7 research outputs found
X-ray Doppler Imaging of 44i Boo with Chandra
Chandra High-Energy Transmission Grating observations of the bright eclipsing
contact binary 44i Boo show X-ray line profiles which are Doppler-shifted by
orbital motions. The X-ray emission spectrum contains a multitude of lines
superimposed on a weak continuum, with strong lines of O VIII, Ne X, Fe XVII,
and Mg XII. The profiles of these lines from the total observed spectrum show
Doppler-broadened widths of ~ 550 km s^{-1}. Line centroids vary with orbital
phase, indicating velocity changes of > 180 km s^{-1}. The first-order light
curve shows significant variability, but no clear evidence for either primary
or secondary eclipses. Flares are observed for all spectral ranges;
additionally, the light curve constructed near the peak of the emission measure
distribution (T_e = 5 to 8 X 10^6 K) shows quiescent variability as well as
flares. The phase-dependences of line profiles and light curves together imply
that at least half of the emission is localized at high latitude. A simple
model with two regions on the primary star at relatively high latitude
reproduces the observed line profile shifts and quiescent light curve. These
first clear X-ray Doppler shifts of stellar coronal material illustrate the
power of Chandra.Comment: 15 pages, 6 figures to be published in Astrophysical Journal Letter
Connected Green function approach to ground state symmetry breaking in -theory
Using the cluster expansions for n-point Green functions we derive a closed
set of dynamical equations of motion for connected equal-time Green functions
by neglecting all connected functions higher than order for the
-theory in dimensions. We apply the equations to the
investigation of spontaneous ground state symmetry breaking, i.e. to the
evaluation of the effective potential at temperature . Within our momentum
space discretization we obtain a second order phase transition (in agreement
with the Simon-Griffith theorem) and a critical coupling of
as compared to a first order phase transition and
from the Gaussian effective potential approach.Comment: 25 Revtex pages, 5 figures available via fpt from the directory
ugi-94-11 of [email protected] as one postscript file (there
was a bug in our calculations, all numerical results and figures have changed
significantly), ugi-94-1
A catalogue of the observations of the mutual phenomena of the Galilean satellites made in 1991 during the PHEMU91 campaign
In this paper, all the light-curves obtained during the PHEMU91
campaign of observations of the mutual phenomena of the Galilean
satellites are presented. These observations give accurate astrometric
positions of major interest for dynamical studies of the motion of the
Galilean satellites. The aim of this work is to give observational
data directly usable for theoretical studies. We made 374 observations
of 111 mutual events from 56 sites. The corresponding data are given in
this paper. The
accuracy of each observation has been deduced from a comparison with the
theoretical predictions. For each
observation, information is given about the telescope, the receptor,
the site and the observational conditions