The detection and characterisation of extra-solar planets is a major theme driving modern astronomy, with the vast majority of such measurements being achieved by Doppler radial-velocity and transit observations. Another technique -direct imaging -can access a parameter space that complements these methods, and paves the way for future technologies capable of detailed characterization of exoplanetary atmospheres and surfaces. However achieving the required levels of performance with direct imaging, particularly from ground-based telescopes which must contend with the Earth's turbulent atmosphere, requires considerable sophistication in the instrument and detection strategy. Here we demonstrate a new generation of photonic pupil-remapping devices which build upon the interferometric framework developed for the Dragonfly instrument: a high contrast waveguide-based device which recovers robust complex visibility observables. New generation Dragonfly devices overcome problems caused by interference from unguided light and low throughput, promising unprecedented on-sky performance. Closure phase measurement scatter of only ∼ 0.2 • has been achieved, with waveguide throughputs of > 70%. This translates to a maximum contrast-ratio sensitivity (between the host star and its orbiting planet) at 1λ /D (1σ detection) of 5.3 × 10 −4 (when a conventional adaptive-optics (AO) system is used) or 1.8 × 10 −4 (for typical 'extreme-AO' performance), improving even further when random error is minimised by averaging over multiple exposures. This is an order of magnitude beyond conventional pupil-segmenting interferometry techniques (such as aperture masking), allowing a previously inaccessible part of the star to planet contrast-separation parameter space to be explored.

One focus of modern astronomy is to detect temperate terrestrial exoplanets well-suited for atmospheric characterisation. A milestone was recently achieved with the detection of three Earth-sized planets transiting (i.e. passing in front of) a star just 8% the mass of the Sun 12 parsecs away1. Indeed, the transiting configuration of these planets combined with the Jupiter-like size of their host star - named TRAPPIST-1 - makes possible in-depth studies of their atmospheric properties with current and future astronomical facilities1,2,3. Here we report the results of an intensive photometric monitoring campaign of that star from the ground and with the Spitzer Space Telescope. Our observations reveal that at least seven planets with sizes and masses similar to the Earth revolve around TRAPPIST-1. The six inner planets form a near-resonant chain such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.21, 12.35 days) are near ratios of small integers. This architecture suggests that the planets formed farther from the star and migrated inward4,5. The seven planets have equilibrium temperatures low enough to make possible liquid water on their surfaces6,7,8.

Abstract. -The fibre-fed echelle spectrograph of Observatoire de Haute-Provence, ELODIE, is presented. This instrument has been in operation since the end of 1993 on the 1.93 m telescope. ELODIE is designed as an updated version of the cross-correlation spectrometer CORAVEL, to perform very accurate radial velocity measurements such as needed in the search, by Doppler shift, for brown-dwarfs or giant planets orbiting around nearby stars. In one single exposure a spectrum at a resolution of 42000 (λ/∆λ) ranging from 3906Å to 6811Å is recorded on a 1024×1024 CCD. This performance is achieved by using a tan θ = 4 echelle grating and a combination of a prism and a grism as cross-disperser. An automatic on-line data treatment reduces all the ELODIE echelle spectra and computes cross-correlation functions. The instrument design and the data reduction algorithms are described in this paper. The efficiency and accuracy of the instrument and its long term instrumental stability allow us to measure radial velocities with an accuracy better than 15 m s −1 for stars up to 9th magnitude in less than 30 minutes exposure time. Observations of 16th magnitude stars are also possible to measure velocities at about 1 km s −1 accuracy. For classic spectroscopic studies (S/N >100) 9th magnitude stars can be observed in one hour exposure time.

Abstract. The G0 V star HD 166435 has been observed by the fiber-fed spectrograph ELODIE as one of the targets in the large extra-solar planet survey that we are conducting at the Observatory of Haute-Provence. We detected coherent, low-amplitude, radial-velocity variations with a period of 3.7987 days, suggesting a possible close-in planetary companion. Subsequently, we initiated a series of high-precision photometric observations to search for possible planetary transits and an additional series of Ca II H and K observations to measure the level of surface magnetic activity and to look for possible rotational modulation. Surprisingly, we found the star to be photometrically variable and magnetically active. A detailed study of the phase stability of the radial-velocity signal revealed that the radial-velocity variability remains coherent only for durations of about 30 days. Analysis of the time variation of the spectroscopic line profiles using line bisectors revealed a correlation between radial velocity and line-bisector orientation. All of these observations, along with a one-quarter cycle phase shift between the photometric and the radial-velocity variations, are well explained by the presence of dark photospheric spots on HD 166435. We conclude that the radial-velocity variations are not due to gravitational interaction with an orbiting planet but, instead, originate from line-profile changes stemming from star spots on the surface of the star. The quasi-coherence of the radial-velocity signal over more than two years, which allowed a fair fit with a binary model, makes the stability of this star unusual among other active stars. It suggests a stable magnetic field orientation where spots are always generated at about the same location on the surface of the star.

