References of "Lagrange, A.-M"
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See detailDirect confirmation of the radial-velocity planet β Pictoris c
Nowak, M.; Lacour, S.; Lagrange, A.-M. et al

in Astronomy and Astrophysics (2020), 642

Context. Methods used to detect giant exoplanets can be broadly divided into two categories: indirect and direct. Indirect methods are more sensitive to planets with a small orbital period, whereas direct ... [more ▼]

Context. Methods used to detect giant exoplanets can be broadly divided into two categories: indirect and direct. Indirect methods are more sensitive to planets with a small orbital period, whereas direct detection is more sensitive to planets orbiting at a large distance from their host star. This dichotomy makes it difficult to combine the two techniques on a single target at once. <BR /> Aims: Simultaneous measurements made by direct and indirect techniques offer the possibility of determining the mass and luminosity of planets and a method of testing formation models. Here, we aim to show how long-baseline interferometric observations guided by radial-velocity can be used in such a way. <BR /> Methods: We observed the recently-discovered giant planet β Pictoris c with GRAVITY, mounted on the Very Large Telescope Interferometer. <BR /> Results: This study constitutes the first direct confirmation of a planet discovered through radial velocity. We find that the planet has a temperature of T = 1250 ± 50 K and a dynamical mass of M = 8.2 ± 0.8 M[SUB]Jup[/SUB]. At 18.5 ± 2.5 Myr, this puts β Pic c close to a `hot start' track, which is usually associated with formation via disk instability. Conversely, the planet orbits at a distance of 2.7 au, which is too close for disk instability to occur. The low apparent magnitude (M[SUB]K[/SUB] = 14.3 ± 0.1) favours a core accretion scenario. <BR /> Conclusions: We suggest that this apparent contradiction is a sign of hot core accretion, for example, due to the mass of the planetary core or the existence of a high-temperature accretion shock during formation. [less ▲]

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See detailThe search for disks or planetary objects around directly imaged companions: a candidate around DH Tauri B
Lazzoni, C.; Zurlo, A.; Desidera, S. et al

in Astronomy and Astrophysics (2020), 641

Context. In recent decades, thousands of substellar companions have been discovered with both indirect and direct methods of detection. While the majority of the sample is populated by objects discovered ... [more ▼]

Context. In recent decades, thousands of substellar companions have been discovered with both indirect and direct methods of detection. While the majority of the sample is populated by objects discovered using radial velocity and transit techniques, an increasing number have been directly imaged. These planets and brown dwarfs are extraordinary sources of information that help in rounding out our understanding of planetary systems. <BR /> Aims: In this paper, we focus our attention on substellar companions detected with the latter technique, with the primary goal of investigating their close surroundings and looking for additional companions and satellites, as well as disks and rings. Any such discovery would shed light on many unresolved questions, particularly with regard to their possible formation mechanisms. <BR /> Methods: To reveal bound features of directly imaged companions, whether for point-like or extended sources, we need to suppress the contribution from the source itself. Therefore, we developed a method based on the negative fake companion technique that first estimates the position in the field of view (FoV) and the flux of the imaged companion with high precision, then subtracts a rescaled model point spread function (PSF) from the imaged companion, using either an image of the central star or another PSF in the FoV. Next it performs techniques, such as angular differential imaging, to further remove quasi-static patterns of the star (i.e., speckle contaminants) that affect the residuals of close-in companions. <BR /> Results: After testing our tools on simulated companions and disks and on systems that were chosen ad hoc, we applied the method to the sample of substellar objects observed with SPHERE during the SHINE GTO survey. Among the 27 planets and brown dwarfs we analyzed, most objects did not show remarkable features, which was as expected, with the possible exception of a point source close to DH Tau B. This candidate companion was detected in four different SPHERE observations, with an estimated mass of ~1M[SUB]Jup[/SUB], and a mass ratio with respect to the brown dwarf of 1/10. This binary system, if confirmed, would be the first of its kind, opening up interesting questions for the formation mechanism, evolution, and frequency of such pairs. In order to address the latter, the residuals and contrasts reached for 25 companions in the sample of substellar objects observed with SPHERE were derived. If the DH Tau Bb companion is real, the binary fraction obtained is ~7%, which is in good agreement with the results obtained for field brown dwarfs. <BR /> Conclusions: While there may currently be many limitations affecting the exploration of bound features to directly imaged exoplanets and brown dwarfs, next-generation instruments from the ground and space (i.e., JWST, ELT, and LUVOIR) will be able to image fainter objects and, thus, drive the application of this technique in upcoming searches for exo-moons and circumplanetary disks. <P />Based on observations collected at Paranal Observatory, ESO (Chile) Program ID: 095.C-0298, 096.C-0241, 097.C-0865, 198.C-0209, and 0104.C-0327(A) and on observations collected at LBT Observatory. [less ▲]

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See detailOrbital and spectral characterization of the benchmark T-type brown dwarf HD 19467B
Maire, Anne-Lise ULiege; Molaverdikhani, K.; Desidera, S. et al

in Astronomy and Astrophysics (2020), 639

Context. Detecting and characterizing substellar companions for which the luminosity, mass, and age can be determined independently is of utter importance to test and calibrate the evolutionary models due ... [more ▼]

