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Flares in gamma-ray burst X-ray afterglows as prompt emission from slightly misaligned structured jets

Duque, Raphaël and Beniamini, Paz and Daigne, Frédéric and Mochkovitch, Robert (2022) Flares in gamma-ray burst X-ray afterglows as prompt emission from slightly misaligned structured jets. Monthly Notices of the Royal Astronomical Society, 513 (1). pp. 951-963. ISSN 0035-8711. doi:10.1093/mnras/stac938.

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We develop a model to explain the flaring activity in gamma-ray burst X-ray afterglows within the framework of slightly misaligned observers to structured jets. We suggest that flares could be the manifestation of prompt dissipation within the core of the jet, appearing to a misaligned observer in the X-ray band because of less favourable Doppler boosting. These flares appear during the afterglow phase because of core–observer light travel delays. In this picture, the prompt emission recorded by this observer comes from material along their line of sight, in the lateral structure of the jet, outside the jet’s core. We start by laying down the basic analytical framework to determine the flares characteristics as a function of those of the gamma-ray pulse an aligned observer would see. We show that there is viable parameter space to explain flares with typical observing times and luminosities. We then analytically explore this model, showing that it naturally produces flares with small aspect ratios, as observed. We perform fits of our model to two Swift/XRT flares representing two different types of morphology, to show that our model can capture both. The ejection time of the core jet material responsible of the flare is a critical parameter. While it always remains small compared to the observed time of the flare, confirming that our model does not require very late central engine activity, late ejection times are strongly favoured, sometimes larger than the observed duration of the parent gamma-ray burst’s prompt emission as measured by T90.

Item Type:Article
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URLURL TypeDescription Paper
Duque, Raphaël0000-0002-9062-3775
Beniamini, Paz0000-0001-7833-1043
Additional Information:© 2022 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2022 April 1. Received 2022 April 1; in original form 2021 December 7. We thank T. Matsumoto, R. Sari, and O. S. Salafia for useful discussion. RD is supported by the European Research Council Advanced Grant ‘JETSET: Launching, propagation and emission of relativistic jets from binary mergers and across mass scales’ (grant no. 884631). PB was supported by the Gordon and Betty Moore Foundation, grant GBMF5076 and by grant (no. 2020747) from the United States-Israel Binational Science Foundation (BSF), Jerusalem, Israel. DATA AVAILABILITY. The data and software underlying this article will be shared on reasonable request to the corresponding author.
Funding AgencyGrant Number
European Research Council (ERC)884631
Gordon and Betty Moore FoundationGBMF5076
Binational Science Foundation (USA-Israel)2020747
Subject Keywords:galaxies: jets, radiation mechanisms: general, (stars:) gamma-ray burst: general, (stars:) gamma-ray burst: individual: GRB060719, (stars:) gamma-ray burst: individual: GRB100816A, X-rays: bursts
Issue or Number:1
Record Number:CaltechAUTHORS:20220525-91541000
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Official Citation:Raphaël Duque, Paz Beniamini, Frédéric Daigne, Robert Mochkovitch, Flares in gamma-ray burst X-ray afterglows as prompt emission from slightly misaligned structured jets, Monthly Notices of the Royal Astronomical Society, Volume 513, Issue 1, June 2022, Pages 951–963,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114922
Deposited By: George Porter
Deposited On:31 May 2022 16:15
Last Modified:31 May 2022 16:15

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