The Transit and Light Curve Modeller

Abstract

Transit and Light Curve Modeller (TLCM), a computer code with the purpose of analysing photometric time series of transits simultaneously with the out-of-transit light variations and radial velocity curves of transiting/eclipsing binary systems, is presented here. Joint light-curve and radial velocity fits are possible with it. The code is based on the combination of a genetic algorithm and simulated annealing. Binning, beaming, reflection, and ellipsoidal effects are included. Both objects may have their own luminosities and therefore one can use TLCM to analyse the eclipses of both exoplanet and well-detached binary systems. A simplified Rossiter–McLaughlin effect is included in the radial velocity fit, and drifts and offsets of different instruments can also be fitted. The impact of poorly known limb darkening on the Rossiter–McLaughlin effect is shortly studied. TLCM is able to manage red-noise effects via wavelet analysis. It is also possible to add parabolic or user-defined baselines and features to the code. I also predict that light variations due to beaming in some systems exhibiting radial velocity drift should be observed by, e.g. PLATO. The fit of the beaming effect is improved by invoking a physical description of the ellipsoidal effects, which has an impact on the modelling of the relativistic beaming; I also point out the difficulties that are stemming from the fact that beaming and first-order reflection effects have the same form of time dependence. Recipe is given, which describes how to analyse grazing transit events. The code is freely available.

GJ 367b: A dense, ultrashort-period sub-Earth planet transiting a nearby red dwarf star

“…Contaminating light from the neighbouring stars estimated from ground-based observations was also taken into account, where a third light contamination parameter, l3, is fitted to correct for the flux dilution in the light curve model. We used a penalty function when the standard deviation of the (red noise corrected) light curve residual was not equal to the mean of the photometric uncertainties (13).…”

“…During the joint fitting the limb darkening coefficients (u+ and u-) were fixed at u+ = 0.62 and u-= 0.15 (105). We used TLCM to search for an initial solution using the Harmony Search type of Genetic Algorithms, refined by Simulated Annealing (13). The estimation of final parameters and their uncertainties were done via an MCMC analysis using 10 independent chains and one million steps in each chain with a thinning factor of 100.…”

“…We obtained the stellar effective temperature, metallicity and log g from the stellar spectral analysis (see above). The mean stellar density is determined from the period and the scaled scaled semi-major axis a/Rs via Kepler's third law (13,108,109). Matching the stellar effective temperature, metallicity and the mean stellar density with isochrones, we obtain a stellar radius Rs = 0.459 ± 0.003 R⊙ and mass Ms = 0.500 ± 0.005 M⊙ which is consistent to the values obtained from SPECMATCH-EMP analysis or via the Gaia-parallax value.…”

pyaneti – II. A multidimensional Gaussian process approach to analysing spectroscopic time-series

“…Fortunately, the wealth of exoplanetary data has spurred the development of a variety of exoplanet numerical tools. To our knowledge, the codes that allow one to analyse jointly RV and transit data are: allesfitter (Günther & Daylan 2020), EXOFAST (Eastman et al 2013(Eastman et al , 2019, exoplanet (Foreman-Mackey et al 2021), Exo-Stricker (Trifonov 2019), juliet (Espinoza et al 2019), MCMCI (Bonfanti & Gillon 2020), PASTIS (Díaz et al 2014;Santerne et al 2015), PlanetPAck (Baluev 2013), TLCM (Csizmadia 2020), and pyaneti (Barragán et al 2019a). These software packages cover a wide range of programming languages and models, and have been used extensively in the literature.…”

Orbital Period Refinement of CoRoT Planets with TESS Observations

“…Aradialvelocitydriftofabout1m/sperdaywasreported for CoRoT-1b from RVs obtained at two epochs in March-April 2007 and in October 2007, at the SOPHIE spectrograph of the 193 cm telescope at the Observatoire Haute Provence, France (Barge et al, 2008;Bonomo et al, 2017;Csizmadia, 2020). Assuming that this drift is real, its influence onto an otherwise linear ephemeris can be expressed by (Deeg et al, 2008,E q .6 ) where E is the epoch number (number of orbits in time-span under consideration), a the system's acceleration in the line of sight, P the orbital period, and c the speed of light.…”