A. Clerici (Avtor), Cristiano Guidorzi (Avtor), V. La Parola (Avtor)

Povzetek

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).

Ključne besede

gamma-ray burst;statistics;Galactic transient;

Podatki

Jezik: Angleški jezik
Leto izida:
Tipologija: 1.01 - Izvirni znanstveni članek
Organizacija: UNG - Univerza v Novi Gorici
UDK: 53
COBISS: 4137979 Povezava se bo odprla v novem oknu
ISSN: 0004-6361
Št. ogledov: 3996
Št. prenosov: 0
Ocena: 0 (0 glasov)
Metapodatki: JSON JSON-RDF JSON-LD TURTLE N-TRIPLES XML RDFA MICRODATA DC-XML DC-RDF RDF

Ostali podatki

URN: URN:SI:UNG
Vrsta dela (COBISS): Delo ni kategorizirano
Strani: str. 1-6
Zvezek: ǂVol. ǂ582
Čas izdaje: Oct. 2015
DOI: 10.1051/0004-6361/201526778
ID: 9123188
Priporočena dela:
, ni podatka o podnaslovu
, ni podatka o podnaslovu
, lecture at University of Science and Technology, Hefei China, 21. June, 2016
, tracing the evolution of high-energy emission from prompt to afterglow
, NOT redshift