simulate the transit light curve and determine the transit depth.”
• THE FLAT TRANSMISSION SPECTRUM OF THE SUPER-EARTH GJ1214b FROM WIDE FIELD CAMERA 3 ON THE HUBBLE SPACE TELESCOPE (2011, background): “For less precise light curves, it is common practice to fix the limb-darkening to a theoretically calculated law, even if this may underestimate the uncertainty in the planetary parameters (see Burke et al. 2007; Southworth 2008).”
• SOPHIE velocimetry of Kepler transit candidates VII. A false-positive rate of 35% for Kepler close-in giant candidates (2012, methodology): “We modeled a binary scenario using stellar atmosphere models of Castelli & Kurucz (2004), light-curve models from JKTEBOP (Southworth 2008) and evolution stracks from Marigo et al. (2008) and Girardi et al. (2010).”
• Analytic Approximations for Transit Light-Curve Observables, Uncertainties, and Covariances (2008, background): “It should be noted that there is evidence that linear limb darkening may not adequately fit high-quality transit light curves relative to higher order models (Brown et al. (2001), Southworth (2008)).”
• New limb-darkening coefficients for Phoenix/1d model atmospheres - II. Calculations for 5000 K ≤ Teff ≤ 10 000 K Kepler, CoRot, Spitzer, uvby, UBVRIJHK, Sloan, and 2MASS photometric systems (2012, background): “The mean average error bars for semi-empirical linear LDC is approximately of 0.1, while for the quadratic approach they are around 0.2 for a and b (see for example, Southworth 2008; Claret 2009).”
• High-precision photometry by telescope defocussing. I. The transiting planetary system WASP-5 (2009, methodology): “In the following sections we discuss our observations and data reduction procedures, and then analyse the data using the methods detailed by Southworth (2008, 2009).”
• Stellar limb-darkening coefficients for CoRot and Kepler (2009, methodology): “With high signal-to-noise (S/N) transit light curves, the limb darkening can be fit and compared to theoretical stellar atmospheric models, providing a method to scrutinize and test different models (e.g. Southworth 2008).”
• WASP-121 b: a hot Jupiter close to tidal disruption transiting an active F star (2015, methodology): “The lightcurve was modelled using the EBOP code (Nelson & Davis 1972, Etzel 1981, Popper & Etzel 1981) extracted from the JKTEBOP package (Southworth 2008).”
• Limb and gravity-darkening coefficients for the TESS satellite at several metallicities, surface gravities, and microturbulent velocities (2016, background): “For details of these comparisons related to eclipsing binaries and planetary transits see for example Claret (2008), Southworth (2008), Claret (2009), Sing (2010), Howarth (2011), Claret & Bloemen (2011), Southworth (2012), Csizmadia et al. (2013), and Müller et al. (2013).”
• A chemical model for the atmosphere of hot Jupiters (2012, background): “Properties of HD 189733b and HD 189733 come from Southworth (2008, 2010).”
• Homogeneous studies of transiting extrasolar planets - III. Additional planets and stellar models (2010, methodology): “In Paper I (Southworth 2008) I analysed the light curves of the fourteen transiting systems for which high-precision photometry was then available, paying careful attention to the roleof limb darkening and to the estimation of comprehensive errorbars.”
• Transits and Occultations (2010, background): “Southworth (2008) investigates the results of fitting the same data set with different limb-darkening laws.”
• ORBITAL PHASE VARIATIONS OF THE ECCENTRIC GIANT PLANET HAT-P-2b (2013, methodology): “As a result, we instead opt to use the ‘residual-permutation’ or ‘prayerbead’ method to estimate the errors in our parameters in the presence of correlated noise (see, for example Jenkins et al. 2002; Southworth 2008; Bean et al. 2008; Winn et al. 2008).”
• PROBABILISTIC FORECASTING OF THE MASSES AND RADII OF OTHER WORLDS (2016, methodology): “For extrasolar planets, we used the TEPCat catalog4 of “wellstudied transiting planets,” curated by John Southworth (Southworth 2008, 2009, 2010, 2011, 2012).”
• One of the closest exoplanet pairs to the 3:2 mean motion resonance: K2-19b and c (2015, methodology): “The light curve was modelled using the EBOP code (Nelson & Davis 1972; Etzel 1981; Popper & Etzel 1981) extracted from the JKTEBOP package (Southworth 2008).”
• Transiting exoplanets from the CoRoT space mission . VI. CoRoT-Exo-3b: the first secure inhabitant of the brown-dwarf desert (2008, methodology): “The limb-darkening parameters issue has been already pointed out by various studies carried out using space-based or ground-based observations (Knutson et al. 2007; Southworth 2008).”