131. Prototype of the SST-1M Telescope Structure for the Cherenkov Telescope ArrayJacek Niemiec, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, 2015, objavljeni znanstveni prispevek na konferenci Ključne besede: very-high energy (VHE) gamma-ray astronomy, Cherenkov Telescope Array (CTA), small-size telescope (SST) for CTA, Davis-Cotton design
Objavljeno v RUNG: 08.11.2016; Ogledov: 4892; Prenosov: 221
 Celotno besedilo (1,35 MB) |
132. FERMI-LAT OBSERVATIONS OF THE LIGO EVENT GW150914Gabrijela Zaharijas, Collaboration Fermi LAT, Collaboration LIGO, 2016, izvirni znanstveni članek Opis: The Fermi Large Area Telescope (LAT) has an instantaneous field of view (FoV) covering ~1 5 of the sky and it completes a survey of the entire sky in high-energy gamma-rays every 3 hr. It enables searches for transient phenomena over timescales from milliseconds to years. Among these phenomena could be electromagnetic counterparts to gravitational wave (GW) sources. In this paper, we present a detailed study of the LAT observations relevant to Laser Interferometer Gravitational-wave Observatory (LIGO) event GW150914, which is the first direct detection of gravitational waves and has been interpreted as being due to the coalescence of two stellar-mass black holes. The localization region for GW150914 was outside the LAT FoV at the time of the GW signal. However, as part of routine survey observations, the LAT observed the entire LIGO localization region within ∼70 minutes of the trigger and thus enabled a comprehensive search for a γ-ray counterpart to GW150914. The study of the LAT data presented here did not find any potential counterparts to GW150914, but it did provide limits on the presence of a transient counterpart above 100 MeV on timescales of hours to days over the entire GW150914 localization region.
Ključne besede: gravitational waves, gamma rays
Objavljeno v RUNG: 20.06.2016; Ogledov: 5645; Prenosov: 0
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133. Sensitivity projections for dark matter searches with the Fermi large area telescopeGabrijela Zaharijas, Collaboration Fermi LAT, 2016, izvirni znanstveni članek Opis: 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 searchtechniques, 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 γ -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 bb ̄ 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 bb ̄(τ+τ−) annihilation channels.
Ključne besede: dark matter, gamma rays
Objavljeno v RUNG: 20.06.2016; Ogledov: 5651; Prenosov: 0
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136. Constraints on the Galactic Dark Matter signal from the Fermi-LAT measurement of the diffuse gamma-ray emissionGabrijela Zaharijas, 2012, objavljeni znanstveni prispevek na konferenci Opis: We study diffuse gamma-ray emission at intermediate Galactic latitudes measured by the Fermi Large Area Telescope with the aim of searching for a signal from dark matter annihilation or decay. In the absence of a robust dark matter signal, constraints are presented. We set both, conservative dark matter limits requiring that the dark matter signal does not exceed the observed diffuse gamma-ray emission and limits derived based on modeling the foreground astrophysical diffuse emission. Uncertainties in several parameters which characterize conventional astrophysical emission are taken into account using a profile likelihood formalism. The resulting limits impact the range of particle masses over which dark matter thermal production in the early Universe is possible, and challenge the interpretation of the PAMELA/Fermi-LAT cosmic ray anomalies as annihilation of dark matter.
Ključne besede: gamma rays, Galactic diffuse emission, dark matter serach
Objavljeno v RUNG: 03.05.2016; Ogledov: 5474; Prenosov: 0
Gradivo ima več datotek! Več... |
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139. Galactic Dark Matter signal and the Fermi-LAT measurement of the diffuse gamma-ray emissionGabrijela Zaharijas, objavljeni znanstveni prispevek na konferenci Opis: We study diffuse gamma-ray emission at intermediate Galactic latitudes measured by the Fermi LAT with the aim of searching for a signal from dark matter annihilation or decay. In the absence of a robust dark matter signal, constraints are presented. We present and improve upon conservative dark matter limits obtained with no modeling of the foreground astrophysical diffuse emission. We do so, by taking into account uncertainties in several parameters which characterize conventional astrophysical emission and using a profile likelihood formalism. The resulting limits impact the range of particle masses over which dark matter thermal production in the early Universe is possible, and challenge the interpretation of the PAMELA/Fermi-LAT cosmic ray anomalies as annihilation of dark matter.
Ključne besede: Dark matter, high-energy gamma rays
Objavljeno v RUNG: 21.03.2016; Ogledov: 5467; Prenosov: 0
Gradivo ima več datotek! Več... |
140. Prospects On Testing Lorentz Invariance Violation With The Cherenkov Telescope ArrayM. K. Daniel, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, 2015, objavljeni znanstveni prispevek na konferenci Ključne besede: Cherenkov Telescope Array (CTA), Lorentz Invariance Violation (LIV), Very High Energy (VHE) gamma-rays, fundamental physics probes, Active Galactic Nuclei (AGN), Gamma Ray Bursts (GRBs), pulsars
Objavljeno v RUNG: 14.03.2016; Ogledov: 5589; Prenosov: 226
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