Search

Of the approximately 25 directly imaged planets to date, all are younger than 500 Myr, and all but six are younger than 100 Myr (ref. 1). Eps Ind A (HD209100, HIP108870) is a K5V star of roughly solar age (recently derived as 3.7–5.7 Gyr (ref. 2) and 3.5−1.3+0.8Gyr (ref. 3)). A long-term radial-velocity trend4,5and an astrometric acceleration6,7led to claims of a giant planet2,8,9orbiting the nearby star (3.6384 ± 0.0013 pc; ref. 10). Here we report JWST coronagraphic images which reveal a giant exoplanet that is consistent with these radial and astrometric measurements but inconsistent with the previously claimed planet properties. The new planet has a temperature of approximately 275 K and is remarkably bright at 10.65 and 15.50 µm. Non-detections between 3.5 and 5.0 µm indicate an unknown opacity source in the atmosphere, possibly suggesting a high-metallicity, high carbon-to-oxygen ratio planet. The best-fitting temperature of the planet is consistent with theoretical thermal evolution models, which were previously untested at this temperature range. The data indicate that this is probably the only giant planet in the system, and therefore we refer to it as b, despite it having significantly different orbital properties than the previously claimed planet b.

Context. We recently reported on the detection of a possible planetary mass companion to βPictorisat a projected separation of 8 AU from the star, using data taken in November 2003 with NaCo, the adaptive-optics system installed on the Very Large Telescope UT4. Even though no second epoch detection was available, there are strong arguments to favor a gravitationally bound companion rather than a background object. If confirmed and located at a physical separation of 8 AU, this companion would be the closest planet ever imaged, and above all, could have formed via core-accretion. Its apparent magnitude would indicate a typical temperature of ~1500 K and a mass of ~8 $M_{\mathrm{Jup}}$. Interestingly, a planet with such characteristics would explain the main morphological and dynamical peculiarities of the βPic system.

Context. Tight binaries discovered in young, nearby associations are ideal targets for providing dynamical mass measurements to test the physics of evolutionary models at young ages and very low masses.

Aims. In the framework of the search for extrasolar planets and brown dwarfs around early-type main-sequence stars, we present the results obtained on the early F-type star θCygni.

We report on the discovery of a substellar companion or a massive Jupiter orbiting the G5V star HD 16760 using the spectrograph SOPHIEinstalled on the OHP 1.93-m telescope. Characteristics and performances of the spectrograph are presented, as well as the SOPHIEexoplanet consortium program. With a minimum mass of 14.3 ${M}_{\rm Jup}$, an orbital period of 465 days and an eccentricity of 0.067, HD 16760b seems to be located just at the end of the mass distribution of giant planets, close to the planet/brown-dwarf transition. Its quite circular orbit supports a formation in a gaseous protoplanetary disk.

We recently reported the photometric and spectroscopic detection of the primary transit of the 111-day-period, eccentric extra-solar planet HD 80606b, at Observatoire de Haute-Provence, France. The whole egress of the primary transit and a section of its central part were observed, allowing the measurement of the planetary radius, and evidence for a spin-orbit misalignment through the observation of the Rossiter-McLaughlin anomaly. The ingress not having been observed for this long-duration transit, uncertainties remained in the parameters of the system. We present here a refined, combined analysis of our photometric and spectroscopic data, together with further published radial velocities, ground-based photometry, and Spitzerphotometry around the secondary eclipse, as well as new photometric measurements of HD 80606 acquired at Mount Hopkins, Arizona, just before the beginning of the primary transit. Although the transit is not detected in those new data, they provide an upper limit for the transit duration, which narrows down the possible behaviour of the Rossiter-McLaughlin anomaly in the unobserved part of the transit. We analyse the whole data with a Bayesian approach using a Markov-chain Monte Carlo integration on all available information. We find $R_{\rm p} = 0.98 \pm 0.03 \,{R}_{\rm Jup}$for the planetary radius, and a total primary transit duration of $11.9 \pm 1.3$h from first to fourth contact. Our analysis reinforces the hypothesis of spin-orbit misalignment in this system (alignment excluded at >95% level), with a positive projected angle between the planetary orbital axis and the stellar rotation (median solution $\lambda \sim 50^\circ$). As HD 80606 is a component of a binary system, the peculiar orbit of its planet could result from a Kozai mechanism.

