arXiv subjects

E. Lagadec

Publications and source records attributed to E. Lagadec.

At least 55 records · Page 3Linked to original sources

arXiv2019

RefPlanets: Search for reflected light from extra-solar planets with SPHERE/ZIMPOL

RefPlanets is a guaranteed time observation (GTO) programme that uses the Zurich IMaging POLarimeter (ZIMPOL) of SPHERE/VLT for a blind search for exoplanets in wavelengths from 600-900 nm. The goals of this study are the characterization of the unprecedented high polarimetic contrast and polarimetric precision capabilities of ZIMPOL for bright targets, the search for polarized reflected light around some of the closest bright stars to the Sun and potentially the direct detection of an evolved cold exoplanet for the first time. For our observations of Alpha Cen A and B, Sirius A, Altair, Eps Eri and Tau Ceti we used the polarimetric differential imaging (PDI) mode of ZIMPOL which removes the speckle noise down to the photon noise limit for angular separations >0.6". We describe some of the instrumental effects that dominate the noise for smaller separations and explain how to remove these additional noise effects in post-processing. We then combine PDI with angular differential imaging (ADI) as a final layer of post-processing to further improve the contrast limits of our data at these separations. For good observing conditions we achieve polarimetric contrast limits of 15.0-16.3 mag at the effective inner working angle of about 0.13", 16.3-18.3 mag at 0.5" and 18.8-20.4 mag at 1.5". The contrast limits closer in (<0.6") depend significantly on the observing conditions, while in the photon noise dominated regime (>0.6"), the limits mainly depend on the brightness of the star and the total integration time. We compare our results with contrast limits from other surveys and review the exoplanet detection limits obtained with different detection methods. For all our targets we achieve unprecedented contrast limits. Despite the high polarimetric contrasts we are not able to find any additional companions or extended polarized light sources in the data that has been taken so far.

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arXiv2019

VLT/SPHERE exploration of the young multiplanetary system PDS70

Context. PDS 70 is a young (5.4 Myr), nearby (~113 pc) star hosting a known transition disk with a large gap. Recent observations with SPHERE and NACO in the near-infrared (NIR) allowed us to detect a planetary mass companion, PDS70b, within the disk cavity. Moreover, observations in H_alpha with MagAO and MUSE revealed emission associated to PDS70b and to another new companion candidate, PDS70c, at a larger separation from the star. Aims. Our aim is to confirm the discovery of the second planet PDS70c using SPHERE at VLT, to further characterize its physical properties, and search for additional point sources in this young planetary system. Methods. We re-analyzed archival SPHERE NIR observations and obtained new data in Y, J, H and K spectral bands for a total of four different epochs. The data were reduced using the data reduction and handling pipeline and the SPHERE data center. We then applied custom routines (e.g. ANDROMEDA and PACO) to subtract the starlight. Results. We re-detect both PDS 70 b and c and confirm that PDS70c is gravitationally bound to the star. We estimate this second planet to be less massive than 5 M Jup and with a T_eff around 900 K. Also, it has a low gravity with log g between 3.0 and 3.5 dex. In addition, a third object has been identified at short separation (~0.12") from the star and gravitationally bound to the star. Its spectrum is however very blue, so that we are probably seeing stellar light reflected by dust and our analysis seems to demonstrate that it is a feature of the inner disk. We, however, cannot completely exclude the possibility that it is a planetary mass object enshrouded by a dust envelope. In this latter case, its mass should be of the order of few tens of M_Earth. Moreover, we propose a possible structure for the planetary system based on our data that, however, cannot be stable on a long timescale.

