332 research outputs found
SPHERE: a `Planet Finder' Instrument for the VLT
No full textSPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) is a second generation instrument for the VLT optimized for the very high-contrast imaging around bright stars [J.-L. Beuzit, M. Feldt, K. Dohlen et al. in Messenger 125, 29 (2006)]. The primary goal is the detection and characterization of new giant planets around a variety of nearby stars. Together with the observation of early planetary systems and disks, and in association with the results of other planet search techniques, SPHERE will be a primary contributor to get a complete picture of the variety of planetary systems and to better understand their mechanisms of formation and evolution. Such results will be obtained before even more ambitious projects for the direct imaging of planets either from the ground with ELTs or from space
Discovery of concentric broken rings at sub-arcsec separations in the HD 141569A gas-rich, debris disk with VLT/SPHERE
No full textObservations with SPHERE of HD141569A revealed a series of concentric ringlets located at 116-46AU and matching the formerly detected extended emission in the mid-IR and visible, although finer details are detected here. The brightest ring at 46AU has sharp edges and presents an unusual strong north/south asymmetry. Such structures may result from planet sheperding or gas/dust interactions.A. Boccaletti, E. Pantin, J-C. Augereau, A-M. Lagrange, R. Galicher, A-L. Maire, J. Mazoyer, J. Milli, G. Rousset, R. Gratton, M. Bonnefoy, W. Brandner, E. Buenzli, M. Langlois, J. Lannier, D. Mesa, S. Peretti, G. Salter, E. Sissa, G. Chauvin, S. Desidera, M. Feldt, A. Vigan, E. Di Folco, A. Dutrey, J. Pércaud, P. Baudoz, M. Benisty, J. De Boer, A. Garufi, J. H. Girard, F. Menard, J. Olofsson, S. P. Quanz, D. Mouillet, V. Christiaens, 17, S. Casassus, J.-L. Beuzit, P. Blanchard, M. Carle, T. Fusco, E. Giro, N. Hubin, D. Maurel, O. Moeller-Nilsson, A. Sevin, L. Webe
Structures in the AU Mic disk are still moving fast …
No full textObservations of AU Mic in 2014 with SPHERE, once combined with former HST data, revealed a series of five arch-like structures of which localization and speed are at odd with keplerian motions. Rather, a complex star/disk interaction is considered. We will present new results from a follow up program in 2015 (intensity and polarimetry), which confirms fast motion of individual structures.C. Thalmann, A.M. Lagrange, M. Janson, J.C. Augereau, G. Schneider, J. Milli, C. Grady, J. Debes, M. Langlois, D. Mouillet, T. Henning, C. Dominik, A.L. Maire, J.L. Beuzit, J. Carson, K. Dohlen, M. Feldt, T. Fusco, C. Ginski, J.H. Girard,
D. Hines, M. Kasper, D. Mawet, F. Ménard, M. Meyer, C. Moutou, J. Olofsson,
T. Rodigas, J.F. Sauvage, J. Schlieder, H.M. Schmid, M. Turatto, S. Udry,
F. Vakili, A. Vigan, Z. Wahhaj, J. Wisniewski
SPHERE-team + US-team Collaboratio
Coronagraphic near-IR photometry of AB Doradus C
No full textInternational audienceContext: Observations of low-mass companions for which the dynamical masses are well constrained help to improve the calibration of evolutionary models. Such observations thereby provide more confidence in the estimation of the mass of a companion using the photometric methods expected for the next generation of planet finder instruments. Aims: The commissioning of a new coronagraph at the Very Large Telescope (VLT) was the occasion to test the performance of this technique on the well-known object AB Dor A and its 0.09 M_ȯ companion AB Dor C. The purpose of this paper is to refine the photometric analysis on this object and to provide an accurate photometric error budget. Methods: In addition to coronagraphy, we calibrated the residual stellar halo with a reference star. We used standard techniques for photometric extraction. Results: The companion AB Dor C is easily detected at 0.185'' from the primary star, and its magnitudes in H and Ks are in agreement with an M 5.5 object, as already known from spectroscopic observations. However, these new measurements make the earlier J-band photometry less reliable. Finally, the comparison with evolutionary models supports an age of (75 ± 25) Myr, contrary to previous analyses. These observations demonstrate that coronagraphic observations can be more efficient than direct imaging, not only to improve contrast, but also to provide a better photometric estimation as long as a good calibration of the stellar halo is achieved