We report the detection of the primary transit of the extra-solar planet HD 80 606 b, thanks to photometric and spectroscopic observations performed at the Observatoire de Haute-Provence, simultaneously with the CCD camera at the 120-cm telescope and the SOPHIEspectrograph on the 193-cm telescope. We observed the whole egress of the transit and partially its central part, in both datasets with the same timings. The ingress occurred before sunset so was not observed. The full duration of the transit was between 9.5 and 17.2 h. The data allows the planetary radius to be measured ($R_{\mathrm{p}} = 0.9 \pm 0.10\,{R}_{\rm Jup}$) and other parameters of the system to be refined. Radial velocity measurements show the detection of a prograde Rossiter-McLaughlin effect, and provide a hint of a spin-orbit misalignment. If confirmed, this misalignment would corroborate the hypothesis that HD 80 606 b owes its unusual orbital configuration to Kozai migration. HD 80 606 b is by far the transiting planet on the longest period detected today. Its unusually small radius reinforces the observed relationship between the planet radius and the incident flux received from the star and opens new questions for theory. Orbiting a bright star ($V=9$), it opens opportunities for numerous follow-up studies.

Aims. Extra-solar planet search programs require high-precision velocity measurements. They need to determine how to differentiate between radial-velocity variations due to Doppler motion and the noise induced by stellar activity.

Aims. Systematic surveys to search for exoplanets have been mostly dedicated to solar-type stars sofar. We developed in 2004 a method to extend such searches to earlier A-F type dwarfs and started spectroscopic surveys to search for planets and quantify the detection limit achievable when taking the stars properties (Spectral Type, vsin i) and their actual levels of intrinsic variations into account. We give here the first results of our southern survey with HARPS.

Aims. We present ground-based observations of the disk around the A-type star βPictoris to obtain scattered light images at the highest angular resolution (60 mas, equivalent to about 1 AU at the distance of the star) and the highest contrast in the very close environment of the star. The purpose of this program is to perform a close inspection of the inner disk morphology.

Aims. In the framework of the search for extrasolar planets and brown dwarfs around early-type stars, we present the results obtained for the F-type main-sequence star HD 60532 (F6V) with HARPS.

The transiting extrasolar planet XO-3b is remarkable, with a high mass and eccentric orbit. These unusual characteristics make it interesting to test whether its orbital plane is parallel to the equator of its host star, as it is observed for other transiting planets. We performed radial velocity measurements of XO-3 with the SOPHIEspectrograph at the 1.93 m telescope of Haute-Provence Observatory during a planetary transit and at other orbital phases. This allowed us to observe the Rossiter-McLaughlin effect and, together with a new analysis of the transit light curve, to refine the parameters of the planet. The unusual shape of the radial velocity anomaly during the transit provides a hint of a nearly transverse Rossiter-McLaughlin effect. The sky-projected angle between the planetary orbital axis and the stellar rotation axis should be λ= 70° ±15° to be compatible with our observations. This suggests that some close-in planets might result from gravitational interaction between planets and/or stars rather than migration due to interaction with the accretion disk. This surprising result requires confirmation by additional observations, especially at lower airmass, to fully exclude the possibility that the signal is due to systematic effects.

We present the detection of a 0.47 $M_{{\rm Jup}}$planet in a 44-day period eccentric trajectory (e= 0.39) orbiting the metal-rich star HD 45652. This planet, the seventh giant planet discovered in the context of the ELODIE metallicity-biased planet search program, is also confirmed using higher precision radial-velocities obtained with the CORALIE and SOPHIE spectrographs. The orbital period of HD 45652b places it in the middle of the “gap” in the period distribution of extra-solar planets.

Aims.Our aim is to determine the presence and location of the emission from polycyclic aromatic hydrocarbons (PAHs) towards low and intermediate mass young stars with disks using large aperture telescopes.

Aims.We present the results of near-infrared, follow-up imaging and spectroscopic observations at VLT, aimed at characterizing the long-period companions of the exoplanet host stars HD 196885, HD 1237 and HD 27442. The three companions were previously discovered in the course of our CFHT and VLT coronographic imaging survey dedicated to the search for faint companions of exoplanet host stars.

Context.Although it is commonly agreed that the presence of a close stellar companion is likely to affect planet formation and evolution, the precise effects and their actual impact on planet occurrence are still debated. Different conclusions have been reached on the theoretical side, while observational constraints are sparse, a consequence of the discrimination against close binaries in Doppler planet searches. Accordingly, basic questions such as how hospitable binaries are to planets and how binary separation and mass ratio impact on planet formation, remain poorly known.

