M. Tsantaki

SWEET-Cat: A catalogue of parameters for Stars With ExoplanETs - I. New atmospheric parameters and masses for 48 stars with planets

Context. Thanks to the importance that the star-planet relation has to our understanding of the planet formation process, the precise determination of stellar parameters for the ever increasing number of discovered extra-solar planets is of great relevance. Furthermore, precise stellar parameters are needed to fully characterize the planet properties. It is thus important to continue the efforts to determine, in the most uniform way possible, the parameters for stars with planets as new discoveries are announced. Aims. In this paper we present new precise atmospheric parameters for a sample of 48 stars with planets. We then take the opportunity to present a new catalogue of stellar parameters for FGK and M stars with planets detected by radial velocity, transit, and astrometry programs. Methods. Stellar atmospheric parameters and masses for the 48 stars were derived assuming local thermodynamic equilibrium (LTE) and using high-resolution and high signal-to-noise spectra. The methodology used is based on the measurement of equivalent widths for a list of iron lines and making use of iron ionization and excitation equilibrium principles. For the catalogue, and whenever possible, we used parameters derived in previous works published by our team, using well-defined methodologies for the derivation of stellar atmospheric parameters. This set of parameters amounts to over 65% of all planet host stars known, including more than 90% of all stars with planets discovered through radial velocity surveys. For the remaining targets, stellar parameters were collected from the literature. Results. The stellar parameters for the 48 stars are presented and compared with previously determined literature values. For the catalogue, we compile values for the effective temperature, surface gravity, metallicity, and stellar mass for almost all the planet host stars listed in the Extrasolar Planets Encyclopaedia. This data will be updated on a continuous basis. The compiled catalogue is available online. The data can be used for statistical studies of the star-planet correlation, as well as for the derivation of consistent properties for known planets.

SOPHIE velocimetry of Kepler transit candidates - XVII. The physical properties of giant exoplanets within 400 days of period

While giant extrasolar planets have been studied for more than two decades now, there are still some open questions such as their dominant formation and migration process, as well as their atmospheric evolution in different stellar environments. In this paper, we study a sample of giant transiting exoplanets detected by the Kepler telescope with orbital periods up to 400 days. We first defined a sample of 129 giant-planet candidates that we followed up with the SOPHIE spectrograph (OHP, France) in a 6-year radial velocity campaign. This allow us to unveil the nature of these candidates and to measure a false-positive rate of 54.6 +/- 6.5 % for giant-planet candidates orbiting within 400 days of period. Based on a sample of confirmed or likely planets, we then derive the occurrence rates of giant planets in different ranges of orbital periods. The overall occurrence rate of giant planets within 400 days is 4.6 +/- 0.6 %. We recover, for the first time in the Kepler data, the different populations of giant planets reported by radial velocity surveys. Comparing these rates with other yields, we find that the occurrence rate of giant planets is lower only for hot jupiters but not for the longer period planets. We also derive a first measurement on the occurrence rate of brown dwarfs in the brown-dwarf desert with a value of 0.29 +/- 0.17 %. Finally, we discuss the physical properties of the giant planets in our sample. We confirm that giant planets receiving a moderate irradiation are not inflated but we find that they are in average smaller than predicted by formation and evolution models. In this regime of low-irradiated giant planets, we find a possible correlation between their bulk density and the Iron abundance of the host star, which needs more detections to be confirmed.

New and updated stellar parameters for 71 evolved planet hosts - On the metallicity–giant planet connection

It is still being debated whether the well-known metallicity - giant planet correlation for dwarf stars is also valid for giant stars. For this reason, having precise metallicities is very important. Different methods can provide different results that lead to discrepancies in the analysis of planet hosts. To study the impact of different analyses on the metallicity scale for evolved stars, we compare different iron line lists to use in the atmospheric parameter derivation of evolved stars. Therefore, we use a sample of 71 evolved stars with planets. With these new homogeneous parameters, we revisit the metallicity - giant planet connection for evolved stars. A spectroscopic analysis based on Kurucz models in local thermodynamic equilibrium (LTE) was performed through the MOOG code to derive the atmospheric parameters. Two different iron line list sets were used, one built for cool FGK stars in general, and the other for giant FGK stars. Masses were calculated through isochrone fitting, using the Padova models. Kolmogorov-Smirnov tests (K-S tests) were then performed on the metallicity distributions of various different samples of evolved stars and red giants. All parameters compare well using a line list set, designed specifically for cool and solar-like stars to provide more accurate temperatures. All parameters derived with this line list set are preferred and are thus adopted for future analysis. We find that evolved planet hosts are more metal-poor than dwarf stars with giant planets. However, a bias in giant stellar samples that are searched for planets is present. Because of a colour cut-off, metal-rich low-gravity stars are left out of the samples, making it hard to compare dwarf stars with giant stars. Furthermore, no metallicity enhancement is found for red giants with planets (

One of the closest exoplanet pairs to the 3.2 mean motion resonance: K2-19b and c

\log g < 3.0

Li abundances in F stars: planets, rotation, and Galactic evolution ,

\,dex) with respect to red giants without planets.

