12,726 research outputs found
Fermi detected blazars seen by INTEGRAL
Multiwavelength observations are essential to constrain physical parameters
of the blazars observed by Fermi/LAT. Among the 187 AGN significantly detected
in public INTEGRAL data above 20 keV by the imager IBIS/ISGRI, 20 blazars were
detected. 15 of these sources allowed significant spectral extraction. They
show hard X-ray spectra with an average photon index of 2.1+-0.1 and a hard
X-ray luminosity of L(20-100 keV) = 1.3e46 erg/s. 15 of the INTEGRAL blazars
are also visible in the first 16 months of the Fermi/LAT data, thus allowing to
constrain the inverse Compton branch in these cases. Among others, we analyse
the LAT data of four blazars which were not included in the Fermi LAT Bright
AGN Sample based on the first 3 months of the mission: QSO B0836+710, H
1426+428, RX J1924.8-2914, and PKS 2149-306. Especially for blazars during
bright outbursts, as already observed simultaneously by INTEGRAL and Fermi
(e.g. 3C 454.3 and Mrk 421), INTEGRAL provides unique spectral coverage up to
several hundred keV. We present the spectral analysis of INTEGRAL and Fermi
data and demonstrate the potential of INTEGRAL observations of Fermi detected
blazars in outburst by analysing the combined data set of the persistent radio
galaxy Cen A.Comment: 5 pages, 5 figures, 2009 Fermi Symposium, eConf Proceedings C09112
A hot bubble at the centre of M81
Context. Messier 81 has the nearest active nucleus with broad H
emission. A detailed study of this galaxy's centre is important for
understanding the innermost structure of the AGN phenomenon.
Aims. Our goal is to seek previously undetected structures using additional
techniques to reanalyse a data cube obtained with the GMOS-IFU installed on the
Gemini North telescope (Schnorr M\"uller et al. 2011).
Method. We analysed the data cube using techniques of noise reduction,
spatial deconvolution, starlight subtraction, PCA tomography, and comparison
with HST images.
Results. We identified a hot bubble with T 43500 K that is associated
with strong emission of [N II]5755\AA\ and a high [O
I]6300/H ratio; the bubble displays a bluish continuum,
surrounded by a thin shell of H + [N II] emission. We also reinterpret
the outflow found by Schnorr M\"uller et al. (2011) showing that the
blueshifted cone nearly coincides with the radio jet, as expected.
Conclusions. We interpret the hot bubble as having been caused by post
starburst events that left one or more clusters of young stars, similar to the
ones found at the centre of the Milky Way, such as the Arches and the IRS 16
clusters. Shocked structures from combined young stellar winds or supernova
remnants are probably the cause of this hot gas and the low ionization
emission.Comment: 5 pages, 4 figures, accepted for publication in A&
Bounds on hep neutrinos
The excess of highest energy solar-neutrino events recently observed by
Superkamiokande can be in principle explained by anomalously high
-neutrino flux . Without using SSM calculations, from the
solar luminosity constraint we derive that cannot exceed
the SSM estimate by more than a factor three. If one makes the additional
hypothesis that neutrino production occurs where the He concentration
is at equilibrium, helioseismology gives an upper bound which is (less then)
two times the SSM prediction. We argue that the anomalous -neutrino flux
of order of that observed by Superkamiokande cannot be explained by
astrophysics, but rather by a large production cross-section.Comment: 7 pages, RevTeX fil
NGC 7097: the AGN and its mirror, revealed by PCA Tomography
Three-dimensional (3D) spectroscopy techniques are becoming more and more
popular, producing an increasing number of large data cubes. The challenge of
extracting information from these cubes requires the development of new
techniques for data processing and analysis. We apply the recently developed
technique of Principal Component Analysis (PCA) Tomography to a data cube from
the center of the elliptical galaxy NGC 7097 and show that this technique is
effective in decomposing the data into physically interpretable information. We
find that the first five principal components of our data are associated with
distinct physical characteristics. In particular, we detect a LINER with a weak
broad component in the Balmer lines. Two images of the LINER are present in our
data, one seen through a disk of gas and dust, and the other after scattering
by free electrons and/or dust particles in the ionization cone. Furthermore, we
extract the spectrum of the LINER, decontaminated from stellar and extended
nebular emission, using only the technique of PCA Tomography. We anticipate
that the scattered image has polarized light, due to its scattered nature.Comment: 12 pages, 5 figures, accepted for publication in ApJ Letter
Properties of (GaIn)O over the whole range
Using density-functional ab initio theoretical techniques, we study
(GaIn)O in both its equilibrium structures (monoclinic
and bixbyite) and over the whole range of composition. We establish
that the alloy exhibits a large and temperature-independent miscibility gap. On
the low- side, the favored phase is isostructural with -GaO;
on the high- side, it is isostructural with bixbyite InO. The
miscibility gap opens between approximately 15\% and 55\% In content for the
bixbyite alloy grown epitaxially on InO, and 15\% and 85\% In content
for the free-standing bixbyite alloy. The gap, volume and band offsets to the
parent compound also exhibit anomalies as function of . Specifically, the
offsets in epitaxial conditions are predominantly type-B staggered, but have
opposite signs in the two end-of-range phases.Comment: 7 pages, 4 figure
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