Aims.It is known that stellar activity may complicate the analysis of high-precision radial-velocity spectroscopic data when looking for exoplanets signatures. We aim at quantifying the impact of stellar spots on stars with various spectral types and rotational velocities and comparing the simulations with data obtained with the HARPS spectrograph.

We report here the discovery of two planet candidates as a result of our planet-search programme biased in favour of high-metallicity stars, using the ELODIE spectrograph at the Observatoire de Haute Provence. One candidate has a minimum mass $m_2\sin{i} = 2.5$MJupand is orbiting the metal-rich star HD 43691with period $P = 40$days and eccentricity $e=0.14$. The other planet has a minimum mass $m_2\sin{i} = 5.6$MJupand orbits the slightly metal-rich star HD 132406with period $P=974$days and eccentricity e= 0.34. Additional observations for both stars were performed using the new SOPHIE spectrograph that replaces the ELODIE instrument, allowing an improved orbital solution for the systems.

We report the discovery of companions to 5 nearby late M dwarfs (>M5), LHS1901, LHS4009, LHS6167, LP869-26 and WT460, and we confirm that the recently discovered mid-T brown dwarf companion to SCR1845-6357 is physically bound to that star. These discoveries result from our adaptive optics survey of all M dwarfs within 12 pc. The new companions have spectral types M5 to L1, and orbital separations between 1 and 10 AU. They add significantly to the number of late M dwarfs binaries in the immediate solar neighbourhood, and will improve the multiplicity statistics of late M dwarfs. The expected periods range from 3 to 130 years. Several pairs thus have good potential for accurate mass determination in this poorly sampled mass range.

Aims.We present the results of multi epoch imaging observations of the companion to the planetary host Gliese 86. Associated with radial velocity measurements, this study aimed at dynamically characterizing with the orbital properties and the mass of this companion (hereafter Gliese 86 B), but also at investigating the possible history of this particular system.

Aims.We present the results of a deep imaging survey of stars surrounded by planets detected with the radial velocity technique. The purpose is to search for and to characterize long-period stellar and substellar companions. The sample contains a total of 26 stars, among which 6 exhibit additional radial velocity drifts.

Doppler velocimetry techniques are frequently used in Shock-Physics experiments to measure material velocities (as a function of time). With such diagnostics, there is no physical contact between the probe and the target, which presents the advantage of not intruding the observed phenomenon. They also provide very good precision on the velocities. Those techniques are either based on homodyne methods (such as Fabry-Pérot and Visar) or on heterodyne methods (such as PDV-Photon Doppler Velocimetry). In particular, PDV technique has recently been developed at LLNL. We present in this paper a PDV system built at CEA DIF, along with our first experimental results which we obtained on a shock tube.

We present here the detection of a brown dwarf orbiting the A9V star HD 180777. The radial velocity measurements, obtained with the ELODIE echelle spectrograph at the Haute-Provence Observatory, show a main variation with a period of 28.4 days. Assuming a primary mass of 1.7 $M_{\odot}$, the best Keplerian fit to the data leads to a minimum mass of 25 $M_{\rm{Jup}}$for the companion (the true mass could be significantly higher). We also show that, after subtraction of the Keplerian solution from the radial velocity measurements, the residual radial velocities are related to phenomena intrinsic to the star, namely pulsations with typical periods of γDor stars. These results show that in some cases, it is possible to disentangle radial velocity variations due to a low mass companion from variations intrinsic to the observed star.

In the frame of the search for extrasolar planets and brown dwarfs around early-type stars, we present the results obtained on βPictoris, which is surrounded by a circumstellar disk that is warped by the presence of a planet. We used 97 spectra acquired with CORALIE and 230 spectra acquired with HARPS to characterize the radial velocity behavior of βPictoris and to infer constraints on the presence of a planet close to this star. With these data, we were able to exclude the presence of an inner giant planet (2 MJupat a distance to the star of 0.05 AU, 9 MJupat 1 AU). We also discuss the origin of the observed radial velocity variations in terms of δScuti type pulsations.

We present here the detection of a planet orbiting around the F6V star HD 33564. The radial velocity measurements, obtained with the ELODIE echelle spectrograph at the Haute-Provence Observatory, show a variation with a period of 388 days. Assuming a primary mass of 1.25 $M_{\odot}$, the best Keplerian fit to the data leads to a minimum mass of 9.1 MJupfor the companion.

