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Start Over Author "A. de Koter" Publisher oxford university press (oup)
22 results on '"A. de Koter"'

1. Images of Betelgeuse with VLTI/MATISSE across the Great Dimming

Author

Drevon, J, primary, Millour, F, additional, Cruzalèbes, P, additional, Paladini, C, additional, Scicluna, P, additional, Matter, A, additional, Chiavassa, A, additional, Montargès, M, additional, Cannon, E, additional, Allouche, F, additional, Hofmann, K-H, additional, Lagarde, S, additional, Lopez, B, additional, Meilland, A, additional, Petrov, R, additional, Robbe-Dubois, S, additional, Schertl, D, additional, Zins, G, additional, Ábrahám, P, additional, Berio, P, additional, Henning, Th, additional, Hron, J, additional, Isbell, J W, additional, Jaffe, W, additional, Labadie, L, additional, Varga, J, additional, Weigelt, G, additional, Woillez, J, additional, van Boekel, R, additional, Pantin, E, additional, Danchi, W C, additional, de Koter, A, additional, Rosas, V Gámez, additional, Hogerheijde, M R, additional, Leftley, J, additional, Stee, P, additional, and Waters, R, additional

Published
2023
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3. The effects of surface fossil magnetic fields on massive star evolution: IV. Grids of models at Solar, LMC, and SMC metallicities

Author

Keszthelyi, Z, primary, de Koter, A, additional, Götberg, Y, additional, Meynet, G, additional, Brands, S A, additional, Petit, V, additional, Carrington, M, additional, David-Uraz, A, additional, Geen, S T, additional, Georgy, C, additional, Hirschi, R, additional, Puls, J, additional, Ramalatswa, K J, additional, Shultz, M E, additional, and ud-Doula, A, additional

Published
2022
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5. Detailed evolutionary models of massive contact binaries – I. Model grids and synthetic populations for the Magellanic Clouds

Author

Menon, Athira, primary, Langer, Norbert, additional, de Mink, Selma E, additional, Justham, Stephen, additional, Sen, Koushik, additional, Szécsi, Dorottya, additional, de Koter, Alex, additional, Abdul-Masih, Michael, additional, Sana, Hugues, additional, Mahy, Laurent, additional, and Marchant, Pablo, additional

Published
2021
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9. The R136 star cluster dissected with Hubble Space Telescope/STIS – II. Physical properties of the most massive stars in R136

Author

Bestenlehner, Joachim M, primary, Crowther, Paul A, additional, Caballero-Nieves, Saida M, additional, Schneider, Fabian R N, additional, Simón-Díaz, Sergio, additional, Brands, Sarah A, additional, de Koter, Alex, additional, Gräfener, Götz, additional, Herrero, Artemio, additional, Langer, Norbert, additional, Lennon, Daniel J, additional, Maíz Apellániz, Jesus, additional, Puls, Joachim, additional, and Vink, Jorick S, additional

Published
2020
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11. Space astrometry of the very massive ∼150 M⊙ candidate runaway star VFTS682

Author

Renzo, M, primary, de Mink, S E, additional, Lennon, D J, additional, Platais, I, additional, van der Marel, R P, additional, Laplace, E, additional, Bestenlehner, J M, additional, Evans, C J, additional, Hénault-Brunet, V, additional, Justham, S, additional, de Koter, A, additional, Langer, N, additional, Najarro, F, additional, Schneider, F R N, additional, and Vink, J S, additional

Published
2018
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13. First Very Large Telescope/X-shooter spectroscopy of early-type stars outside the Local Group★

Author

Hugues Sana, O. E. Hartoog, Lex Kaper, and A. de Koter

Subjects
Physics, Interstellar medium, Stars, Electron density, Space and Planetary Science, Flux, Local Group, Astronomy and Astrophysics, Astrophysics, Giant star, Spectroscopy, Galaxy
Abstract

