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

A. B. Higgins, R. L.C. Starling, D. Götz, S. Mereghetti, K. Wiersema, T. Maccarone, J. P. Osborne, N. R. Tanvir, P. T. O'Brien, A. J. Bird, A. Rowlinson, N. Gehrels

Research output: Contribution to journalArticle

5 Scopus citations

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, IGRW151019, 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.

Original languageEnglish
Pages (from-to)314-323
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Volume470
Issue number1
DOIs
StatePublished - Sep 1 2017

Keywords

  • Gamma-ray burst: general

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