Photodynamical mass determination of the multiplanetary system K2-19

Aims. The K2 mission has recently begun to discover new and diverse planetary systems. In December 2014, Campaign 1 data from the mission was released, providing high-precision photometry for similar to 22 000 objects over an 80-day timespan. We searched these data with the aim of detecting more important new objects. Methods. Our search through two separate pipelines led to the independent discovery of K2-19b and c, a two-planet system of Neptune-sized objects (4.2 and 7.2 R-circle plus), orbiting a K dwarf extremely close to the 3: 2 mean motion resonance. The two planets each show transits, sometimes simultaneously owing to their proximity to resonance and the alignment of conjunctions. Results. We obtained further ground-based photometry of the larger planet with the NITES telescope, demonstrating the presence of large transit timing variations (TTVs), and used the observed TTVs to place mass constraints on the transiting objects under the hypothesis that the objects are near but not in resonance. We then statistically validated the planets through the PASTIS tool,

Chemical abundances and kinematics of 257 G-, K-type field giants. Setting a base for further analysis of giant-planet properties orbiting evolved stars

Aims. We aim, on the one hand, to study the possible differences of Li abundances between planet hosts and stars without detected planets at effective temperatures hotter than the Sun, and on the other hand, to explore the Li dip and the evolution of Li at high metallicities. Methods. We present lithium abundances for 353 main sequence stars with and without planets in the Teff range 5900–7200 K. We observed 265 stars of our sample with HARPS spectrograph during different planets search programs. We observed the remaining targets with a variety of high-resolution spectrographs. The abundances are derived by a standard local thermodynamic equilibrium analysis using spectral synthesis with the code MOOG and a grid of Kurucz ATLAS9 atmospheres. Results. We find that hot jupiter host stars within the Teff range 5900–6300 K show lower Li abundances, by 0.14 dex, than stars without detected planets. This offset has a significance at the level 7σ, pointing to a stronger effect of planet formation on Li abundances when the planets are more massive and migrate close to the star. However, we also find that the average v sini of (a fraction of) stars with hot jupiters is higher on average than for single stars in the same Teff region, suggesting that rotational-induced mixing (and not the presence of planets) might be the cause for a greater depletion of Li. We confirm that the mass-metallicity dependence of the Li dip is extended towards [Fe/H] ∼ 0.4 dex (beginning at [Fe/H] ∼− 0.4 dex for our stars) and that probably reflects the mass-metallicity correlation of stars of the same Teff on the main sequence. We find that for the youngest stars (<1.5 Gyr) around the Li dip, the depletion of Li increases with v sini values, as proposed by rotationally-induced depletion models. This suggests that the Li dip consists of fast rotators at young ages whereas the most Li-depleted old stars show lower rotation rates (probably caused by the spin-down during their long lifes). We have also explored the Li evolution with [Fe/H] taking advantage of the metal-rich stars included in our sample. We find that Li abundance reaches its maximum around solar metallicity, but decreases in the most metal-rich stars, as predicted by some models of Li Galactic production.

Homogeneous spectroscopic parameters for bright planet host stars from the northern hemisphere. The impact on stellar and planetary mass

K2-19 is the second multiplanetary system discovered with K2 observations. The system is composed of two Neptune size planets close to the 3: 2 mean-motion resonance. To better characterize the system we obtained two additional transit observations of K2-19b and five additional radial velocity observations. These were combined with K2 data and fitted simultaneously with the system dynamics ( photodynamical model) which increases the precision of the transit time measurements. The higher transit time precision allows us to detect the chopping signal of the dynamic interaction of the planets that in turn permits to uniquely characterize the system. Although the reflex motion of the star was not detected, dynamic modelling of the system allowed us to derive planetary masses of M-b = 44 +/- 12 M-circle plus and M-c = 15.9 +/- 7.0 M-circle plus for the inner and the outer planets, respectively, leading to densities close to Uranus. We also show that our method allows the derivation of mass ratios using only the 80 d of observations during the first campaign of K2.

Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program: II. Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Eu⋆⋆⋆

This work was supported by the European Research Council/European Community under the FP7 through Starting Grant agreement number 239953. This work was also supported by the Gaia Research for European Astronomy Training (GREATITN) Marie Curie network, funded through the European Union Seventh Framework Programme ([FP7/2007-2013]) under grant agreement number 264895. V.Zh.A. and S.G.S acknowledge the support from the Fundacao para a Ciencia e a Tecnologia, FCT (Portugal) in the form of the fellowships SFRH/BPD/70574/2010 and SFRH/BPD/47611/2008, respectively. NCS was supported by FCT through the Investigator FCT contract reference IF/00169/2012 and POPH/FSE (EC) by FEDER funding through the programme ‘Programa Operacional de Factores de Competitividade’ – COMPETE. SA acknowledges Post-Doctoral Fellowship from the CAPES brazilian agency (BEX-2077140), and also support by Iniciativa Cientifica Milenio through grant IC120009, awarded to The Millennium Institute of Astrophysics. GI acknowledges financial support from the Spanish Ministry project MINECO AYA2011-29060. AM received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement number 313014 (ETAEARTH).

Searching for Li-rich giants in a sample of 12 open clusters - Li enhancement in two stars with substellar companions

Aims. In this work we derive new precise and homogeneous parameters for 37 stars with planets. For this purpose, we analyze high resolution spectra obtained by the NARVAL spectrograph for a sample composed of bright planet host stars in the northern hemisphere. The new parameters are included in the SWEET-Cat online catalogue. Methods. To ensure that the catalogue is homogeneous, we use our standard spectroscopic analysis procedure, ARES+MOOG, to derive effective temperatures, surface gravities, and metallicities. These spectroscopic stellar parameters are then used as input to compute the stellar mass and radius, which are fundamental for the derivation of the planetary mass and radius. Results. We show that the spectroscopic parameters, masses, and radii are generally in good agreement with the values available in online databases of exoplanets. There are some exceptions, especially for the evolved stars. These are analyzed in detail focusing on the effect of the stellar mass on the derived planetary mass. Conclusions. We conclude that the stellar mass estimations for giant stars should be managed with extreme caution when using them to compute the planetary masses. We report examples within this sample where the differences in planetary mass can be as high as 100% in the most extreme cases.