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arXiv2019

SPHERE: the exoplanet imager for the Very Large Telescope

Observations of circumstellar environments to look for the direct signal of exoplanets and the scattered light from disks has significant instrumental implications. In the past 15 years, major developments in adaptive optics, coronagraphy, optical manufacturing, wavefront sensing and data processing, together with a consistent global system analysis have enabled a new generation of high-contrast imagers and spectrographs on large ground-based telescopes with much better performance. One of the most productive is the Spectro-Polarimetic High contrast imager for Exoplanets REsearch (SPHERE) designed and built for the ESO Very Large Telescope (VLT) in Chile. SPHERE includes an extreme adaptive optics system, a highly stable common path interface, several types of coronagraphs and three science instruments. Two of them, the Integral Field Spectrograph (IFS) and the Infra-Red Dual-band Imager and Spectrograph (IRDIS), are designed to efficiently cover the near-infrared (NIR) range in a single observation for efficient young planet search. The third one, ZIMPOL, is designed for visible (VIR) polarimetric observation to look for the reflected light of exoplanets and the light scattered by debris disks. This suite of three science instruments enables to study circumstellar environments at unprecedented angular resolution both in the visible and the near-infrared. In this work, we present the complete instrument and its on-sky performance after 4 years of operations at the VLT.

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arXiv2019

The polarimetric imaging mode of VLT/SPHERE/IRDIS I: Description, data reduction and observing strategy

Context. Polarimetric imaging is one of the most effective techniques for high-contrast imaging and characterization of protoplanetary disks, and has the potential to be instrumental in characterizing exoplanets. VLT/SPHERE contains the InfraRed Dual-band Imager and Spectrograph (IRDIS) with a dual-beam polarimetric imaging (DPI) mode, which offers the capability to obtain linear polarization images at high contrast and resolution. Aims. We aim to provide an overview of IRDIS/DPI and study its optical design to improve observing strategies and data reduction. Methods. For H-band observations of TW Hya, we compare two data reduction methods that correct for instrumental polarization effects in different ways: a minimization of the noise image, and a polarimetric-model-based correction method that we present in Paper II of this study. Results. We use observations of TW Hya to illustrate the data reduction. In the images of the protoplanetary disk around this star we detect variability in the polarized intensity and angle of linear polarization with pointing-dependent instrument configuration. We explain these variations as instrumental polarization effects and correct for these effects using our model-based correction method. Conclusions. IRDIS/DPI has proven to be a very successful and productive high-contrast polarimetric imaging system. However, the instrument performance depends on the specific instrument configuration. We suggest adjustments to future observing strategies to optimize polarimetric efficiency in field tracking mode by avoiding unfavourable derotator angles. We recommend reducing on-sky data with the pipeline called IRDAP that includes the model-based correction method (described in Paper II) to optimally account for the remaining telescope and instrumental polarization effects and to retrieve the true polarization state of the incident light.

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arXiv2019

The polarimetric imaging mode of VLT/SPHERE/IRDIS II: Characterization and correction of instrumental polarization effects

Context. Circumstellar disks and self-luminous giant exoplanets or companion brown dwarfs can be characterized through direct-imaging polarimetry at near-infrared wavelengths. SPHERE/IRDIS at the Very Large Telescope has the capabilities to perform such measurements, but uncalibrated instrumental polarization effects limit the attainable polarimetric accuracy. Aims. We aim to characterize and correct the instrumental polarization effects of the complete optical system, i.e. the telescope and SPHERE/IRDIS. Methods. We create a detailed Mueller matrix model in the broadband filters Y-, J-, H- and Ks, and calibrate it using measurements with SPHERE's internal light source and observations of two unpolarized stars. We develop a data-reduction method that uses the model to correct for the instrumental polarization effects, and apply it to observations of the circumstellar disk of T Cha. Results. The instrumental polarization is almost exclusively produced by the telescope and SPHERE's first mirror and varies with telescope altitude angle. The crosstalk primarily originates from the image derotator (K-mirror). At some orientations, the derotator causes severe loss of signal (>90% loss in H- and Ks-band) and strongly offsets the angle of linear polarization. With our correction method we reach in all filters a total polarimetric accuracy of <0.1% in the degree of linear polarization and an accuracy of a few degrees in angle of linear polarization. Conclusions. The correction method enables us to accurately measure the polarized intensity and angle of linear polarization of circumstellar disks, and is a vital tool for detecting unresolved (inner) disks and measuring the polarization of substellar companions. We have incorporated the correction method in a highly-automatic end-to-end data-reduction pipeline called IRDAP which is publicly available at https://irdap.readthedocs.io.

