77 research outputs found
Image-based deep learning for classification of noise transients in gravitational wave detectors
The detection of gravitational waves has inaugurated the era of gravitational
astronomy and opened new avenues for the multimessenger study of cosmic
sources. Thanks to their sensitivity, the Advanced LIGO and Advanced Virgo
interferometers will probe a much larger volume of space and expand the
capability of discovering new gravitational wave emitters. The characterization
of these detectors is a primary task in order to recognize the main sources of
noise and optimize the sensitivity of interferometers. Glitches are transient
noise events that can impact the data quality of the interferometers and their
classification is an important task for detector characterization. Deep
learning techniques are a promising tool for the recognition and classification
of glitches. We present a classification pipeline that exploits convolutional
neural networks to classify glitches starting from their time-frequency
evolution represented as images. We evaluated the classification accuracy on
simulated glitches, showing that the proposed algorithm can automatically
classify glitches on very fast timescales and with high accuracy, thus
providing a promising tool for online detector characterization.Comment: 25 pages, 8 figures, accepted for publication in Classical and
Quantum Gravit
The gamma-ray pulsar in the Gamma Cygni supernova remnant
We report updated results on PSR J2021+4026, based on the latest data collected by the Fermi Large Area Telescope. This pulsar was discovered using blind search techniques in the error box of the EGRET source 3EG J2020+4017 in the Gamma Cygni supernova remnant (SNR G78.2+2.1). This source is located in a quite complex region, mainly because of the highly structured diffuse Galactic background. Since its discovery in gamma rays no other pulsed counterparts for PSR
J2021+4026 have been found at other wavelengths (e.g., radio), and this could put important constraints on its emission characteristics. We present recent results of the analysis of the gamma-ray emission from this pulsar, including spatial analysis, as well as of the temporal and spectral analysis of this source
Model and simulation of gamma-ray pulsar emission in GLAST
La tesi descrive un lavoro di simulazione di pulsar a raggi gamma di utilita’ per la missione GLAS
Searching for Gamma-Ray counterparts to Gravitational Waves from merging binary neutron stars with the Cherenkov Telescope Array
The merger of binary neutron star (BNS) systems are predicted to be
progenitors of short gamma-ray bursts (GRBs); the definitive probe of this
association came with the recent detection of gravitational waves (GWs) from a
BNS merger by Advanced LIGO and Advanced Virgo (GW170817), in coincidence with
the short GRB 170817A observed by Fermi-GBM and INTEGRAL. Short GRBs are also
expected to emit very-high energy (VHE, > 100 GeV) photons and VHE
electromagnetic (EM) upper limits have been set with observations performed by
ground-based gamma-ray detectors and during the intense EM follow-up campaign
associated with GW170817/GRB 170817A. In the next years, the searches for VHE
EM counterparts will become more effective thanks to the Cherenkov Telescope
Array (CTA): this instrument will be fundamental for the EM follow-up of
transient GW events at VHE, owing to its unprecedented sensitivity, rapid
response (few tens of seconds) and capability to monitor large sky areas via
survey-mode operation. We present a comprehensive study on the prospects for
joint GW and VHE EM observations of merging BNSs with Advanced LIGO, Advanced
Virgo and CTA, based on detailed simulations of the multi-messenger emission
and detection. We propose a new observational strategy optimized on the prior
assumptions about the EM emission. The method can be further generalized to
include other electromagnetic emission models. According to this study CTA will
cover most of the region of the GW skymap for the intermediate and most
energetic on-axis GRBs associated to the GW event. We estimate the expected
joint GW and VHE EM detection rates and we found this rate goes from 0.08 up to
0.5 events per year for the most energetic EM sources.Comment: 26 pages, 8 figures. Submitted to JCA
Prospects for joint observations of gravitational waves and gamma rays from merging neutron star binaries
The detection of the events GW150914 and GW151226, both consistent with the
merger of a binary black hole system (BBH), opened the era of gravitational
wave (GW) astronomy. Besides BBHs, the most promising GW sources are the
coalescences of binary systems formed by two neutron stars or a neutron star
and a black hole. These mergers are thought to be connected with short Gamma
Ray Bursts (GRBs), therefore combined observations of GW and electromagnetic
(EM) signals could definitively probe this association. We present a detailed
study on the expectations for joint GW and high-energy EM observations of
coalescences of binary systems of neutron stars with Advanced Virgo and LIGO
and with the \emph{Fermi} gamma-ray telescope. To this scope, we designed a
dedicated Montecarlo simulation pipeline for the multimessenger emission and
detection by GW and gamma-ray instruments, considering the evolution of the GW
detector sensitivities. We show that the expected rate of joint detection is
low during the Advanced Virgo and Advanced LIGO 2016-2017 run; however, as the
interferometers approach their final design sensitivities, the rate will
increase by a factor of ten. Future joint observations will help to
constrain the association between short GRBs and binary systems and to solve
the puzzle of the progenitors of GWs. Comparison of the joint detection rate
with the ones predicted in this paper will help to constrain the geometry of
the GRB jet.Comment: 24 pages, 4 figure
Recommended from our members
GLAST LAT And Pulsars: What Do We Learn from Simulations?