We present the performances of a radial velocity measurement method that we developed for A-F type stars. These perfomances are evaluated through an extensive set of simulations, together with actual radial velocity observations of such stars using the ELODIE and HARPS spectrographs. We report the case of stars constant in radial velocity, the example of a binary detection on HD 48097 (an A2V star, with $v\sin{i}$equal to 90 km s$^{\rm -1}$) and a confirmation of the existence of a 3.9 MJupplanet orbiting around HD 120136 (Tau Boo). The instability strip problem is also discussed. We show that with this method, it is in principle possible to detect planets and brown dwarfs around A-F type stars, thus allowing further study of the impact of stellar masses on planetary system formation over a wider range of stellar masses than is currently done.

We report deep imaging observations of the young, nearby star AB Pic, a member of the large Tucana-Horologium association. We have detected a faint, red source $5.5''$South of the star with JHKcolors compatible with that of a young substellar L dwarf. Follow-up observations at two additional epochs confirm, with a confidence level of 4.7σ, that the faint red object is a companion to AB Pic rather than it being a stationary background object. A low resolution K-band spectrum indicates an early-L spectral type for the companion. Finally, evolutionary model predictions based on the JHKphotometry of AB Pic b indicate a mass of 13 to 14 $M_{{\rm Jup}}$if its age is ~30 Myr. Is AB Pic b a massive planet or a minimum mass brown dwarf?

We report new VLT/NACO imaging observations of the young, nearby brown dwarf 2MASSW J1207334-393254 and its suggested planetary mass companion (2M1207 b). Three epochs of VLT/NACO measurements obtained over nearly one year show that the planetary mass companion candidate shares the same proper motion and, with a high confidence level, is not a stationary background object. This result confirms the status of 2M1207 b as of planetary mass (5 times the mass of Jupiter) and the first image of a planetary mass companion in a different system than our own. This discovery offers new perspectives for our understanding of chemical and physical properties of planetary mass objects as well as their mechanisms of formation.

The core of the nebula surrounding Eta Carinae has been observed with the VLT Adaptive Optics system NACO and with the interferometer VLTI/MIDI to constrain spatially andspectrally the warm dusty environment and the central object. In particular, narrow-band images at 3.74 μm and 4.05 μm reveal the butterfly shaped dusty environment close to the central star with unprecedented spatial resolution. A void whose radius corresponds to the expected sublimation radius has been discovered around the central source. Fringes have been obtained in the Mid-IR which reveal a correlated flux of about 100 Jy situated 0$\farcs$3 south-east of the photocenter of the nebula at 8.7 μm, which corresponds with the location of the star as seen in other wavelengths. This correlated flux is partly attributed to the central object, and these observations provide an upper limit for the SED of the central source from 2.2 μm to 13.5 μm. Moreover, we have been able to spectrally disperse the signal from the nebula itself at PA = 318 degree, i.e. in the direction of the bipolar nebula (~310°) within the MIDI field of view of 3″. A large amount of corundum (Al2O3) is discovered, peaking at 0$\farcs$6–1$\farcs$2 south-east from the star, whereas the dust content of the Weigelt blobs is dominated by silicates. We discuss the mechanisms of dust formation which are closely related to the geometry of this Butterfly nebulae.

We present the discovery of a tight M8V binary, with a separation of only 1.2 astronomical units, obtained with the PUEO and NACO adaptive optics systems, respectively at the CFHT and VLT telescopes. The estimated period of LP 349-25 is approximately 5 years, and this makes it an excellent candidate for a precise mass measurement.

We report VLT/NACO imaging observations of the stars GSC 08047-00232 and HIP 6856, probable members of the large Tucana-Horologium association. During our previous ADONIS/SHARPII deep imaging survey, a substellar candidate companion was discovered around each star. Based on VLT/NACO astrometric measurements, we find that GSC 08047-00232 and the faint candidate companion near to it share the same proper motion with a significance of 3.1 σ. On the contrary, the candidate companion to HIP 6856 is probably a background object with a significance of 4.3 σ. We also detect a new fainter and closer candidate companion to HIP 6856, but which is likely a background object too with a significance of 4 σ. Recent VLT/NACO spectroscopic measurements of GSC 08047-00232 finally confirm the substellar nature of this young brown dwarf with a derived spectral type M $9.5\pm1$. GSC 08047-00232 B, with an estimated mass of $25\pm10~M_{\rm{Jup}}$and an effective temperature of $2100\pm200$K, is presently the third substellar companion identified among young, nearby associations.

