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See detailUnveiling the β Pictoris system, coupling high contrast imaging, interferometric, and radial velocity data
Lagrange, A. M.; Rubini, P.; Nowak, M. et al

in Astronomy and Astrophysics (2020), 642

Context. The nearby and young β Pictoris system hosts a well resolved disk, a directly imaged massive giant planet orbiting at ≃9 au, as well as an inner planet orbiting at ≃2.7 au, which was recently ... [more ▼]

Context. The nearby and young β Pictoris system hosts a well resolved disk, a directly imaged massive giant planet orbiting at ≃9 au, as well as an inner planet orbiting at ≃2.7 au, which was recently detected through radial velocity (RV). As such, it offers several unique opportunities for detailed studies of planetary system formation and early evolution. <BR /> Aims: We aim to further constrain the orbital and physical properties of β Pictoris b and c using a combination of high contrast imaging, long base-line interferometry, and RV data. We also predict the closest approaches or the transit times of both planets, and we constrain the presence of additional planets in the system. <BR /> Methods: We obtained six additional epochs of SPHERE data, six additional epochs of GRAVITY data, and five additional epochs of RV data. We combined these various types of data in a single Markov-chain Monte Carlo analysis to constrain the orbital parameters and masses of the two planets simultaneously. The analysis takes into account the gravitational influence of both planets on the star and hence their relative astrometry. Secondly, we used the RV and high contrast imaging data to derive the probabilities of presence of additional planets throughout the disk, and we tested the impact of absolute astrometry. <BR /> Results: The orbital properties of both planets are constrained with a semi-major axis of 9.8 ± 0.4 au and 2.7 ± 0.02 au for b and c, respectively, and eccentricities of 0.09 ± 0.1 and 0.27 ± 0.07, assuming the HIPPARCOS distance. We note that despite these low fitting error bars, the eccentricity of β Pictoris c might still be over-estimated. If no prior is provided on the mass of β Pictoris b, we obtain a very low value that is inconsistent with what is derived from brightness-mass models. When we set an evolutionary model motivated prior to the mass of β Pictoris b, we find a solution in the 10-11 M[SUB]Jup[/SUB] range. Conversely, β Pictoris c's mass is well constrained, at 7.8 ± 0.4 M[SUB]Jup[/SUB], assuming both planets are on coplanar orbits. These values depend on the assumptions on the distance of the β Pictoris system. The absolute astrometry HIPPARCOS-Gaia data are consistent with the solutions presented here at the 2σ level, but these solutions are fully driven by the relative astrometry plus RV data. Finally, we derive unprecedented limits on the presence of additional planets in the disk. We can now exclude the presence of planets that are more massive than about 2.5 M[SUB]Jup[/SUB] closer than 3 au, and more massive than 3.5 M[SUB]Jup[/SUB] between 3 and 7.5 au. Beyond 7.5 au, we exclude the presence of planets that are more massive than 1-2 M[SUB]Jup[/SUB]. <BR /> Conclusions: Combining relative astrometry and RVs allows one to precisely constrain the orbital parameters of both planets and to give lower limits to potential additional planets throughout the disk. The mass of β Pictoris c is also well constrained, while additional RV data with appropriate observing strategies are required to properly constrain the mass of β Pictoris b. [less ▲]

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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 detailRetrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e
Mollière, P.; Stolker, T.; Lacour, S. et al

in Astronomy and Astrophysics (2020), 640

Context. Clouds are ubiquitous in exoplanet atmospheres and they represent a challenge for the model interpretation of their spectra. When generating a large number of model spectra, complex cloud models ... [more ▼]

Context. Clouds are ubiquitous in exoplanet atmospheres and they represent a challenge for the model interpretation of their spectra. When generating a large number of model spectra, complex cloud models often prove too costly numerically, whereas more efficient models may be overly simplified. <BR /> Aims: We aim to constrain the atmospheric properties of the directly imaged planet HR 8799e with a free retrieval approach. <BR /> Methods: We used our radiative transfer code petitRADTRANS for generating the spectra, which we coupled to the PyMultiNest tool. We added the effect of multiple scattering which is important for treating clouds. Two cloud model parameterizations are tested: the first incorporates the mixing and settling of condensates, the second simply parameterizes the functional form of the opacity. <BR /> Results: In mock retrievals, using an inadequate cloud model may result in atmospheres that are more isothermal and less cloudy than the input. Applying our framework on observations of HR 8799e made with the GPI, SPHERE, and GRAVITY, we find a cloudy atmosphere governed by disequilibrium chemistry, confirming previous analyses. We retrieve that C/O = 0.60[SUB]-0.08[/SUB][SUP]+0.07[/SUP]. Other models have not yet produced a well constrained C/O value for this planet. The retrieved C/O values of both cloud models are consistent, while leading to different atmospheric structures: either cloudy or more isothermal and less cloudy. Fitting the observations with the self-consistent Exo-REM model leads to comparable results, without constraining C/O. <BR /> Conclusions: With data from the most sensitive instruments, retrieval analyses of directly imaged planets are possible. The inferred C/O ratio of HR 8799e is independent of the cloud model and thus appears to be a robust. This C/O is consistent with stellar, which could indicate that the HR 8799e formed outside the CO[SUB]2[/SUB] or CO iceline. As it is the innermost planet of the system, this constraint could apply to all HR 8799 planets. [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 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 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 detailThe GJ 504 system revisited. Combining interferometric, radial velocity, and high contrast imaging data
Bonnefoy, M.; Perraut, K.; Lagrange, A.-M. et al