Context. Detecting and characterizing substellar companions for which the luminosity, mass, and age can be determined independently is of utter importance to test and calibrate the evolutionary models due to uncertainties in their formation mechanisms. HD 19467 is a bright and nearby star hosting a cool brown dwarf companion detected with radial velocities and imaging, making it a valuable object for such studies. <BR /> Aims: We aim to further characterize the orbital, spectral, and physical properties of the HD 19467 system. <BR /> Methods: We present new high-contrast imaging data with the SPHERE and NaCo instruments. We also analyze archival data from the instruments HARPS, NaCo, HIRES, UVES, and ASAS. Furthermore, we use proper motion data of the star from HIPPARCOS and Gaia. <BR /> Results: We refined the properties of the host star and derived an age of 8.0[SUP]+2.0[/SUP][SUB]-1.0[/SUB] Gyr based on isochrones, gyrochronology, and chemical and kinematic arguments. This age estimate is slightly younger than previous age estimates of ~9-11 Gyr based on isochrones. No orbital curvature is seen in the current imaging, radial velocity, and astrometric data. From a joint fit of the data, we refined the orbital parameters for HD 19467B, including: a period of 398[SUP]+95[/SUP][SUB]-93[/SUB] yr, an inclination of 129.8[SUP]+8.1[/SUP][SUB]-5.1[/SUB] deg, an eccentricity of 0.56 ± 0.09, a longitude of the ascending node of 134.8 ± 4.5 deg, and an argument of the periastron of 64.2[SUP]+5.5[/SUP][SUB]-6.3[/SUB] deg. We assess a dynamical mass of 74[SUP]+12[/SUP][SUB]-9[/SUB] M[SUB]J[/SUB]. The fit with atmospheric models of the spectrophotometric data of the companion indicates an atmosphere without clouds or with very thin clouds, an effective temperature of 1042[SUP]+77[/SUP][SUB]-71[/SUB] K, and a high surface gravity of 5.34[SUP]+0.8[/SUP][SUB]-0.9[/SUB] dex. The comparison to model predictions of the bolometric luminosity and dynamical mass of HD 19467B, assuming our system age estimate, indicates a better agreement with the Burrows et al. (1997, ApJ, 491, 856) models; whereas, the other evolutionary models used tend to underestimate its cooling rate. <P />The reduced images shown in Fig. 3 are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/639/A47">http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/639/A47</A> <P />Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 1100.C-0481, 0100.C-0234, 096.C-0602, 072.C-0488, 183.C-0972, 084.D-0965, 188.C-0265, 192.C-0852, and 0100.D-0444. [less ▲]

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See detailSearching for the near-infrared counterpart of Proxima c using multi-epoch high-contrast SPHERE data at VLT★
Gratton, R.; Zurlo, A.; Le Coroller, H. et al

in Astronomy and Astrophysics (2020), 638

Context. Proxima Centauri is the closest star to the Sun and it is known to host an Earth-like planet in its habitable zone; very recently a second candidate planet was proposed based on radial velocities ... [more ▼]

Context. Proxima Centauri is the closest star to the Sun and it is known to host an Earth-like planet in its habitable zone; very recently a second candidate planet was proposed based on radial velocities. At quadrature, the expected projected separation of this new candidate is larger than 1 arcsec, making it a potentially interesting target for direct imaging. <BR /> Aims: While identification of the optical counterpart of this planet is expected to be very difficult, successful identification would allow for a detailed characterization of the closest planetary system. <BR /> Methods: We searched for a counterpart in SPHERE images acquired over four years through the SHINE survey. In order to account for the expected large orbital motion of the planet, we used a method that assumes the circular orbit obtained from radial velocities and exploits the sequence of observations acquired close to quadrature in the orbit. We checked this with a more general approach that considers Keplerian motion, called K-stacker. <BR /> Results: We did not obtain a clear detection. The best candidate has signal-to-noise ratio (S/N) = 6.1 in the combined image. A statistical test suggests that the probability that this detection is due to random fluctuation of noise is <1%, but this result depends on the assumption that the distribution of noise is uniform over the image, a fact that is likely not true. The position of this candidate and the orientation of its orbital plane fit well with observations in the ALMA 12 m array image. However, the astrometric signal expected from the orbit of the candidate we detected is 3σ away from the astrometric motion of Proxima as measured from early Gaia data. This, together with the unexpectedly high flux associated with our direct imaging detection, means we cannot confirm that our candidate is indeed Proxima c. <BR /> Conclusions: On the other hand, if confirmed, this would be the first observation in imaging of a planet discovered from radial velocities and the second planet (after Fomalhaut b) of reflecting circumplanetary material. Further confirmation observations should be done as soon as possible. <P />The reduced images are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/638/A120">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/638/A120</A> <P />Based on data collected at the European Southern Observatory, Chile (ESO Programs 095.D-0309, 096.C-0241, 096.D-0252, 097.C-0865, 198.C-D0209, 099.D-0098, 099.C-0127. [less ▲]

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See detailSPHERE+: Imaging young Jupiters down to the snowline
Boccaletti, A.; Chauvin, G.; Mouillet, D. et al

E-print/Working paper (2020)

SPHERE (Beuzit et al,. 2019) has now been in operation at the VLT for more than 5 years, demonstrating a high level of performance. SPHERE has produced outstanding results using a variety of operating ... [more ▼]

