A Unique Solution of Planet and Star Parameters from an Extrasolar Planet Transit Light Curve

By Sara Seager, G. Mallén-Ornelas. 2002

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There is a unique solution of the planet and star parameters from a planet transit light curve with two or more transits if the planet has a circular orbit and the light curve is observed in a bandpass where limb darkening is negligible. The existence of this unique solution is very useful for current planet transit surveys for several reasons. First, there is an analytic solution that allows a quick parameter estimate, in particular of Rp. Second, the stellar density can be uniquely derived from the transit light curve alone. The stellar density can then be used to immediately rule out a giant star (and hence a much larger than planetary companion) and can also be used to put an upper limit on the stellar and planet radius even considering slightly evolved stars. Third, the presence of an additional fully blended star that contaminates an eclipsing system to mimic a planet transit can be largely ruled out from the transit light curve given a spectral type for the central star. Fourth, the period can be estimated from a single-transit light curve and a measured spectral type. All of these applications can be used to select the best planet transit candidates for mass determination by radial velocity follow-up. To use these applications in practice, the photometric precision and time sampling of the light curve must be high (better than 0.005 mag precision and 5 minute time sampling for a two-transit light curve).

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/f6b001a4bddad02d637adfa0d0d90357c6bf4275

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Citations in the corpus

Morphological Lightcurve Distortions due to Finite Integration Time (2010, background): “Let us define the apparent contact points as t′: t′I = tI − I/2 (5) t′II = tII + I/2 (6) t′III = tIII − I/2 (7) t′IV = tIV + I/2 (8) Seager & Mallén-Ornelas (2003) showed that several physical system parameters may be retrieved by analysis of the lightcurve morphology.”
Optimized transit detection algorithm to search for periodic transits of small planets (2019, background): “The horizontal cutoff at T14/P = 1.12 × 10−1 is a global threshold.”
TrES-1: The Transiting Planet of a Bright K0 V Star (2004, background): “One of these estimates comes from the eclipse depth, and the other from the duration of the eclipse’s ingress and egress portions (Brown et al. 2001; Seager & Mallén-Ornelas 2003).”
Mass-Radius Relationships for Solid Exoplanets (2007, background): “This is partly because a/R∗ (a measure of stellar density) can be determined with high precision from the planet transit light curve for planet’s with zero orbital eccentricity (Seager & Mallén-Ornelas 2003).”
Transits and Occultations (2010, background): “(30) This can be derived from Kepler’s third law (Seager & Mallen-Ornelas 2003).”
Homogeneous studies of transiting extrasolar planets – IV. Thirty systems with space-based light curves (2011, background): “…for the planet: T ′eq = Teff ( RA 2a )1/2 = Teff ( rA 2 )1/2 (4) and also its Safronov (1972) number: Θ = 1 2 ( Vesc Vorb )2 = ( a Rb )( Mb MA ) = 1 rb Mb MA (5) Three quantities are independent of stellar theory:gb (Southworth et al. 2007b),ρA (Seager & Mallén-Ornelas 2003) andT ′eq (Paper III).”
Analytic Approximations for Transit Light-Curve Observables, Uncertainties, and Covariances (2008, methodology): “Seager & Mallén-Ornelas (2003) presented an approximate model of a transit light curve with the desired level of simplicity, but did not provide analytic estimates of uncertainties and covariances.”
WASP-19b: THE SHORTEST PERIOD TRANSITING EXOPLANET YET DISCOVERED (2010, methodology): “The stellar density is dependent on the shape of the transit and largely independent of any assumptions or models (Seager & Mallén-Ornelas 2003).”
LACK OF INFLATED RADII FOR KEPLER GIANT PLANET CANDIDATES RECEIVING MODEST STELLAR IRRADIATION (2011, methodology): “The advantage of this approach is that the stellar density is well constrained by the transit lightcurve photometry (Seager & Mallén-Ornelas 2003), yielding better results than using the surface gravity derived from the spectroscopic analysis.”
The nature of the TRAPPIST-1 exoplanets. (2018, methodology): “, along with the well constrained stellar density ρ? determined photometrically from the Spitzer dataset (Seager & Mallén-Ornelas 2003).”
Accurate Empirical Radii and Masses of Planets and Their Host Stars with Gaia Parallaxes (2016, background): “This is due to a well-known degeneracy, first pointed out in the case of transiting planets by Seager & Mallén-Ornelas (2003).”
LOW FALSE POSITIVE RATE OF KEPLER CANDIDATES ESTIMATED FROM A COMBINATION OF SPITZER AND FOLLOW-UP OBSERVATIONS (2015, methodology): “One method consists of in-depth statistical validation of candidates by ruling out false positive scenarios one-by-one (e.g., BLENDER, Torres et al. 2004, 2011; Fressin et al. 2011); it fully exploits the information from the shape of a transit lightcurve (Seager & Mallén-Ornelas 2003).”
THE STATISTICS OF ALBEDO AND HEAT RECIRCULATION ON HOT EXOPLANETS (2009, methodology): “For shorthand, we define the geometrical factor a∗ = a/R∗, which is directly constrained by transit lightcurves (Seager & Mallén-Ornelas 2003).”
ECCENTRICITY FROM TRANSIT PHOTOMETRY: SMALL PLANETS IN KEPLER MULTI-PLANET SYSTEMS HAVE LOW ECCENTRICITIES (2015, background): “Transit durations for circular orbits are governed by the mean stellar density (Seager & Mallén-Ornelas 2003).”
WASP-121 b: a hot Jupiter close to tidal disruption transiting an active F star (2015, neutral): “2, b′, W , P , √ e cos ω and √ e sin ω (see e.g. Seager & Mallén-Ornelas 2003 and Winn 2010).”
Efficient identification of exoplanetary transit candidates from SuperWASP light curves (2007, methodology): “Seager & Mallén-Ornelas (2003) chose the former approach, imposing a main-sequence mass-radius relation on the primary of the form R∗ ∝ M0.”