Exploration of the brown dwarf regime around solar-like stars by CoRoT

Aims. A summary of the CoRoT brown dwarf investigations are presented. Methods. Transiting brown dwarfs around solar like stars were studied by using the photometric time-series of CoRoT, and ground based radial velocity measurements. Results. CoRoT detected three transiting brown dwarfs around F and G dwarf stars. The occurence rate of brown dwarfs was found to be 0.20 +/- 0.15% around solar-like stars which is compatible with the value obtained by Kepler-data.Comment: To be appeared in 'The CoroT legacy book', 2016, Scientific Editors: Annie Baglin et al., Publisher: EDP Sciences, ISBN: 978-2-7598-1876-

The power of wavelets in analysis of transit and phase curves in presence of stellar variability and instrumental noise III. Accuracy of transit parameters

Correlated noise in exoplanet light curves, such as noises from stellar activity, convection noise, and instrumental noises distorts the exoplanet transit light curves, and leads to biases in the best-fit transit parameters. An optimal fitting algorithm is stable against the presence of correlated noises and lead to statistically consistent results, i.e. the actual biases are usually within the error interval. This is not automatically satisfied by most of the algorithms in everyday use, and the testing of the algorithms is necessary. In this paper, we describe a bootstrapping-like test to handle with the general case, and apply this to the wavelet-based TLCM (Transit and Light Curve Modeller) algorithm, testing it for the stability against the correlated noise. We contrast the results to the FITSH algorithm that is based on a white noise assumption. We simulated transit light curves with previously known parameters in the presence of a correlated noise model generated by an ARIMA (Autoregressive Integretad Moving Average) process. Then we solved the simulated observations, and examined the resulting parameters and error intervals. We have found that the assumption of FITSH that only white noise is present led to inconsistencies in the results: the distribution of best-fit parameters is by a factor of 3--6 broader then the determined error intervals. On the other hand, the wavelet-based TLCM algorithm handles the correlated noise properly, leading to properly determined parameter and error intervals which are perfectly consistent with the actual biases.Comment: Submitted to A&A, favorable referee report received, 11 pages, 8 figure

Transit timing variations in eccentric hierarchical triple exoplanetary systems. I. Perturbations on the time-scale of the orbital period of the perturber

We study the long-term time-scale (i.e. period comaprable to the orbital period of the outer perturber object) transit timing variations in transiting exoplanetary systems which contain a further, more distant (a_2>>a_1) either planetary, or stellar companion. We give an analytical form of the O-C diagram (which describes such TTV-s) in trigonometric series, valid for arbitrary mutual inclinations, up to the sixth order in the inner eccentricity. We show that the dependence of the O-C on the orbital and physical parameters can be separated into three parts. Two of these are independent of the real physical parameters (i.e. masses, separations, periods) of a concrete system, and depend only on dimensionless orbital elements, and so, can be analyzed in general. We analyze these dimensionless amplitudes for different arbitrary initial parameters, as well as for two particular systems CoRoT-9b and HD 80606b. We find in general, that while the shape of the O-C strongly varies with the angular orbital elements, the net amplitude (departing from some specific configurations) depends only weakly on these elements, but strongly on the eccentricities. As an application, we illustrate how the formulae work for the weakly eccentric CoRoT-9b, and the highly eccentric HD 80606b. We consider also the question of detection, as well as the correct identification of such perturbations. Finally, we illustrate the operation and effectiveness of Kozai cycles with tidal friction (KCTF) in the case of HD 80606b.Comment: Submitted to Astronomy and Astrophysics; Revised versio

Catalogue of exoplanets accessible in reflected starlight to the Nancy Grace Roman Space Telescope. A population study and prospects for phase-curve measurements

Reflected starlight measurements will open a new path in the characterization of directly imaged exoplanets. However, we still lack a population study of known targets amenable to this technique. Here, we investigate which of the about 4300 exoplanets confirmed to date are accessible to the Roman Space Telescope's coronagraph (CGI) in reflected starlight at reference wavelengths $\lambda$=575, 730 and 825 nm. We carry out a population study and also address the prospects for phase-curve measurements. We used the NASA Exoplanet Archive as a reference for planet and star properties, and explored the impact of their uncertainties on the exoplanet's detectability by applying statistical arguments. We define a planet as Roman-accessible on the basis of the instrument inner and outer working angles and its minimum planet-to-star constrast (IWA, OWA, $C_{min}$). We adopt for these technical specifications three plausible configurations labeled as pessimistic, intermediate and optimistic. Our key outputs for each exoplanet are its probability of being Roman-accessible ($P_{access}$), the range of observable phase angles, the evolution of its equilibrium temperature, the number of days per orbit that it is accessible and its transit probability. In the optimistic scenario, we find 26 Roman-accessible exoplanets with $P_{access}$>25% and host stars brighter than $V$=7 mag. This population is biased towards planets more massive than Jupiter but also includes the super-Earths tau Cet e and f which orbit near their star's habitable zone. A total of 13 planets are part of multiplanet systems, 3 of them with known transiting companions, offering opportunities for contemporaneous characterization. The intermediate and pessimistic scenarios yield 10 and 3 Roman-accessible exoplanets, respectively. We find that inclination estimates (e.g. with astrometry) are key for refining the detectability prospects.Comment: Accepted for publication in A&A. 34 pages, 12 Tables, 24 Figure

Simultaneous multicolour optical and near-IR transit photometry of GJ 1214b with SOFIA

