Introduction to Stellar Winds

Lamers, H. J. G. L. M.; Cassinelli, J. P.

doi:10.1017/cbo9781139175012

Cited by 842 publications

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“…This results in a deviation from a spherically symmetric shape and possibly the formation of an outflowing disk (Lamers & Cassinelli 1999). Disks of this kind have been discovered in B[e] and Be stars (Zickgraf et al 1985).…”

Section: Modeling Resultsmentioning

confidence: 99%

Medium resolution spectroscopy of the supergiant O31f Cyg OB2 No. 7

Maryeva

Zhuchkov

2012

Astrophysics

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We examine the feasibility of using medium resolution spectra for determining the parameters of atmospheres of hot stars by means of numerical simulations. We chose the star Cyg OB2 №7 as a test object and obtained its spectrum (λ/∆λ = 2500) with Russian-Turkish RTT150 telescope. The CMFGEN code was used to construct a model of the atmosphere of Cyg OB2 №7 . For the first time we have detected the NIV λλ7103.2 − 7129.2lines in the spectrum of this star and used them to determine the physical parameters of the wind. The rate of mass loss measured using the Hα line exceeds the loss rate measured using lines formed in the wind. This indicates that the wind is nonuniform, apparently due to rotation.

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Section: Modeling Resultsmentioning

confidence: 99%

Medium resolution spectroscopy of the supergiant O31f Cyg OB2 No. 7

Maryeva

Zhuchkov

2012

Astrophysics

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“…Through these interactions the radially outgoing photons transfer their momentum to dust grains, driving them outward. This also results in an outflow of the gas particles that are coupled to dust grains through collisions (Lamers & Cassinelli 1999;Gray 2012). As outflowing waves move farther from the star, they become cooler and denser and form the CSE.…”

Section: Oh Samples Near Evolved Starsmentioning

confidence: 99%

DICKE’S SUPERRADIANCE IN ASTROPHYSICS. II. THE OH 1612 MHz LINE

Rajabi

Houde

2016

ApJ

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We apply the concept of superradiance that was introduced by Dicke in 1954 to the OH molecule 1612 MHz spectral line, which is often used for the detection of masers in the circumstellar envelopes of evolved stars. Because the detection of 1612 MHz OH masers in the outer shells of envelopes of these stars implies the existence of a population inversion and a high level of velocity coherence, and that these are two necessary requirements for superradiance, we investigate whether superradiance can also happen in these regions. Superradiance is characterized by high-intensity, spatially compact, burst-like features taking place over timescales on the order of seconds to years, depending on the size and physical conditions present in the regions harboring such sources of radiation. Our analysis suggests that superradiance provides a valid explanation for previous observations of intensity flares detected in that spectral line for the U Orionis Mira star and the IRAS 18276-1431 preplanetary nebula.

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“…The swept up ISM material by the stellar wind should on the other hand almost coincide in velocity with the neutral gas, but there the gas rapidly cools to ≈ 10 4 K which is not sufficient to produce N 4+ (Lamers & Cassinelli 1999). As a consequence, the GRB afterglow ionizing flux appears as the natural mechanism to produce kinematically cold N V lines, i.e.…”

Section: Ionized Gasmentioning

confidence: 99%

Probing the Interstellar Medium and Stellar Environments of Long-Duration GRBs

2007

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Abstract.We review the properties of the gas surrounding high-redshift gamma-ray bursts (GRBs) assessed through the analysis of damped Lyman-alpha systems (DLAs) identified in their afterglow spectra. These GRB-DLAs are characterized by large H I column densities with a median of N (H I) = 10 21. 7 cm −2 , no molecular gas signatures, metallicities ranging from 1/100 to nearly solar with a median exceeding 1/10 solar, and no anomalous abundance patterns. The detection of the atomic Mg lines and the time-variability of the fine-structure lines demonstrates that the majority of the neutral gas along the GRB sightlines is located between 50 pc and a few kpc from the GRB. This implies that this gas is presumably associated with the ambient interstellar medium of the host galaxy and that the derived properties from low-ionization lines do not directly constrain the local environment of the GRB progenitor. The highly ionized gas, traced by N V lines, which could result from a pre-existing H II region produced by the GRB progenitor and neighboring OB stars, appears on the other hand to be very local to the GRB at about 10 pc, yielding a snapshot of the medium's physical conditions at this radius.

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Introduction to Stellar Winds

Cited by 842 publications

References 0 publications

Medium resolution spectroscopy of the supergiant O31f Cyg OB2 No. 7

Medium resolution spectroscopy of the supergiant O31f Cyg OB2 No. 7

DICKE’S SUPERRADIANCE IN ASTROPHYSICS. II. THE OH 1612 MHz LINE

Probing the Interstellar Medium and Stellar Environments of Long-Duration GRBs

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