A LOFAR prompt search for radio emission accompanying X-ray flares in GRB 210112A

Abstract

The composition of relativistic gamma-ray burst (GRB) jets and their emission mechanisms are still debated, and they could be matter or magnetically dominated. One way to distinguish these mechanisms arises because a Poynting flux dominated jet may produce low-frequency radio emission during the energetic prompt phase, through magnetic reconnection at the shock front. We present a search for radio emission coincident with three GRB X-ray flares with the LOw Frequency ARray (LOFAR), in a rapid response mode follow-up of long GRB 210112A (at z~2) with a 2 hour duration, where our observations began 511 seconds after the initial swift-BAT trigger. Using timesliced imaging at 120-168 MHz, we obtain upper limits at 3 sigma confidence of 42 mJy averaging over 320 second snapshot images, and 87 mJy averaging over 60 second snapshot images. LOFAR's fast response time means that all three potential radio counterparts to X-ray flares are observable after accounting for dispersion at the estimated source redshift. Furthermore, the radio pulse in the magnetic wind model was expected to be detectable at our observing frequency and flux density limits which allows us to disfavour a region of parameter space for this GRB. However, we note that stricter constraints on redshift and the fraction of energy in the magnetic field are required to further test jet characteristics across the GRB population.

13 pages, 7 figures, accepted for publication in MNRAS

References in corpus (20)

• Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
• A bright millisecond radio burst of extragalactic origin
• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• A census of baryons in the Universe from localized fast radio bursts
• Post-correlation radio frequency interference classification methods
• The First Survey of X-ray Flares from Gamma Ray Bursts Observed by Swift: Temporal Properties and Morphology
• The First Survey of X-ray Flares from Gamma Ray Bursts Observed by Swift: Spectral Properties and Energetics
• LOFAR/H-ATLAS: The low-frequency radio luminosity - star-formation rate relation
• The SVOM Mission
• Internal Energy Dissipation of Gamma-Ray Bursts Observed with Swift: Precursors, Prompt Gamma-rays, Extended emission and Late X-ray Flares
• NE2001. II. Using Radio Propagation Data to Construct a Model for the Galactic Distribution of Free Electrons
• A common stochastic process rules gamma-ray burst prompt emission and X-ray flares
• Statistical study of gamma-ray bursts with jet break feature in multi-wavelength afterglow emissions
• The Arcminute Microkelvin Imager Catalogue of Gamma-ray Burst afterglows at 15.7 GHz
• The X-/Gamma-ray camera ECLAIRs for the Gammay-ray burst mission SVOM
• Flares in gamma-ray burst X-ray afterglows as prompt emission from slightly misaligned structured jets
• Early multi-wavelength emission from Gamma-ray Bursts: from Gamma-ray to X-ray
• LOFAR early-time search for coherent radio emission from GRB 180706A
• Calculating transient rates from surveys
• LOFAR detectability of prompt low-frequency radio emission during gamma-ray burst X-ray flares

Cited by in corpus (1)

• A Search for Low-frequency Radio Pulses from Long Gamma-ray Bursts with the Murchison Widefield Array