Evolution of fallback discs around millisecond magnetars: effect of supercritical accretion on GRB afterglows

Sercan Çlklntoǧlu*, Sinem Åaşmaz, M. Hakan Erkut, K. Yavuz Ekşi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Some models of gamma-ray bursts (GRBs) invoke nascent millisecond magnetars as the central engine and address the X-ray afterglows with the interaction of magnetar magnetospheres with fallback discs. We study the evolution of fallback discs interacting with the millisecond magnetars. Initially, the accretion rate in the fallback disc is very high, well above the rate required for the Eddington limit. The inner parts of such a disc, even if it is cooling by the neutrino emission, get spherical due to the radiation pressure, which regulates the mass-accretion rate within the spherization radius. Such a disc can not penetrate the light cylinder radius for the typical magnetic fields, and the initial spin frequencies invoked for the magnetars. As a result of the autoregulation of the accretion flow, the fallback disc can not interact directly with the magnetar's magnetosphere within the first few days. This has implications for the fallback disc models of GRB afterglows since the accretion and propeller luminosities, in the presence of radiation pressure, are too low to address the typical luminosities of X-ray afterglows.

Original languageEnglish
Pages (from-to)5009-5014
Number of pages6
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - 1 Nov 2023

Bibliographical note

Publisher Copyright:
© 2023 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.


SS and KYE acknowledge support from the Scientific and Technological Research Council of Turkey (TÜBİTAK) with project number 118F028.

FundersFunder number
Türkiye Bilimsel ve Teknolojik Araştırma Kurumu118F028


    • accretion, accretion discs
    • gamma-ray burst: general
    • stars: neutron


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