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

2. 2 A question: 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. Why do all magnetars are isolated? Two possible explanations Large kick velocities Particular evolutionary path

3. 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. 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. 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. 6 Results of calculations

7. 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 total number 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.