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Title:A search for Galactic transients disguised as gamma-ray bursts
Authors:Clerici, Aurora (Author)
Guidorzi, Cristiano (Author)
La Parola, Valentina (Author)
Files:This document has no files. This document may have a phisical copy in the library of the organization, check the status via COBISS. Link is opened in a new window
Language:English
Work type:Not categorized (r6)
Tipology:1.01 - Original Scientific Article
Organization:UNG - University of Nova Gorica
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).
Keywords:gamma-ray burst, statistical, Galactic transient
Year of publishing:2015
Number of pages:6
Numbering:582, A106
COBISS_ID:4137979 Link is opened in a new window
URN:URN:SI:UNG:REP:TBGTWOZ7
DOI:10.1051/0004-6361/201526778 Link is opened in a new window
License:CC BY-NC-ND 4.0
This work is available under this license: Creative Commons Attribution Non-Commercial No Derivatives 4.0 International
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Record is a part of a journal

Title:Astronomy and Astrophysics
Shortened title:A&A
Publisher:Hans Publishers (汉斯出版社)EDP Sciences
ISSN:0004-6361

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