in Astronomy and Astrophysics (2018), 618

Context. The G-type star GJ504A is known to host a 3-35 M[SUB]Jup[/SUB] companion whose temperature, mass, and projected separation all contribute to making it a test case for planet formation theories ... [more ▼]

Context. The G-type star GJ504A is known to host a 3-35 M[SUB]Jup[/SUB] companion whose temperature, mass, and projected separation all contribute to making it a test case for planet formation theories and atmospheric models of giant planets and light brown dwarfs. <BR /> Aims: We aim at revisiting the system age, architecture, and companion physical and chemical properties using new complementary interferometric, radial-velocity, and high-contrast imaging data. <BR /> Methods: We used the CHARA interferometer to measure GJ504A's angular diameter and obtained an estimation of its radius in combinationwith the HIPPARCOS parallax. The radius was compared to evolutionary tracks to infer a new independent age range for the system. We collected dual imaging data with IRDIS on VLT/SPHERE to sample the near-infrared (1.02-2.25 μm) spectral energy distribution (SED) of the companion. The SED was compared to five independent grids of atmospheric models (petitCODE,Exo-REM, BT-SETTL, Morley et al., and ATMO) to infer the atmospheric parameters of GJ 504b and evaluate model-to-model systematic errors. In addition, we used a specific model grid exploring the effect of different C/O ratios. Contrast limits from 2011 to 2017 were combined with radial velocity data of the host star through the MESS2 tool to define upper limits on the mass of additional companions in the system from 0.01 to 100 au. We used an MCMC fitting tool to constrain the companion'sorbital parameters based on the measured astrometry, and dedicated formation models to investigate its origin. <BR /> Results: We report a radius of 1.35 ± 0.04 R[SUB]☉[/SUB] for GJ504A. The radius yields isochronal ages of 21 ± 2 Myr or 4.0 ± 1.8 Gyr for the system and line-of-sight stellar rotation axis inclination of 162.4[SUB]-4.3[/SUB][SUP]+3.8[/SUP] degrees or 186.6[SUB]-3.8[/SUB][SUP]+4.3[/SUP] degrees. We re-detect the companion in the Y2, Y3, J3, H2, and K1 dual-band images. The complete 1-4 μm SED shape of GJ504b is best reproduced by T8-T9.5 objects with intermediate ages (≤ 1.5Gyr), and/or unusual dusty atmospheres and/or super-solar metallicities. All atmospheric models yield T[SUB]eff[/SUB] = 550 ± 50 K for GJ504b and point toward a low surface gravity (3.5-4.0 dex). The accuracy on the metallicity value is limited by model-to-model systematics; it is not degenerate with the C/O ratio. We derive log L/L[SUB]☉[/SUB] = -6.15 ± 0.15 dex for the companion from the empirical analysis and spectral synthesis. The luminosity and T[SUB]eff[/SUB] yield masses of M = 1.3[SUB]-0.3[/SUB][SUP]+0.6[/SUP] M[SUB]Jup[/SUB] and M = 23[SUB]-9[/SUB][SUP]+10[/SUP] M[SUB]Jup[/SUB] for the young and old age ranges, respectively. The semi-major axis (sma) is above 27.8 au and the eccentricity is lower than 0.55. The posterior on GJ 504b's orbital inclination suggests a misalignment with the rotation axis of GJ 504A. We exclude additional objects (90% prob.) more massive than 2.5 and 30 M[SUB]Jup[/SUB] with semi-major axes in the range 0.01-80 au for the young and old isochronal ages, respectively. <BR /> Conclusions: The mass and semi-major axis of GJ 504b are marginally compatible with a formation by disk-instability if the system is 4 Gyr old. The companion is in the envelope of the population of planets synthesized with our core-accretion model. Additional deep imaging and spectroscopic data with SPHERE and JWST should help to confirm the possible spin-orbit misalignment and refine the estimates on the companion temperature, luminosity, and atmospheric composition. <P />Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programs 093.C-0500, 095.C-0298, 096.C-0241, and 198.C-0209, and on interferometric observations obtained with the VEGA instrument on the CHARA Array. [less ▲]