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arXiv2019

A thin shell of ionized gas explaining the IR excess of classical Cepheids

Despite observational evidences, InfraRed (IR) excess of classical Cepheids are seldom studied and poorly understood, but probably induces systematics on the Period-Luminosity (PL) relation used in the calibration of the extragalactic distance scale. This study aims to understand the physical origin of the IR excess found in the spectral energy distribution (SED) of 5 Cepheids : RS Pup (P=41.46d), zeta Gem (P=10.15d), eta Aql (P=7.18d), V Cen (P=5.49d) and SU Cyg (P=3.85d). A time series of atmospheric models along the pulsation cycle are fitted to a compilation of data, including optical and near-IR photometry, Spitzer spectra (secured at a specific phase), interferometric angular diameters, effective temperature and radial velocity measurements. Herschel images in two bands are also analyzed qualitatively. In this fitting process, based on the SPIPS algorithm, a residual is found in the SED, whatever the pulsation phase, and for wavelengths larger than about $1.2μ$m, which corresponds to the so-determined infrared excess of Cepheids. This IR excess is then corrected from interstellar medium absorption in order to infer or not the presence of dust shells, and is finally used in order to fit a model of a shell of ionized gas. For all Cepheids, we find a continuum IR excess increasing up to about -0.1 magnitudes at 30$μ$m, which cannot be explained by a hot or cold dust model of CircumStellar Environment (CSE). We show, for the first time, that the IR excess of Cepheids can be explained by free-free emission from a thin shell of ionized gas, with a thickness of about 15% of the star radius, a mass of $10^{-9}-10^{-7}$ Msol and a temperature ranging from 3500 to 4500K. This result has to be tested with interferometers operating in visible, in the mid-IR or in the radio domain. The impact of such CSEs of ionized gas on the PL relation of Cepheids needs also more investigations.

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arXiv2019

30-micron sources in galaxies with different metallicities

We present an analysis and comparison of the 30 micron dust features seen in the Spitzer Space Telescope spectra of 207 carbon-rich asymptotic giant branch (AGB) stars, post-AGB objects, and planetary nebulae located in the Milky Way, the Magellanic Clouds (MCs), or the Sagittarius dwarf spheroidal galaxy (Sgr dSph), which are characterised by different average metallicities. We investigated whether the formation of the 30 micron feature carrier may be a function of the metallicity. Through this study we expect to better understand the late stages of stellar evolution of carbon-rich stars in these galaxies. Our analysis uses the `Manchester method' as a basis for estimating the temperature of dust for the carbon-rich AGB stars and the planetary nebulae in our sample. We used a black-body function with a single temperature deduced from the Manchester method or its modification to approximate the continuum under the 30 micron feature. The most important conclusion of our work is the fact that the formation of the 30 micron feature is affected by metallicity. Specifically that, as opposed to more metal-poor samples of AGB stars in the MCs, the feature is seen at lower mass-loss rates, higher temperatures, and has seen to be more prominent in Galactic carbon stars. The averaged feature (profile) in the AGB, post-AGB objects, and PNe seems unaffected by metallicity at least between a fifth and solar metallicity, but in the case of PNe it is shifted to significantly longer wavelengths.

