Magnetically confined winds of hot stars

2003 ◽  
Vol 9 ◽  
pp. 277-277
Author(s):  
J. Babel
Keyword(s):  
Hot Stars ◽  
Magnetically Confined

scholarly journals X-Ray Emission from Magnetically Confined Winds

1999 ◽  
Vol 169 ◽  
pp. 187-190
Author(s):  
Jacques Babel
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Hot Stars ◽  
X Ray ◽  
Magnetically Confined ◽  
Circumstellar Environment

AbstractWe consider the effect of large scale magnetic fields on the circumstellar environment of hot stars. In these stars, magnetic fields of order of 100 G lead to magnetically confined wind shocks (MCWS) and then to the existence of large X-ray emitting region. MCWS lead also to the presence of corotating cooling disks around hot stars.We discuss the case of θ1 Ori C, which is perhaps the hottest analog to Bp stars and consider the effect from rotation and instabilities. We finally discuss the case of the Herbig Ae-Be HD 104237 and show that MCWS might also explain the X-ray emission from this star.

scholarly journals On the accuracy of the binary-collision algorithm in particle-in-cell simulations of magnetically confined fusion plasmas

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Timo P. Kiviniemi ◽  
Eero Hirvijoki ◽  
Antti J. Virtanen
Keyword(s):  
Finite Difference ◽  
Electric Fields ◽  
Finite Size ◽  
Binary Collision ◽  
Conserved Quantities ◽  
Fusion Plasmas ◽  
Fusion Plasma ◽  
Particle In Cell ◽  
Magnetically Confined ◽  
Scale Length

Ideally, binary-collision algorithms conserve kinetic momentum and energy. In practice, the finite size of collision cells and the finite difference in the particle locations affect the conservation properties. In the present work, we investigate numerically how the accuracy of these algorithms is affected when the size of collision cells is large compared with gradient scale length of the background plasma, a parameter essential in full- $f$ fusion plasma simulations. Additionally, we discuss implications for the conserved quantities in drift-kinetic formulations when fluctuating magnetic and electric fields are present: we suggest how the accuracy of the algorithms could potentially be improved with minor modifications.

Layered synthetic microstructures for soft x‐ray spectroscopy of magnetically confined plasmas (invited)

1990 ◽  
Vol 61 (10) ◽  
pp. 2733-2737 ◽  
Author(s):  
W. Moos ◽  
A. P. Zwicker ◽  
S. P. Regan ◽  
M. Finkenthal
Keyword(s):  
X Ray ◽  
Confined Plasmas ◽  
Magnetically Confined ◽  
Magnetically Confined Plasmas ◽  
Synthetic Microstructures

A test program on thermomechanical and thermal-hydraulic aspects of nuclear systems for magnetically confined fusion power reactors

1982 ◽  
Vol 68 (3) ◽  
pp. 311-321 ◽  
Author(s):  
R.E. Nygren ◽  
H. Herman ◽  
C.C. Baker
Keyword(s):  
Test Program ◽  
Fusion Power ◽  
Magnetically Confined ◽  
Nuclear Systems

Stimulated Raman Backscatter from a Magnetically Confined Plasma Column

1982 ◽  
Vol 49 (6) ◽  
pp. 371-375 ◽  
Author(s):  
A. A. Offenberger ◽  
R. Fedosejevs ◽  
W. Tighe ◽  
W. Rozmus
Keyword(s):  
Plasma Column ◽  
Magnetically Confined ◽  
Raman Backscatter ◽  
Stimulated Raman

Measurement of spiraling in a magnetically confined electron beam for use in collision studies

1974 ◽  
Vol 45 (4) ◽  
pp. 538-544 ◽  
Author(s):  
P. O. Taylor ◽  
K. T. Dolder ◽  
W. E. Kauppila ◽  
G. H. Dunn
Keyword(s):  
Electron Beam ◽  
Magnetically Confined

scholarly journals Refining the true parameters of the open cluster NGC 4852

2009 ◽  
Vol 5 (S266) ◽  
pp. 539-539
Author(s):  
Gladys Solivella ◽  
Edgard Giorg ◽  
Rubén Vázquez ◽  
Giovanni Carraro
Keyword(s):  
Emission Line ◽  
Open Cluster ◽  
Open Clusters ◽  
Occurrence Rate ◽  
Hot Stars ◽  
Cluster Area ◽  
Young Object ◽  
Cluster Distance ◽  
Be Star ◽  
Compact Cluster