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See detailDiscovery of a planetary-mass companion within the gap of the transition disk around PDS 70
Keppler, M.; Benisty, M.; Müller, A. et al

in Astronomy and Astrophysics (2018), 617

Context. Young circumstellar disks are the birthplaces of planets. Their study is of prime interest to understand the physical and chemical conditions under which planet formation takes place. Only very ... [more ▼]

Context. Young circumstellar disks are the birthplaces of planets. Their study is of prime interest to understand the physical and chemical conditions under which planet formation takes place. Only very few detections of planet candidates within these disks exist, and most of them are currently suspected to be disk features. <BR /> Aims: In this context, the transition disk around the young star PDS 70 is of particular interest, due to its large gap identified in previous observations, indicative of ongoing planet formation. We aim to search for the presence of an embedded young planet and search for disk structures that may be the result of disk-planet interactions and other evolutionary processes. <BR /> Methods: We analyse new and archival near-infrared images of the transition disk PDS 70 obtained with the VLT/SPHERE, VLT/NaCo, and Gemini/NICI instruments in polarimetric differential imaging and angular differential imaging modes. <BR /> Results: We detect a point source within the gap of the disk at about 195 mas ( 22 au) projected separation. The detection is confirmed at five different epochs, in three filter bands and using different instruments. The astrometry results in an object of bound nature, with high significance. The comparison of the measured magnitudes and colours to evolutionary tracks suggests that the detection is a companion of planetary mass. The luminosity of the detected object is consistent with that of an L-type dwarf, but its IR colours are redder, possibly indicating the presence of warm surrounding material. Further, we confirm the detection of a large gap of 54 au in size within the disk in our scattered light images, and detect a signal from an inner disk component. We find that its spatial extent is very likely smaller than 17 au in radius, and its position angle is consistent with that of the outer disk. The images of the outer disk show evidence of a complex azimuthal brightness distribution which is different at different wavelengths and may in part be explained by Rayleigh scattering from very small grains. <BR /> Conclusions: The detection of a young protoplanet within the gap of the transition disk around PDS 70 opens the door to a so far observationally unexplored parameter space of planetary formation and evolution. Future observations of this system at different wavelengths and continuing astrometry will allow us to test theoretical predictions regarding planet-disk interactions, planetary atmospheres, and evolutionary models. <P />Based on observations performed with ESO Telescopes at the Paranal Observatory under programmes 095.C-0298, 095.C-0404, 096.C-0333, 097.C-0206, 097.C-1001, and 099.C-0891.The reduced images and datacubes 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/617/A44">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/617/A44</A> [less ▲]

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See detailOrbital and atmospheric characterization of the planet within the gap of the PDS 70 transition disk
Müller, A.; Keppler, M.; Henning, Th et al

in Astronomy and Astrophysics (2018), 617

Context. The observation of planets in their formation stage is a crucial but very challenging step in understanding when, how, and where planets form. PDS 70 is a young pre-main sequence star surrounded ... [more ▼]

Context. The observation of planets in their formation stage is a crucial but very challenging step in understanding when, how, and where planets form. PDS 70 is a young pre-main sequence star surrounded by a transition disk, in the gap of which a planetary-mass companion has recently been discovered. This discovery represents the first robust direct detection of such a young planet, possibly still at the stage of formation. <BR /> Aims: We aim to characterize the orbital and atmospheric properties of PDS 70 b, which was first identified on May 2015 in the course of the SHINE survey with SPHERE, the extreme adaptive-optics instrument at the VLT. <BR /> Methods: We obtained new deep SPHERE/IRDIS imaging and SPHERE/IFS spectroscopic observations of PDS 70 b. The astrometric baseline now covers 6 yr, which allowed us to perform an orbital analysis. For the first time, we present spectrophotometry of the young planet which covers almost the entire near-infrared range (0.96-3.8 μm). We use different atmospheric models covering a large parameter space in temperature, log g, chemical composition, and cloud properties to characterize the properties of the atmosphere of PDS 70 b. <BR /> Results: PDS 70 b is most likely orbiting the star on a circular and disk coplanar orbit at 22 au inside the gap of the disk. We find a range of models that can describe the spectrophotometric data reasonably well in the temperature range 1000-1600 K and log g no larger than 3.5 dex. The planet radius covers a relatively large range between 1.4 and 3.7 R[SUB]J[/SUB] with the larger radii being higher than expected from planet evolution models for the age of the planet of 5.4 Myr. <BR /> Conclusions: This study provides a comprehensive data set on the orbital motion of PDS 70 b, indicating a circular orbit and a motion coplanar with the disk. The first detailed spectral energy distribution of PDS 70 b indicates a temperature typical of young giant planets. The detailed atmospheric analysis indicates that a circumplanetary disk may contribute to the total planetflux. <P />Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 095.C-0298, 097.C-0206, 097.C-1001, 1100.C-0481. [less ▲]

