Parameters Of Exoplanets Research Articles

Performance of PSG in retrieving exoplanet parameters from JWST data simulated with several tools

Abstract Our research explores different methods of utilizing several known tools (petitRADTRANS, PandExo, and PSG) to simulate spectral data acquired by the James Webb Space Telescope (JWST). We specifically focus on how the choice of method affects the performance of the Planetary Spectrum Generator (PSG) in retrieving exoplanet parameters from such data. To investigate this, we consider the case of exoplanet TOI-1266 c being observed by JWST’s Near Infrared Spectrograph in the Bright Object Time Series mode. Our results show that differences between PSG and PandExo regarding their noise simulation and method of adjusting spectral resolution lead to significant differences in retrieval quality. When utilizing PandExo to simulate noise for non-binned down spectral data, we recommend ensuring that the resolution of the theoretical forward model spectrum input into PandExo closely matches the resolution of the output spectral data, within the same order of magnitude.

Machine Learning Implementation on TTV Analysis using TTVFast

Exoplanet research has undergone rapid development lately due to the increasing number of space telescopes and satellite surveys launched in recent years. Two missions with the most exoplanet discoveries using transit methods are Kepler and TESS missions. Both missions focused on photometric surveys to detect planets by observing the periodic dimming of a stars brightness as a planet passes in front of it. There is another method that could take advantage of transit observations called transit timing variation method. By observing the deviation of the transit time of transiting planet we could infer the existence of another body in the system. Performing exoplanet parameter estimation using TTV data is an extensive process. Estimating exoplanet parameters using TTV, we must fit the TTV data using a wide range of parameters using n-body simulation. N-body simulation in this scale is computationally costly. To estimate planet parameters, we need to run thousands of n-body simulations. With the increasing trend of using machine learning methods in the research process, we try to implement the machine learning method to make TTV analysis more effective and efficient. We implement the application of machine learning to n-body simulation using REBOUND and TTVFAST and compare the results. REBOUND is a Python-based library designed for simulating the dynamics of n-body systems, particularly celestial bodies like planets, stars, and other objects that interact gravitationally. While TTVFAST is a modified n-body simulation code that is specifically designed to calculate TTV on transiting planetary systems. We found that TTVFAST is much faster than REBOUND when generating samples for training and testing while still maintaining similar accuracy. Also, the machine learning model generated from both data samples is performed similarly.

The Possibility of Detecting our Solar System through Astrometry

Searching for exoplanets with different methods has always been the focus of astronomers over the past few years. Among multiple planet detection techniques, astrometry stands out for its capability to accurately determine the orbital parameters of exoplanets. In this study, we examine the likelihood of extraterrestrial intelligent civilizations detecting planets in our solar system using the astrometry method. By conducting injection-recovery simulations, we investigate the detectability of the four giant planets in our solar system under different observing baselines and observational errors. Our findings indicate that extraterrestrial intelligence could detect and characterize all four giant planets, provided they are observed for a minimum of 90 yr with signal-noise ratios exceeding 1. For individual planets such as Jupiter, Saturn, and Neptune, a baseline that surpasses half of their orbital periods is necessary for detection. However, Uranus requires longer observing baselines since its orbital period is roughly half of that of Neptune. If the astrometry precision is equal to or better than 10 μas, all 8707 stars located within 30 pc of our solar system possess the potential to detect the four giant planets within 100 yr. Additionally, our prediction suggests that over 300 stars positioned within 10 pc from our solar system could detect our Earth if they achieve an astrometry precision of 0.3 μas.