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arXiv2019

The homogeneous internal structure of CM-like asteroid (41) Daphne

Context. CM-like asteroids (Ch and Cgh classes) are a major population within the broader C-complex, encompassing about 10% of the mass of the main asteroid belt. Their internal structure has been predicted to be homogeneous, based on their compositional similarity as inferred from spectroscopy (Vernazza et al., 2016, AJ 152, 154) and numerical modeling of their early thermal evolution (Bland & Travis, 2017, Sci. Adv. 3, e1602514). Aims. Here we aim to test this hypothesis by deriving the density of the CM-like asteroid (41) Daphne from detailed modeling of its shape and the orbit of its small satellite. Methods. We observed Daphne and its satellite within our imaging survey with the Very Large Telescope extreme adaptive-optics SPHERE/ZIMPOL camera (ID 199.C-0074, PI P. Vernazza) and complemented this data set with earlier Keck/NIRC2 and VLT/NACO observations. We analyzed the dynamics of the satellite with our Genoid meta-heuristic algorithm. Combining our high-angular resolution images with optical lightcurves and stellar occultations, we determine the spin period, orientation, and 3-D shape, using our ADAM shape modeling algorithm. Results. The satellite orbits Daphne on an equatorial, quasi-circular, prograde orbit, like the satellites of many other large main-belt asteroids. The shape model of Daphne reveals several large flat areas that could be large impact craters. The mass determined from this orbit combined with the volume computed from the shape model implies a density for Daphne of 1.77+/-0.26 g/cm3 (3 σ). This density is consistent with a primordial CM-like homogeneous internal structure with some level of macroporosity (~17%). Conclusions. Based on our analysis of the density of Daphne and 75 other Ch/Cgh-type asteroids gathered from the literature, we conclude that the primordial internal structure of the CM parent bodies was homogeneous.

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arXiv2018

Post conjunction detection of $β$ Pictoris b with VLT/SPHERE

With an orbital distance comparable to that of Saturn in the solar system, \bpic b is the closest (semi-major axis $\simeq$\,9\,au) exoplanet that has been imaged to orbit a star. Thus it offers unique opportunities for detailed studies of its orbital, physical, and atmospheric properties, and of disk-planet interactions. With the exception of the discovery observations in 2003 with NaCo at the Very Large Telescope (VLT), all following astrometric measurements relative to \bpic have been obtained in the southwestern part of the orbit, which severely limits the determination of the planet's orbital parameters. We aimed at further constraining \bpic b orbital properties using more data, and, in particular, data taken in the northeastern part of the orbit. We used SPHERE at the VLT to precisely monitor the orbital motion of beta \bpic b since first light of the instrument in 2014. We were able to monitor the planet until November 2016, when its angular separation became too small (125 mas, i.e., 1.6\,au) and prevented further detection. We redetected \bpic b on the northeast side of the disk at a separation of 139\,mas and a PA of 30$^{\circ}$ in September 2018. The planetary orbit is now well constrained. With a semi-major axis (sma) of $a = 9.0 \pm 0.5$ au (1 $σ$), it definitely excludes previously reported possible long orbital periods, and excludes \bpic b as the origin of photometric variations that took place in 1981. We also refine the eccentricity and inclination of the planet. From an instrumental point of view, these data demonstrate that it is possible to detect, if they exist, young massive Jupiters that orbit at less than 2 au from a star that is 20 pc away.

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arXiv2018

High-Contrast study of the candidate planets and protoplanetary disk around HD~100546

The nearby Herbig Be star HD100546 is known to be a laboratory for the study of protoplanets and their relation with the circumstellar disk that is carved by at least 2 gaps. We observed the HD100546 environment with high contrast imaging exploiting several different observing modes of SPHERE, including datasets with/without coronagraphs, dual band imaging, integral field spectroscopy and polarimetry. The picture emerging from these different data sets is complex. Flux-conservative algorithms images clearly show the disk up to 200au. More aggressive algorithms reveal several rings and warped arms overlapping the main disk. The bright parts of this ring lie at considerable height over the disk mid-plane at about 30au. Our images demonstrate that the brightest wings close to the star in the near side of the disk are a unique structure, corresponding to the outer edge of the intermediate disk at ~40au. Modeling of the scattered light from the disk with a geometrical algorithm reveals that a moderately thin structure can well reproduce the light distribution in the flux-conservative images. We suggest that the gap between 44 and 113 au span between the 1:2 and 3:2 resonance orbits of a massive body located at ~70au that might coincide with the candidate planet HD100546b detected with previous thermal IR observations. In this picture, the two wings can be the near side of a ring formed by disk material brought out of the disk at the 1:2 resonance with the same massive object. While we find no clear evidence confirming detection of the planet candidate HD100546c in our data, we find a diffuse emission close to the expected position of HD100546b. This source can be described as an extremely reddened substellar object surrounded by a dust cloud or its circumplanetary disk. Its astrometry is broadly consistent with a circular orbital motion on the disk plane.

