On Young Neutron Stars as Propellers and Accretors Ma Bo, Department of Astronomy, Nju, Nanjing Citations: Alpar,M.A.,APJ554,1245,2000 Illarionov and Sunyaev.1975 Nature,440,772

SGRs and AXPs Soft Gamma Repeaters were discovered as high- energy transient burst sources; some were later found also to be persistent X-ray pulsars, with periods of several seconds, that are spinning down rapidly. Anomalous X-ray Pulsars are identified through their persistent pulsations and rapid spin down; some have also been found to emit SGR-like bursts.

SGR giant flare on

P-M dot Diagram of AXP,SGR,DTN

Are they magenetars? Large P and Pdot led to suggestion of magnetars: For RXJ ,P=8.39s,P dot =2.9E-11 s/s

P dot Similarity A non-accreting neutron star, energy dissipation (Alpar et al.1984) The luminosities of RX J , RX J , and the other DTNs (Treves et al. 2000) give The measured spin-down rates of AXPs and SGRs all fall in this range, providing another similarity, in addition to the periods, between the DTNs, AXPs, and SGRs.

Propeller Spin-Down The order of magnitude of this spin-down torque is (Illarionov and Sunyaev.1975 ， Alpar et al. 1984) The magnetic dipole represents a “propeller”, rotating with a supersonic velocity in the accreting gas.

Accretion Starts The propeller phase will last until accretion starts when a critical rotation period Pc is reached. (Illarionov & Sunyaev. 1975, A&A, 39, 185) For RX J ,

The Asymptotic Spin-down Regime Spin-down near equilibrium can be modeled as This can explain the similarity of P for SGR AXP,DTN

A debris disk around an isolated young neutron star (Nature,440,772)

Conclusions Key Idea. The signature of a young neutron star depends on the presence and nature of the mass inflow of fallback material from the supernova explosion. 1 All neutron stars born with similar order of magnitude B~1E12 Gauss 2 Radio pulsars are formed if there is no mass inflow or not enough to protrude the light cylinder. Higher mass inflow rates do not allow radio pulsar activity, leading instead to DTNs, AXPs, and RQNSs.

Conclusion 3 The similarity in the rotation periods of these sources is not a coincidence but rather a consequence of the asymptotic approach to rotational equilibrium under a wide range of mass inflow rates. 4 With low M dot the spin-down is too slow for the source to go through the propeller stage and reach the accretion stage before the circumstellar mass is depleted. These sources, observed as DTNs, are propellers for as long as 1E5~1E6 yr and make up the most numerous class. 6 The DTNs are the first observed examples of neutron stars in the propeller phase.

7 A nonaccreting neutron star under propeller spin-down has a luminosity provided by energy dissipation inside the star. 8 The RQNSs are the young neutron stars for which Comptonization washes out beaming so that the rotation period is not observable.

Summary Picture

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