Short gamma-ray bursts within 200 Mpc

S. Dichiara; E. Troja; B. O'Connor; F. E. Marshall; P. Beniamini; J. K. Cannizzo; A. Y. Lien; T. Sakamoto

doi:10.1093/mnras/staa124

paper

Short gamma-ray bursts within 200 Mpc

arXiv:1912.08698 · doi:10.1093/mnras/staa124

Abstract

We present a systematic search for short-duration gamma-ray bursts (GRBs) in the local Universe based on 14 years of observations with the Neil Gehrels Swift Observatory. We cross-correlate the GRB positions with the GLADE catalogue of nearby galaxies, and find no event at a distance $≲$ 100 Mpc and four plausible candidates in the range 100 Mpc $≲$ $D$ $≲$ 200 Mpc. Although affected by low statistics, this number is higher than the one expected for chance alignments to random galaxies, and possibly suggests a physical association between these bursts and nearby galaxies. By assuming a local origin, we use these events to constrain the range of properties for X-ray counterparts of neutron star mergers. Optical upper limits place tight constraints on the onset of a blue kilonova, and imply either low masses ( $≲ 1 0^{- 3} M_{⊙}$ ) of lanthanide-poor ejecta or unfavorable orientations ( $θ_{o b s} ≳$ 30 deg). Finally, we derive that the all-sky rate of detectable short GRBs within 200 Mpc is $1. 3_{- 0.8}^{+ 1.7}$ yr $^{- 1}$ (68\% confidence interval), and discuss the implications for the GRB outflow structure. If these candidates are instead of cosmological origin, we set a upper limit of $≲$ 2.0 yr $^{- 1}$ (90\% confidence interval) to the rate of nearby events detectable with operating gamma-ray observatories, such as Swift and Fermi.

13 pages, 9 figures, 1 table, accepted for publication in MNRAS

Short gamma-ray bursts within 200 Mpc

Abstract

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