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Understanding Magnetars: Origins and Progenitors with Enhanced Rotation

This study investigates the origins of magnetars, which are neutron stars (NSs) exhibiting strong magnetic fields. Despite 10% of neutron stars being expected to be in binary systems, all known magnetars are isolated. Potential explanations for their isolation include large kick velocities and unique evolutionary paths. The research utilizes the "Scenario Machine" code to run population synthesis of binaries, estimating the fraction of NS progenitors with enhanced rotation. Results indicate that 13-16% of NSs may originate as magnetars, mostly isolated due to coalescences or system disruptions.

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Understanding Magnetars: Origins and Progenitors with Enhanced Rotation

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  1. Magnetars origin and progenitors with enhanced rotation S.B. Popov, M.E. Prokhorov (Sternberg Astronomical Institute) Poster N 21 Physics of neutrons stars - 2005 (astro-ph/0505406)

  2. • 10 % of NSs are expected to be binary. • All known magnetars (or candidates) are single objects. • At the moment from the statistical point of view it is not a miracle, however, it’s time to ask this question. A question: Why do all magnetars are isolated? Two possible explanations • Large kick velocities • Particular evolutionary path

  3. Magnetars origin • Probably, magnetars are isolated due to their origin • Fast rotation is necessary (Thompson, Duncan) • Two possibilities to spin-up during evolution in a binary 1) Spin-up of a progenitor star in a binary via accretion or synchronization 2) Coalescence

  4. The code We use the “Scenario Machine” code. Developed in SAI (Moscow) since 1983 by Lipunov, Postnov, Prokhorov et al. (http://xray.sai.msu.ru/~mystery/articles/review/) We run the population synthesis of binaries to estimate the fraction of NS progenitors with enhanced rotation.

  5. The model Among all possible evolutionary paths that result in formation of NSs we select those that lead to angular momentum increase of progenitors. • Coalescence prior to a NS formation. • Roche lobe overflow by a primary. • Roche lobe overflow by a primary with a common envelope. • Roche lobe overflow by a secondary without a common envelope. • Roche lobe overflow by a secondary with a common envelope.

  6. Results of calculations

  7. Conclusions • We made population synthesis of binary systems to derive the relative number of NSs originated from progenitors with enhanced rotation –”magnetars”. • With an inclusion of single stars (with the totalnumber equal to the total number of binaries) the fraction of “magnetars” is ~13-16%. • Most of these NSs are isolated due to coalescences of components prior to NS formation, or due to a system disruption after a SN explosion. • The fraction of “magnetars” in survived binaries is about 1% or lower. • The most numerous companions of ``magnetars'' are BHs.

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