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916 results on '"CIRCUMSTELLAR DISK"'

1. Spectral Classification of Embedded Stars

Author

André, Philippe, Gargaud, Muriel, editor, Irvine, William M., editor, Amils, Ricardo, editor, Claeys, Philippe, editor, Cleaves, Henderson James, editor, Gerin, Maryvonne, editor, Rouan, Daniel, editor, Spohn, Tilman, editor, Tirard, Stéphane, editor, and Viso, Michel, editor

Published
2023
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2. Circumstellar Disk

Author

Gargaud, Muriel, editor, Irvine, William M., editor, Amils, Ricardo, editor, Claeys, Philippe, editor, Cleaves, Henderson James, editor, Gerin, Maryvonne, editor, Rouan, Daniel, editor, Spohn, Tilman, editor, Tirard, Stéphane, editor, and Viso, Michel, editor

Published
2023
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4. GRMHD simulations of accretion flows onto massive binary black hole mergers embedded in a thin slab of gas

Author

Fedrigo, G, Cattorini, F, Giacomazzo, B, Colpi, M, Fedrigo G., Cattorini F., Giacomazzo B., Colpi M., Fedrigo, G, Cattorini, F, Giacomazzo, B, Colpi, M, Fedrigo G., Cattorini F., Giacomazzo B., and Colpi M.

Abstract

We present general relativistic magnetohydrodynamic simulations of merging equal-mass spinning black holes embedded in an equatorial thin slab of magnetized gas. We explore configurations with black holes that are nonspinning, with spins aligned to the orbital angular momentum, and with misaligned spins. The rest-mass density of the gas slab follows a Gaussian profile symmetric relative to the equatorial plane and it is initially either stationary or with Keplerian rotational support. As part of our diagnostics, we track the accretion of matter onto the black hole horizons and the Poynting luminosity. Throughout the inspiral phase, configurations with nonzero spins display modulations in the mass accretion rate that are proportional to the orbital frequency and its multiples. Frequency analysis suggests that these modulations are a generic feature of inflows on merging binaries. In contrast to binary models evolved in a gas cloud scenario, we do not observe a significant increase in the mass accretion rate after the merger in any of our simulations, suggesting the possibility of not detecting a peak luminosity at the time of merger in future electromagnetic observations.

Published
2024

5. Massive Stars in Rapidly Evolving Systems

Author

Shepard, Katherine

Subjects
Eclipsing Binary, Circumstellar Disk, Circumbinary material, Emission Line Star, Interferometry, Spectroscopy
Abstract

As massive binary companions age they will swell to dimensions comparable to the distance between stars. The larger star will likely begin transferring mass to its companion, which will accrete mass and angular momentum and may spin up to near critical velocity. Additional mass transfer may lead to large scale mass loss. Here, we present an observational study of three systems that are experiencing or are products of mass transfer. VFTS~102 and VFTS~285 are the fastest rotating stars currently known. We present an analysis of their far-ultraviolet and visible band spectral features and determine their physical properties and angular momentum loss processes. We conclude that VFTS~102 is the result of a stellar merger and that VFTS~285 was ejected when its companion exploded in a supernova. Lastly, the interacting binary W~Serpentis is emerging from its most intense phase of mass transfer. W~Serpentis is an eclipsing binary and the prototype of the Serpentid class of interacting binaries. We present an observational analysis of high quality, visible band spectroscopy and the first near-IR, long-baseline interferometric observations. We present examples of the appearance and radial velocities of the primary spectral components: prominent emission lines, strong shell lines, and weak absorption lines. We find some of the weak absorption features are associated with the cool mass donor, and we present the first radial velocity curve for the donor star. The donor’s absorption lines are rotationally broadened, and we derive a mass ratio of 0.49 +\- 0.07. We also derive the orbital inclination and mass estimates of 3.5 M⊙ and 7.2 M⊙ for the donor and gainer, respectively. The partially resolved interferometric measurements are consistent with our derived orbital properties and the Gaia EDR3 distance. Spectroscopic evidence indicates that the gainer is obscured by an opaque disk that channels the mass transfer stream into an outflow through the L3 region and out into a circumbinary disk. The results demonstrate that binary stars may lose a significant fraction of their mass during the fleeting but transformative stage of mass transfer.