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arXiv2018

SPHERE / ZIMPOL high resolution polarimetric imager. I. System overview, PSF parameters, coronagraphy, and polarimetry

We describe the Zurich Imaging Polarimeter (ZIMPOL), the visual focal plane subsystem of the SPHERE "VLT planet finder", which pushes the limits of current AO systems to shorter wavelengths, higher spatial resolution, and much improved polarimetric performance. We provide new benchmarks for the performance of high contrast instruments, in particular for polarimetric differential imaging. We have analyzed SPHERE/ZIMPOL point spread functions and measure the peak surface brightness, the encircled energy, and the full width half maximum (FWHM) for different wavelengths, atmospheric conditions, star brightness, and instrument modes. Coronagraphic images are described and analized and the performance for different coronagraphs is compared with tests for the binary alpha Hyi with a separation of 92 mas and a contrast of 6 mag. For the polarimetric mode we made the instrument calibrations using zero polarization and high polarization standard stars and here we give a recipe for the absolute calibration of polarimetric data. The data show a small <1 mas but disturbing differential polarimetric beam shifts, which can be explained as Goos-Hähnchen shifts from the inclined mirrors, and we discuss how to correct this effect. The polarimetric sensitivity is investigated with non-coronagraphic and deep, coronagraphic observations of the dust scattering around the symbiotic Mira variable R Aqr. SPHERE/ZIMPOL achieves imaging performances in the visual range with unprecedented characteristics, in particular very high spatial resolution and very high polarimetric contrast. This instrument opens up many new research opportunities for the detailed investigation of circumstellar dust, in scattered and therefore polarized light, for the investigation of faint companions, and for the mapping of circumstellar Halpha emission.

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arXiv2018

The gravitational mass of Proxima Centauri measured with SPHERE from a microlensing event

Proxima Centauri, our closest stellar neighbour, is a low-mass M5 dwarf orbiting in a triple system. An Earth-mass planet with an 11 day period has been discovered around this star. The star's mass has been estimated only indirectly using a mass-luminosity relation, meaning that large uncertainties affect our knowledge of its properties. To refine the mass estimate, an independent method has been proposed: gravitational microlensing. By taking advantage of the close passage of Proxima Cen in front of two background stars, it is possible to measure the astrometric shift caused by the microlensing effect due to these close encounters and estimate the gravitational mass of the lens (Proxima Cen). Microlensing events occurred in 2014 and 2016 with impact parameters, the closest approach of Proxima Cen to the background star, of 1\farcs6 $\pm$ 0\farcs1 and 0\farcs5 $\pm$ 0\farcs1, respectively. Accurate measurements of the positions of the background stars during the last two years have been obtained with HST/WFC3, and with VLT/SPHERE from the ground. The SPHERE campaign started on March 2015, and continued for more than two years, covering 9 epochs. The parameters of Proxima Centauri's motion on the sky, along with the pixel scale, true North, and centering of the instrument detector were readjusted for each epoch using the background stars visible in the IRDIS field of view. The experiment has been successful and the astrometric shift caused by the microlensing effect has been measured for the second event in 2016. We used this measurement to derive a mass of 0.150$^{\textrm{+}0.062}_{-0.051}$ (an error of $\sim$ 40\%) \MSun for Proxima Centauri acting as a lens. This is the first and the only currently possible measurement of the gravitational mass of Proxima Centauri.