The Comparison of Five Methods of Detecting Exoplanets

Detecting exoplanets has become a hot topic, where various detection scenarios have been proposed. Five of these methods have all found more than 50 exoplanets, which are the transit method, the radial velocity method, the microlensing method, the imaging method, and the timing method. This paper aims to find their pros and cons, and the type of exoplanet that is suitable for each method by comparing the characteristics of exoplanets found by each method and the detection result of each method. The transit method is suitable for exoplanets with short periods possessing the advantages of measuring various parameters of exoplanets simultaneously, but can confuse exoplanets and other celestial bodies with the same radius of planets. The radial velocity method is best for exoplanets with small orbit radius or large mass, whereas it can only determine the minimum mass of exoplanets. The microlensing method can find exoplanets that are extremely far from the Earth or even rogue planets, as well as their mass. However, it does not allow researchers to observe the exoplanets found by it twice. The imaging method offers a tool to directly observe exoplanets in the infrared band. It can detect exoplanets that are extremely far from their host star with relatively high temperatures or rogue planets, but these are also the types of exoplanets that it can be detected. The timing method allows observers to discover exoplanets around pulsars, pulsating stars, eclipsing binaries, and planetary systems with discovered planets, but it is limited to these types.

Understanding and predicting cadence effects in the characterization of exoplanet transits

ABSTRACT We investigate the effect of observing cadence on the precision of radius ratio values obtained from transit light curves by performing uniform Markov chain Monte Carlo fits of 46 exoplanets observed by the Transiting Exoplanet Survey Satellite (TESS) in multiple cadences. We find median improvements of almost 50 per cent when comparing fits to 20 and 120 s cadence light curves to 1800 s cadence light curves, and of 37 per cent when comparing 600 s cadence to 1800 s cadence. Such improvements in radius precision are important, for example, to precisely constrain the properties of the radius valley or to characterize exoplanet atmospheres. We also implement a numerical information analysis to predict the precision of parameter estimates for different observing cadences. We tested this analysis on our sample and found that it reliably predicts the effect of shortening observing cadence with errors in the predicted percentage precision of $\lesssim0.5~{{\ \rm per\ cent}}$ for most cases. We apply this method to 157 TESS objects of interest that have only been observed with 1800 s cadence to predict the precision improvement that could be obtained by reobservations with shorter cadences and provide the full table of expected improvements. We report the 10 planet candidates that would benefit the most from reobservations at short cadence. Our implementation of the information analysis for the prediction of the precision of exoplanet parameters, Prediction of Exoplanet Precisions using Information in Transit Analysis, is made publicly available.

Exploring multi-planet system wasp-148 using n-body simulation and deep learning

The search of exoplanets this day is focusing on finding planet with small mass or exoplanet with similar mass with Earth. One of the detection methods that sensitive enough to detect this kind of planet is transit timing variation method (TTV). This method detects planet using its perturbation to the transiting planet that could be observed by its small variation on the transit curve. From the TTV signal, the planets parameter such as mass and eccentricity could be estimated. One of the methods to determine exoplanet parameters from TTV signal is using N-body simulation to find the best planet configuration that could replicate the TTV signal from observation. However, this method is computationally expensive because there are so many combinations of planet configuration that must be simulated to find the best configuration. By using machine learning technique, we can make this simulation faster and more efficient by predicting the initial condition before hands. We combine photometric data from space and ground based observation for exoplanet system WASP-148 and use that data as input on our machine learning model. Then finally we can estimate the exoplanet parameters using N-body simulation

Impact of the measured parameters of exoplanets on the inferred internal structure

