Examinando por Autor "Dominik, C."

Mostrando 1 - 3 de 3
  • Miniatura
    Ítem
    Disks around T Tauri Stars with SPHERE (DARTTS-S). I. SPHERE/IRDIS Polarimetric Imaging of Eight Prominent T Tauri Disks
    (Institute of Physics Publishing, 2018-08) Avenhaus, H.; Quanz, S.P.; Garufi, A.; Perez, S.; Casassus, S.; Pinte, C.; Bertrang, G.H.-M.; Caceres, C.; Benisty, M.; Dominik, C.
    We present the first part of our Disks ARound T Tauri Stars with SPHERE (DARTTS-S) survey: observations of eight T Tauri stars that were selected based on their strong (sub)millimeter excesses using SPHERE/IRDIS polarimetric differential imaging in the J and H bands. All observations successfully detect the disks, which appear vastly different in size, from ≈80 au in scattered light to >400 au, and display total polarized disk fluxes between 0.06% and 0.89% of the stellar flux. For five of these disks, we are able to determine the three-dimensional structure and the flaring of the disk surface, which appears to be relatively consistent across the different disks, with flaring exponents α between ≈1.1 and ≈1.6. We also confirm literature results with regard to the inclination and position angle of several of our disks and are able to determine which side is the near side of the disk in most cases. While there is a clear trend of disk mass with stellar ages (≈1 to >10 Myr), no correlations of disk structures with age were found. There are also no correlations with either stellar mass or submillimeter flux. We do not detect significant differences between the J and H bands. However, we note that while a high fraction (7/8) of the disks in our sample show ring-shaped substructures, none of them display spirals, in contrast to the disks around more massive Herbig Ae/Be stars, where spiral features are common. © 2018. The American Astronomical Society. All rights reserved.
  • Miniatura
    Ítem
    VLTI-MATISSE chromatic aperture-synthesis imaging of η Carinae's stellar wind across the Br α line: Periastron passage observations in February 2020
    (Astronomy and Astrophysics, 2021-08) Weigelt, G.; Hofmann, K.-H.; Schertl, D.; Lopez, B.; Petrov, R.G.; Lagarde, S.; Berio, Ph.; Jaffe, W.; Henning, Th.; Millour, F.; Meilland, A.; Allouche, F.; Robbe-Dubois, S.; Matter, A.; Cruzalèbes, p.; Hillier, D.J.; Russell, C.M.P.; Madura, T.; Gull, T.R.; Corcoran, M.F.; Damineli, A.; Moffat, A.F.J.; Morris, P.W.; Richardson, N.D.; Paladini, C.; Schöller, M.; Mérand, A.; Glindemann, A.; Beckmann, U.; Heininger, M.; Bettonvil, F.; Bettonvil, F.; Zins, G.; Woillez, J.; Bristow, P.; Sanchez-Bermudez, J.; Ohnaka, K.; Kraus, S.; Mehner, A.; Wittkowski, M.; Hummel, C.A.; Stee, P.; Vakili, F.; Hartman, H.; Navarete, F.; Hamaguchi, K.; Espinoza-Galeas, D.A.; Stevens, I.R.; Van Boekel, R.; Wolf, S.; Hogerheijde, M.R.; Dominik, C.; Augereau, J.-C.; Pantin, E.; Waters, L.B.F.M.; Meisenheimer, K.; Varga, J.; Klarmann, L.; Gámez Rosas, V.; Burtscher, L.; Leftley, J.; Isbell, J.W.; Hocdé, V.; Yoffe, G.; Kokoulina, E.; Hron, J.; Groh, J.; Kreplin, A.; Rivinius, Th.; De Wit, W.-J.; Danchi, W.-C.; De Souza A., Domiciano; Drevon, J.; Labadie, L.; Connot, C.; Nußbaum, E.; Lehmitz, M.; Antonelli, P.; Graser, U.; Leinert, C.