The first wide ultracool binary dwarf in the field: DENIS-J055146.0-443412.2 (M8.5 + L0)
No full textInternational audienceWe present observations of a new very low mass field binary, discovered during an infrared imaging survey of 250 DENIS L and very late-M dwarfs. DENIS-J055146.0-443412.2 is an M8.5 + L0 pair, with a physical separation of over 200 AU. This makes it the widest very low mass binary known in the field, by an order of magnitude. Such a system is fragile, and it would not have survived a close encounter with a third body. Its existence demonstrate that some very low mass stars/brown dwarfs form without ejection from a multiple system, or any other strong dynamical interaction
Le parcours de Pierre-Jakez Hélias vu par l'historien de l'éducation ou La mythologie de l'école républicaine
No full textColloque inaugural du Pôle universitaire Pierre-Jakez Hélias organisé et publié avec le soutien du Conseil Général du Finistère et de la Ville de Quimper. Édité dans la revue KREIZ, n° 15. Resp. de la publication D. Guillou-Beuzit, J.-L. Le Cam, mise en page Cl. Roy, cartographie G. CouixBased on the autobiographical passages of the work of P.-J. Hélias and archives of his secondary school in Quimper (France, Brittany), this text presents the educational travel of the Breton writer as emblematic of the great social and cultural change the most dynamic elements of rural society experienced, through the school of the Republic, in the first half of the twentieth century.Sur la base des passages autobiographiques de l'œuvre de P.-J. Hélias et des archives du Lycée de Quimper (France, Finistère), ce texte présente le parcours scolaire de l'écrivain breton comme emblématique de la grande mutation culturelle et sociale qu'ont vécue, grâce à l'école de la République, les éléments les plus dynamiques de la société rurale dans la première moitié du XXe siècle
The puzzling Luminous Blue Variable-like object HD 5980 in the Small Magellanic Cloud.
No full textpeer reviewedWe have observed the exceptional SMC star HD 5980 during several runs from 1989 to 1995 at ESO La Silla. CASPEC at the 3.6m telescope and EMMI in echelle and long slit modes at NTT were used for spectroscopy. Sub-arcsecond images were obtained using SUSI at NTT and also an adaptive optics system at the 3.6m telescope. In all our spectra taken before 1994 September HD 5980 shows a spectral type of WN6. The 1994 September spectra were taken shortly after the maximum of the visual light-curve of the LBV-like phenomenon (Bateson & Jones, 1993PVSS...19...50B) and about one month before the observations of Barba et al. (1995ApJ...446L..23B). Near maximum visual brightness, HD 5980 displays a WN11-like spectrum with the HeI lines and the Balmer lines Hdelta and Hgamma showing well-developed PCyg profiles. The sub-arcsecond images (0.17" FWHM), through the near infrared bands J, H, and K, obtained in 1993 and 1996, show no stellar components down to 6.7 mag fainter than HD 5980 in K at a separation of 1.0" and the 3sigma level. For a separation of 0.3" this upper bound is 4.1mag fainter than HD 5980. The observed behavior of this object raises serious problems for our comprehension of the LBV phenomenon in the conventional scenarios of massive star evolution. The present observations cover a crucial period in the evolution of HD 5980 and will therefore be helpful for better understanding this peculiar object especially during its outburst as well as the evolution of W-R stars in general
The young, tight, and low-mass binary TWA22AB: a new calibrator for evolutionary models? Orbit, spectral types, and temperature