Context. Exoplanet characterization is one of the main foci of current exoplanetary science. For super-Earths and sub-Neptunes, we mostly rely on mass and radius measurements, which allow us to derive the mean density of the body and give a rough estimate of the bulk composition of the planet. However, the determination of planetary interiors is a very challenging task. In addition to the uncertainty in the observed fundamental parameters, theoretical models are limited owing to the degeneracy in determining the planetary composition. Aims. We aim to study several aspects that affect the internal characterization of super-Earths and sub-Neptunes: observational uncertainties, location on the M–R diagram, impact of additional constraints such as bulk abundances or irradiation, and model assumptions. Methods. We used a full probabilistic Bayesian inference analysis that accounts for observational and model uncertainties. We employed a nested sampling scheme to efficiently produce the posterior probability distributions for all the planetary structural parameter of interest. We included a structural model based on self-consistent thermodynamics of core, mantle, high-pressure ice, liquid water, and H–He envelope. Results. Regarding the effect of mass and radius uncertainties on the determination of the internal structure, we find three different regimes: below the Earth-like composition line and above the pure-water composition line smaller observational uncertainties lead to better determination of the core and atmosphere mass, respectively; and between these regimes internal structure characterization only weakly depends on the observational uncertainties. We also find that using the stellar Fe/Si and Mg/Si abundances as a proxy for the bulk planetary abundances does not always provide additional constraints on the internal structure. Finally we show that small variations in the temperature or entropy profiles lead to radius variations that are comparable to the observational uncertainty. This suggests that uncertainties linked to model assumptions can eventually become more relevant to determine the internal structure than observational uncertainties.

Precise calibration of the dependence of surface brightness–colour relations on colour and class for late-type stars

Context. Surface brightness–colour relations (SBCRs) are used to derive the stellar angular diameters from photometric observations. They have various astrophysical applications, such as the distance determination of eclipsing binaries or the determination of exoplanet parameters. However, strong discrepancies between the SBCRs still exist in the literature, in particular for early and late-type stars. Aims. We aim to calibrate new SBCRs as a function of the spectral type and the luminosity class of the stars. Our goal is also to apply homogeneous criteria to the selection of the reference stars and in view of compiling an exhaustive and up-to-date list of interferometric late-type targets. Methods. We implemented criteria to select measurements in the JMMC Measured Diameters Catalog. We then applied additional criteria on the photometric measurements used to build the SBCRs, together with stellar characteristics diagnostics. Results. We built SBCRs for F5/K7–II/III, F5/K7–IV/V, M–II/III and M–V stars, with respective rms of σFV = 0.0022 mag, σFV = 0.0044 mag, σFV = 0.0046 mag, and σFV = 0.0038 mag. This results in a precision on the angular diameter of 1.0%, 2.0%, 2.1%, and 1.7%, respectively. These relations cover a large V − K colour range of magnitude, from 1 to 7.5. Our work demonstrates that SBCRs are significantly dependent on the spectral type and the luminosity class of the star. Through a new set of interferometric measurements, we demonstrate the critical importance of the selection criteria proposed for the calibration of SBCR. Finally, using the Gaia photometry for our samples, we obtained (G − K) SBCRs with a precision on the angular diameter between 1.1% and 2.4%. Conclusions. By adopting a refined and homogeneous methodology, we show that the spectral type and the class of the star should be considered when applying an SBCR. This is particularly important in the context of PLATO.

Tidal response of rocky and ice-rich exoplanets

The amount of detected planets with sizes comparable to that of the Earth is increasing drastically. Most of the Earth-size planet candidates orbit at close distances from their central star, and therefore are subjected to large tidal forces. Accurate determination of the tidal parameters of exoplanets taking into account their interior structure and rheology is essential to better constrain their rotational and orbital history, and hence their impact on climate stability and planetary habitability. In the present study, we compute the tidal response of rocky and ice-rich solid exoplanets for masses ranging between 0.1 and 10 Earth masses using a multilayer approach and an Andrade rheology. We show that the amplitude of tidal response, characterized by the gravitational Love number,k2, is mostly controlled by self-gravitation and increases as a function of planet mass. For rocky planets,k2depends mostly on the relative size of the iron core, and hence on the bulk iron fraction. For ice-rich planets, the presence of outer ice layers reduces the amplitude of tidal response compared to ice-free rocky planets of similar masses. For both types of planet (rocky and ice-rich), we propose relatively simple scaling laws to predict the potential Love number value as a function of radius, planet mass and composition. For the dissipation rate, characterized by theQ−1factor, we did not find any direct control by the planet mass. The dissipation rate is mostly sensitive to the forcing frequency and to the internal viscosity, which depends on the thermal evolution of the planet, which is in turn controlled by the planet mass and composition. The methodology described in the present study can be applied to any kind of solid planet and can be easily implemented into any thermal and orbital evolution code.

