12,224 research outputs found
Transient Relativistically-Shifted Lines as a Probe of Black Hole Systems
X-ray spectra of Seyfert galaxies have revealed a new type of X-ray spectral
feature, one which appears to offer important new insight into the black hole
system. XMM/Chandra revealed several narrow emission lines redward of Fe Kalpha
in NGC 3516. Since that discovery the phenomenon has been observed in other
Seyfert galaxies, e.g. NGC 7314 and ESO 198-G24. We present new evidence for a
redshifted Fe line in XMM spectra of Mrk 766. These data reveal the first
evidence for a significant shift in the energy of such a line, occurring over a
few tens of kiloseconds. This shift may be interpreted as deceleration of an
ejected blob of gas traveling close to the escape velocity.Comment: 13 pages, 5 figures (4 color) accepted by Ap
Remarkable Spectral Variability of PDS 456
We report on the highest to date signal-to-noise-ratio X-ray spectrum of the
luminous quasar PDS 456, as obtained during two XMM-Newton orbits in September
2007. The present spectrum is considerably different from several previous
X-ray spectra recorded for PDS 456 since 1998. The ultra-high-velocity outflow
seen as recently as February 2007 is not detected in absorption. Conversely, a
significant reflection component is detected. The reflection model suggests the
reflecting medium may be outflowing at a velocity v/c = -0.06 +/- 0.02. The
present spectrum is analyzed in the context of the previous ones in an attempt
to understand all spectra within the framework of a single model. We examine
whether an outflow with variable partial covering of the X-ray source along the
line of sight that also reflects the source from other lines of sight can
explain the dramatic variations in the broad-band spectral curvature of PDS
456. It is established that absorption plays a major role in shaping the
spectrum of other epochs, while the 2007 XMM-Newton spectrum is dominated by
reflection, and the coverage of the source by the putative outflow is small (<
20%).Comment: submitted to Ap
Cereal variety trials, 1961-62
DURING the 1961-62 season cereal variety trials were sown at eight research stations in the medium and low rainfall areas of Western Australia
Linseed variety trials, 1963-64 season
RESULTS of 1963-64 linseed variety trials are available for four trials on research stations and for four trials on farmers\u27 properties.
These are shown in the table below. Excellent yields were obtained at some sites, while disappointing results were obtained at Chapman and Esperance.
Poor results at Esperance were due to the poor finish to the season
The Global Implications of the Hard X-ray Excess in Type 1 AGN
Recent evidence for a strong 'hard excess' of flux at energies > 20 keV in
some Suzaku observations of type 1 Active Galactic Nuclei (AGN) has motivated
an exploratory study of the phenomenon in the local type 1 AGN population. We
have selected all type 1 AGN in the Swift Burst Alert Telescope (BAT) 58-month
catalog and cross-correlated them with the holdings of the Suzaku public
archive. We find the hard excess phenomenon to be a ubiquitous property of type
1 AGN. Taken together, the spectral hardness and equivalent width of Fe K alpha
emission are consistent with reprocessing by an ensemble of Compton-thick
clouds that partially cover the continuum source. In the context of such a
model, ~ 80 % of the sample has a hardness ratio consistent with > 50% covering
of the continuum by low-ionization, Compton-thick gas. More detailed study of
the three hardest X-ray spectra in our sample reveal a sharp Fe K absorption
edge at ~ 7 keV in each of them, indicating that blurred reflection is not
responsible for the very hard spectral forms. Simple considerations place the
distribution of Compton-thick clouds at or within the optical broad line
region.Comment: Accepted for publication in Ap
Oats and barley in Western Australia
Over the five seasons 1948/49 to 1952/53, the latest for which figures are available, the acreages sown to oats and barley in Western Australia, have considerably expanded. Steady progress in clearing and land settlement and reasonably good export prices have been important factors in these increases
Trends in wheat area and production in W.A. since 1946
Statistical examination of data associated with wheat grown in Western Australia during the 29- year period ending in 1974 shows that areas sown and total production increased substantially. Average yields and protein per hectare both increased significantly, while wheat protein percentage increased slightly, but not significantly
The Variable X-ray Spectrum of Markarian 766 - II. Time-Resolved Spectroscopy
CONTEXT: The variable X-ray spectra of AGN systematically show steep
power-law high states and hard-spectrum low states. The hard low state has
previously been found to be a component with only weak variability. The origin
of this component and the relative importance of effects such as absorption and
relativistic blurring are currently not clear. AIMS: In a follow-up of previous
principal components analysis, we aim to determine the relative importance of
scattering and absorption effects on the time-varying X-ray spectrum of the
narrow-line Seyfert 1 galaxy Mrk~766. METHODS: Time-resolved spectroscopy,
slicing XMM and Suzaku data down to 25 ks elements, is used to investigate
whether absorption or scattering components dominate the spectral variations in
Mrk 766.Time-resolved spectroscopy confirms that spectral variability in Mrk
766 can be explained by either of two interpretations of principal components
analysis. Detailed investigation confirm rapid changes in the relative
strengths of scattered and direct emission or rapid changes in absorber
covering fraction provide good explanations of most of the spectral
variability. However, a strong correlation between the 6.97 keV absorption line
and the primary continuum together with rapid opacity changes show that
variations in a complex and multi-layered absorber, most likely a disk wind,
are the dominant source of spectral variability in Mrk 76
Wheat breeding and variety trials, 1963-64
A review of the wheat breeding and pedigree seed production by the Department of Agriculture.
Yields from the wheat variety trials at agricultural research stations during the 1963-64 season are presented and discussed
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