We present deep VLT/NACO infrared imaging and spectroscopic observations of the brown dwarf 2MASSWJ 1207334-393254, obtained during our on-going adaptive optics survey of southern young, nearby associations. This ~25 $M_{\rm{Jup}}$brown dwarf, located ~70 pc from Earth, has been recently identified as a member of the TW Hydrae Association (age ~ 8 Myr). Using adaptive optics infrared wavefront sensing to acquire sharp images of its circumstellar environment, we discovered a very faint and very red object at a close separation of ~780 mas (~55 AU). Photometry in the H, ${K}_{\rm s}$and ${L}'$bands and upper limit in J-band are compatible with a spectral type L5-L9.5. Near-infrared spectroscopy is consistent with this spectral type estimate. Different evolutionary models predict an object within the planetary regime with a mass of ${M}=5\pm2~M_{\rm{Jup}}$and an effective temperature of ${T}_{\rm{eff}}=1250\pm200$K.

We present K, Land Mdiffraction-limited images of NGC 1068, obtained with NAOS+CONICA at VLT/YEPUN over a $3.5\arcsec \times 3.5\arcsec$region around the central engine. Hot dust ($T_{\rm col} = 550{-}650$K) is found to be distributed in three main structurally different regions: (a) in the true nucleus, seen as a quasi-spherical, however slightly NS elongated, core of extremely hot dust, resolvedin Kand Lwith respective diameters of ≈5 pc and 8.5 pc; (b) along the North–South direction, according to a spiral arm like structure and a southern tongue; (c) as a set of parallel elongated nodules (wave-like) on each side, albeit mainly at north, of the jet, at a distance of 50 to 70 pc from the central engine. The IR images reveal several structures also clearly observed on either radio maps, mid-IR or HST UV-visible maps, so that a very precise registration of the respective emissions can be done for the first time from UV to 6 cm. These results do support the current interpretion that source (a) corresponds to emission from dust near sublimation temperature delimiting the walls of the cavity in the central obscuring torus. Structure (b) is thought to be a mixture of hot dust and active star forming regions along a micro spiral structure that could trace the tidal mechanism bringing matter to the central engine. Structure c) which was not known, exhibits too high a temperature for “classical” grains; it is most probably the signature of transiently heated very small dust grains (VSG): nano-diamonds, which are resistant and can form in strong UV field or in shocks, are very attractive candidates. The “waves” can be condensations triggered by jet induced shocks, as predicted by recent models. First estimates, based on a simple VSG model and on a detailed radiative transfer model, do agree with those interpretations, both qualitatively and quantitatively.

We report on Galactic Center L'-band observations made during NAOS/CONICA Science Verification. Colors of the inner 2´´ stars reveal an infrared excess of S2, the closest star to the black hole, that could sign the first thermal infrared detection of Sgr A*. A multi-wavelength maximum likelihood analysis has allowed us to eliminate all but two of the candidates for gravitational lensing proposed by [CITE]. Our observations of the thin and intersecting structures of the Northern Arm could trace several shocks heating the neighbooring dust rather than a stream of matter in orbit around the central mass as previously thought.

Near-infrared observations of line emission from excited H2and in the continuum are reported in the direction of the Orion molecular cloud OMC1, using the European Southern Observatory Very Large Telescope UT4, equipped with the NAOS adaptive optics system on the CONICA infrared array camera. Spatial resolution has been achieved at close to the diffraction limit of the telescope ($0.08''\!{-}0.12''$) and images show a wealth of morphological detail. Structure is not fractal but shows two preferred scale sizes of $2.''$(1100 AU) and $1.2''$(540 AU), where the larger scale may be associated with star formation.

We have imaged at high angular resolution the close environement of the very red source Orion n with NACO at the VLT UT4. We report the detection of a faint point like object $0.6''$away from this source. Assuming a distance of $450_{-50}^{+50}$pc and an age of 1 Myr, the photometry of this candidate companion is consistent with an object of mass 70-150 $M_{\rm{J}}$assuming a visible extinction of $A_{\rm{V}} = 3{-}17$. The relationship between this object and Orion n is discussed hereafter.

