Chandra Observations of the Newly Discovered Magnetar Swift J1818.0-1607

Swift J1818.0-1607 is a new radio-loud magnetar discovered by the Swift Burst Alert Telescope on 2020 March 12. It has a magnetic field B similar to 2.5 x 10(14) G, spin-down luminosity similar to 7.2 x 10(35) erg s(-1), and characteristic age tau(c) similar to 470 yr. Here we report on the Chandra observations of Swift J1818.0-1607, which allowed for a high-resolution imaging and spectroscopic study of the magnetar and its environment. The 1-10 keV spectrum of the magnetar is best described by a single blackbody model with a temperature of 1.2 0.1 keV and an unabsorbed flux of 1.9(-0.3)(+0.4) x 10(-11) erg cm(-2) s(-1). This implies an X-ray luminosity of 9.6(-1.5)(+2.0)x10(34) d(6.5)(2) erg s(-1) and efficiency of d(6.5)(2) at a distance of 6.5 kpc. The Chandra image also shows faint diffuse emission out to from the magnetar, with its spectrum adequately described by a power law with a photon index of 2.0 0.5 and a luminosity of similar to 8.1 x 10(33)B pulsars and magnetars, and could be powered at least partly by its high spin-down, similar to rotation-powered pulsars.