SPHERE (Beuzit et al,. 2019) has now been in operation at the VLT for more than 5 years, demonstrating a high level of performance. SPHERE has produced outstanding results using a variety of operating modes, primarily in the field of direct imaging of exoplanetary systems, focusing on exoplanets as point sources and circumstellar disks as extended objects. The achievements obtained thus far with SPHERE (~200 refereed publications) in different areas (exoplanets, disks, solar system, stellar physics...) have motivated a large consortium to propose an even more ambitious set of science cases, and its corresponding technical implementation in the form of an upgrade. The SPHERE+ project capitalizes on the expertise and lessons learned from SPHERE to push high contrast imaging performance to its limits on the VLT 8m-telescope. The scientific program of SPHERE+ described in this document will open a new and compelling scientific window for the upcoming decade in strong synergy with ground-based facilities (VLT/I, ELT, ALMA, and SKA) and space missions (Gaia, JWST, PLATO and WFIRST). While SPHERE has sampled the outer parts of planetary systems beyond a few tens of AU, SPHERE+ will dig into the inner regions around stars to reveal and characterize by mean of spectroscopy the giant planet population down to the snow line. Building on SPHERE's scientific heritage and resounding success, SPHERE+ will be a dedicated survey instrument which will strengthen the leadership of ESO and the European community in the very competitive field of direct imaging of exoplanetary systems. With enhanced capabilities, it will enable an even broader diversity of science cases including the study of the solar system, the birth and death of stars and the exploration of the inner regions of active galactic nuclei. [less ▲]

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See detailPeering into the formation history of beta Pictoris b with VLTI/GRAVITY long baseline interferometry
Nowak, M.; Lacour, S.; Mollière, P. et al

in Astronomy and Astrophysics (2019), 633

Our objective is to estimate the C/O ratio in the atmosphere of beta Pictoris b and obtain an estimate of the dynamical mass of the planet, as well as to refine its orbital parameters using high-precision ... [more ▼]

Our objective is to estimate the C/O ratio in the atmosphere of beta Pictoris b and obtain an estimate of the dynamical mass of the planet, as well as to refine its orbital parameters using high-precision astrometry. We used the GRAVITY instrument with the four 8.2 m telescopes of the Very Large Telescope Interferometer to obtain K-band spectro-interferometric data on $\beta$ Pic b. We extracted a medium resolution (R=500) K-band spectrum of the planet and a high-precision astrometric position. We estimated the planetary C/O ratio using two different approaches (forward modeling and free retrieval) from two different codes (ExoREM and petitRADTRANS, respectively). Finally, we used a simplified model of two formation scenarios (gravitational collapse and core-accretion) to determine which can best explain the measured C/O ratio. Our new astrometry disfavors a circular orbit for $\beta$ Pic b ($e=0.15^{+0.05}_{-0.04}$). Combined with previous results and with Hipparcos/GAIA measurements, this astrometry points to a planet mass of $M = 12.7\pm{}2.2\,M_\mathrm{Jup}$. This value is compatible with the mass derived with the free-retrieval code petitRADTRANS using spectral data only. The forward modeling and free-retrieval approches yield very similar results regarding the atmosphere of beta Pic b. In particular, the C/O ratios derived with the two codes are identical ($0.43\pm{}0.05$ vs $0.43^{+0.04}_{-0.03}$). We argue that if the stellar C/O in $\beta$ Pic is Solar, then this combination of a very high mass and a low C/O ratio for the planet suggests a formation through core-accretion, with strong planetesimal enrichment. [less ▲]

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See detailSpatially Resolving the Quasar Broad Emission Line Region
Gravity Collaboration; Abuter, R.; Accardo, M. et al

in Messenger (2019), 178

The angular resolution of the Very Large Telescope Interferometer (VLTI) and the excellent sensitivity of GRAVITY have led to the first detection of spatially resolved kinematics of high velocity atomic ... [more ▼]

The angular resolution of the Very Large Telescope Interferometer (VLTI) and the excellent sensitivity of GRAVITY have led to the first detection of spatially resolved kinematics of high velocity atomic gas near an accreting super- massive black hole, revealing rotation on sub-parsec scales in the quasar 3C 273 at a distance of 550 Mpc. The observations can be explained as the result of circular orbits in a thick disc configuration around a 300 million solar mass black hole. Within an ongoing Large Programme, this capability will be used to study the kinematics of atomic gas and its relation to hot dust in a sample of quasars and Seyfert galaxies. We will measure a new radius-luminosity relation from spatially resolved data and test the current methods used to measure black hole mass in large surveys. [less ▲]

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See detailVLT/SPHERE exploration of the young multiplanetary system PDS70
Mesa, D.; Keppler, M.; Cantalloube, F. et al

in Astronomy and Astrophysics (2019), 632

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 ... [more ▼]