Context. The benchmark exoplanet GJ 1214b is one of the best studied transiting planets in the transition zone between rocky Earth-sized planets and gas or ice giants. This class of super-Earth or mini-Neptune planets is unknown in our solar system, yet is one of the most frequently detected classes of exoplanets. Understanding the transition from rocky to gaseous planets is a crucial step in the exploration of extrasolar planetary systems, in particular with regard to the potential habitability of this class of planets. Aims: GJ 1214b has already been studied in detail from various platforms at many different wavelengths. Our airborne observations with the Stratospheric Observatory for Infrared Astronomy (SOFIA) add information in the Paschen-? cont. 1.9 ľm infrared wavelength band, which is not accessible by any other current ground- or space-based instrument due to telluric absorption or limited spectral coverage. Methods: We used FLIPO, the combination of the High-speed Imaging Photometer for Occultations (HIPO) and the First Light Infrared TEst CAMera (FLITECAM) and the Focal Plane Imager (FPI+) on SOFIA to comprehensively analyse the transmission signal of the possible water-world GJ 1214b through photometric observations during transit in three optical and one infrared channels. Results: We present four simultaneous light curves and corresponding transit depths in three optical and one infrared channel, which we compare to previous observations and current synthetic atmospheric models of GJ 1214b. The final precision in transit depth is between 1.5 and 2.5 times the theoretical photon noise limit, not sensitive enough to constrain the theoretical models any better than previous observations. This is the first exoplanet observation with SOFIA that uses its full set of instruments available to exoplanet spectrophotometry. Therefore we use these results to evaluate SOFIA's potential in this field and suggest future improvements. Tables of the lightcurve data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/608/A120</A

Naprendszeren kívüli bolygók kutatása = Researches on planets beyond the Solar System

Exobolygó-rendszerek megfigyelésével és dinamikájával kapcsolatos kutatásokat folytattunk. A KH 15D születő bolygórendszer fotometriai megfigyelésével hozzájárultunk a csillag körüli anyag bolygókeletkezést megelőző sűrűséghullámainak kimutatásához. IRAS, ISOPHOT és Spitzer adatokat felhasználva összeállítottuk a Nap-rendszer 120 parszek környezetében található legfényesebb törmelékkorongok katalógusát, valamint meghatároztuk fő paramétereiket és fejlődési diagramjaikat. Numerikus módszerek alkalmazásával létrehoztunk egy dinamikai stabilitási katalógust, mely sok millió kezdőfeltételre megadja a pályák stabilitási viszonyait. A katalógus alapján ismert exobolygó-rendszerek lakhatósági zónáinak stabilitási viszonyait határoztuk meg. Exobolygók kialakulásával és dinamikai fejlődésével kapcsolatos modellt dolgoztunk ki. Módszereket dolgoztunk ki hatékony dinamikai vizsgálatokhoz, és tranzit fotometria adatokból pályaelemek meghatározására. | We have conducted researches on the observations and dynamics of exoplanetary systems. By making photometric observations of the planet-forming system KH 15D, we contributed to the detection of the density waves in the circumstellar matter which preceed planet formation. By using IRAS, ISOPHOT and Spitzer data we compiled a catalogue of the brightest debris disks in the 120 pc neighbourhood of the Sun. We also determined their main parameters and evolution diagrams. By using numerical methods we developed a catalogue of dynamical stability giving stability properties of orbits for millions of initial conditions. We determined the stability features of the habitable zones of known exoplanetary systems. We developed a model for the formation and evolution of one class of exoplanets. We developed efficient methods for dynamical investigations and for the estimation of orbital data from transit photometry

Probing the atmosphere of a sub-Jovian planet orbiting a cool dwarf

We derive the 0.01-ľm binned transmission spectrum, between 0.74 and 1.0 ľm, of WASP-80b from low-resolution spectra obtained with the Focal Reducer and low-dispersion Spectrograph 2 instrument attached to ESO's Very Large Telescope. The combination of the fact that WASP-80 is an active star, together with instrumental and telluric factors, introduces correlated noise in the observed transit light curves, which we treat quantitatively using Gaussian processes. Comparison of our results together with those from previous studies to theoretically calculated models reveals an equilibrium temperature in agreement with the previously measured value of 825 K, and a subsolar metallicity, as well as an atmosphere depleted of molecular species with absorption bands in the infrared (ť5?). Our transmission spectrum alone shows evidence for additional absorption from the potassium core and wing, whereby its presence is detected from analysis of narrow 0.003 ľm bin light curves (ť5?). Further observations with visible and near-ultraviolet filters will be required to expand this spectrum and provide more in-depth knowledge of the atmosphere. These detections are only made possible through an instrument-dependent baseline model and a careful analysis of systematics in the data

Three Super-Earths Transiting the Nearby Star GJ 9827

We report on the discovery of three transiting planets around GJ 9827. The planets have radii of 1.75 ą 0.18, 1.36 ą 0.14, and {2.11}-0.21+0.22 R ?, and periods of 1.20896, 3.6480, and 6.2014 days, respectively. The detection was made in Campaign 12 observations as part of our K2 survey of nearby stars. GJ 9827 is a V = 10.39 mag K6V star at a distance of 30.3 ą 1.6 parsecs and the nearest star to be found hosting planets by Kepler and K2. The radial velocity follow-up, high-resolution imaging, and detection of multiple transiting objects near commensurability drastically reduce the false positive probability. The orbital periods of GJ 9827 b, c, and d planets are very close to the 1:3:5 mean motion resonance. Our preliminary analysis shows that GJ 9827 planets are excellent candidates for atmospheric observations. Besides, the planetary radii span both sides of the rocky and gaseous divide, hence the system will be an asset in expanding our understanding of the threshold