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The emerging statistical properties from the first 50 extrasolar planets are startlingly different from the picture that was imagined prior to 1995. About 0.75% of nearby solar type stars harbor jovian planets in 3 to 5 day circular orbits. Another ∽7% of stars have jupiter–mass companions orbiting in eccentric orbits within 3.5 AU. The mass distribution of substellar companions rises abruptly near 5 MJup and continues increasing down to the detection limit near 1 MJup-Orbital eccentricities correlate positively with semimajor axes, even for planets beyond the tidal circularization zone within 0.1 AU, distinguishing planets from binary stars. The planet bearing stars are metal–rich relative to both nearby stars and to the Sun. Analogs of Solar System planets have not been detected to date as they require precision of 3 m s−1 maintained for more than a decade.
6 new extra-solar planet candidates (HD 6434 b, HD 19994 b, HD 83443c, HD 92788b, HD 121504b, HD 190228b) are announced as part of our planet-search programmes in the northern and southern hemispheres. HD 83443 c is member of a 2-planet system with Saturnian and sub-Saturnian masses. Another system including a planet + a very low-mass brown dwarf orbiting HD 168443 is also presented. These 2 new systems and the new planetary detections rise to 25 the number of ELODIE and CORALIE candidates with minimum masses ≤20MJup. The orbital element distributions of giant-planet candidates, like the secondary mass function, the eccentricity and period distributions, compared to the equivalent distributions for spectroscopic binaries, strongly suggest different formation mechanisms for the two populations.
The Doppler residuals to the Keplerian fits for extrasolar planets reveal important properties of the planets and host stars. Stellar magnetic fields modify the photospheric velocity fields, causing Doppler fluctuations with unknown time scales. This Doppler “jitter”, seen prominently in the magnetic stars Epsilon Eridani and ξ Boo A, compromises the detectability of planets. The Doppler residuals during the transit of HD209458 reveal that the planet orbits in the same direction as the star spins. Moreover, the transit path across the star is nearly parallel to the stellar equator. Most interestingly, the Doppler residuals of known planets often reveal additional coherent variations, probably caused by additional companions. Both 55 Cancri and HD168443 reveal such coherent Doppler residuals. Another five planet–bearing stars observed at Lick show trends in the Doppler residuals indicating the presence of additional companions. Remarkably, about half of the known extrasolar planets reveal such coherent variations. This suggests that stars with planets have a high occurrence rate of harboring more distant companions, planetary or otherwise.
We present a summary of the McDonald Observatory Planetary Search program. We first summarize results on the star ∊ Eridani, in which we combine McDonald Observatory data with data from CFHT, Lick, and ESO, to detect a planet in orbit around this very nearby star. We then concentrate on results from the first 4 years of the Texas Hyades survey using the HIRES spectrograph on Keck 1. The Hyades constitute a very homogeneous sample of stars, in which the major independent variable is the stellar mass. In this survey, we have achieved 3 m s−1 internal error on a sample of about 100 Hyades dwarfs. We discuss the rms radial velocity jitter of the sample stars, and its relationship to spectral type, stellar rotation, and chromospheric activity.
We present results from our precision radial velocity (RV) program at ESO La Silla. The achievable RV precision after the upgrade of the CES spectrograph is demonstrated. We apply the method of pooled variance diagrams to compare our short-term with our long-term precision. For the active planet-hosting star ι Hor we determine the influence of stellar activity and the rotation period, and address the question of a second long-period planet. For the RV signal in ∊ Eri we demonstrate the distinctness of the time scales present in the RV and Call data, providing further support for the planetary interpretation in this active star.
Specially-designed microlensing searches, some of which have been underway for several years, are sensitive to extrasolar planets orbiting the most common stars in our Galaxy. Microlensing is particularly well-suited to the detection of Jupiter-mass planets orbiting their parent stars at several AU. Since Jovian analogs are thought to influence the subsequent evolution of most planetary systems, they are particularly important to study. The orbital radii and distances to the planetary systems probed by microlensing are larger than those currently studied by radial velocity techniques; the two methods are thus complementary. Recent results from microlensing searches are discussed, including constraints on Jovian analogs orbiting typical Galactic stars. Benefits and drawbacks of the technique for the characterization of planetary systems, and future prospects are briefly reviewed.
We now know of one extrasolar planet, HD 209458 b, that is seen to transit the disk of its parent star, and we may expect many others to be discovered in due course. These transiting planets will be important to our understanding of planets in general because they allow many kinds of measurements of the physical properties of the planet – measurements that are not possible for less fortuitous orbital alignments. These include, among others, estimates of the density, temperature, and composition of the planetary atmosphere. Moreover, transits provide a means of detecting planets that cannot yet be seen by other methods. In this paper I describe the progress that has been made so far in making some of these measurements, and the prospects for the future
Using Hipparcos and Tycho-2 data, together with the radial velocity information, a statistical analysis is applied to all the orbital solutions of planetary candidates, in order to avoid a bias towards small inclinations. There are hints of additional, longer period companions.