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, PDS 70 b, within the disk cavity. Moreover, observations in H[SUB]α[/SUB] with MagAO and MUSE revealed emission associated to PDS 70 b and to another new companion candidate, PDS 70 c, at a larger separation from the star. PDS 70 is the only multiple planetary system at its formation stage detected so far through direct imaging. <BR /> Aims: Our aim is to confirm the discovery of the second planet PDS 70 c using SPHERE at VLT, to further characterize its physical properties, and search for additional point sources in this young planetary system. <BR /> 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. <BR /> Results: We re-detect both PDS 70 b and c and confirm that PDS 70 c is gravitationally bound to the star. We estimate this second planet to be less massive than 5 M[SUB]Jup[/SUB] and with a T[SUB]eff[/SUB] around 900 K. Also, it has a low gravity with logg 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, meaning 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 cannot however 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 a few tens of M[SUB]⊕[/SUB]. Moreover, we propose a possible structure for the planetary system based on our data, and find that this structure cannot be stable on a long timescale. <P />The reduced images are also available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/632/A25">http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/632/A25</A> <P />Based on observation made with European Southern Observatory (ESO) telescopes at Paranal Observatory in Chile, under programs ID 095.C-0298(B), 1100.C-0481(D), 1100.C-0481(L) and 1100.C-0481(M). [less ▲]

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See detailMapping of shadows cast on a protoplanetary disk by a close binary system
D'Orazi, V.; Gratton, R.; Desidera, S. et al

in Nature Astronomy (2019), 3

For a comprehensive understanding of planetary formation and evolution, we need to investigate the environment in which planets form: circumstellar disks. Here we present high-contrast imaging ... [more ▼]

For a comprehensive understanding of planetary formation and evolution, we need to investigate the environment in which planets form: circumstellar disks. Here we present high-contrast imaging observations of V4046 Sagittarii, a 20-Myr-old close binary known to host a circumbinary disk. We have discovered the presence of rotating shadows in the disk, caused by mutual occultations of the central binary. Shadow-like features are often observed in disks[SUP]1,2[/SUP], but those found thus far have not been due to eclipsing phenomena. We have used the phase difference due to light travel time to measure the flaring of the disk and the geometrical distance of the system. We calculate a distance that is in very good agreement with the value obtained from the Gaia mission's Data Release 2 (DR2), and flaring angles of α = (6.2 ± 0.6)° and α = (8.5 ± 1.0)° for the inner and outer disk rings, respectively. Our technique opens up a path to explore other binary systems, providing an independent estimate of distance and the flaring angle, a crucial parameter for disk modelling. [less ▲]

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See detailOrbital and spectral analysis of the benchmark brown dwarf HD 4747B
Peretti, S.; Ségransan, D.; Lavie, B. et al

in Astronomy and Astrophysics (2019), 631

Context. The study of high-contrast imaged brown dwarfs and exoplanets depends strongly on evolutionary models. To estimate the mass of a directly imaged substellar object, its extracted photometry or ... [more ▼]

Context. The study of high-contrast imaged brown dwarfs and exoplanets depends strongly on evolutionary models. To estimate the mass of a directly imaged substellar object, its extracted photometry or spectrum is used and adjusted with model spectra together with the estimated age of the system. These models still need to be properly tested and constrained. HD 4747B is a brown dwarf close to the H burning mass limit, orbiting a nearby (d = 19.25 ± 0.58 pc), solar-type star (G9V); it has been observed with the radial velocity method for over almost two decades. Its companion was also recently detected by direct imaging, allowing a complete study of this particular object. <BR /> Aims: We aim to fully characterize HD 4747B by combining a well-constrained dynamical mass and a study of its observed spectral features in order to test evolutionary models for substellar objects and to characterize its atmosphere. <BR /> Methods: We combined the radial velocity measurements of High Resolution Echelle Spectrometer (HIRES) and CORALIE taken over two decades and high-contrast imaging of several epochs from NACO, NIRC2, and SPHERE to obtain a dynamical mass. From the SPHERE data we obtained a low-resolution spectrum of the companion from Y to H band, and two narrow band-width photometric measurements in the K band. A study of the primary star also allowed us to constrain the age of the system and its distance. <BR /> Results: Thanks to the new SPHERE epoch and NACO archival data combined with previous imaging data and high- precision radial velocity measurements, we were able to derive a well- constrained orbit. The high eccentricity (e = 0.7362 ± 0.0025) of HD 4747B is confirmed, and the inclination and the semi-major axis are derived (i = 47.3 ± 1.6°, a = 10.01 ± 0.21 au). We derive a dynamical mass of m[SUB]B[/SUB] = 70.0 ± 1.6 M[SUB]Jup[/SUB], which is higher than a previous study but in better agreement with the models. By comparing the object with known brown dwarfs spectra, we derive a spectral type of L9 and an effective temperature of 1350 ± 50 K. With a retrieval analysis we constrain the oxygen and carbon abundances and compare them with the values from the HR 8799 planets. <P />Based on observations made with the instrument SPHERE (Prog. ID 198.C-0209) and NaCo (Prog. ID 081.C-0917(A)) at the Paranal observatory and with the CORALIE echelle spectrograph mounted on the 1.2 m Swiss telescope at La Silla Observatory. [less ▲]

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See detailSpatially resolved spectroscopy of the debris disk HD 32297. Further evidence of small dust grains
Bhowmik, T.; Boccaletti, A.; Thébault, P. et al

in Astronomy and Astrophysics (2019), 630

Context. Spectro-photometry of debris disks in total intensity and polarimetry can provide new insight into the properties of the dust grains therein (size distribution and optical properties). <BR ... [more ▼]

