2 Soft gamma ray repeaters

SGRs are slowly rotating ($P\sim 5-8~{\rm s}$) pulsars that produce multiple bursts of soft $\gamma$-rays, often at super-Eddington luminosities (see, e.g., Hurley, Kouveliotou, these proceedings). Four of these objects have been discovered. The inferred ages and velocities of SGRs and AXPs suggest that their characteristic spin-down ages are not their true ages. For instance, the period, P=5.16 s, and the period derivative, $\dot P=1.1\ 10^{-10}$, of SGR 1900+14 (Hurley et al. 1998c and references therein) yield a characteristic age $\tau= P/2\dot P\approx 750~{\rm y}$, much younger than the age of its nearby supernova remnant (SNR) G42.8+0.6. Moreover, if the characteristic age of SGR 1900+14 represents its true age and if it was born at the center of the SNR, it must have moved with perpendicular velocity $v_\perp\sim 40000\ (D/5.7~{\rm kpc})~{\rm km}~{\rm s}^{-1}$ to its present location (Hurley et al. 1998a,b). A similar "age/separation crisis'' seems to exist for other SGRs. I propose that the characteristic age of SGR is the age of the (di)quark star (QS) born by a first order phase transition in a neutron star (NS) that has cooled and spun down sufficiently. Its typical velocity is that of ordinary pulsars, $v\sim 500~{\rm km~s}^{-1}$, much larger than the typical velocities, $(\sim 100~{\rm km~s}^{-1})$, of young pulsars produced in SNe, such as the Crab pulsar (Caraveo & Mignani 1999) and the Vela pulsar (Nasuti et al. 1997), and of all millisecond pulsars (Toscano et al. 1998). Because of their large natal velocities, SGRs are not expected to be found in binaries. The quiescent thermal X-ray emission from the cooling QSs (SGRs and AXPs) may be used to verify that their radii are significantly smaller than those of millisecond pulsars. After cooling by X-ray and wind emission, the QSs become the slowly rotating normal radio pulsars.