The Braking Index of Millisecond Magnetars

Paul D. Lasky, Cristiano Leris, Antonia Rowlinson, Kostas Glampedakis

Research output: Contribution to journalArticleResearchpeer-review

31 Citations (Scopus)


We make the first measurement of the braking index n of two putative millisecond magnetars born in short gamma-ray bursts. We measure n = 2.9 ± 0.1 and n 2.6 ± 0.1 for millisecond magnetars born in GRB 130603B and GRB 140903A, respectively. The neutron star born in GRB 130603B has the only known a braking index consistent with the fiducial n = 3 value. This value is ruled out with 99.95% confidence for GRB 140903A. We discuss possible causes of n < 3braking indices in millisecond magnetars, showing that several models can account for the measurement of the braking index in GRB 140903A, while it is more difficult to account for a braking index consistent with n = 3.

Original languageEnglish
Article numberL1
Number of pages6
JournalThe Astrophysical Journal Letters
Issue number1
Publication statusPublished - 1 Jul 2017


  • gamma-ray burst: individual (GRB 130603B, GRB 140903A)
  • stars: magnetars
  • stars: neutron

Cite this