Homogeneously derived transit timings for 17 exoplanets and reassessed TTV trends for WASP-12 and WASP-4

ABSTRACT We homogeneously analyse ∼3.2 × 105 photometric measurements for ∼1100 transit light curves belonging to 17 exoplanet hosts. The photometric data cover 16 years (2004–2019) and include amateur and professional observations. Old archival light curves were reprocessed using up-to-date exoplanetary parameters and empirically debiased limb-darkening models. We also derive self-consistent transit and radial-velocity fits for 13 targets. We confirm the non-linear transit timing variation (TTV) trend in the WASP-12 data at a high significance, and with a consistent magnitude. However, Doppler data reveal hints of a radial acceleration of about −7.5 ± 2.2 m s−1 yr−1, indicating the presence of unseen distant companions, and suggesting that roughly 10 per cent of the observed TTV was induced via the light-travel (or Roemer) effect. For WASP-4, a similar TTV trend suspected after the recent TESS observations appears controversial and model dependent. It is not supported by our homogeneous TTV sample, including 10 ground-based EXPANSION light curves obtained in 2018 simultaneously with TESS. Even if the TTV trend itself does exist in WASP-4, its magnitude and tidal nature are uncertain. Doppler data cannot entirely rule out the Roemer effect induced by possible distant companions.

Atmospheric scintillation noise in ground-based exoplanet photometry

ABSTRACT Atmospheric scintillation caused by optical turbulence in the Earth’s atmosphere can be the dominant source of noise in ground-based photometric observations of bright targets, which is a particular concern for ground-based exoplanet transit photometry. We demonstrate the implications of atmospheric scintillation for exoplanet transit photometry through contemporaneous turbulence profiling and transit observations. We find a strong correlation between measured intensity variations and scintillation determined through optical turbulence profiling. This correlation indicates that turbulence profiling can be used to accurately model the amount of scintillation noise present in photometric observations on another telescope at the same site. We examine the conditions under which scintillation correction would be beneficial for transit photometry through turbulence profiling, and find that for the atmosphere of La Palma, scintillation dominates for bright targets of magnitude above V ∼ 10.1 mag for a 0.5 m telescope, and at V ∼ 11.7 mag for a 4.2 m telescope under median atmospheric conditions. Through Markov-chain Monte Carlo methods we examine the effect of scintillation noise on the uncertainty of the measured exoplanet parameters, and determine the regimes where scintillation correction is especially beneficial. The ability to model the amount of noise in observations due to scintillation, given an understanding of the atmosphere, is a crucial test for our understanding of scintillation and the overall noise budget of our observations.

Secular spin-axis dynamics of exoplanets

Context. Seasonal variations and climate stability of a planet are very sensitive to the planet obliquity and its evolution. This is of particular interest for the emergence and sustainability of land-based life, but orbital and rotational parameters of exoplanets are still poorly constrained. Numerical explorations usually realised in this situation are therefore in heavy contrast with the uncertain nature of the available data. Aims. We aim to provide an analytical formulation of the long-term spin-axis dynamics of exoplanets, linking it directly to physical and dynamical parameters, but still giving precise quantitative results if the parameters are well known. Together with bounds for the poorly constrained parameters of exoplanets, this analysis is designed to enable a quick and straightforward exploration of the spin-axis dynamics. Methods. The long-term orbital solution is decomposed into quasi-periodic series and the spin-axis Hamiltonian is expanded in powers of eccentricity and inclination. Chaotic zones are measured by the resonance overlap criterion. Bounds for the poorly known parameters of exoplanets are obtained from physical grounds (rotational breakup) and dynamical considerations (equipartition of the angular momentum deficit). Results. This method gives accurate results when the orbital evolution is well known. The detailed structure of the chaotic zones for the solar system planets can be retrieved from simple analytical formulas. For less-constrained planetary systems, the maximal extent of the chaotic regions can be computed, requiring only the mass, the semi-major axis, and the eccentricity of the planets present in the system. Additionally, some estimated bounds of the precession constant allow to classify which observed exoplanets are necessarily out of major spin-orbit secular resonances (unless the precession rate is affected by the presence of massive satellites).