No full textContext. Tight binaries discovered in young, nearby associations are ideal targets for providing dynamical mass measurements to test the physics of evolutionary models at young ages and very low masses. Aims. We report the binarity of TWA22 for the first time. We aim at monitoring the orbit of this young and tight system to determine its total dynamical mass using an accurate distance determination. We also intend to characterize the physical properties (luminosity, effective temperature, and surface gravity) of each component based on near-infrared photometric and spectroscopic observations. Methods. We used the adaptive-optics assisted imager NACO to resolve the components, to monitor the complete orbit and to obtain the relative near-infrared photometry of TWA22 AB. The adaptive-optics assisted integral field spectrometer SINFONI was also used to obtain medium-resolution (R(lambda) = 1500-2000) spectra in JHK bands. Comparison with empirical and synthetic librairies were necessary for deriving the spectral type, the effective temperature, and the surface gravity for each component of the system. Results. Based on an accurate trigonometric distance (17.5 +/- 0.2 pc) determination, we infer a total dynamical mass of 220 +/- 21 M(Jup) for the system. From the complete set of spectra, we find an effective temperature T(eff) = 2900(-200)(+200) K for TWA22A and T(eff) = 2900(-100)(+200) for TWA22 B and surface gravities between 4.0 and 5.5 dex. From our photometry and an M6 +/- 1 spectral type for both components, we find luminosities of log(L/L(circle dot)) = -2.11 +/- 0.13 dex and log(L/L(circle dot)) = -2.30 +/- 0.16 dex for TWA22 A and B, respectively. By comparing these parameters with evolutionary models, we question the age and the multiplicity of this system. We also discuss a possible underestimation of the mass predicted by evolutionary models for young stars close to the substellar boundary.ANR - Agence National de la Recherche(CNRS/INSU) Programmes Nationaux de Plantologie et de Physique Stellaire (PNP & PNPS), in Franc
Direct characterization of young giant exoplanets at high spectral resolution by coupling SPHERE and CRIRES+
No full textThis is the final version. Available on open access from EDP Sciences via the DOI in this recordStudies of atmospheres of directly imaged extrasolar planets with high-resolution spectrographs have shown that their characterization
is predominantly limited by noise on the stellar halo at the location of the studied exoplanet. An instrumental combination of highcontrast imaging and high spectral resolution that suppresses this noise and resolves the spectral lines can therefore yield higher quality
spectra. We study the performance of the proposed HiRISE fiber coupling between the direct imager SPHERE and the spectrograph
CRIRES+ at the Very Large Telescope for spectral characterization of directly imaged planets. Using end-to-end simulations of
HiRISE we determine the signal-to-noise ratio (S/N) of the detection of molecular species for known extrasolar planets in H and K
bands, and compare them to CRIRES+. We investigate the ultimate detection limits of HiRISE as a function of stellar magnitude, and
we quantify the impact of different coronagraphs and of the system transmission. We find that HiRISE largely outperforms CRIRES+
for companions around bright hosts like β Pictoris or 51 Eridani. For an H = 3.5 host, we observe a gain of a factor of up to 36 in
observing time with HiRISE to reach the same S/N on a companion at 200 mas. More generally, HiRISE provides better performance
than CRIRES+ in two-hour integration times between 50–400 mas for hosts with H < 8.5 and between 50–800 mas for H < 7. For
fainter hosts like PDS 70 and HIP 65426, no significant improvements are observed. We find that using no coronagraph yields the
best S/N when characterizing known exoplanets due to higher transmission and fiber-based starlight suppression. We demonstrate
that the overall transmission of the system is in fact the main driver of performance. Finally, we show that HiRISE outperforms the
best detection limits of SPHERE for bright stars, opening major possibilities for the characterization of future planetary companions
detected by other techniquesEuropean Union Horizon 202
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