A note on the puzzling spindown behavior of the Galactic center magnetar SGR J1745-2900

Abstract

SGR J1745$-$2900 is a magnetar near the Galactic center. X-ray observations of this source found a decreasing X-ray luminosity accompanied by an enhanced spindown rate. This negative correlation between X-ray luminosity and spindown rate is hard to understand. The wind braking model of magnetars is employed to explain this puzzling spindown behavior. During the release of magnetic energy of magnetars, a system of particles may be generated. Some of these particles remain trapped in the magnetosphere and may contribute to the X-ray luminosity. The rest of the particles can flow out and take away the rotational energy of the central neutron star. A smaller polar cap angle will cause the decrease of X-ray luminosity and enhanced spindown rate of SGR J1745$-$2900. This magnetar is expected to have a maximum spindown rate shortly.

7 pages, 1 figure; accepted by Research in Astronomy and Astrophysics

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• Central compact objects, superslow X-ray pulsars, gamma-ray bursts: do they have anything to do with magnetars?
• Strong screening effects on resonant nuclear reaction ${}^{23}$Mg $(p,\gamma )$ ${}^{24}$Al in the surface of magnetars
• Two predictions for the spin down behavior of magnetar SGR J1745-2900