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arXiv2018

The SPHERE view of Wolf-Rayet 104

Context. WR104 is an emblematic dusty Wolf-Rayet star and the prototypical member of a subgroup hosting spirals that are mainly observable with high-angular resolution techniques. Previous aperture masking observations showed that WR104 is likely an interacting binary star at the end of its life. However, several aspects of the system are still unknown. This includes the opening angle of the spiral, the dust formation locus, and the link between the central binary star and a candidate companion star detected with the Hubble Space Telescope (HST) at 1". Aims. Our aim was to directly image the dusty spiral or "pinwheel" structure around WR104 for the first time and determine its physical properties at large spatial scales. We also wanted to address the characteristics of the candidate companion detected by the HST. Methods. For this purpose, we used SPHERE and VISIR at the Very Large Telescope to respectively image the system in the near-and mid-infrared. Both instruments furnished an excellent view of the system at the highest angular resolution a single, ground-based telescope can provide. Based on these direct images, we then used analytical and radiative transfer models to determine several physical properties of the system. Results. Employing a different technique than previously used, our new images have allowed us to confirm the presence of the dust pinwheel around the central star. We have also detected up to 5 revolutions of the spiral pattern of WR104 in the K-band for the first time. The circumstellar dust extends up to 2 arcsec from the central binary star in the N-band, corresponding to the past 20 years of mass loss. Moreover, we found no clear evidence of a shadow of the first spiral coil onto the subsequent ones, which likely points to a dusty environment less massive than inferred in previous studies. We have also confirmed that the stellar candidate companion previously detected by the HST is gravitationally bound to WR104 and herein provide information about its nature and orbital elements.

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arXiv2018

Astrometric and photometric accuracies in high contrast imaging: The SPHERE speckle calibration tool (SpeCal)

The consortium of the Spectro-Polarimetric High-contrast Exoplanet REsearch installed at the Very Large Telescope (SPHERE/VLT) has been operating its guaranteed observation time (260 nights over five years) since February 2015. The main part of this time (200 nights) is dedicated to the detection and characterization of young and giant exoplanets on wide orbits. The large amount of data must be uniformly processed so that accurate and homogeneous measurements of photometry and astrometry can be obtained for any source in the field. To complement the European Southern Observatory pipeline, the SPHERE consortium developed a dedicated piece of software to process the data. First, the software corrects for instrumental artifacts. Then, it uses the speckle calibration tool (SpeCal) to minimize the stellar light halo that prevents us from detecting faint sources like exoplanets or circumstellar disks. SpeCal is meant to extract the astrometry and photometry of detected point-like sources (exoplanets, brown dwarfs, or background sources). SpeCal was intensively tested to ensure the consistency of all reduced images (cADI, Loci, TLoci, PCA, and others) for any SPHERE observing strategy (ADI, SDI, ASDI as well as the accuracy of the astrometry and photometry of detected point-like sources. SpeCal is robust, user friendly, and efficient at detecting and characterizing point-like sources in high contrast images. It is used to process all SPHERE data systematically, and its outputs have been used for most of the SPHERE consortium papers to date. SpeCal is also a useful framework to compare different algorithms using various sets of data (different observing modes and conditions). Finally, our tests show that the extracted astrometry and photometry are accurate and not biased.

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arXiv2018

Observations of fast-moving features in the debris disk of AU Mic on a three-year timescale: Confirmation and new discoveries

The nearby and young M star AU Mic is surrounded by a debris disk in which we previously identified a series of large-scale arch-like structures that have never been seen before in any other debris disk and that move outward at high velocities. We initiated a monitoring program with the following objectives: 1) track the location of the structures and better constrain their projected speeds, 2) search for new features emerging closer in, and ultimately 3) understand the mechanism responsible for the motion and production of the disk features. AU Mic was observed at 11 different epochs between August 2014 and October 2017 with the IR camera and spectrograph of SPHERE. These high-contrast imaging data were processed with a variety of angular, spectral, and polarimetric differential imaging techniques to reveal the faintest structures in the disk. We measured the projected separations of the features in a systematic way for all epochs. We also applied the very same measurements to older observations from the Hubble Space Telescope (HST) with the visible cameras STIS and ACS. The main outcomes of this work are 1) the recovery of the five southeastern broad arch-like structures we identified in our first study, and confirmation of their fast motion (projected speed in the range 4-12 km/s); 2) the confirmation that the very first structures observed in 2004 with ACS are indeed connected to those observed later with STIS and now SPHERE; 3) the discovery of two new very compact structures at the northwest side of the disk (at 0.40" and 0.55" in May 2015) that move to the southeast at low speed; and 4) the identification of a new arch-like structure that might be emerging at the southeast side at about 0.4" from the star (as of May 2016). Abridged.

