Investigating the nature of the INTEGRAL gamma-ray bursts and sub-threshold triggers with Swift follow-up

Journal
Date Issued
2017
Author(s)
Higgins, A. B.
•
Starling, R. L. C.
•
Götz, D.
•
•
Wiersema, K.
•
Maccarone, T.
•
Osborne, J. P.
•
Tanvir, N. R.
•
O'Brien, P. T.
•
Bird, A. J.
•
Rowlinson, A.
•
Gehrels, N.
DOI
Abstract
We explore the potential of the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) to improve our understanding of the low-fluence regime for explosive transients, such as Gamma-ray Bursts (GRBs). We probe the nature of the so-called 'WEAK' INTEGRAL triggers, when the gamma-ray instruments record intensity spikes that are below the usual STRONG significance thresholds. In a targeted Swift follow-up campaign, we observed 15 WEAK triggers. We find six of these can be classified as GRBs. This includes GRB 150305A, a GRB discovered from our campaign alone. We also identified a source coincident with one trigger, IGRW 151019, as a candidate active galactic nucleus. We show that real events such as GRBs exist within the INTEGRAL Burst Alert System (IBAS) WEAK trigger population. A comparison of the fluence distributions of the full INTEGRAL IBAS and Swift-BAT GRB samples showed that the two are similar. We also find correlations between the prompt gamma-ray and X-ray properties of the two samples, supporting previous investigations. We find that both satellites reach similar, low fluence levels regularly, although Swift is more sensitive to short, low-fluence GRBs.
Volume
470
Issue
1
Start page
314
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2017MNRAS.470..314H
Rights
open.access
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