Document Type

Article

Publication Date

8-6-2021

Publication Title

Monthly Notices of the Royal Astronomical Society: Letters

Volume

508

Issue

1

First page number:

L48

Last page number:

L52

Abstract

Magnetic flares create hot relativistic shocks outside the light cylinder radius of a magnetized star. Radio emission produced in such a shock or at a radius smaller than the shock undergoes free–free absorption while passing through the shocked medium. In this work, we demonstrate that this free–free absorption can lead to a negative drift in the frequency-time spectra. Whether it is related to the downward drift pattern observed in fast radio bursts (FRBs) is unclear. However, if the FRB down-drifting is due to this mechanism then it will be pronounced in those shocks that have isotropic kinetic energies ≳1044 erg. In this model, for an internal shock with a Lorentz factor ∼100, the normalized drift rate |DRobs|/νmean is ∼10−2 per ms, where νmean is the central frequency of the radio pulses. The corresponding radius of the shocked shell is, therefore, in the range of 1010 cm and 1011 cm. This implies that, for an outflow consisting of hydrogen ion, the upper limit on the mass of the relativistic shocks is a few × 10−10 M⊙, which is considerably low compared to that ejected from SGR 1806-20 during the 2004 outburst.

Keywords

Radio continuum: transients; Shock waves; Stars: magnetars

Disciplines

Astrophysics and Astronomy | Radiochemistry

File Format

pdf

File Size

528 KB

Language

English

Comments

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2021 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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