Gamma-ray pulsars are among the best targets for the Large Area Telescope (LAT) aboard the GLAST mission. The higher sensitivity, time and energy resolution of the LAT will provide data of fundamental importance to understand the physics of these fascinating objects. Powerful tools for studying the LAT capabilities for pulsar science are the simulation programs developed within the GLAST Collaboration. Thanks to these simulations it is possible to produce a detailed distribution of gamma-ray photons in energy and phase that can be folded through the LAT Instrument Response Functions (IRFs). Here we present some of the main interesting results from the simulations developed to study the discovery potential of the LAT. In particular we will focus on the capability of the LAT to discover new radio-loud gamma-ray pulsars, on the discrimination between Polar Cap and Outer Gap models, and on the LAT pulsar sensitivity
Sensitivity Projections for Dark Matter Searches with the Fermi Large Area Telescope
The nature of dark matter is a longstanding enigma of physics; it may consist
of particles beyond the Standard Model that are still elusive to experiments.
Among indirect search techniques, which look for stable products from the
annihilation or decay of dark matter particles, or from axions coupling to
high-energy photons, observations of the -ray sky have come to
prominence over the last few years, because of the excellent sensitivity of the
Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope mission. The
LAT energy range from 20 MeV to above 300 GeV is particularly well suited for
searching for products of the interactions of dark matter particles. In this
report we describe methods used to search for evidence of dark matter with the
LAT, and review the status of searches performed with up to six years of LAT
data. We also discuss the factors that determine the sensitivities of these
searches, including the magnitudes of the signals and the relevant backgrounds,
considering both statistical and systematic uncertainties. We project the
expected sensitivities of each search method for 10 and 15 years of LAT data
taking. In particular, we find that the sensitivity of searches targeting dwarf
galaxies, which provide the best limits currently, will improve faster than the
square root of observing time. Current LAT limits for dwarf galaxies using six
years of data reach the thermal relic level for masses up to 120 GeV for the
annihilation channel for reasonable dark matter density profiles.
With projected discoveries of additional dwarfs, these limits could extend to
about 250 GeV. With as much as 15 years of LAT data these searches would be
sensitive to dark matter annihilations at the thermal relic cross section for
masses to greater than 400 GeV (200 GeV) in the ()
annihilation channels.Comment: Updated with a few additional and corrected references; otherwise,
text is identical to previous version. Submitted on behalf of the Fermi-LAT
collaboration. Accepted for publication in Physics Reports, 59 pages, 34
figures; corresponding author: Eric Charles ([email protected]
POLARIX: a pathfinder mission of X-ray polarimetry
Since the birth of X-ray astronomy, spectral, spatial and timing observation
improved dramatically, procuring a wealth of information on the majority of the
classes of the celestial sources. Polarimetry, instead, remained basically
unprobed. X-ray polarimetry promises to provide additional information
procuring two new observable quantities, the degree and the angle of
polarization. POLARIX is a mission dedicated to X-ray polarimetry. It exploits
the polarimetric response of a Gas Pixel Detector, combined with position
sensitivity, that, at the focus of a telescope, results in a huge increase of
sensitivity. Three Gas Pixel Detectors are coupled with three X-ray optics
which are the heritage of JET-X mission. POLARIX will measure time resolved
X-ray polarization with an angular resolution of about 20 arcsec in a field of
view of 15 arcmin 15 arcmin and with an energy resolution of 20 % at 6
keV. The Minimum Detectable Polarization is 12 % for a source having a flux of
1 mCrab and 10^5 s of observing time. The satellite will be placed in an
equatorial orbit of 505 km of altitude by a Vega launcher.The telemetry
down-link station will be Malindi. The pointing of POLARIX satellite will be
gyroless and it will perform a double pointing during the earth occultation of
one source, so maximizing the scientific return. POLARIX data are for 75 % open
to the community while 25 % + SVP (Science Verification Phase, 1 month of
operation) is dedicated to a core program activity open to the contribution of
associated scientists. The planned duration of the mission is one year plus
three months of commissioning and SVP, suitable to perform most of the basic
science within the reach of this instrument.Comment: 42 pages, 28 figure
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