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arXiv2018

Discovery of a brown dwarf companion to the star HIP 64892

We report the discovery of a bright, brown dwarf companion to the star HIP 64892, imaged with VLT/SPHERE during the SHINE exoplanet survey. The host is a B9.5V member of the Lower-Centaurus-Crux subgroup of the Scorpius Centaurus OB association. The measured angular separation of the companion ($1.2705\pm0.0023$") corresponds to a projected distance of $159\pm12$ AU. We observed the target with the dual-band imaging and long-slit spectroscopy modes of the IRDIS imager to obtain its SED and astrometry. In addition, we reprocessed archival NACO L-band data, from which we also recover the companion. Its SED is consistent with a young (<30 Myr), low surface gravity object with a spectral type of M9$_γ\pm1$. From comparison with the BT-Settl atmospheric models we estimate an effective temperature of $T_{\textrm{eff}}=2600 \pm 100$ K, and comparison of the companion photometry to the COND evolutionary models yields a mass of $\sim29-37$ M$_{\text{J}}$ at the estimated age of $16^{+15}_{-7}$ Myr for the system. HIP 64892 is a rare example of an extreme-mass ratio system ($q\sim0.01$) and will be useful for testing models relating to the formation and evolution of such low-mass objects.

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arXiv2018

Investigating the young Solar System analog HD95086

HD95086 (A8V, 17Myr) hosts a rare planetary system for which a multi-belt debris disk and a giant planet of 4-5MJup have been directly imaged. Our study aims to characterize the physical and orbital properties of HD95086b, search for additional planets at short and wide orbits and image the cold outer debris belt in scattered light. We used HARPS at the ESO 3.6m telescope to monitor the radial velocity of HD95086 over 2 years and investigate the existence of giant planets at less than 3au orbital distance. With the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE at VLT, we imaged the faint circumstellar environment beyond 10au at six epochs between 2015 and 2017. We do not detect additional giant planets around HD95086. We identified the nature (bound companion or background contaminant) of all point-like sources detected in the IRDIS field of view. None of them correspond to the ones recently discovered near the edge of the cold outer belt by ALMA. HD95086b is resolved for the first time in J-band with IFS. Its near-infrared spectral energy distribution is well fitted by a few dusty and/or young L7-L9 dwarf spectral templates. The extremely red 1-4um spectral distribution is typical of low-gravity objects at the L/T spectral type transition. The planet's orbital motion is resolved between January 2015 and May 2017. Together with past NaCo measurements properly re-calibrated, our orbital fitting solutions favor a retrograde low to moderate-eccentricity orbit e=0.2 (0.0 to 0.5), with a semi-major axis 52au corresponding to orbital periods of 288$ yrs and an inclination that peaks at i = 141deg, which is compatible with a planet-disk coplanar configuration. Finally, we report the detection in polarimetric differential imaging of the cold outer debris belt between 100 and 300au, consistent in radial extent with recent ALMA 1.3mm resolved observations.

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arXiv2017

The SPHERE data center: a reference for high contrast imaging processing

The objective of the SPHERE Data Center is to optimize the scientific return of SPHERE at the VLT, by providing optimized reduction procedures, services to users and publicly available reduced data. This paper describes our motivation, the implementation of the service (partners, infrastructure and developments), services, description of the on-line data, and future developments. The SPHERE Data Center is operational and has already provided reduced data with a good reactivity to many observers. The first public reduced data have been made available in 2017. The SPHERE Data Center is gathering a strong expertise on SPHERE data and is in a very good position to propose new reduced data in the future, as well as improved reduction procedures.

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