20,119 research outputs found
SN/GRB connection: a statistical approach with BATSE and Asiago Catalogues
Recent observations suggest that some types of GRB are physically connected
with SNe of type Ib/c. However, it has been pointed out by several authors that
some GRBs could be associated also with other types of core-collapse SNe (type
IIdw/IIn). On the basis of a comphrensive statistical study, which has made use
of the BATSE and Asiago catalogues, we have found that: i) the temporal and
spacial distribution of SNe-Ib/c is marginally correlated with that of the
BATSE GRBs; ii) we do not confirm the existence of an association between GRBs
and SNe-IIdw/IIn.Comment: Proceeding of the 4th workshop on Gamma Ray Bursts in the Afterglow
Era, Rome, 2004; 4 page
Mining the XRT archive to probe the X-ray absorber structure in the AGN population
One of the key ingredients of the Unified Model of Active Galactic Nuclei
(AGN) is the presence of a torus-like optically thick medium composed by dust
and gas around the putative supermassive black hole. However, the structure,
size and composition of this circumnuclear medium are still matter of debate.
To this end, the search for column density variations through X-ray monitoring
on different timescales (months, weeks and few days) is fundamental to
constrain size, kinematics and location of the X-ray absorber(s). Here we
describe our project of mining the Swift-XRT archive to assemble a sample of
AGN with extreme column density variability and determining the physical
properties of the X-ray absorber(s). We also present the results obtained from
a daily-weekly Swift-XRT follow-up monitoring recently performed on one of the
most interesting new candidates for variability discovered so far, Mrk 915.Comment: 6 pages, 3 figures. To appear in Proceedings of Science for the
"Swift: 10 years of Discovery" meeting, held in Rome (2-5 December 2014
The structure of the X-ray absorber in Mrk 915 revealed by Swift
In this paper we present the results obtained with a monitoring programme (23
days long) performed with Swift-XRT on the local Seyfert galaxy Mrk 915. The
light-curve analysis shows a significant count rate variation (about a factor
of 2-3) on a time-scale of a few days, while the X-ray colours show a change in
the spectral curvature below 2 keV and the presence of two main spectral
states. From the spectral analysis we find that the observed variations can be
explained by the change of the intrinsic nuclear power (about a factor of 1.5)
coupled with a change of the properties of an ionized absorber. The quality of
the data prevents us from firmly establishing if the spectral variation is due
to a change in the ionization state and/or in the covering factor of the
absorbing medium. The latter scenario would imply a clumpy structure of the
ionized medium. By combining the information provided by the light curve and
the spectral analyses, we can derive some constraints on the location of the
absorber under the hypotheses of either homogeneous or clumpy medium. In both
cases, we find that the absorber should be located inside the outer edge of an
extended torus and, in particular, under the clumpy hypothesis, it should be
located near, or just outside, to the broad emission line region.Comment: 8 pages, 6 figures, 1 table. Accepted for publication on MNRA
Securing the church of Madonna del Sole during the emergency phase of 2016 earthquake: interoperability of different actors as an instrument for reducing seismic risk of damaged built heritage
XMM-Newton and NuSTAR joint observations of Mrk 915: a deep look into the X-ray properties
We report on the X-ray monitoring programme (covering slightly more than 11
days) carried out jointly by XMM-Newton and NuSTAR on the intermediate Seyfert
galaxy Mrk 915. The light curves extracted in different energy ranges show a
variation in intensity but not a significant change in spectral shape. The
X-ray spectra reveal the presence of a two-phase warm absorber: a fully
covering mildly ionized structure [log xi/(erg cm/s)~2.3, NH~1.3x10^21 cm-2]
and a partial covering (~90 per cent) lower ionized one [log xi/(erg cm/s)~0.6,
NH~2x10^22 cm-2]. A reflection component from distant matter is also present.
Finally, a high-column density (NH~1.5x10^23 cm-2) distribution of neutral
matter covering a small fraction of the central region is observed, almost
constant, in all observations. Main driver of the variations observed between
the datasets is a decrease in the intrinsic emission by a factor of ~1.5.
Slight variations in the partial covering ionized absorber are detected, while
the data are consistent with no variation of the total covering absorber. The
most likely interpretation of the present data locates this complex absorber
closer to the central source than the narrow line region, possibly in the broad
line region, in the innermost part of the torus, or in between. The neutral
obscurer may either be part of this same stratified structure or associated
with the walls of the torus, grazed by (and partially intercepting) the line of
sight.Comment: 14 pages, 10 figures, 4 tables. Accepted for publication in MNRA
Antiproton modulation in the Heliosphere and AMS-02 antiproton over proton ratio prediction
We implemented a quasi time-dependent 2D stochastic model of solar modulation
describing the transport of cosmic rays (CR) in the heliosphere. Our code can
modulate the Local Interstellar Spectrum (LIS) of a generic charged particle
(light cosmic ions and electrons), calculating the spectrum at 1AU. Several
measurements of CR antiparticles have been performed. Here we focused our
attention on the CR antiproton component and the antiproton over proton ratio.
We show that our model, using the same heliospheric parameters for both
particles, fit the observed anti-p/p ratio. We show a good agreement with
BESS-97 and PAMELA data and make a prediction for the AMS-02 experiment
Le spectromètre de masse à temps de vol DEPIL et son utilisation pour la mesure de masses de protéines élevées dépassant 5 000 u : insuline et lyzozyme
Un spectromètre de masse à temps de vol a été construit à l'Institut de Physique Nucléaire d'Orsay pour mesurer des masses de molécules diverses. La gamme de masses accessibles est comprise entre 1 et 20 000 u. Nous présentons ici une description succincte de l'appareillage avec des exemples de mesures de hautes masses
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