Abstract
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 language | English |
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Article number | L1 |
Number of pages | 6 |
Journal | The Astrophysical Journal Letters |
Volume | 843 |
Issue number | 1 |
DOIs | |
Publication status | Published - 1 Jul 2017 |
Keywords
- gamma-ray burst: individual (GRB 130603B, GRB 140903A)
- stars: magnetars
- stars: neutron