The advent of the NAOS/CONICA adaptive optics system at the ESO Very Large Telescope recently gave us the opportunity to map the surface of Titan and to search for atmospheric variations at high spatial resolution and contrast. We report here the first results from a series of observations of Titan performed with this instrument in a number of near-infrared narrow-band filters, covering various altitude regions and three different longitudes (out of the 16 days of Titan's orbit). We have achieved unequaled contrast on images showing complex topography on Titan's trailing hemisphere and have found robust evidence for the north-south asymmetry inversion. The presence of other interesting atmospheric features at Titan's South Pole is described.

We present high-contrast imaging data on the disk of the classical T Tauri star TW Hya. The images were obtained through the polarimetric differential imaging technique with the adaptive optics system NACO. Our commissioning data show the presence of polarized disk emission between 0.1´´ and 1.4´´ from the star. We derive the first Ks-band radial polarized intensity distribution. We show that the polarized intensity compares well to shorter wavelengths surface brightness observations and confirm the previously reported gradual slope change around 0.8´´. These results show the potential of the new polarimetric differential imaging technique at 8 m-class telescopes to map the inner regions of protoplanetary disks.

Observations of the standard late type M8 star LHS 2397aA were obtained at the ESO-VLT 8 m telescope “Yepun” using the NAOS/CONICA Adaptive Optics facility. The observations were taken during the NACO commissioning, and the infrared standard star LHS 2397aA was observed in the H, and Ks broad band filters. In both bands the brown dwarf companion LHS 2397aB was detected. Using a program recently developed (Bouy et al. [CITE]) for the detection of stellar binaries we calculated the principal astrometric parameters (angular binary separation and position angle PA) and the photometry of LHS 2397aA and LHS 2397aB. Our study largely confirms previous results obtained with the AO-Hokupa'a facility at Gemini-North (Freed et al. [CITE]); however a few discrepancies are observed.

We present new high angular resolution observations at near-IR wavelengths of the core of the Luminous Blue Variable ηCarinae, using NAOS-CONICA at the VLT and VINCI at the VLT Interferometer (VLTI). The latter observations provide spatial information on a scale of 5 milli-arcsec or ~11 AU at the distance of ηCarinae. The present-day stellar wind of ηCarinae is resolved on a scale of several stellar radii. Assuming spherical symmetry, we find a mass loss rate of $1.6\times10^{-3}~M_{\odot}$/yr and a wind clumping factor of 0.26. The VLTI data taken at a baseline of 24 m show that the object is elongated with a de-projected axis ratio of approximately 1.5; the major axis is aligned with that of the large bi-polar nebula that was ejected in the 19th century. The most likely explanation for this observation is a counter-intuitive model in which stellar rotation near the critical velocity causes enhanced mass loss along the rotation axis. This results from the large temperature difference between pole and equator in rapidly rotating stars. ηCarinae must rotate in excess of 90 percent of its critical velocity to account for the observed shape. The large outburst may have been shaped in a similar way. Our observations provide strong support for the existence of a theoretically predicted rotational instability, known as the Ωlimit.

This article presents coronagraphic images of the low-mass companion to the star HR?7672 observed at the Palomar 200 inch telescope and first detected at Gemini and Keck in the Kband by [CITE]. We obtained additional photometry in J($1.2~\mu$m), H($1.6~\mu$m) and Ks($2.2~\mu$m) bands to cover the full near-IR domain and hence to further constrain the nature of the companion. A mass estimate of 58-71 ${M_J}$is derived from evolutionary models of very low-mass objects.?

We report the detection of a possible subsolar mass companion to the triple young system TY?CrA using the NACO instrument at the VLT UT4 during its commissioning. Assuming for TY?CrA a distance similar to that of the close binary system HD?176386, the photometric spectral type of this fourth stellar component candidate is consistent with an ~M 4 star. We discuss the dynamical stability of this possible quadruple system as well as the possible location of dusty particles inside or outside the system.

We present the results of an adaptive optics (AO) imaging survey of the common associations of Tucana and Horologium, carried out at the ESO 3.6 m telescope with the ADONIS/SHARPII system. Based on our observations of two dozen probable association members, HIP 1910 and HIP 108422 appear to have low-mass stellar companions, while HIP 6856 and GSC 8047-0232 have possible sub-stellar candidate companions. Astrometric measurements, performed in November 2000 and October 2001, indicate that HIP 1910 B likely is bound to its primary, but are inconclusive in the case of the candidate companion to HIP 6856. Additional observations are needed to confirm the HIP 6856 companionship as well as for HIP 108422 and GSC 8047-0232.