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See detailVizieR Online Data Catalog: Light curves of WASP-52 (Mancini+, 2017)
Mancini, L.; Southworth, J.; Raia, G. et al

Textual, factual or bibliographical database (2018)

Light curves of transit events of the extrasolar planet WASP-52b. One of the datasets was obtained using the Cassini 1.52m Telescope (Gunn r) at the Astronomical Observatory of Bologna in Loiano (Italy ... [more ▼]

Light curves of transit events of the extrasolar planet WASP-52b. One of the datasets was obtained using the Cassini 1.52m Telescope (Gunn r) at the Astronomical Observatory of Bologna in Loiano (Italy). Three of the datasets were obtained using the Zeiss 1.23m telescope (Cousins R and Cousins I) at the German-Spanish Astronomical Centre at Calar Alto (Spain). Four of the datasets were obtained using the MPG 2.2m telescope (Sloan g, Sloan r, Sloan i, Sloan z) at the ESO Observatory in La Silla (Chile). Four of the datasets were obtained using the 1.54m Danish Telescope at the ESO Observatory in La Silla (Chile). (2 data files). [less ▲]

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See detailDiscovery of a warm, dusty giant planet around HIP 65426
Chauvin, G.; Desidera, S.; Lagrange, A.-M. et al

in Astronomy and Astrophysics (2017), 605

<BR /> Aims: The SHINE program is a high-contrast near-infrared survey of 600 young, nearby stars aimed at searching for and characterizing new planetary systems using VLT/SPHERE's unprecedented high ... [more ▼]

<BR /> Aims: The SHINE program is a high-contrast near-infrared survey of 600 young, nearby stars aimed at searching for and characterizing new planetary systems using VLT/SPHERE's unprecedented high-contrast and high-angular-resolution imaging capabilities. It is also intended to place statistical constraints on the rate, mass and orbital distributions of the giant planet population at large orbits as a function of the stellar host mass and age to test planet-formation theories. <BR /> Methods: We used the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE to acquire high-contrast coronagraphic differential near-infrared images and spectra of the young A2 star HIP 65426. It is a member of the 17 Myr old Lower Centaurus-Crux association. <BR /> Results: At a separation of 830 mas (92 au projected) from the star, we detect a faint red companion. Multi-epoch observations confirm that it shares common proper motion with HIP 65426. Spectro-photometric measurements extracted with IFS and IRDIS between 0.95 and 2.2 μm indicate a warm, dusty atmosphere characteristic of young low-surface-gravity L5-L7 dwarfs. Hot-start evolutionary models predict a luminosity consistent with a 6-12 M[SUB]Jup[/SUB], T[SUB]eff[/SUB] = 1300-1600 K and R = 1.5 ± 0.1 R[SUB]Jup[/SUB] giant planet. Finally, the comparison with Exo-REM and PHOENIX BT-Settl synthetic atmosphere models gives consistent effective temperatures but with slightly higher surface gravity solutions of log (g) = 4.0-5.0 with smaller radii (1.0-1.3 R[SUB]Jup[/SUB]). <BR /> Conclusions: Given its physical and spectral properties, HIP 65426 b occupies a rather unique placement in terms of age, mass, and spectral-type among the currently known imaged planets. It represents a particularly interesting case to study the presence of clouds as a function of particle size, composition, and location in the atmosphere, to search for signatures of non-equilibrium chemistry, and finally to test the theory of planet formation and evolution. <P />Based on observations collected at La Silla and Paranal Observatory, ESO (Chile) Program ID: 097.C-0865 and 098.C-0209 (SPHERE).The planet spectrum is only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (<A href="http://130.79.128.5">http://130.79.128.5</A>) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/605/L9">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/605/L9</A> [less ▲]

