Long optical plateau in the afterglow of the short GRB 150424A with extended emission: Evidence for energy injection by a magnetar?

Fabian Knust, Jochen Greiner, Hendrik Van Eerten, P. Schady, D. A. Kann, T. W. Chen, Corentin Delvaux, John F. Graham, S. Klose, T. Krühler, N.J. McConnell, Ana Nicuesa Guelbenzu, D. A. Perley, S. Schmidl, Tassilo Schweyer, Mohit Tanga, K. Varela

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

Short-duration GRBs with extended emission form a subclass of short GRBs, comprising about 15% of the short-duration sample. Afterglow detections of short GRBs are also rare (about 30%) due to their smaller luminosity. We present a multi-band data set of the short burst with extended emission GRB 150424A, comprising of GROND observations, complemented with data from Swift/UVOT, Swift/XRT, HST, Keck/LRIS and data points from the literature. The GRB 150424A afterglow shows an extended plateau phase, lasting about 8hrs. The analysis of this unique GRB afterglow might shed light on the understanding of afterglow plateau emission, the nature of which is still under debate.
We present a phenomenological analysis by applying fireball closure relations, and interpret the findings in the context of the fireball model. We discuss the plausibility of a magnetar as a central engine, being responsible for additional and prolonged energy injection into the fireball.
We find convincing evidence for energy injection into the afterglow of GRB 150424A. We find that a magnetar spin down as source for a prolonged energy injection requires that at least 4% of the spin-down energy is converted to radiation.
Original languageEnglish
Article numberA84
Pages (from-to)A84
Number of pages12
JournalAstronomy & Astrophysics
Volume607
Issue number11
Early online date20 Nov 2017
DOIs
Publication statusPublished - Nov 2017

Keywords

  • gamma-ray bursts: general
  • methods: observational
  • methods: data analysis
  • gamma-ray bursts: individual - GRB 150424A

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