Stellar ages, masses, and radii from asteroseismic modeling are robust to systematic errors in spectroscopy

Context. The search for twins of the Sun and Earth relies on accurate characterization of stellar and the exoplanetary parameters age, mass, and radius. In the modern era of asteroseismology, parameters of solar-like stars are derived by fitting theoretical models to observational data, which include measurements of their oscillation frequencies, metallicity [Fe/H], and effective temperature Teff. Furthermore, combining this information with transit data yields the corresponding parameters for their associated exoplanets. Aims. While values of [Fe/H] and Teff are commonly stated to a precision of ∼0.1 dex and ∼100 K, the impact of systematic errors in their measurement has not been studied in practice within the context of the parameters derived from them. Here we seek to quantify this. Methods. We used the Stellar Parameters in an Instant (SPI) pipeline to estimate the parameters of nearly 100 stars observed by Kepler and Gaia, many of which are confirmed planet hosts. We adjusted the reported spectroscopic measurements of these stars by introducing faux systematic errors and, separately, artificially increasing the reported uncertainties of the measurements, and quantified the differences in the resulting parameters. Results. We find that a systematic error of 0.1 dex in [Fe/H] translates to differences of only 4%, 2%, and 1% on average in the resulting stellar ages, masses, and radii, which are well within their uncertainties (∼11%, 3.5%, 1.4%) as derived by SPI. We also find that increasing the uncertainty of [Fe/H] measurements by 0.1 dex increases the uncertainties of the ages, masses, and radii by only 0.01 Gyr, 0.02 M⊙, and 0.01 R⊙, which are again well below their reported uncertainties (∼0.5 Gyr, 0.04 M⊙, 0.02 R⊙). The results for Teff at 100 K are similar. Conclusions. Stellar parameters from SPI are unchanged within uncertainties by errors of up to 0.14 dex or 175 K. They are even more robust to errors in Teff than the seismic scaling relations. Consequently, the parameters for their exoplanets are also robust.

New Rotation Period Measurements for M Dwarfs in the Southern Hemisphere: An Abundance of Slowly Rotating, Fully Convective Stars

Abstract Stellar rotation periods are valuable both for constraining models of angular momentum loss and for understanding how magnetic features impact inferences of exoplanet parameters. Building on our previous work in the northern hemisphere, we have used long-term, ground-based photometric monitoring from the MEarth Observatory to measure 234 rotation periods for nearby, southern hemisphere M dwarfs. Notable examples include the exoplanet hosts GJ 1132, LHS 1140, and Proxima Centauri. We find excellent agreement between our data and K2 photometry for the overlapping subset. Among the sample of stars with the highest quality data sets, we recover periods in 66%; as the length of the data set increases, our recovery rate approaches 100%. The longest rotation periods we detect are around 140 days, which we suggest represent the periods that are reached when M dwarfs are as old as the local thick disk (about 9 Gyr).

