19,430 research outputs found
Akn 564: an unusual component in the X-ray spectra of NLSy1 galaxies
We present an ASCA observation of the NLSy1 Ark 564. The X-ray light curve
shows rapid variability, but no evidence for energy-dependence to these
variations, within the 0.6 -- 10 keV bandpass. A strong (EW ~ 70 eV) spectral
feature is observed close to 1 keV. A similar feature has been observed in TON
S180 (another NLSy1) but has not been observed in broad-line Seyfert galaxies.
The feature energy suggests a large contribution from Fe L-shell lines but its
intensity is difficult to explain in terms of emission and/or absorption from
photoionized gas. Models based on gas in thermal equilibrium with kT ~1 keV
provide an alternative parameterization of the soft spectrum. The latter may be
interpreted as the hot intercloud medium, undergoing rapid cooling and
producing strong Fe L-shell recombination lines. In all cases the physical
conditions are rather different from those observed in broad-line Seyferts. The
hard X-ray spectrum shows a broad and asymmetric Fe Kalpha line of large
equivalent width (~550 eV) which can be explained by a neutral disk viewed at ~
60 degrees to the line-of-sight, contrary to the hypothesis that NLSy1s are
viewed pole-on. The large EW of this line, the strong 1 keV emission and the
strong optical Fe emission lines all suggest an extreme Fe abundance in this
and perhaps other NLSy1s.Comment: 15 pages, 5 figures. LaTeX with encapsulated postscript. Accepted for
publication in the Astrophysical Journa
Carbon Dioxide Reduction Systems
The Methoxy system for regenerating oxygen from carbon dioxide was studied. Experiments indicate that the reaction between carbon dioxide and hydrogen can be carried out with ease in an efficient manner and with excellent heat conservation. A small reactor capable of handling the C02 expired by three men has been built and operated. The decomposition of methane by therma1,arc and catalytic processes was studied. Both the arc and catalytic processes gave encouraging results with over 90 percent of the methane being decomposed to carbon and hydrogen in some of the catalytic processes. Control of the carbon deposition in both the catalytic and arc processes is of great importance to prevent catalyst deactivation and short circuiting of electrical equipment. Sensitive analytical techniques have been developed for all of the components present in the reactor effluent streams
ASCA observations of type-2 Seyfert galaxies: II. The Importance of X-ray Scattering and Reflection
We discuss the importance of X-ray scattering and Compton reflection in
type-2 Seyfert galaxies, based upon the analysis of ASCA observations of 25
such sources. Consideration of the iron Kalpha, [O III] line and X-ray
variability suggest that NGC 1068, NGC 4945, NGC 2992, Mrk 3, Mrk 463E and Mrk
273 are dominated by reprocessed X-rays. We examine the properties of these
sources in more detail.
We find that the iron Kalpha complex contains significant contributions from
neutral and high-ionization species of iron. Compton reflection, hot gas and
starburst emission all appear to make significant contributions to the observed
X-ray spectra.
Mrk 3 is the only source in this subsample which does not have a significant
starburst contamination. The ASCA spectrum below 3 keV is dominated by hot
scattering gas with U_X ~ 5, N_H ~ 4 x 10^23 cm^-2. This material is more
highly ionized than the zone of material comprising the warm absorber seen in
Seyfert~1 galaxies, but may contain a contribution from shock-heated gas
associated with the jet. Estimates of the X-ray scattering fraction cover 0.25
- 5%. The spectrum above 3 keV appears to be dominated by a Compton reflection
component although there is evidence that the primary continuum component
becomes visible close to 10 keV.Comment: 27 pages, 6 figures. LaTeX with encapsulated postscript. To appear in
the Astrophysical Journal. Also available via
http://lheawww.gsfc.nasa.gov/~george/papers/gnt_s2p2/abstract.htm
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