Late-time radio observations of the short GRB 200522A: Constraints on the magnetar model

G. Bruni*, B. O'connor*, T. Matsumoto*, E. Troja, T. Piran, L. Piro, R. Ricci

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

GRB 200522A is a short duration gamma-ray burst (GRB) at redshift z=0.554 characterized by a bright infrared counterpart. A possible, although not unambiguous, interpretation of the observed emission is the onset of a luminous kilonova powered by a rapidly rotating and highly magnetized neutron star, known as magnetar. A bright radio flare, arising from the interaction of the kilonova ejecta with the surrounding medium, is a prediction of this model. Whereas the available data set remains open to multiple interpretations (e.g. afterglow, r-process kilonova, magnetar-powered kilonova), long-term radio monitoring of this burst may be key to discriminate between models. We present our late-time upper limit on the radio emission of GRB 200522A, carried out with the Karl G. Jansky Very Large Array at 288 d after the burst. For kilonova ejecta with energy Eej≈ 1053erg, as expected for a long-lived magnetar remnant, we can already rule out ejecta masses Mej≲ 0.03Mfor the most likely range of circumburst densities n ≳ 10-3cm-3. Observations on timescales of ≈3-10 yr after the merger will probe larger ejecta masses up to Mej∼0.1M, providing a robust test to the magnetar scenario.

Original languageEnglish
Pages (from-to)L41-L45
JournalMonthly Notices of the Royal Astronomical Society: Letters
Volume505
Issue number1
DOIs
StatePublished - 1 Jul 2021

Bibliographical note

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© 2021 Oxford University Press. All rights reserved.

Keywords

  • Gamma-ray bursts: individual: GRB 200522A
  • Stars: magnetars
  • Stars: neutron

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