    Context. Eta Carinae is a highly eccentric, massive binary system (semimajor axis ~15.5 au) with powerful stellar winds and a phase-dependent wind-wind collision (WWC) zone. The primary star, η Car A, is a luminous blue variable (LBV); the secondary, η Car B, is a Wolf-Rayet or O star with a faster but less dense wind. Aperture-synthesis imaging allows us to study the mass loss from the enigmatic LBV η Car. Understanding LBVs is a crucial step toward improving our knowledge about massive stars and their evolution. Aims. Our aim is to study the intensity distribution and kinematics of η Car's WWC zone. Methods. Using the VLTI-MATISSE mid-infrared interferometry instrument, we perform Brα imaging of η Car's distorted wind. Results. We present the first VLTI-MATISSE aperture-synthesis images of η Car A's stellar windin several spectral channels distributed across the Brα 4.052 μm line (spectral resolving power R ~ 960). Our observations were performed close to periastron passage in February 2020 (orbital phase ~ 14.0022). The reconstructed iso-velocity images show the dependence of the primary stellar wind on wavelength or line-of-sight (LOS) velocity with a spatial resolution of 6 mas (~14 au). The radius of the faintest outer wind regions is ~26 mas (~60 au). At several negative LOS velocities, the primary stellar wind is less extended to the northwest than in other directions. This asymmetry is most likely caused by the WWC. Therefore, we see both the velocity field of the undisturbed primary wind and the WWC cavity. In continuum spectral channels, the primary star wind is more compact than in line channels. A fit of the observed continuum visibilities with the visibilities of a stellar wind CMFGEN model (CMFGEN is an atmosphere code developed to model the spectra of a variety of objects) provides a full width at half maximum fit diameter of the primary stellar wind of 2.84 ± 0.06 mas (6.54 ± 0.14 au). We comparethe derived intensity distributions with the CMFGEN stellar wind model and hydrodynamic WWC models.
  • No hay miniatura disponible
    Ítem
    VLTI-MATISSE L - And N -band aperture-synthesis imaging of the unclassified B[e] star FS Canis Majoris
    (EDP Sciences, 2022-02-01) Hofmann, K.-H.; Bensberg, A.; Schertl, D.; Weigelt, G.; Wolf, S.; Meilland, A.; Millour, F.; Waters, L.B.F.M.; Kraus, S.; Ohnaka, K.; Lopez, B.; Petrov, R.G.; Lagarde, S.; Berio, Ph.; Allouche, F.; Robbe-Dubois, S.; Jaffe, W.; Henning, Th.; Paladini, C.; Schöller, M.; Mérand, A.; Glindemann, A.; Beckmann, U.; Heininger, M.; Bettonvil, F.; Zins, G.; Woillez, J.; Bristow, P.; Stee, P.; Vakili, F.; Van Boekel, R.; Hogerheijde, M.R.; Dominik, C.; Augereau, J.-C.; Matter, A.; Hron, J.; Pantin, E.; Rivinius, Th.; De Wit, W.-J.; Varga, J.; Klarmann, L.; Meisenheimer, K.; Gámez Rosas, V.; Burtscher, L.; Leftley, J.; Isbell, J.W.; Yoffe, G.; Kokoulina, E.; Danchi, W.C.; Cruzalèbes, P.; Domiciano De Souza, A.; Drevon, J.; Hocdé, V.; Kreplin, A.; Labadie, L.; Connot, C.; Nußbaum, E.; Lehmitz, M.; Antonelli, P.; Graser, U.; Leinert, C.
    Context. FS Canis Majoris (FS CMa, HD 45677) is an unclassified B[e] star surrounded by an inclined dust disk. The evolutionary stage of FS CMa is still debated. Perpendicular to the circumstellar disk, a bipolar outflow was detected. Infrared aperture-synthesis imaging provides us with a unique opportunity to study the disk structure. Aims. Our aim is to study the intensity distribution of the disk of FS CMa in the mid-infrared L and N bands. Methods. We performed aperture-synthesis imaging of FS CMa with the MATISSE instrument (Multi AperTure mid-Infrared SpectroScopic Experiment) in the low spectral resolution mode to obtain images in the L and N bands. We computed radiative transfer models that reproduce the L- and N-band intensity distributions of the resolved disks. Results. We present L- and N-band aperture-synthesis images of FS CMa reconstructed in the wavelength bands of 3.4-3.8 and 8.6-9.0 μm. In the L-band image, the inner rim region of an inclined circumstellar disk and the central object can be seen with a spatial resolution of 2.7 milliarcsec (mas). An inner disk cavity with an angular diameter of ~6 × 12 mas is resolved. The L-band disk consists of a bright northwestern (NW) disk region and a much fainter southeastern (SE) region. The images suggest that we are looking at the bright inner wall of the NW disk rim, which is on the far side of the disk. In the N band, only the bright NW disk region is seen. In addition to deriving the inclination and the inner disk radius, fitting the reconstructed brightness distributions via radiative transfer modelling allows one to constrain the innermost disk structure, in particular the shape of theinner disk rim. © K.-H. Hofmann et al. 2022.