We employ high resolution spectroscopy and spectropolarimetry to derive the physical properties and magnetic characteristics of the multiple system HD 164492C, located in the young open cluster M20. The spectrum reveals evidence of 3 components: a broad-lined early B star (HD 164492C1), a narrow-lined early B star (HD 164492C2), and a late B star (HD 164492C3). Components C2 and C3 exhibit significant (> 100 km/s) bulk radial velocity variations with a period of 12.5351(7) d that we attribute to eccentric binary motion around a common centre-of-mass. Component C1 exhibits no detectable radial velocity variations. Using constraints derived from modeling the orbit of the C2+C3 binary and from synthesis of the combined spectrum, we determine the approximate physical characteristics of the components. We conclude that a coherent evolutionary solution consistent with the published age of M20 implies a distance to M20 of 0.9 ± 0.2 kpc, corresponding to the smallest published values. We confirm the detection of a strong magnetic field in the combined spectrum. The field is clearly associated with the broad-lined C1 component of the system. Repeated measurement of the longitudinal magnetic field allows the derivation of the rotation period of the magnetic star, P rot = 1.36986(6) d. We derive the star's magnetic geometry, finding i = 63±6• , β = 33 ± 6• and a dipole polar strength B d = 7.9 +1.2 −1.0 kG. Strong emission -varying according to the magnetic period -is detected in the Hα profile. This is consistent with the presence of a centrifugal magnetosphere surrounding the rapidly rotating magnetic C1 component.
10" 1 -5xl0" 2 of the value estimated from the Bohm coefficient of ^kT/eB and is larger than the classical value by 3 orders of magnitude. The magnitude as well as the T e dependence of the conductivity in the electron temperature range of T e >l eV is similar to the particle diffusion coefficient as reported by Chen. 7 This indicates that the same mechanism may be responsible for the anomalous electron thermal diffusion and the particle diffusion.In the determination of the value K x , we simplified the equation as well as the geometrical factors. The electron energy loss due to ionizing neutral gas is neglected in Eq. (2). However, the change in electron temperature due to ionization is less than 30% during the time interval of 0.3 msec used to determine the electron thermal conductivity. The variation of plasma volume in the radial direction, dV/dip, should also be taken into account. The change of dV/dip is less than 20% in the 2.0-cm radial extent over which the measurements were carried out, and was therefore assumed constant.In conclusion, the electron thermal conductivity was measured by utilizing the localized upper hybrid resonance heating. The observed K x increases with an increase of T e . This dependence is similar to that of the particle diffusion coefficient. The absolute value K ± is j^-w °* the Bohm coefficient. The success of the present Direct evidence that the spins of the 3 He atoms in the A phase of the liquid are correlated in a most unusual way has been furnished through previous observations of a large shift in the position of the nuclear magnetic resonance line. 1 Leggett 2 * 3 has given a microscopic theory of the NMR behavior of the liquid in this phase in terms of a BCS-type 4 superfluid in which the atoms form Cooper pairs in a triplet spin state. He has con-approach suggests that other types of resonant heating, such as lower hybrid resonance and ioncyclotron resonance, may be applicable to obtain electron and ion thermal conductivities in tokamak devices.
1) Le recouvrement des fonctions d'onde atomiques de deux atomes 3He et 4He proches voisins donne naissance à une fréquence de transposition 3He-4He par effet tunnel J' de l'ordre du MHz. Cet effet tunnel couple les degrés de liberté des impuretés 4He aux interactions d'échange de Pauli 3He-3He, elles-mêmes couplées aux interactions Zeeman par interaction dipolaire magnétique. 2) A basse température le processus de relaxation spin-réseau est un couplage des phonons aux impuretés 4He. On peut relier le temps de relaxation observé au temps de vie de diffusion Rayleigh des phonons lui-même déduit des mesures de conductibilité thermique. L'accord avec les résultats expérimentaux est satisfaisant. 3) On discute l'influence de la transposition isotopique sur la largeur de la raie de résonance et la possibilité de déterminer par ce biais la fréquence J'. 4) A la capacité calorifique spin-spin contribuent les transpositions isotopiques ainsi que les interactions atomiques entre isotopes d'espèces différentes. Ces interactions résultent de la différence des mouvements de point zéro et sont responsables de la ségrégation isotopique observée en dessous de 0,38 °K. Les mesures de relaxation permettent également une estimation de l'interaction atomique entre impuretés 4He en accord raisonnable avec les valeurs déduites de la ligne de ségrégation isotopique
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