The method of stellar velocity variations measurement has recently shown its capability by discovering tens of extra-solar planets. Accuracies achieved today are in the range of 3 to 10 m/s. The spectrograph EMILIE coupled to the Absolute Astronomical Accelerometer (AAA) system and established at the 1.52 m telescope of the Observatoire de Haute Provence is an instrument which aims at reaching an accuracy better than 1 m/s, long term. Results on some typical stars are presented.
Gilliland et al. (2000) have reported HST photometric observations of 34000 stars in the globular cluster 47 Tuc, showing an absence of close-in giant planets in that cluster relative to their frequency in the solar neighborhood. Here we describe the methods of time-series analysis that were used to search the 47 Tuc data for transits by giant extrasolar planets, and the means by which these methods were validated.
The NASA Ames Research Center's Vulcan photometer is being used in a search for close–in giant extrasolar planets. With our current data reduction system we achieve 0.2–0.8% hour–to–hour relative photometric precision on ∽ 6000 stars brighter than 13th magnitude. Three Galactic-plane fields have so far yielded hundreds of variable stars, including ∽ 50 eclipsing or interacting binaries per field. Several candidate detections have been followed up with radial velocity observations. High-resolution spectroscopy revealed many of the strongest candidates to be grazing eclipsing binaries.
We observed 4 planetary transits of HD 209458 with the STIS spectrograph on HST, and generated a photometric time series with extremely rapid cadence and high precision. We use these data to better constrain the orbital, stellar, and planetary parameters, and to search for circumplanetary rings and planetary satellites.
We present new results derived from high-resolution optical spectra of the τ Boo system, secured in March-May 2000. The results do not show the same feature reported by Cameron et al (1999) as a candidate reflected-light signature from the planet. Together with earlier results from the 1998 and 1999 seasons, the new data yield a 99.9% upper limit on the opposition planet/star flux ratio ∊ < 3.5 × 10−5 between 387.4 and 586.3 nm, a factor 3 deeper than the upper limit of Charbonneau et al (1999). For an assumed planet radius Rp = 1.2RJ, the upper limit on the mean geometric albedo is p < 0.22, 40% that of Jupiter. We find new evidence that the star's rotation is synchronised with the planet's orbital motion. Using a Monte Carlo analysis we infer that the planet's mass must lie in the range 5.5 to 10 times the mass of Jupiter.
We present the results of five years of high precision radial velocity (RV) monitoring of the α Centauri system. Observations were performed with the ESO 1.4m CAT telescope and the Coudé Echelle Spectrometer (CES) on La Silla. From the achieved RV precision we establish the detection threshold for Jovian planets in orbit around α Centauri A & B. Together with the known dynamical limits for stable planetary orbits we can set strong constraints on the presence of giant planets in our neighbouring binary system.
We describe a method by which hot extrasolar planets close to their parent star may be directly detected through the signature of water vapour or methane in their infrared spectra, lying on top of the spectrum of the parent star. Upper limits derived from low resolution K band spectra of several ‘hot Jupiter’ systems are presented. We find no water vapour to 3-σ limits of between 1 part in 200 and 1 part in 600 for each star. Comparison with an initial model indicates that constraints can be set on the size, albedo, temperature and dust content of the planets.
We report the discovery of an extrasolar planetary system with two Saturnian planets around the star HD 83443. The new planetary system is unusual by more than one aspect, as it contains two very low–mass gaseous giant planets, both on very tight orbits. Among the planets detected so far, the inner planet has the smallest semi–major axis (0.038 AU) and period (2.985 days) whereas the outer planet is the lightest one with m2 sin i = 0.53 MSat. A preliminary dynamical study confirms the stability of the system.
In this paper we present the results of the spectral classification of stars included in the EXPORT (EXoPlanetary Observational Research Team) sample and observed during the 1998–1999 International Time campaigns in the Canary Island observatories. Intermediate resolution spectra obtained with the Isaac Newton Telescope (INT) were used in this work. In addition to the confirmation of some spectral types and changes to previous classifications, we report new results for stars whose spectral type had not been accurately assigned before.
Light curve analysis by MDW of the photometry and RV data accumulated to date on HD 209458 has made use of a simulations database created for an 8-day HST observing project led by RLG to look for transits in 47 Tuc. We report progress in developing a consistent set of parameters obtained with our versions of the Wilson-Devinney program, WD98 and wd98k93, specially modified to treat large grid sizes, corresponding to objects with radii exceeding 0.7RJ and masses greater than 0.1 MJ.
This work is supported in part by grants to EFM by Canadian NSERC and by the Univ. of Calgary Research Grants Committee.
The transit of the planet orbiting HD209458 has been observed using VLT/UVES, in search for faint signatures of an extended envelope of gas possibly surrounding the planet, called exosphere. Preliminary results are shown and described. They show no evidence so far of exospheric signatures.