Formation rates and evolution histories of magnetars

Paz Beniamini, Kenta Hotokezaka, Alexander Van Der Horst, Chryssa Kouveliotou

Research output: Contribution to journalArticlepeer-review


We constrain the formation rate of Galactic magnetars directly from observations. Combining spin-down rates,magnetic activity, and association with supernova remnants, we put a 2σ limit on their Galactic formation rate at 2.3-20 kyr-1. This leads to a fraction 0.4+0.6-0.28 of neutron stars being born as magnetars. We study evolutionary channels that can account for this rate as well as for the periods, period derivatives, and luminosities of the observed population. We find that their typical magnetic fields at birth are 3 × 1014-1015 G, and that those decay on a timescale of ∼104 yr, implying a maximal magnetar period of Pmax ≈ 13 s. A sizable fraction of the magnetars' energy is released in outbursts. Giant Flares with E ≥ 1046 erg are expected to occur in the Galaxy at a rate of ∼5kyr-1. Outside our Galaxy, such flares remain observable by Swift up to a distance of ∼100 Mpc, implying a detection rate of ∼5 yr-1. The specific form of magnetic energy decay is shown to be strongly tied to the total number of observable magnetars in the Galaxy. A systematic survey searching for magnetars could determine the former and inform physical models of magnetic field decay.

Original languageEnglish
Pages (from-to)1426-1438
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - 21 Jul 2019
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2018 The Author(s).


  • Magnetic fields
  • Stars: Evolution
  • Stars: Magnetars


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