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21.
Galactic Center gamma-ray "excess" from an active past of the Galactic Centre?
Gabrijela Zaharijas, Pasquale D. Serpico, Jovana Petrović, 2014, original scientific article

Found in: ključnih besedah
Keywords: gamma rays, diffuse emission, Galactic center
Published: 09.05.2017; Views: 1629; Downloads: 11
URL Fulltext (0,00 KB)

22.
Sensitivity projections for dark matter searches with the Fermi large area telescope
Gabrijela Zaharijas, Collaboration Fermi LAT, 2016, original scientific article

Abstract: 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.
Found in: ključnih besedah
Keywords: dark matter, gamma rays
Published: 20.06.2016; Views: 2384; Downloads: 0
.pdf Fulltext (4,66 MB)

23.
FERMI-LAT OBSERVATIONS OF THE LIGO EVENT GW150914
Gabrijela Zaharijas, Collaboration Fermi LAT, Collaboration LIGO, 2016, original scientific article

Abstract: 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.
Found in: ključnih besedah
Summary of found: ...survey of the entire sky in high-energy gamma-rays every 3 hr. It enables searches for...
Keywords: gravitational waves, gamma rays
Published: 20.06.2016; Views: 2440; Downloads: 0
.pdf Fulltext (2,04 MB)

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High Energy Emission from Gamma Ray Bursts
Lili Yang, invited lecture at foreign university

Abstract: Gamma Ray Bursts (GRBs) are the most energetic explosions in the universe, and they have been proposed as the most promising candidate sources of ultra-high energy cosmic rays (UHECRs). As a result of interactions of UHECR within the host environment and during their propagation towards Earth, high energy neutrinos and photons are also expected from both prompt and afterglow emission. In this talk, I will review the standard theory of particle acceleration and production in a GRB fireball, and multi-wavelength and multi-messeger observations of GRB emission. I will present the prediction of PeV — EeV neutrino production and evidence of GeV gamma ray radiation, and the expected detection in IceCube, Pierre Auger Observatory and CTA (the next generation of Imaging Atmospheric Cherenkov Telescopes). The investigation of high-energy particles will provide insight into the nature and complicated mechanisms of GRBs.
Found in: ključnih besedah
Keywords: Gamma-Ray Bursts, high-energy emission, blastwave afterglow
Published: 06.12.2016; Views: 2198; Downloads: 0
.pdf Fulltext (20,49 MB)

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