9 research outputs found
Probable detection of starlight reflected from the giant exoplanet orbiting tau Bootis
Giant planets orbiting stars other than the Sun are clearly detectable
through precise radial-velocity measurements of the orbital reflex motion of
the parent star. In the four years since the discovery of the companion to the
star 51 Peg, similar low-amplitude ``Doppler star wobbles'' have revealed the
presence of some 20 planets orbiting nearby solar-type stars. Several of these
newly-discovered planets are very close to their parent stars, in orbits with
periods of only a few days. Being an indirect technique, however, the
reflex-velocity method has little to say about the sizes or compositions of the
planets, and can only place lower limits on their masses. Here we report the
use of high-resolution optical spectroscopy to achieve a probable detection of
the Doppler-shifted signature of starlight reflected from one of these objects,
the giant exoplanet orbiting the star tau Bootis. Our data give the planet's
orbital inclination i=29 degrees, indicating that its mass is some 8 times that
of Jupiter, and suggest strongly that the planet has the size and reflectivity
expected for a gas-giant planet.Comment: 15 pages, 4 figures. (Fig 1 and equation for epsilon on p1 para 2
revised; changed from double to single spacing
119Sn and 57Fe Mössbauer study of the local structure of perovskite-type ferrites CaFe2−xNxO5 (N = Sc, Al) and manganite CaMn7O12
Anion-deficient substituted ferrites Ca2Fe2 − x N x O5 (N = Sc3+, Al3+) and mixed manganite CaMn7O12 have been investigated by 119Sn and 57Fe probe Mössbauer spectroscopy. The mechanism of charge compensation for heterovalent impurity Sn4+ ions in the structure of the ferrite Ca2Fe2O5 has been established. The presence of nonequivalent crystallographic positions of manganese cations, caused by their charge ordering in the structure of the manganite CaMn7O12, is shown. Magnetic ordering of Mn3+ and Mn4+ cations in the octahedral sublattice of CaMn7O12 at T < T M2 ≈ 90 K is established