Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bolonia study programme

Options:
  Reset


1 - 3 / 3
First pagePrevious page1Next pageLast page
1.
A search for Galactic transients disguised as gamma-ray bursts
Valentina La Parola, Cristiano Guidorzi, Aurora Clerici, 2015, original scientific article

Abstract: A significant fraction of cosmological gamma-ray bursts (GRBs) are characterised by a fast rise and exponential decay (FRED) temporal structure. This is not a distinctive feature of this class, since it is observed in many Galactic transients and is likely descriptive of a sudden release of energy followed by a diffusion process. Possible evidence has recently been reported by Tello et al. (2012) for a Galactic contamination in the sample of FRED GRBs discovered with Swift. We searched for possible Galactic intruders disguised as FRED GRBs in the Swift catalogue up to September 2014. We selected 181 FRED GRBs (2/3 with unknown redshift) and considered different subsamples. We tested the degree of isotropy through the dipole and the quadrupole moment distributions, both with reference to the Galaxy and in a coordinate-system-independent way, as well as with the two-point angular autocovariance function. In addition, we searched for possible indicators of a Galactic origin among the spectral and temporal properties of individual GRBs. We found marginal (~3 sigma) evidence for an excess of FREDs with unknown redshift towards the Galactic plane compared with what is expected for an isotropic distribution corrected for the non-uniform sky exposure. However, when we account for the observational bias against optical follow-up observations of low-Galactic latitude GRBs, the evidence for anisotropy decreases to ~2 sigma. In addition, we found no statistical evidence for different spectral or temporal properties from the bulk of cosmological GRBs. We found marginal evidence for the presence of a disguised Galactic population among Swift GRBs with unknown redshift. The estimated fraction is f=(19 +- 11)%, with an upper limit of 34% (90% confidence).
Found in: ključnih besedah
Summary of found: ...~2 sigma. In addition, we found no statistical evidence for different spectral or temporal properties...
Keywords: gamma-ray burst, statistical, Galactic transient
Published: 03.02.2016; Views: 2127; Downloads: 0
.pdf Fulltext (173,64 KB)

2.
Le camere a tempo di volo per il rilievo geomatico
Marco Turlon, 2017, original scientific article

Abstract: Nell’ultimo decennio una nuova tecnologia di misurazione si è diffusa sempre più nel mercato del rilievo strumentale. Le camere a tempo di volo
Found in: ključnih besedah
Summary of found: ...TOF Cameras, Cultural Heritage, preservation, monitoring, survey, statistical test...
Keywords: TOF Cameras, Cultural Heritage, preservation, monitoring, survey, statistical test
Published: 05.07.2017; Views: 1553; Downloads: 1

3.
Search for anisotropy of ultrahigh energy cosmic rays with the Telescope Array experiment
J. P. Lundquist, T. Abu-Zayyad, 2012, original scientific article

Abstract: We study the anisotropy of Ultra-High Energy Cosmic Ray (UHECR) events collected by the Telescope Array (TA) detector in the first 40 months of operation. Following earlier studies, we examine event sets with energy thresholds of 10 EeV, 40 EeV, and 57 EeV. We find that the distributions of the events in right ascension and declination are compatible with an isotropic distribution in all three sets. We then compare with previously reported clustering of the UHECR events at small angular scales. No significant clustering is found in the TA data. We then check the events with E > 57 EeV for correlations with nearby active galactic nuclei. No significant correlation is found. Finally, we examine all three sets for correlations with the large-scale structure (LSS) of the universe. We find that the two higher-energy sets are compatible with both an isotropic distribution and the hypothesis that UHECR sources follow the matter distribution of the universe (the LSS hypothesis), while the event set with E > 10 EeV is compatible with isotropy and is not compatible with the LSS hypothesis at 95% CL unless large deflection angles are also assumed. We show that accounting for UHECR deflections in a realistic model of the Galactic magnetic field can make this set compatible with the LSS hypothesis.
Found in: ključnih besedah
Summary of found: ...astroparticle physics, cosmic rays, magnetic fields, methods: statistical, relativistic processes...
Keywords: acceleration of particles, astroparticle physics, cosmic rays, magnetic fields, methods: statistical, relativistic processes
Published: 19.05.2020; Views: 393; Downloads: 0
.pdf Fulltext (1,04 MB)

Search done in 0 sec.
Back to top