Published
2024

9. Optical and Near-Infrared Monitoring of Gamma-ray Binaries Hosting Be Stars

Author

Yuki Moritani and Akiko Kawachi

Subjects
gamma-ray binaries, optical and near-infrared, Be stars, circumstellar disk, gamma-ray binaries—individual (PSR B1259−63, LSI+61 303, HESS J0632+057), Elementary particle physics, QC793-793.5
Abstract

Optical and near-infrared observations are compiled for the three gamma-ray binaries hosting Be stars: PSR B1259−63, LSI+61 303, and HESS J0632+057. The emissions from the Be disk are considered to vary according to the changes in its structure, some of which are caused by interactions with the compact object (e.g., tidal forces). Due to the high eccentricity and large orbit of these systems, the interactions—and, hence the resultant observables—depend on the orbital phase. To explore such variations, multi-band photometry and linear polarization were monitored for the three considered systems, using two 1.5 m-class telescopes: IRSF at the South African Astronomical Observatory and Kanata at the Higashi–Hiroshima Observatory.

Published
2021
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10. Spectral Classification of Embedded Stars

Author

André, Philippe, Gargaud, Muriel, editor, Irvine, William M., editor, Amils, Ricardo, editor, Cleaves, Henderson James (Jim), II, editor, Pinti, Daniele L., editor, Quintanilla, José Cernicharo, editor, Rouan, Daniel, editor, Spohn, Tilman, editor, Tirard, Stéphane, editor, and Viso, Michel, editor

Published
2015
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28. Simulation of a Hydrodynamic Stellar Wind from a Rapidly Rotating Star.

Author

Bogovalov, S. V., Romanikhin, S. M., and Tronin, I. V.

Subjects
*STELLAR winds, *STELLAR rotation, *REYNOLDS number, *STELLAR mass, *SURFACE temperature, *STARS
Abstract

The mechanism for the formation of disk-like flows from rapidly rotating Be stars is not yet clear. An axisymmetric hydrodynamic stellar wind flow from a rapidly rotating star has been simulated numerically as a step in solving this problem. The change in the shape of the star as it rotates and the turbulence excited in the stellar wind at Reynolds numbers ∼109−1013 are taken into account. Calculations show the formation of a disk-like flow from the stellar surface at the equator, which expands into the polar regions due to a pressure gradient on scales of the order of the stellar radius. A poloidal velocity vortex is formed at high latitudes. No turbulence is excited near the equator within the simplest standard models and, therefore, no quasi-Keplerian disk-like flow emerges in the equatorial plane. A dependence of the total mass flux on the stellar rotation rate at various surface temperatures has been obtained. [ABSTRACT FROM AUTHOR]

Published
2019
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31. The James Webb Space Telescope

Author

Gardner, Jonathan P, Mather, John C., Clampin, Mark, Doyon, Rene, Flanagan, Kathryn A., Franx, Marijn, Greenhouse, Matthew A., Hammel, Heidi B., Hutchings, John B., Jakobsen, Peter, Lilly, Simon J., Lunine, Jonathan I., McCaughrean, Mark J., Mountain, Matt, Rieke, George H., Rieke, Marcia J., Sonneborn, George, Stiavelli, Massimo, Windhorst, Rogier, Wright., Gillian S., Burton, W.B., editor, Christensen, Lars Lindberg, editor, Thronson, Harley A., editor, Stiavelli, Massimo, editor, and Tielens, Alexander, editor

Published
2009
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34. (Sub)mm Interferometry Applications in Star Formation Research