Context. Spectro-photometry of debris disks in total intensity and polarimetry can provide new insight into the properties of the dust grains therein (size distribution and optical properties). <BR /> Aims: We aim to constrain the morphology of the highly inclined debris disk HD 32297. We also intend to obtain spectroscopic and polarimetric measurements to retrieve information on the particle size distribution within the disk for certain grain compositions. <BR /> Methods: We observed HD 32297 with SPHERE in Y, J, and H bands in total intensity and in J band in polarimetry. The observations are compared to synthetic models of debris disks and we developed methods to extract the photometry in total intensity overcoming the data-reduction artifacts, namely the self-subtraction. The spectro-photometric measurements averaged along the disk mid-plane are then compared to model spectra of various grain compositions. <BR /> Results: These new images reveal the very inner part of the system as close as 0.15″. The disk image is mostly dominated by the forward scattering making one side (half- ellipse) of the disk more visible, but observations in total intensity are deep enough to also detect the back side for the very first time. The images as well as the surface brightness profiles of the disk rule out the presence of a gap as previously proposed. We do not detect any significant asymmetry between the northeast and southwest sides of the disk. The spectral reflectance features a "gray to blue" color which is interpreted as the presence of grains far below the blowout size. <BR /> Conclusions: The presence of sub-micron grains in the disk is suspected to be the result of gas drag and/or "avalanche mechanisms". The blue color of the disk could be further investigated with additional total intensity and polarimetric observations in K and H bands respectively to confirm the spectral slope and the fraction of polarization. <P />Reduced images are also available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/630/A85">http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/630/A85</A>Based on data collected at the European Southern Observatory, Chile under the programs 098.C-0686(A) and 098.C-0686(B). [less ▲]

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See detailDetermining mass limits around HD 163296 through SPHERE direct imaging data
Mesa, D.; Langlois, M.; Garufi, Antonio et al

in Monthly Notices of the Royal Astronomical Society (2019), 488

HD 163296 is a Herbig Ae/Be star known to host a protoplanetary disc with a ringed structure. To explain the disc features, previous works proposed the presence of planets embedded into the disc. We have ... [more ▼]

HD 163296 is a Herbig Ae/Be star known to host a protoplanetary disc with a ringed structure. To explain the disc features, previous works proposed the presence of planets embedded into the disc. We have observed HD 163296 with the near-infrared (NIR) branch of SPHERE composed by IRDIS (InfraRed Dual-band Imager and Spectrograph) and IFS (integral field spectrograph) with the aim to put tight constraints on the presence of substellar companions around this star. Despite the low rotation of the field of view during our observation we were able to put upper mass limits of few M[SUB]Jup[/SUB] around this object. These limits do not allow to give any definitive conclusion about the planets proposed through the disc characteristics. On the other hand, our results seem to exclude the presence of the only candidate proposed until now using direct imaging in the NIR even if some caution has to be taken considered the different wavelength bands of the two observations. [less ▲]

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See detailHigh-contrast Imaging Study on the Candidate Companions Around the Star AH Lep
Brown Sevilla, Samantha B.; Cantalloube, Faustine; Brandner, Wolfgang et al

in Research Notes of the American Astronomical Society (2019), 3(7), 100

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See detailConstraining the properties of HD 206893 B. A combination of radial velocity, direct imaging, and astrometry data
Grandjean, A.; Lagrange, A.-M.; Beust, H. et al

in Astronomy and Astrophysics (2019), 627

Context. High contrast imaging enables the determination of orbital parameters for substellar companions (planets, brown dwarfs) from the observed relative astrometry and the estimation of model and age ... [more ▼]

Context. High contrast imaging enables the determination of orbital parameters for substellar companions (planets, brown dwarfs) from the observed relative astrometry and the estimation of model and age- dependent masses from their observed magnitudes or spectra. Combining astrometric positions with radial velocity gives direct constraints on the orbit and on the dynamical masses of companions. A brown dwarf was discovered with the VLT/SPHERE instrument at the Very Large Telescope (VLT) in 2017, which orbits at ̃11 au around HD 206893. Its mass was estimated between 12 and 50 M[SUB]J[/SUB] from evolutionary models and its photometry. However, given the significant uncertainty on the age of the system and the peculiar spectrophotometric properties of the companion, this mass is not well constrained. <BR /> Aims: We aim at constraining the orbit and dynamical mass of HD 206893 B. <BR /> Methods: We combined radial velocity data obtained with HARPS spectra and astrometric data obtained with the high contrast imaging VLT/SPHERE and VLT/NaCo instruments, with a time baseline less than three years. We then combined those data with astrometry data obtained by HIPPARCOS and Gaia with a time baseline of 24 yr. We used a Markov chain Monte Carlo approach to estimate the orbital parameters and dynamical mass of the brown dwarf from those data. <BR /> Results: We infer a period between 21 and 33 yr and an inclination in the range 20-41° from pole-on from HD 206893 B relative astrometry. The RV data show a significant RV drift over 1.6 yr. We show that HD 206893 B cannot be the source of this observed RV drift as it would lead to a dynamical mass inconsistent with its photometry and spectra and with HIPPARCOS and Gaia data. An additional inner (semimajor axis in the range 1.4-2.6 au) and massive (̃15 M[SUB]J[/SUB]) companion is needed to explain the RV drift, which is compatible with the available astrometric data of the star, as well as with the VLT/SPHERE and VLT/NaCo nondetection. <P />HARPS run 089.C-0739(A), 192.C-0224(C), 099.C-0205(A), 098.C-0739(A) and 1101.C-0557(A); SPHERE run 096.C-0388, 097.C-0865(D) and 099.C-0708(A); Gaia DR2. [less ▲]