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See detailSpectral and atmospheric characterization of 51 Eridani b using VLT/SPHERE
Samland, M.; Mollière, P.; Bonnefoy, M. et al

in Astronomy and Astrophysics (2017), 603

Context. 51 Eridani b is an exoplanet around a young (20 Myr) nearby (29.4 pc) F0-type star, which was recently discovered by direct imaging. It is one of the closest direct imaging planets in angular and ... [more ▼]

Context. 51 Eridani b is an exoplanet around a young (20 Myr) nearby (29.4 pc) F0-type star, which was recently discovered by direct imaging. It is one of the closest direct imaging planets in angular and physical separation ( 0.5'', 13 au) and is well suited for spectroscopic analysis using integral field spectrographs. <BR /> Aims: We aim to refine the atmospheric properties of the known giant planet and to constrain the architecture of the system further by searching for additional companions. <BR /> Methods: We used the extreme adaptive optics instrument SPHERE at the Very Large Telescope (VLT) to obtain simultaneous dual-band imaging with IRDIS and integral field spectra with IFS, extending the spectral coverage of the planet to the complete Y- to H-band range and providing additional photometry in the K12-bands (2.11, 2.25 μm). The object is compared to other known cool and peculiar dwarfs. The posterior probability distributions for parameters of cloudy and clear atmospheric models are explored using MCMC. We verified our methods by determining atmospheric parameters for the two benchmark brown dwarfs Gl 570D and HD 3651B. We used archival VLT-NACO (L') Sparse Aperture Masking data to probe the innermost region for additional companions. <BR /> Results: We present the first spectrophotometric measurements in the Y and K bands for the planet and revise its J-band flux to values 40% fainter than previous measurements. Cloudy models with uniform cloud coverage provide a good match to the data. We derive the temperature, radius, surface gravity, metallicity, and cloud sedimentation parameter f[SUB]sed[/SUB]. We find that the atmosphere is highly super-solar ([Fe/H] = 1.0 ± 0.1 dex), and the low f[SUB]sed[/SUB] = 1.26[SUP]+0.36[/SUP][SUB]-0.29[/SUB] value is indicative of a vertically extended, optically thick cloud cover with small sized particles. The model radius and surface gravity estimates suggest higher planetary masses of M[SUB]gravity[/SUB] = 9.1[SUP]+4.9[/SUP][SUB]-3.3[/SUB] M[SUB]J[/SUB]. The evolutionary model only provides a lower mass limit of > 2 M[SUB]J[/SUB] (for pure hot- start). The cold-start model cannot explain the luminosity of the planet. The SPHERE and NACO/SAM detection limits probe the 51 Eri system at solar system scales and exclude brown-dwarf companions more massive than 20 M[SUB]J[/SUB] beyond separations of 2.5 au and giant planets more massive than 2 M[SUB]J[/SUB] beyond 9 au. <P />Based on observations made with ESO Telescopes at the Paranal Observatory under program ID 095.C-0298, 096.C-0241 and 084.C-0739(A).Spectra, covariances, and petitCODE (fits files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/603/A57 [less ▲]

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See detailOrbital alignment and star-spot properties in the WASP-52 planetary system
Mancini, L.; Southworth, J.; Raia, G. et al

in Monthly Notices of the Royal Astronomical Society (2017), 465

We report 13 high-precision light curves of eight transits of the exoplanet WASP-52 b, obtained by using four medium-class telescopes, through different filters, and adopting the defocussing technique ... [more ▼]

We report 13 high-precision light curves of eight transits of the exoplanet WASP-52 b, obtained by using four medium-class telescopes, through different filters, and adopting the defocussing technique. One transit was recorded simultaneously from two different observatories and another one from the same site but with two different instruments, including a multiband camera. Anomalies were clearly detected in five light curves and modelled as star-spots occulted by the planet during the transit events. We fitted the clean light curves with the JKTEBOP code, and those with the anomalies with the PRISM+GEMC codes in order to simultaneously model the photometric parameters of the transits and the position, size and contrast of each star-spot. We used these new light curves and some from the literature to revise the physical properties of the WASP-52 system. Star-spots with similar characteristics were detected in four transits over a period of 43 d. In the hypothesis that we are dealing with the same star-spot, periodically occulted by the transiting planet, we estimated the projected orbital obliquity of WASP-52 b to be λ = 3.8° ± 8.4°. We also determined the true orbital obliquity, ψ = 20° ± 50°, which is, although very uncertain, the first measurement of ψ purely from star-spot crossings. We finally assembled an optical transmission spectrum of the planet and searched for variations of its radius as a function of wavelength. Our analysis suggests a flat transmission spectrum within the experimental uncertainties. [less ▲]

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