322 research outputs found
Multi-wavelength INTEGRAL NEtwork (MINE) observations of the microquasar GRS 1915+105
We present the international collaboration MINE (Multi-lambda Integral
NEtwork) aimed at conducting multi-wavelength observations of X-ray binaries
and microquasars simultaneously with the INTEGRAL gamma-ray satellite. We will
focus on the 2003 March-April campaign of observations of the peculiar
microquasar GRS 1915+105 gathering radio, IR and X-ray data. The source was
observed 3 times in the plateau state, before and after a major radio and X-ray
flare. It showed strong steady optically thick radio emission corresponding to
powerful compact jets resolved in the radio images, bright near-infrared
emission, a strong QPO at 2.5 Hz in the X-rays and a power law dominated
spectrum without cutoff in the 3-300 keV range. We compare the different
observations, their multi-wavelength light curves, including JEM-X, ISGRI and
SPI, and the parameters deduced from fitting the spectra obtained with these
instruments on board INTEGRAL.Comment: 4 pages, 9 fig., Proc. of the 5th INTEGRAL Workshop (Feb. 16-20
2004), to be published by ES
Simultaneous multi-wavelength observations of microquasars (the MINE collaboration)
We present the international collaboration MINE (Multi-lambda INTEGRAL
NEtwork) aimed at conducting multi-wavelength observations of microquasars
simultaneously with the INTEGRAL satellite. The first results on GRS 1915+105
are encouraging and those to come should help us to understand the physics of
the accretion and ejection phenomena around a compact object.Comment: 2 p, 3 fig., proc. of the IAU Coll. 194, ``Compact Binaries in the
Galaxy and Beyond'', Nov. 2003, La Paz, Mexico, to be published in the Conf.
Series of Revista Mexicana de Astronomia y Astrofisica, Eds. G. Tovmassian &
E. Sio
Impact of spatial inhomogeneities on on-axis pulse reconstruction in femtosecond filaments
We demonstrate a strong influence of the spatial beam profile on the vacuum-propagated on-axis pulse shapes for a femtosecond filament in argon. The effects can be minimized by transmitting the filament into the far-field by a laser-drilled pinhole setup. Using this method, we can monitor the pulse compression dynamics along the entire longitudinal extension of the filament, including the ionization-induced plasma channel
Epidemics and percolation in small-world networks
We study some simple models of disease transmission on small-world networks,
in which either the probability of infection by a disease or the probability of
its transmission is varied, or both. The resulting models display epidemic
behavior when the infection or transmission probability rises above the
threshold for site or bond percolation on the network, and we give exact
solutions for the position of this threshold in a variety of cases. We confirm
our analytic results by numerical simulation.Comment: 6 pages, including 3 postscript figure
INTEGRAL-RXTE observations of Cygnus X-1
We present first results from contemporaneous observations of Cygnus X-1 with
INTEGRAL and RXTE, made during INTEGRAL's performance verification phase in
2002 November and December. Consistent with earlier results, the 3-250 keV data
are well described by Comptonization spectra from a Compton corona with a
temperature of kT~50-90 keV and an optical depth of tau~1.0-1.3 plus reflection
from a cold or mildly ionized slab with a covering factor of Omega/2pi~0.2-0.3.
A soft excess below 10 keV, interpreted as emission from the accretion disk, is
seen to decrease during the 1.5 months spanned by our observations. Our results
indicate a remarkable consistency among the independently calibrated detectors,
with the remaining issues being mainly related to the flux calibration of
INTEGRAL.Comment: 6 pages, 3 figures. Figs. 2 and 3 are best viewed in color. Accepted
for publication in the INTEGRAL special edition of A&A
Bimetallic Carbonyl Complexes Based on Iridium and Rhodium: Useful Tools for Hydrodefluorination Reactions
A set of bimetallic complexes based on iridium and rhodium with bis(diphenylphosphino)methane, bis(diâisoâpropylphosphino)methane, diphenylâ2âpyridylphosphine and 2â(diâisoâpropylphosphino)imidazole bridging ligands was prepared. The complexes were characterized by NMR and IR spectroscopy and studied quantumâchemically using DFT methods. The bimetallic systems succeeded in catalytic hydrodefluorination reactions of lower fluorinated aryl fluorides using molecular hydrogen and sodium tertâbutoxide as a base. Effects of (i) ligand variation, (ii) monoâ vs bimetallic nuclearity, and (iii) Ir vs Rh metal identity were studied and rationalized en route to achieve an effective hydrodefluorination.Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)Peer Reviewe
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