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Signs of the Blandford & Znajek mechanism in GRB afterglow lightcurves
Antonios Nathanail ITP Frankfurt, University of Athens Geneva 2015
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We want to argue that the rapid decay phase of the afterglow (X-rays), is nicely described as the spin down of a slowly rotating black hole (Blandford-Znajek mechanism)
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ANATOMY OF A BURST
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ANATOMY OF A BURST Central engine extended activity
Tagliaferi et al. 2005 Ghiselini et al. 2009 Zhang et al. 2014
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ANATOMY OF A BURST Central engine extended activity Off-axis radiation
Tagliaferi et al. 2005 Ghiselini et al. 2009 Zhang et al. 2014 Off-axis radiation Steep power law
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Small Break for theory
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Why not a slowly rotating black hole
Small Break for theory Spin of BH … Why not a slowly rotating black hole
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Small Break for theory Loosing Energy as ……. Stellar mass black hole
slowly rotating Ω angular velocity Strong magnetic fields expected Loosing Energy as …….
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Small Break for theory Loosing Energy as ……. Stellar mass black hole
slowly rotating Ω angular velocity Strong magnetic fields expected Loosing Energy as …….
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Small Break for theory Loosing Energy as ……. magnetic flux
Blanford & Znajek 1977 ……... magnetic flux
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Small Break for theory Loosing Energy as …
Nathanail & Contopoulos 2015 Nathanail, Strantzalis & Contopoulos 2015
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Small Break for theory Loosing Energy as …
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Can This Be observed Luminosity?
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ANATOMY OF A BURST
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Zoom in the rapid decay phase
Nathanail, Strantzalis & Contopoulos 2015
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From 343 Long GRBs 30% had this sign
Nathanail, Strantzalis & Contopoulos 2015
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Duration of a GRB depends on the magnetic field strength
Nathanail, Strantzalis & Contopoulos 2015
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Extraordinary duration ...
Easy to explain Ultra Long GRBs Extraordinary duration ... Nathanail & Contopoulos 2015
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magnetic field strength
From the timescale we can estimate the magnetic field strength at the black hole Nathanail & Contopoulos 2015 Nathanail, Strantzalis & Contopoulos 2015
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The Rest 70% The rapid decay phase is not entirely seen sparse data
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Mass infall-Flaring Activity
Proga & Zhang 2006 magnetic barrier X-rays spin down mass infall again spin down (spin up) in preparation . . .
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30% of Long GRBs show signs of Black Hole Spin Down
Summary 30% of Long GRBs show signs of Black Hole Spin Down Duration of a GRB depends on the magnetic field strength
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