884 research outputs found
An XMM-Newton look at the strongly variable radio-weak BL Lac Fermi J1544-0639
Fermi J1544-0639/ASASSN-17gs/AT2017egv was identified as a gamma-ray/optical
transient on May 15, 2017. Subsequent multiwavelength observations suggest that
this source may belong to the new class of radio-weak BL Lacs. We studied the
X-ray spectral properties and short-term variability of Fermi J1544-0639 to
constrain the X-ray continuum emission mechanism of this peculiar source. We
present the analysis of an XMM-Newton observation, 56 ks in length, performed
on February 21, 2018. The source exhibits strong X-ray variability, both in
flux and spectral shape, on timescales of ~10 ks, with a harder-when-brighter
behaviour typical of BL Lacs. The X-ray spectrum is nicely described by a
variable broken power law, with a break energy of around 2.7 keV consistent
with radiative cooling due to Comptonization of broad-line region photons. We
find evidence for a `soft excess', nicely described by a blackbody with a
temperature of ~0.2 keV, consistent with being produced by bulk Comptonization
along the jet.Comment: 11 pages, 12 figures. Accepted for publication in Astronomy &
Astrophysic
Hard X-ray selected giant radio galaxies - I. The X-ray properties and radio connection
We present the first broad-band X-ray study of the nuclei of 14 hard X-ray
selected giant radio galaxies, based both on the literature and on the analysis
of archival X-ray data from NuSTAR, XMM-Newton, Swift and INTEGRAL. The X-ray
properties of the sources are consistent with an accretion-related X-ray
emission, likely originating from an X-ray corona coupled to a radiatively
efficient accretion flow. We find a correlation between the X-ray luminosity
and the radio core luminosity, consistent with that expected for AGNs powered
by efficient accretion. In most sources, the luminosity of the radio lobes and
the estimated jet power are relatively low compared with the nuclear X-ray
emission. This indicates that either the nucleus is more powerful than in the
past, consistent with a restarting of the central engine, or that the giant
lobes are dimmer due to expansion losses.Comment: 11 pages, 3 figures. Accepted for publication in MNRA
A simple beam model to analyse the durability of adhesively bonded tile floorings in presence of shrinkage
A simple beam model for the evaluation of tile debonding due to substrate shrinkage is presented. The tile-adhesive-substrate package is modeled as an Euler-Bernoulli beam laying on a two-layer elastic foundation. An effective discrete model for inter-tile grouting is introduced with the aim of modelling workmanship defects due to partial filled groutings. The model is validated using the results of a 2D FE model. Different defect configurations and adhesive typologies are analysed, focusing the attention on the prediction of normal stresses in the adhesive layer under the assumption of Mode I failure of the adhesive
INTEGRAL high energy behaviour of 4U 1812-12
The low mass X-ray binary system 4U 1812-12 was monitored with the INTEGRAL
observatory in the period 2003-2004 and with BeppoSAX on April 20, 2000. We
report here on the spectral and temporal analysis of both persistent and burst
emission. The full data set confirms the persistent nature of this burster, and
reveals the presence of emission up to 200 keV. The persistent spectrum is well
described by a comptonization (CompTT) model plus a soft blackbody component.
The source was observed in a hard spectral state with a 1-200 keV luminosity of
2*10^(36) ergs/s and L/LEdd~1% and no meaningful flux variation has been
revealed, as also confirmed by a 2004 RXTE observation. We have also detected 4
bursts showing double peaked profiles and blackbody spectra with temperatures
ranging from 1.9 to 3.1 keV.Comment: 6 pages, 4 figures. Accepted for publication by A&
On the Combined Use of Ground Penetrating Radar and Crack Meter Sensors for Structural Monitoring: Application to the Historical Consoli Palace in Gubbio, Italy
The paper deals with joint use of non-invasive monitoring technologies and civil engineering analysis methods aimed at providing multi-sensing information about the structural health of historical and cultural assets. Specifically, linear variable displacement transducers (LVDT) and ground penetrating radar (GPR) are considered for monitoring a significant crack affecting the Consoli Palace in Gubbio, Italy, precisely one of the walls of the cross-hall leading to the Loggia. In this frame, LVDT is adopted to control horizontal amplitude variations of the crack, while GPR is applied to investigate the wall interior and to detect the occurrence of inner issues related to the visible appearance of the crack on the wall surface. The effectiveness of GPR surveys is improved by means of a microwave tomography-based data processing strategy. The main result is that there is a consistency between the monitoring outputs of LVDT, which allowed us to display the crack widening/contraction due to the seasonal temperature variations, and the fact that no significant changes of the geometry of the inner areas of the walls were observed by the GPR
INTEGRAL/IBIS search for e-e+ annihilation radiation from the Galactic Center Region
Electron-positron annihilation radiation from the Galactic Center region has
been detected since the seventies, but its astrophysical origin is still a
topic of a scientific debate. We have analyzed data of the gamma-ray imager
IBIS/ISGRI onboard of ESA's INTEGRAL platform in the ee line.
During the first year of the missions Galactic Center Deep Exposure no evidence
for point sources at 511 keV has been found in the ISGRI data; the
upper limit for resolved single point sources is estimated to be .Comment: 6 pages, 3 figures; Cospar 2004. To be published in: Advances in
Space Researc
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