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See detailConstraints on HD 113337 fundamental parameters and planetary system. Combining long-base visible interferometry, disc imaging, and high-contrast imaging
Borgniet, S.; Perraut, K.; Su, K. et al

in Astronomy and Astrophysics (2019), 627

Context. HD 113337 is a main-sequence F6V field star more massive than the Sun. This star hosts one confirmed giant planet and possibly a second candidate, detected by radial velocities (RVs). The star ... [more ▼]

Context. HD 113337 is a main-sequence F6V field star more massive than the Sun. This star hosts one confirmed giant planet and possibly a second candidate, detected by radial velocities (RVs). The star also hosts a cold debris disc detected through the presence of an infrared excess, making it an interesting system to explore. <BR /> Aims: We aim to bring new constraints on the star's fundamental parameters, debris disc properties, and planetary companion(s) by combining complementary techniques. <BR /> Methods: We used the VEGA interferometer on the CHARA array to measure the angular diameter of HD 113337. We derived its linear radius using the parallax from the Gaia Second Data Release. We computed the bolometric flux to derive its effective temperature and luminosity, and we estimated its mass and age using evolutionary tracks. Then, we used Herschel images to partially resolve the outer debris disc and estimate its extension and inclination. Next, we acquired high-contrast images of HD 113337 with the LBTI to probe the 10-80 au separation range. Finally, we combined the deduced contrast maps with previous RVs of the star using the MESS2 software to bring upper mass limits on possible companions at all separations up to 80 au. We took advantage of the constraints on the age and inclination brought by fundamental parameter analysis and disc imaging, respectively, for this analysis. <BR /> Results: We derive a limb-darkened angular diameter of 0.386 ± 0.009 mas that converts into a linear radius of 1.50 ± 0.04 R[SUB]⊙[/SUB] for HD 113337. The fundamental parameter analysis leads to an effective temperature of 6774 ± 125 K and to two possible age solutions: one young within 14-21 Myr and one old within 0.8-1.7 Gyr. We partially resolve the known outer debris disc and model its emission. Our best solution corresponds to a radius of 85 ± 20 au, an extension of 30 ± 20 au, and an inclination within 10-30° for the outer disc. The combination of imaging contrast limits, published RV, and age and inclination solutions allows us to derive a first possible estimation of the true masses of the planetary companions: 7[SUB]-2[/SUB][SUP]+4[/SUP] M[SUB]Jup[/SUB] for HD 113337 b (confirmed companion) and 16[SUB]-3[/SUB][SUP]+10[/SUP] M[SUB]Jup[/SUB] for HD 113337 c (candidate companion). We also constrain possible additional companions at larger separations. Partly based on observations made with the VEGA/CHARA spectro-interferometer. [less ▲]

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See detailTwo cold belts in the debris disk around the G-type star NZ Lupi
Boccaletti, A.; Thébault, P.; Pawellek, N. et al

in Astronomy and Astrophysics (2019), 625

Context. Planetary systems hold the imprint of the formation and of the evolution of planets especially at young ages, and in particular at the stage when the gas has dissipated leaving mostly secondary ... [more ▼]

Context. Planetary systems hold the imprint of the formation and of the evolution of planets especially at young ages, and in particular at the stage when the gas has dissipated leaving mostly secondary dust grains. The dynamical perturbation of planets in the dust distribution can be revealed with high-contrast imaging in a variety of structures. <BR /> Aims: SPHERE, the high-contrast imaging device installed at the VLT, was designed to search for young giant planets in long period, but is also able to resolve fine details of planetary systems at the scale of astronomical units in the scattered-light regime. As a young and nearby star, NZ Lup was observed in the course of the SPHERE survey. A debris disk had been formerly identified with HST/NICMOS. <BR /> Methods: We observed this system in the near-infrared with the camera in narrow and broad band filters and with the integral field spectrograph. High contrasts are achieved by the mean of pupil tracking combined with angular differential imaging algorithms. <BR /> Results: The high angular resolution provided by SPHERE allows us to reveal a new feature in the disk which is interpreted as a superimposition of two belts of planetesimals located at stellocentric distances of 85 and 115 au, and with a mutual inclination of about 5°. Despite the very high inclination of the disk with respect to the line of sight, we conclude that the presence of a gap, that is, a void in the dust distribution between the belts, is likely. <BR /> Conclusions: We discuss the implication of the existence of two belts and their relative inclination with respect to the presence of planets. <P />Reduced images of Fig. 1 are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-stras bg.fr">http://cdsarc.u-strasbg.fr</A>(ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/625/A21">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/625/A21</A>Based on data collected at the European Southern Observatory, Chile under programs 097.C-0523, 097.C-0865, 198.C-0209. [less ▲]

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See detailExploring the R CrA environment with SPHERE. Discovery of a new stellar companion
Mesa, D.; Bonnefoy, M.; Gratton, R. et al

in Astronomy and Astrophysics (2019), 624

<BR /> Aims: R Coronae Australis (R CrA) is the brightest star of the Coronet nebula of the Corona Australis (CrA) star forming region. This star is very red in color, probably due to dust absorption, and ... [more ▼]