Author

Beuther, H., Beig, R., editor, Beiglböck, W., editor, Domcke, W., editor, Englert, B.-G., editor, Frisch, U., editor, Hänggi, P., editor, Hasinger, G., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, Löhneysen, H.v., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, Bacciotti, Francesca, editor, Testi, Leonardo, editor, and Whelan, Emma, editor

Published
2008
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35. Observations of YSO Jets from Space: HST and Beyond

Author

Bacciotti, F., McCaughrean, M., Ray, T., Beig, R., editor, Beiglböck, W., editor, Domcke, W., editor, Englert, B.-G., editor, Frisch, U., editor, Hänggi, P., editor, Hasinger, G., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, Löhneysen, H.v., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, Bacciotti, Francesca, editor, Testi, Leonardo, editor, and Whelan, Emma, editor

Published
2008
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38. Near-Infrared Fiber Imager for the VLTI

Author

Neuhäuser, Ralph, Tünnermann, Andreas, Hempel, Marc, Stecklum, Bringfried, Ruske, Jena-Peter, Guenther, Eike, Hatzes, Artie, Chini, Rolf, Lemke, Roland, Wuchterl, Günther, Lühe, Oskar von der, Leibundgut, Bruno, editor, Richichi, A., editor, Delplancke, F., editor, Paresce, F., editor, and Chelli, A., editor

Published
2008
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42. FU Orionis - The MIDI Perspective

Author

Quanz, Sascha P., Henning, Thomas, Leinert, Christoph, Ratzka, Thorsten, Wolf, Sebastian, Leibundgut, Bruno, editor, Richichi, A., editor, Delplancke, F., editor, Paresce, F., editor, and Chelli, A., editor

Published
2008
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47. An Unbiased Mineral Compositional Analysis Technique for Circumstellar Disks

Author

Yung Kipreos and Inseok Song

Subjects
Mineral, Materials science, General Medicine, Astrophysics, Circumstellar disk
Abstract

A circumstellar disk that surrounds a star is composed of gas, dust, and rocky objects that are in orbit around it. Around infant stars, this disk can act as a source of material that can be used to form planetesimals, which can then accrete more material and form into planets. Studying the mineral composition of these disks can provide insight into the processes that created our solar system. The purpose of this paper is to analyze the mineral composition of these disks by using a newly created python package, Min-CaLM. This package determines the relative mineral abundance within a disk by using a linear regression technique called non-negative least square minimization. The circumstellar disks that are capable of undergoing compositional analysis must have a spectrum with both a detectable mid-infrared excess and prominent silicate features. From our sample, there are only eight debris disks that qualify to be candidates for the Min-CaLM program. The mineral compositions calculated by Min-CaLM are then compared to the Tholen asteroid classification scheme. HD 23514, HD 105234, HD 15407A, BD+20 307, HD 69830, and HD 172555 are found to have a compositions similar to that expected for C-type asteroids, TYC 9410-532-1 resembles the composition of S-type asteroids, and HD 100546 resembles D-type asteroids. Min-CaLM also calculates the mineral compositions of the comets Tempel 1 and Hale-Bopp, and they are used as a comparison between the material in our early solar system and the debris disk compositions. KEYWORDS: Debris disk; Mineral; Composition; Analysis; Asteroid; Circumstellar; Spectroscopy; Python

Published
2021
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50. Pre-main Sequence Stars

Author

Kogure, Tomokazu, Leung, Kam-Ching, Burton, W. B., editor, Bertola, F., editor, Cassinelli, J. P., editor, Cesarsky, C. J., editor, Ehrenfreund, P., editor, Engvold, O., editor, Heck, A., editor, van den Heuvel, E. P. J., editor, Kaspi, V. M., editor, Kuijpers, J. M. E., editor, van der Laan, H., editor, Murdin, P. G., editor, Pacini, F., editor, Radhakrishnan, V., editor, Somov, B. V., editor, Sunyaev, R. A., editor, Kogure, Tomokazu, and Leung, Kam-Ching

Published
2007
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