The Penn State - Toruń Centre for Astronomy Planet Search stars

Context. Our knowledge of the intrinsic parameters of exoplanets is as precise as our determinations of their stellar hosts parameters. In the case of radial velocity searches for planets, stellar masses appear to be crucial. But before estimating stellar masses properly, detailed spectroscopic analysis is essential. With this paper we conclude a general spectroscopic description of the Pennsylvania-Toruń Planet Search (PTPS) sample of stars. Aims. We aim at a detailed description of basic parameters of stars representing the complete PTPS sample. We present atmospheric and physical parameters for dwarf stars observed within the PTPS along with updated physical parameters for the remaining stars from this sample after the first Gaia data release. Methods. We used high resolution (R = 60 000) and high signal-to-noise-ratio (S/N = 150–250) spectra from the Hobby-Eberly Telescope and its High Resolution Spectrograph. Stellar atmospheric parameters were determined through a strictly spectroscopic local thermodynamic equilibrium analysis (LTE) of the equivalent widths of Fe I and Fe II lines. Stellar masses, ages, and luminosities were estimated through a Bayesian analysis of theoretical isochrones. Results. We present Teff, log g, [Fe/H], microturbulence velocities, absolute radial velocities, and rotational velocities for 156 stars from the dwarf sample of PTPS. For most of these stars these are the first determinations. We refine the definition of PTPS subsamples of stars (giants, subgiants, and dwarfs) and update the luminosity classes for all PTPS stars. Using available Gaia and HIPPARCOS parallaxes, we redetermine the stellar parameters (masses, radii, luminosities, and ages) for 451 PTPS stars. Conclusions. The complete PTPS sample of 885 stars is composed of 132 dwarfs, 238 subgiants, and 515 giants, of which the vast majority are of roughly solar mass; however, 114 have masses higher than 1.5 M⊙ and 30 of over 2 M⊙. The PTPS extends toward much less metal abundant and much more distant stars than other planet search projects aimed at detecting planets around evolved stars; 29% of our targets belong to the Galactic thick disc and 2% belong to the halo.

Exoplanet Biosignatures: A Framework for Their Assessment.

Finding life on exoplanets from telescopic observations is an ultimate goal of exoplanet science. Life produces gases and other substances, such as pigments, which can have distinct spectral or photometric signatures. Whether or not life is found with future data must be expressed with probabilities, requiring a framework of biosignature assessment. We present a framework in which we advocate using biogeochemical “Exo-Earth System” models to simulate potential biosignatures in spectra or photometry. Given actual observations, simulations are used to find the Bayesian likelihoods of those data occurring for scenarios with and without life. The latter includes “false positives” wherein abiotic sources mimic biosignatures. Prior knowledge of factors influencing planetary inhabitation, including previous observations, is combined with the likelihoods to give the Bayesian posterior probability of life existing on a given exoplanet. Four components of observation and analysis are necessary. (1) Characterization of stellar (e.g., age and spectrum) and exoplanetary system properties, including “external” exoplanet parameters (e.g., mass and radius), to determine an exoplanet's suitability for life. (2) Characterization of “internal” exoplanet parameters (e.g., climate) to evaluate habitability. (3) Assessment of potential biosignatures within the environmental context (components 1–2), including corroborating evidence. (4) Exclusion of false positives. We propose that resulting posterior Bayesian probabilities of life's existence map to five confidence levels, ranging from “very likely” (90–100%) to “very unlikely” (<10%) inhabited. Key Words: Bayesian statistics—Biosignatures—Drake equation—Exoplanets—Habitability—Planetary science. Astrobiology 18, 709–738.

High-precision Stellar Limb-darkening in Exoplanetary Transits

Abstract Characterization of the atmospheres of transiting exoplanets relies on accurate measurements of the extent of the optically thick area of the planet at multiple wavelengths with a precision parts per million (ppm). Next-generation instruments onboard the James Webb Space Telescope (JWST) are expected to achieve ∼10 ppm precision for several tens of targets. A similar precision can be obtained in modeling only if other astrophysical effects, including the stellar limb-darkening, are properly accounted for. In this paper, we explore the limits on precision due to the mathematical formulas currently adopted to approximate the stellar limb-darkening, and due to the use of limb-darkening coefficients obtained either from stellar-atmosphere models or empirically. We recommend the use of a two-coefficient limb-darkening law, named “power-2,” which outperforms other two-coefficient laws adopted in the exoplanet literature in most cases, and particularly for cool stars. Empirical limb-darkening based on two-coefficient formulas can be significantly biased, even if the light-curve residuals are nearly photon-noise limited. We demonstrate an optimal strategy to fitting for the four-coefficient limb-darkening in the visible, using prior information on the exoplanet orbital parameters to break some of the degeneracies that otherwise would prevent the convergence of the fit. Infrared observations taken with the JWST will provide accurate measurements of the exoplanet orbital parameters with unprecedented precision, which can be used as priors to improve the stellar limb-darkening characterization, and therefore the inferred exoplanet parameters, from observations in the visible, such as those taken with Kepler/K2, the JWST, and other past and future instruments.