<BR /> Aims: R Coronae Australis (R CrA) is the brightest star of the Coronet nebula of the Corona Australis (CrA) star forming region. This star is very red in color, probably due to dust absorption, and is strongly variable. High-contrast instruments allow for an unprecedented direct exploration of the immediate circumstellar environment of this star. <BR /> Methods: We observed R CrA with the near-infrared (NIR) channels (IFS and IRDIS) of SPHERE at the Very Large Telescope (VLT). In this paper, we used four different epochs, three of which are from open time observations while one is from SPHERE guaranteed time. The data were reduced using the data reduction and handling pipeline and the SPHERE Data Center. We implemented custom IDL routines on the reduced data with the aim to subtract the speckle halo. We have also obtained pupil-tracking H-band (1.45-1.85 μm) observations with the VLT/SINFONI NIR medium-resolution (R ̃ 3000) spectrograph. <BR /> Results: A companion was found at a separation of 0.156″ from the star in the first epoch and increasing to 0.184″ in the final epoch. Furthermore, several extended structures were found around the star, the most noteworthy of which is a very bright jet-like structure northeast from the star. The astrometric measurements of the companion in the four epochs confirm that it is gravitationally bound to the star. The SPHERE photometry and SINFONI spectrum, once corrected for extinction, point toward a spectral type object that is early M with a mass between 0.3 and 0.55 M[SUB]☉[/SUB]. The astrometric analyis provides constraints on the orbit paramenters: e ̃ 0.4, semimajor axis at 27-28 au, inclination of ̃70°, and a period larger than 30 yr. We were also able to put constraints of few M[SUB]Jup[/SUB] on the mass of possible other companions down to separations of few tens of au. <P />Based on observations made with European Southern Observatory (ESO) telescopes at Paranal Observatory in Chile, under programs ID 095.C-0787(A), 097.C-0591(A), 1100.C-0481(H), 0101.C-0350(A) and 2101.C-5048(A).The SPHERE and SINFONI images are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/624/A4">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/624/A4</A> [less ▲]

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See detailHint of curvature in the orbital motion of the exoplanet 51 Eridani b using 3 yr of VLT/SPHERE monitoring
Maire, Anne-Lise ULiege; Rodet, L.; Cantalloube, F. et al

in Astronomy and Astrophysics (2019), 624

Context. The 51 Eridani system harbors a complex architecture with its primary star forming a hierarchical system with the binary GJ 3305AB at a projected separation of 2000 au, a giant planet orbiting ... [more ▼]

Context. The 51 Eridani system harbors a complex architecture with its primary star forming a hierarchical system with the binary GJ 3305AB at a projected separation of 2000 au, a giant planet orbiting the primary star at 13 au, and a low-mass debris disk around the primary star with possible cold and warm components inferred from the spectral energy distribution. <BR /> Aims: We aim to better constrain the orbital parameters of the known giant planet. <BR /> Methods: We monitored the system over three years from 2015 to 2018 with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument at the Very Large Telescope (VLT). <BR /> Results: We measure an orbital motion for the planet of 130 mas with a slightly decreasing separation ( 10 mas) and find a hint of curvature. This potential curvature is further supported at 3σ significance when including literature Gemini Planet Imager (GPI) astrometry corrected for calibration systematics. Fits of the SPHERE and GPI data using three complementary approaches provide broadly similar results. The data suggest an orbital period of 32[SUB]-9[/SUB][SUP]+17[/SUP] yr (i.e., 12[SUB]-2[/SUB][SUP]+4[/SUP] au in semi-major axis), an inclination of 133[SUB]-7[/SUB][SUP]+14[/SUP] deg, an eccentricity of 0.45[SUB]-0.15[/SUB][SUP]+0.10[/SUP], and an argument of periastron passage of 87[SUB]-30[/SUB][SUP]+34[/SUP] deg [mod 180°]. The time at periastron passage and the longitude of node exhibit bimodal distributions because we do not yet detect whether the planet is accelerating or decelerating along its orbit. Given the inclinations of the orbit and of the stellar rotation axis (134-144°), we infer alignment or misalignment within 18° for the star-planet spin- orbit. Further astrometric monitoring in the next 3-4 yr is required to confirm at a higher significance the curvature in the motion of the planet, determine if the planet is accelerating or decelerating on its orbit, and further constrain its orbital parameters and the star-planet spin-orbit. <P />The fitted orbits and the histogram distributions of the orbital parameters are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/624/A118">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/624/A118</A>Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 095.C-0298, 096.C-0241, 198.C-0209, and 1100.C-0481. [less ▲]

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See detailFirst direct detection of an exoplanet by optical interferometry. Astrometry and K-band spectroscopy of HR 8799 e
Gravity Collaboration; Lacour, S.; Nowak, M. et al

in Astronomy and Astrophysics (2019), 623

<BR /> Aims: To date, infrared interferometry at best achieved contrast ratios of a few times 10[SUP]-4[/SUP] on bright targets. GRAVITY, with its dual-field mode, is now capable of high contrast ... [more ▼]