AbstractNGC 4852 is a moderately compact cluster centered at α2000 = 13 : 00 : 09; δ = −59 : 36 : 48, located near the center of an Hα superring. This cluster forms part of an extended region including young stellar aggregates inside a circle with a radius of 3 degrees, where many show an abundance of emission line stars. In the field of this cluster, two stars of known type exist: Wray 15–1039 (emission-line object) and CD −58:4845 (emission-line star). We do not yet know whether the Be phase is transient or whether it is just what randomly happens in some hot stars. It appears that Be star may be found even in clusters as old as 70 Myr with a high occurrence rate in clusters of 25–27 Myr old. A recent photometric survey in NGC 4852 down to V = 22 – 23 mag established that NGC 4852 is about 200 – 250 Myr old, located at 1.1 kpc from the Sun and with a mean E(B − V) = 0.45 mag. Since the presence of potential Be-type stars in the cluster area suggests it may be a very young object instead of moderately old, we decided to carry out spectroscopy for 33 selected stars and CCD UBVI photometry for the bright objects in the cluster area. This way, we attempt to clarify their evolutionary state and include them in the framework of emission-line stars and open clusters. From our analysis, we agree with the cluster distance and reddening determined by earlier studies, but we derive that the age of NGC 4852 is younger than 40 Myr.

scholarly journals Angular momentum loss and stellar spin-down in magnetic massive stars

2008 ◽  
Vol 4 (S259) ◽  
pp. 423-424
Author(s):  
Asif ud-Doula ◽  
Stanley P. Owocki ◽  
Richard H.D. Townsend
Keyword(s):  
Angular Momentum ◽  
Massive Stars ◽  
Solid Angle ◽  
Magnetic Confinement ◽  
Dipole Field ◽  
Hot Stars ◽  
Momentum Loss ◽  
Dipole Magnetic Field ◽  
Angular Momentum Loss ◽  
Compare And Contrast

AbstractWe examine the angular momentum loss and associated rotational spin-down for magnetic hot stars with a line-driven stellar wind and a rotation-aligned dipole magnetic field. Our analysis here is based on our previous 2-D numerical MHD simulation study that examines the interplay among wind, field, and rotation as a function of two dimensionless parameters, W(=Vrot/Vorb) and ‘wind magnetic confinement’, η∗ defined below. We compare and contrast the 2-D, time variable angular momentum loss of this dipole model of a hot-star wind with the classical 1-D steady-state analysis by Weber and Davis (WD), who used an idealized monopole field to model the angular momentum loss in the solar wind. Despite the differences, we find that the total angular momentum loss averaged over both solid angle and time follows closely the general WD scaling ~ ṀΩR2A. The key distinction is that for a dipole field Alfvèn radius RA is significantly smaller than for the monopole field WD used in their analyses. This leads to a slower stellar spin-down for the dipole field with typical spin-down times of order 1 Myr for several known magnetic massive stars.

Observations of the ultraviolet and x-ray brightness profiles and cooling rates of Kr and Ar in magnetically confined fusion plasmas

2000 ◽  
Vol 61 (3) ◽  
pp. 3042-3052 ◽  
Author(s):  
M. May ◽  
K. Fournier ◽  
D. Pacella ◽  
H. Kroegler ◽  
J. Rice ◽  
...  
Keyword(s):  
Fusion Plasmas ◽  
Cooling Rates ◽  
X Ray ◽  
Magnetically Confined

scholarly journals The circumstellar environment of the B[e] star GG Car: an interferometric modeling

2014 ◽  
Vol 9 (S307) ◽  
pp. 291-292
Author(s):  
A. Domiciano de Souza ◽  
M. Borges Fernandes ◽  
A. C. Carciofi ◽  
O. Chesneau
Keyword(s):  
Binary System ◽  
Primary Component ◽  
Compact Ring ◽  
Hot Stars ◽  
Self Consistent ◽  
Grain Formation ◽  
Formation And Evolution ◽  
Circumstellar Environments ◽  
Consistent Treatment ◽  
Circumstellar Environment

AbstractThe research of stars with the B[e] phenomenon is still in its infancy, with several unanswered questions. Physically realistic models that treat the formation and evolution of their complex circumstellar environments are rare. The code HDUST (developed by A. C. Carciofi and J. Bjorkman) is one of the few existing codes that provides a self-consistent treatment of the radiative transfer in a gaseous and dusty circumstellar environment seen around B[e] supergiant stars. In this work we used the HDUST code to study the circumstellar medium of the binary system GG Car, where the primary component is probably an evolved B[e] supergiant. This system also presents a disk (probably circumbinary), which is responsible for the molecular and dusty signatures seen in GG Car spectra. We obtained VLTI/MIDI data on GG~Car at eight baselines, which allowed to spatially resolve the gaseous and dusty circumstellar environment. From the interferometric visibilities and SED modeling with HDUST, we confirm the presence of a compact ring, where the hot dust lies. We also show that large grains can reproduce the lack of structure in the SED and visibilities across the silicate band. We conclude the dust condensation site is much closer to the star than previously thought. This result provides stringent constraints on future theories of grain formation and growth around hot stars.

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