163 research outputs found
Fermi-LAT Observation of Non-Blazar AGNs
We report on a detailed investigation of the -ray emission from 26
non-blazar AGNs based on the Fermi LAT data accumulated for 7 years. The photon
index of non-blazar AGNs changes in the range of 1.84-2.86 and the flux varies
from a few times to . Over long time periods, power-law provides an adequate
description of the -ray spectra of almost all sources. Significant
curvature is observed in the -ray spectra of NGC 1275, NGC 6251, SBS
0846+513 and PMN J0948+0022 and their spectra are better described by
log-parabola or power-law with exponential cut-off models. The -ray
spectra of PKS 0625-25 and 3C 380 show a possible deviation from a simple
power-law shape, indicating a spectral cutoff around the observed photon energy
of GeV and GeV, respectively.
Our analysis confirms the previous finding of an unusual spectral turnover in
the -ray spectrum of Cen A: the photon index changes from
to at GeV. In the plane, the
luminosity of non-blazar AGNs is spread in the range of , where the lowest luminosity have FRI radio galaxies (but
typically appear with a harder photon index) and the highest- SSRQs/NLSY1s
(with softer photon indexes). We confirm the previously reported
short-timescale flux variability of NGC 1275 and 3C 120. The -ray
emission from NLSY1s, 1H 0323+342, SBS 0846+513 and PMN J0948+0022, is
variable, showing flares in short scales sometimes accompanied by a moderate
hardening of their spectra (e.g., on MJD 56146.8 the -ray photon index
of SBS 0846+513 was ). 3C 111, Cen A core, 3C 207, 3C 275.1, 3C
380, 4C+39.23B, PKS 1502+036 and PKS 2004-447 show a long-timescale flux
variability in the -ray band.Comment: Accepted for publication in Astronomy & Astrophysics. The abstract
has been shortened to comply with the size limit set by arXi
Comparing 3C 120 jet emission at small and large scales
Context. Important information on the evolution of the jet can be obtained by
comparing the physical state of the plasma at its propagation through the
broad-line region (where the jet is most likely formed) into the intergalactic
medium, where it starts to significantly decelerate. Aims. We compare the
constraints on the physical parameters in the innermost ( pc) and outer
( kpc) regions of the 3C 120 jet by means of a detailed multiwavelength
analysis and theoretical modeling of their broadband spectra. Methods.The data
collected by Fermi LAT, Swift and Chandra are analyzed together and the
spectral energy distributions are modeled using a leptonic synchrotron and
inverse Compton model, taking into account the seed photons originating inside
and outside of the jet. The model parameters are estimated using the MCMC
method. Results. The -ray flux from the inner jet of 3C 120 was
characterized by rapid variation from MJD 56900 to MJD 57300. Two strong flares
were observed on April 24, 2015 when, within 19.0 minutes and 3.15 hours the
flux was as high as and
respectively. The broadband
emission in the quiet and flaring states can be described as SSC emission while
IC scattering of dusty torus photons cannot be excluded for the flaring states.
The X-ray emission from the knots can be well reproduced by IC scattering of
CMB photons only if the jet is highly relativistic (since even when
still ). These extreme requirements can be somewhat
softened assuming the X-rays are from the synchrotron emission of a second
population of very-high-energy electrons. Conclusions. We found that the jet
power estimated at two scales is consistent, suggesting that the jet does not
suffer severe dissipation, it simply becomes radiatively inefficient.Comment: Accepted for publication in Astronomy & Astrophysics. The abstract
has been shortened to comply with the size limit set by arXi
Control and measuring devices for controlling the temperature regime of the cooking cabinet
The article considers issues connected to natural lighting in rooms. The problem of lack of natural light in an apartment of a typical building of the M111-90 series in Belarus is described and ways of its solution are presented
Control and measuring devices for controlling the temperature regime of the cooking cabinet
The article considers issues connected to natural lighting in rooms. The problem of lack of natural light in an apartment of a typical building of the M111-90 series in Belarus is described and ways of its solution are presented
PION: Simulations of wind-blown nebulae
Computational astrophysic
Constraints on the intergalactic magnetic field using Fermi-LAT and H.E.S.S. blazar observations
Magnetic fields in galaxies and galaxy clusters are believed to be the result
of the amplification of intergalactic seed fields during the formation of
large-scale structures in the universe. However, the origin, strength, and
morphology of this intergalactic magnetic field (IGMF) remain unknown. Lower
limits on (or indirect detection of) the IGMF can be obtained from observations
of high-energy gamma rays from distant blazars. Gamma rays interact with the
extragalactic background light to produce electron-positron pairs, which can
subsequently initiate electromagnetic cascades. The -ray signature of
the cascade depends on the IGMF since it deflects the pairs. Here we report on
a new search for this cascade emission using a combined data set from the Fermi
Large Area Telescope and the High Energy Stereoscopic System. Using
state-of-the-art Monte Carlo predictions for the cascade signal, our results
place a lower limit on the IGMF of G for a coherence
length of 1 Mpc even when blazar duty cycles as short as 10 yr are assumed.
This improves on previous lower limits by a factor of 2. For longer duty cycles
of () yr, IGMF strengths below G
( G) are excluded, which rules out specific models for IGMF
generation in the early universe.Comment: 20 pages, 7 figures, 4 tables. Accepted for publication in ApJ
Letters. Auxiliary data is provided in electronic format at
https://zenodo.org/record/801431
HESS J1809193: a halo of escaped electrons around a pulsar wind nebula?
Context. HESS J1809193 is an unassociated very-high-energy -ray
source located on the Galactic plane. While it has been connected to the nebula
of the energetic pulsar PSR J18091917, supernova remnants and molecular
clouds present in the vicinity also constitute possible associations. Recently,
the detection of -ray emission up to energies of 100 TeV with the
HAWC observatory has led to renewed interest in HESS J1809193.
Aims. We aim to understand the origin of the -ray emission of HESS
J1809193.
Methods. We analysed 93.2 h of data taken on HESS J1809193 above 0.27 TeV
with the High Energy Stereoscopic System (H.E.S.S.), using a multi-component,
three-dimensional likelihood analysis. In addition, we provide a new analysis
of 12.5 yr of Fermi-LAT data above 1 GeV within the region of HESS J1809193.
The obtained results are interpreted in a time-dependent modelling framework.
Results. For the first time, we were able to resolve the emission detected
with H.E.S.S. into two components: an extended component that exhibits a
spectral cut-off at 13 TeV, and a compact component that is located close
to PSR J18091917 and shows no clear spectral cut-off. The Fermi-LAT analysis
also revealed extended -ray emission, on scales similar to that of the
extended H.E.S.S. component.
Conclusions. Our modelling indicates that based on its spectrum and spatial
extent, the extended H.E.S.S. component is likely caused by inverse Compton
emission from old electrons that form a halo around the pulsar wind nebula. The
compact component could be connected to either the pulsar wind nebula or the
supernova remnant and molecular clouds. Due to its comparatively steep
spectrum, modelling the Fermi-LAT emission together with the H.E.S.S.
components is not straightforward. (abridged)Comment: 14 pages, 10 figures. Accepted for publication in A&A. Corresponding
authors: Vikas Joshi, Lars Mohrman
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