<BR /> Aims: To date, infrared interferometry at best achieved contrast ratios of a few times 10[SUP]-4[/SUP] on bright targets. GRAVITY, with its dual-field mode, is now capable of high contrast observations, enabling the direct observation of exoplanets. We demonstrate the technique on HR 8799, a young planetary system composed of four known giant exoplanets. <BR /> Methods: We used the GRAVITY fringe tracker to lock the fringes on the central star, and integrated off-axis on the HR 8799 e planet situated at 390 mas from the star. Data reduction included post-processing to remove the flux leaking from the central star and to extract the coherent flux of the planet. The inferred K band spectrum of the planet has a spectral resolution of 500. We also derive the astrometric position of the planet relative to the star with a precision on the order of 100 μas. <BR /> Results: The GRAVITY astrometric measurement disfavors perfectly coplanar stable orbital solutions. A small adjustment of a few degrees to the orbital inclination of HR 8799 e can resolve the tension, implying that the orbits are close to, but not strictly coplanar. The spectrum, with a signal-to-noise ratio of ≈5 per spectral channel, is compatible with a late-type L brown dwarf. Using Exo-REM synthetic spectra, we derive a temperature of 1150 ± 50 K and a surface gravity of 10[SUP]4.3 ± 0.3[/SUP] cm s[SUP]2[/SUP]. This corresponds to a radius of 1.17[SUB]-0.11[/SUB][SUP]+0.13[/SUP] R[SUB]Jup[/SUB] and a mass of 10[SUB]-4[/SUB][SUP]+7[/SUP] M[SUB]Jup[/SUB], which is an independent confirmation of mass estimates from evolutionary models. Our results demonstrate the power of interferometry for the direct detection and spectroscopic study of exoplanets at close angular separations from their stars. <P />The reduced spectrum is available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/623/L11">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/623/L11</A>.Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, ID 60.A-9102(G). [less ▲]

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See detailA search for accreting young companions embedded in circumstellar disks. High-contrast Hα imaging with VLT/SPHERE
Cugno, G.; Quanz, S. P.; Hunziker, S. et al

in Astronomy and Astrophysics (2019), 622

Context. In recent years, our understanding of giant planet formation progressed substantially. There have even been detections of a few young protoplanet candidates still embedded in the circumstellar ... [more ▼]

Context. In recent years, our understanding of giant planet formation progressed substantially. There have even been detections of a few young protoplanet candidates still embedded in the circumstellar disks of their host stars. The exact physics that describes the accretion of material from the circumstellar disk onto the suspected circumplanetary disk and eventually onto the young, forming planet is still an open question. <BR /> Aims: We seek to detect and quantify observables related to accretion processes occurring locally in circumstellar disks, which could be attributed to young forming planets. We focus on objects known to host protoplanet candidates and/or disk structures thought to be the result of interactions with planets. <BR /> Methods: We analyzed observations of six young stars (age 3.5-10 Myr) and their surrounding environments with the SPHERE/ZIMPOL instrument on the Very Large Telescope (VLT) in the Hα filter (656 nm) and a nearby continuum filter (644.9 nm). We applied several point spread function (PSF) subtraction techniques to reach the highest possible contrast near the primary star, specifically investigating regions where forming companions were claimed or have been suggested based on observed disk morphology. <BR /> Results: We redetect the known accreting M-star companion HD142527 B with the highest published signal to noise to date in both Hα and the continuum. We derive new astrometry (r=62.8[SUB]-2.7[/SUB][SUP]+2.1[/SUP] mas and PA=(98.7±1.8)°) and photometry (∆N_Ha = 6.3[SUB]-0.3[/SUB][SUP]+0.2[/SUP] mag, ∆B_Ha = 6.7 ± 0.2 mag and ∆Cnt_Ha = 7.3[SUB]-0.2[/SUB][SUP]+0.3[/SUP] mag) for the companion in agreement with previous studies, and estimate its mass accretion rate (Ṁ ≈ 1-2 × 10[SUP]-10[/SUP] M[SUB]☉[/SUB]yr[SUP]-1[/SUP]). A faint point-like source around HD135344 B (SAO206462) is also investigated, but a second deeper observation is required to reveal its nature. No other companions are detected. In the framework of our assumptions we estimate detection limits at the locations of companion candidates around HD100546, HD169142, and MWC 758 and calculate that processes involving Hα fluxes larger than 8 × 10[SUP]-14[/SUP]-10[SUP]-15[/SUP] erg s[SUP]-1[/SUP] cm[SUP]-2[/SUP] (Ṁ > 10[SUP]-10[/SUP]-10[SUP]-12[/SUP] M[SUB]☉[/SUB]yr[SUP]-1[/SUP]) can be excluded. Furthermore, flux upper limits of 10[SUP]-14[/SUP]-10[SUP]-15[/SUP] erg s[SUP]-1[/SUP] cm[SUP]-2[/SUP] (Ṁ < 10[SUP]-11[/SUP]-10[SUP]-12[/SUP] M[SUB]☉[/SUB]yr[SUP]-1[/SUP]) are estimated within the gaps identified in the disks surrounding HD135344 B and TW Hya. The derived luminosity limits exclude Hα signatures at levels similar to those previously detected for the accreting planet candidate LkCa15 b. <P />Based on observations collected at the Paranal Observatory, ESO (Chile). Program ID: 096.C-0248(B), 096.C-0267(A),096.C-0267(B), 095.C-0273(A), 095.C-0298(A).The reduced images (FITS files) are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/622/A156">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/622/A156</A> [less ▲]

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