282 research outputs found
Uber Terpene. LXXXIV.* Ober die Struktur des Arctiopikrin - des Sesquiterpenlactons aus Arctium minus B e r n h.
Es wurde die Struktur des friiher beschriebenen Lactons aus Arctium minus B er n h. studiert und bewiesen, dass dieser Stoff, welchem die Autoren die Bezeichnung Arctiopikrin gaben, die sumare Formel C19H28O6 hat. Weiter stellten sie fest, dass Arctiopikrin der Ester- der B-Hydroxyisobuttersaure und des monocyklischen Dihydroxylactons C15H22O4 (Arctiolid) ist, der einen zehngliedrigen Kohlenstoffcyklus mit zwei Doppelbindungen enthalt. Fiir Arctiopikrin wurden zwei alternative Formeln I oder II vorgeschlagen
A 0535+26 in the August/September 2005 outburst observed by RXTE and INTEGRAL
In this Letter we present results from INTEGRAL and RXTE observations of the
spectral and timing behavior of the High Mass X-ray Binary A 0535+26 during its
August/September 2005 normal (type I) outburst with an average flux
F(5-100keV)~400mCrab. The search for cyclotron resonance scattering features
(fundamental and harmonic) is one major focus of the paper. Our analysis is
based on data from INTEGRAL and RXTE Target of Opportunity Observations
performed during the outburst. The pulse period is determined. X-ray pulse
profiles in different energy ranges are analyzed. The broad band INTEGRAL and
RXTE pulse phase averaged X-ray spectra are studied. The evolution of the
fundamental cyclotron line at different luminosities is analyzed. The pulse
period P is measured to be 103.39315(5)s at MJD 53614.5137. Two absorption
features are detected in the phase averaged spectra at E_1~45keV and
E_2~100keV. These can be interpreted as the fundamental cyclotron resonance
scattering feature and its first harmonic and therefore the magnetic field can
be estimated to be B~4x10^12G.Comment: 4 pages, 5 figures, accepted for publication in A&A Letter
Timing Analysis with INTEGRAL: Comparing Different Reconstruction Algorithms
INTEGRAL is one of the few instruments capable of detecting X-rays above 20keV. It is therefore in principle well suited for studying X-ray variability in this regime. Because INTEGRAL uses coded mask instruments for imaging, the reconstruction of light curves of X-ray sources is highly non-trivial. We present results from the comparison of two commonly employed algorithms, which primarily measure flux from mask deconvolution (ii-lc-extract) and from calculating the pixel illuminated fraction (ii-light). Both methods agree well for timescales above about 10 s, the highest time resolution for which image reconstruction is possible. For higher time resolution, ii-light produces meaningful results, although the overall variance of the lightcurves is not preserved
Spectro-timing analysis of Cygnus X-1 during a fast state transition
We present the analysis of two long, quasi-uninterrupted RXTE observations of
Cygnus X-1 that span several days within a 10 d interval. The spectral
characteristics during this observation cover the region where previous
observations have shown the source to be most dynamic. Despite that the source
behavior on time scales of hours and days is remarkably similar to that on year
time scales. This includes a variety of spectral/temporal correlations that
previously had only been observed over Cyg X-1's long-term evolution.
Furthermore, we observe a full transition from a hard to a soft spectral state
that occurs within less than 2.5 hours - shorter than previously reported for
any other similar Cyg X-1 transition. We describe the spectra with a
phenomenological model dominated by a broken power law, and we fit the X-ray
variability power spectra with a combination of a cutoff power law and
Lorentzian components. The spectral and timing properties are correlated: the
power spectrum Lorentzian components have an energy-dependent amplitude, and
their peak frequencies increase with photon spectral index. Averaged over
3.2-10 Hz, the time lag between the variability in the 4.5-5.7 keV and 9.5-15
keV bands increases with decreasing hardness when the variability is dominated
by the Lorentzian components during the hard state. The lag is small when there
is a large power law noise contribution, shortly after the transition to the
soft state. Interestingly, the soft state not only shows the shortest lags, but
also the longest lags when the spectrum is at its softest and faintest. We
discuss our results in terms of emission models for black hole binaries.Comment: 13 pages, 15 figures, accepted for publication in Astronomy and
Astrophysic
Finding a 24-day orbital period for the X-ray binary 1A 1118-616
We report the first determination of the binary period and orbital ephemeris
of the Be X-ray binary containing the pulsar 1A 1118-616 (35 years after the
discovery of the source). The orbital period is found to be Porb = 24.0 +/- 0.4
days. The source was observed by RXTE during its last large X-ray outburst in
January 2009, which peaked at MJD 54845.4, by taking short observations every
few days, covering an elapsed time comparable to the orbital period. Using the
phase connection technique, pulse arrival time delays could be measured and an
orbital solution determined. The data are consistent with a circular orbit, and
the time of 90 degrees longitude was found to be T90 = MJD 54845.37(10), which
is coincident with that of the peak X-ray flux.Comment: 5 pages, 7 figures, accepted by A&
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