The Homogeneous Study of Transiting Systems (HoSTS) – II. The influence of the line list on stellar parameters

The use of high resolution, high signal-to-noise stellar spectra is essential in order to determine the most accurate and precise stellar atmospheric parameters via spectroscopy. This is particularly important for determining the fundamental parameters of exoplanets, which directly depend on the stellar properties. However, different techniques can be implemented when analysing these spectra which will influence the results. These include performing an abundance analysis relative to the solar values in order to negate uncertainties in atomic data, and fixing the surface gravity (log g) to an external value such as those from asteroseismology. The choice of lines used will also influence the results. In this paper, we investigate differential analysis and fixing log g for a set of FGK stars that already have accurate fundamental parameters known from external methods. We find that a differential line list gives slightly more accurate parameters compared to a laboratory line list, however the laboratory line list still gives robust parameters. We also find that fixing the log g does not improve the spectroscopic parameters. We investigate the effects of line selection on the stellar parameters and find that the choice of lines used can have a significant effect on the parameters. In particular, removal of certain low excitation potential lines can change the Teff by up to 50 K. For future HoSTS papers we will use the differential line list with a solar microturbulence value of 1 km/s, and we will not fix the log g to an external value.

Radii, masses, and ages of 18 bright stars using interferometry and new estimations of exoplanetary parameters

Accurate stellar parameters are needed in numerous domains of astrophysics. The position of stars on the H-R diagram is an important indication of their structure and evolution, and it helps improve stellar models. Furthermore, the age and mass of stars hosting planets are required elements for studying exoplanetary systems. We aim at determining accurate parameters of a set of 18 bright exoplanet host and potential host stars from interferometric measurements, photometry, and stellar models. Using the VEGA/CHARA interferometer, we measured the angular diameters of 18 stars, ten of which host exoplanets. We combined them with their distances to estimate their radii. We used photometry to derive their bolometric flux and, then, their effective temperature and luminosity to place them on the H-R diagram. We then used the PARSEC models to derive their best fit ages and masses, with error bars derived from MC calculations. Our interferometric measurements lead to an average of 1.9% uncertainty on angular diameters and 3% on stellar radii. There is good agreement between measured and indirect estimations of angular diameters (from SED fitting or SB relations) for MS stars, but not as good for more evolved stars. For each star, we provide a likelihood map in the mass-age plane; typically, two distinct sets of solutions appear (an old and a young age). The errors on the ages and masses that we provide account for the metallicity uncertainties, which are often neglected by other works. From measurements of its radius and density, we also provide the mass of 55 Cnc independently of models. From the stellar masses, we provide new estimates of semi-major axes and minimum masses of exoplanets with reliable uncertainties. We also derive the radius, density, and mass of 55 Cnc e, a super-Earth that transits its stellar host. Our exoplanetary parameters reflect the known population of exoplanets.

Characterization of transiting exoplanets by way of differential photometry

This paper describes a simple activity for plotting and characterizing the light curve from an exoplanet transit event by way of differential photometry analysis. Using free digital imaging software, participants analyse a series of telescope images with the goal of calculating various exoplanet parameters, including size, orbital radius and habitability. The activity has been designed for a high-school or undergraduate university level and introduces fundamental concepts in astrophysics and an understanding of the basis for exoplanetary science, the transit method and digital photometry.