As part of the VLT/X-shooter science verification, we obtained the first optica l mediumresolution spectrum of a previously identified bright O-typ e object in NGC 55, an LMC-like galaxy at a distance of∼2.0 Mpc. Based on the stellar and nebular spectrum, we investigate the nature and evolutionary status of the central object(s) and its influence on the surrounding interstellar medium. We conclude that the source, NGC 55 C1 31, is a composite object, likely a stellar cluster, which contains one or several hot ( Teff ≃ 50 000 K) WN stars with a high mass-loss rate (∼3× 10 −5 M⊙ yr −1 ) and a helium-rich composition (NHe/NH = 0.8). The visual flux is dominated by OB-type (super)giant stars wi th Teff . 35 000 K, solar helium abundance (NHe/NH = 0.1), and mass-loss rate ∼2× 10 −6 M⊙ yr −1 . The surrounding Hii region has an electron density ne 6 10 2 cm −3 and an electron temperature T (Oiii) ≃ 11 500± 600 K. The oxygen abundance of this region is [O/H] = 8.18± 0.03 which corresponds to Z = 0.31± 0.04 Z⊙. We observed no significant gradients in T (Oiii), ne or [O/H] on a scale of 73 pc extending in four directions from the ionising source. The properties of the Hii region can be reproduced by a CLOUDY model which uses the central cluster as ionising source, thus providing a self-consistent interpreta tion of the data. We also report on the serendipitous discovery of Heii nebular emission associated with the nearby source NGC 55 C2 35, a feature usually associated with strong X-ray sources.

Published
2012
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14. Circumstellar disc geometry constrained by infrared line fluxes

Author

Carol E. Jones, A. Lenorzer, A. de Koter, A. Molak, T. A. A. Sigut, Sorin Popa, and Low Energy Astrophysics (API, FNWI)

Subjects
Physics, Infrared, Diagram, Astronomy, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Stars, Flux (metallurgy), Luminous blue variable, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics, Line (formation)
Abstract

Lenorzer et al. introduce ratios of hydrogen infrared recombination lines as a diagnostic tool to constrain the spatial distribution and physical condition of circumstellar material around hot massive stars. They demonstrate that the observed line flux ratios Hu14/Brα and Hu14/Pfγ from different types of objects associated with circumstellar material, such as Be stars, B[e] stars, and Luminous Blue Variable (LBV) stars are well separated in a diagnostic diagram. In this paper, we investigate this diagnostic tool using a non-LTE disc code developed by Sigut & Jones focusing on Be discs. We find good agreement between the empirical and predicted locations of Be stars in the Hu14/Brα versus Hu14/Pfγ diagram and show that indeed this diagnostic tool can be used to constrain basic properties of the discs of these stars.

Published
2009
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15. The optical spectrum of the planetary nebula NGC 6543

Author

Lawrence H. Aller, Woo-Baik Lee, Walter A. Feibelman, Siek Hyung, and A. de Koter

Subjects
Physics, Nebula, Astrophysics::High Energy Astrophysical Phenomena, Doubly ionized oxygen, Astronomy, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Radiation, Planetary nebula, Emission nebula, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Electron temperature, Halo, Astrophysics::Galaxy Astrophysics, Visible spectrum
Abstract

We investigate the electron temperature of the inner halo and nebular core regions of NGC 6543, using archival Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) images taken through narrow band (O iii) filters. Balick et al. (2001) showed that the inner halo consists of a number of spherical shells. We find the temperature of this inner halo to be much higher (�15000 K) than that of the bright core nebula (�8500 K). Photo-ionization models indicate that hardening of the UV radiation from the central star cannot be the main source of the higher temperature in the halo region. Using a radiation hydrodynamic simulation, we show that mass loss and velocity variations in the AGB wind can explain the observed shells, as well as the higher electron temperature.

Published
2000
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16. The R136 star cluster dissected withHubble Space Telescope/STIS. I. Far-ultraviolet spectroscopic census and the origin of He ii λ1640 in young star clusters

Author

Crowther, Paul A., primary, Caballero-Nieves, S. M., additional, Bostroem, K. A., additional, Apellániz, J. Maíz, additional, Schneider, F. R. N., additional, Walborn, N. R., additional, Angus, C. R., additional, Brott, I., additional, Bonanos, A., additional, de Koter, A., additional, de Mink, S. E., additional, Evans, C. J., additional, Gräfener, G., additional, Herrero, A., additional, Howarth, I. D., additional, Langer, N., additional, Lennon, D. J., additional, Puls, J., additional, Sana, H., additional, and Vink, J. S., additional

Published
2016
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18. R144 revealed as a double-lined spectroscopic binary★

Author

Sana, H., primary, van Boeckel, T., additional, Tramper, F., additional, Ellerbroek, L. E., additional, de Koter, A., additional, Kaper, L., additional, Moffat, A. F. J., additional, Schnurr, O., additional, Schneider, F. R. N., additional, and Gies, D. R., additional

Published
2013
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