Interpreting the X-ray afterglows of gamma-ray bursts with radiative losses and millisecond magnetars

Nikhil Sarin, Paul D. Lasky, Gregory Ashton

Research output: Contribution to journalArticleResearchpeer-review

16 Citations (Scopus)


The spin-down energy of millisecond magnetars has been invoked to explain X-ray afterglow observations of a significant fraction of short and long gamma-ray bursts. Here, we extend models previously introduced in the literature, incorporating radiative losses with the spin-down of a magnetar central engine through an arbitrary braking index. Combining this with a model for the tail of the prompt emission, we show that our model can better explain the data than millisecond-magnetar models without radiative losses or those that invoke spin-down solely through vacuum dipole radiation. We find that our model predicts a subset of X-ray flares seen in some gamma-ray bursts. We can further explain the diversity of X-ray plateaus by altering the radiative efficiency and measure the braking index of newly born millisecond magnetars. We measure the braking index of GRB061121 as n = 4.85+001115 suggesting the millisecond-magnetar born in this gamma-ray burst spins down predominantly through gravitational-wave emission.

Original languageEnglish
Pages (from-to)5986-5992
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - 2020


  • Gamma-ray burst: general – gamma-ray bursts

Cite this