To understand the formation and evolution of solar-type stars in the solar neighborhood, we need to measure their stellar parameters to high accuracy. We present a catalogue of accurate stellar parameters for 451 stars that represent the HARPS Guaranteed Time Observations (GTO) "high precision" sample. Spectroscopic stellar parameters were measured using high signal-to-noise (S /N) spectra acquired with the HARPS spectrograph. The spectroscopic analysis was completed assuming LTE with a grid of Kurucz atmosphere models and the recent ARES code for measuring line equivalent widths. We show that our results agree well with those ones presented in the literature (for stars in common). We present a useful calibration for the effective temperature as a function of the index color B − V and [Fe/H]. We use our results to study the metallicity-planet correlation, namely for very low mass planets. The results presented here suggest that in contrast to their jovian couterparts, neptune-like planets do not form preferentially around metal-rich stars. The ratio of jupiter-to-neptunes is also an increasing function of stellar metallicity. These results are discussed in the context of the core-accretion model for planet formation.

times Earth's radius (R ⊕ ), indicating that it is intermediate in stature betweenEarth and the ice giants of the Solar System. We find that the planetary mass and radius are consistent with a composition of primarily water enshrouded by a hydrogen-helium envelope that is only 0.05% of the mass of the planet. The atmosphere is probably escaping hydrodynamically, indicating that it has undergone significant evolution during its history.As the star is small and only 13 parsecs away, the planetary atmosphere is amenable to study with current observatories.The recently commissioned MEarth Project 10,11 uses an array of eight identical 40-cm automated telescopes to photometrically monitor 2,000 nearby M dwarfs with masses between

Context. Searching for planets around stars with different masses probes the outcome of planetary formation for different initial conditions. The low-mass M dwarfs are also the most frequent stars in our Galaxy and potentially therefore, the most frequent planet hosts. Aims. This drives observations of a sample of 102 southern nearby M dwarfs, using a fraction of our guaranteed time on the ESO/HARPS spectrograph. We observed 460 hours and gathered 1965 precise (∼ 1 − 3 m/s) radial velocities, spanning the period from Feb. 11th, 2003 to Apr. 1st 2009. Methods. This paper makes available the sample's time series, presents their precision and variability. We apply systematic searches for long-term trends, periodic signals and Keplerian orbits (from 1 to 4 planets). We analyze the subset of stars with detected signals and apply several diagnostics to discriminate whether the observed Doppler shifts are caused by stellar surface inhomogeneities or by the radial pull of orbiting planets. To prepare for the statistical view of our survey we also compute the limits on possible unseen signals, and derive a first estimate of the frequency of planets orbiting M dwarfs. Results. We recover the planetary signals corresponding to 9 planets already announced by our group (Gl 176 b, Gl 581 b, c, d & e, Gl 674 b, Gl 433 b, Gl 667C b and Gl 667C c). We present radial velocities that confirm GJ 849 hosts a Jupiter-mass planet, plus a long-term radial-velocity variation. We also present RVs that precise the planetary mass and period of Gl 832b. We detect longterm RV changes for Gl 367, Gl 680 and Gl 880 betraying yet unknown long-period companions. We identify candidate signals in the radial-velocity time series of 11 other M dwarfs. Spectral diagnostics and/or photometric observations demonstrate however that they are most probably caused by stellar surface inhomogeneities. Finally, we find our survey sensitive to few Earth-mass planets for periods up to several hundred days. We derive a first estimate of the occurrence of M-dwarf planets as a function of their minimum mass and orbital period. In particular, we find that giant planets (m sin i = 100 − 1, 000 M ⊕ ) have a low frequency (e.g. f 1% for P = 1 − 10 d and f = 0.02 +0.03 −0.01 for P = 10 − 100 d), whereas super-Earths (m sin i = 1 − 10 M ⊕ ) are likely very abundant ( f = 0.36 +0.25 −0.10 for P = 1 − 10 d and f = 0.35 +0.45 −0.11 for P = 10 − 100 d). We also obtained η ⊕ = 0.41 +0.54 −0.13 , the frequency of habitable planets orbiting M dwarfs (1 ≤ m sin i ≤ 10 M ⊕ ). For the first time, η ⊕ is a direct measure and not a number extrapolated from the statistic of more massive and/or shorter-period planets.

Since the discovery of short-period exoplanets a decade ago, photometric surveys have been recognized as a feasible method to detect transiting hot Jupiters. Many transit surveys are now under way, with instruments ranging from 10-cm cameras to the Hubble Space Telescope. However, the results of these surveys have been much below the expected capacity, estimated in the dozens of detections per year. One of the reasons is the presence of systematics (``red noise'') in photometric time series. In general, yield predictions assume uncorrelated noise (``white noise''). In this paper, we show that the effect of red noise on the detection threshold and the expected yields cannot be neglected in typical ground-based surveys. We develop a simple method to determine the effect of red noise on photometric planetary transit detections. This method can be applied to determine detection thresholds for transit surveys. We show that the detection threshold in the presence of systematics can be much higher than with the assumption of white noise, and obeys a different dependence on magnitude, orbital period and the parameters of the survey. Our method can also be used to estimate the significance level of a planetary transit candidate (to select promising candidates for spectroscopic follow-up). We apply our method to the OGLE planetary transit search, and show that it provides a reliable description of the actual detectionthreshold with real correlated noise. We point out in what way the presence of red noise could be at least partly responsible for the dearth of transiting planet detections from existing surveys, and examine some possible adaptations in survey planning and strategy. Finally, we estimate the photometric stability necessary to the detection of transiting ``hot Neptunes''.Comment: 14 pages, 15 figures, to appear in MNRA