Chandra observations of the newly discovered magnetar Swift J1818.0-1607 (2011.00324v1)

Abstract: 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~2.5e14 G, spin-down luminosity of 7.2e35 ergs/s, and characteristic age of ~470yr. 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\pm0.1 keV and an unabsorbed flux of 1.9e-11 ergs/cm^2/s. This implies an X-ray luminosity of ~9.6e34 ergs/s and an efficiency of ~0.13 at a distance of 6.5 kpc. The Chandra image also shows faint diffuse emission out to >10" from the magnetar, with its spectrum adequately described by a powerlaw with a photon index of 2.0\pm0.5 and a luminosity of ~8.1e33 ergs/s. The extended emission is likely dominated by a dust scattering halo and future observations of the source in quiescence will reveal any underlying compact wind nebula. We conclude that Swift J1818.0-1607 is a transient source showing properties between high-B pulsars and magnetars, and could be powered at least partly by its high spin-down similar to the rotation-powered pulsars.

• The paper identifies Swift J1818.0-1607 as one of the youngest magnetars, with a magnetic field near 2.5×10^14 G and a spin-down luminosity of 7.2×10^35 ergs/s.
• It employs high-resolution Chandra imaging and spectroscopy to model the 1–10 keV spectrum using a single blackbody fit with a temperature of about 1.2 keV.
• The study reveals faint diffuse emission around the magnetar, suggesting a dust scattering halo and the potential presence of an underlying compact wind nebula.

Analyzing Chandra Observations of Magnetar Swift J1818.0--1607

The research paper focuses on the Chandra X-ray Observatory's observations of the newly discovered magnetar, Swift J1818.0--1607, which presents intriguing findings in the field of astrophysics, particularly concerning neutron stars and magnetars. The magnetar, identified by the Swift Burst Alert Telescope, is characterized by a remarkably high magnetic field and a radio-loud nature, placing it uniquely within the spectrum of known neutron stars. This paper provides insights into its properties using high-resolution imaging and spectroscopic data from Chandra.

The authors report that the magnetar has a magnetic field strength of approximately $2.5 \times 10^{14}$ G, with a spin-down luminosity of $7.2 \times 10^{35}$ ergs s$^{-1}$, and a characteristic age of about 470 years. This makes Swift J1818.0--1607 one of the youngest known magnetars. The Chandra observations allowed the researchers to analyze the magnetar’s 1-10 keV spectrum, which is best described by a single blackbody model with a temperature of 1.2 keV and an unabsorbed flux of approximately $1.9 \times 10^{-11}$ ergs cm$^{-2}$ s$^{-1}$. This results in an X-ray luminosity of $9.6 \times 10^{34}$ ergs s$^{-1}$ and an efficiency $L_X/\dot{E}$ of about 0.13, assuming a distance of 6.5 kpc.

The observational data also indicated the presence of faint diffuse emission surrounding the magnetar, extending to more than 10 arcseconds, with a spectrum that can be adequately described by a power-law model with a photon index of 2.0, contributing a luminosity of around $8.1 \times 10^{33}$ ergs s$^{-1}$. This diffuse emission is likely dominated by a dust scattering halo, though it leaves open the potential for an underlying compact wind nebula being revealed in future quiescent observations.

One of the paper's critical findings is the classification of Swift J1818.0--1607 as a transitional object, exhibiting characteristics of both high magnetic field pulsars and traditional magnetars. This dual nature suggests that the magnetar may be, at least in part, powered by its rapid spin-down, akin to rotation-powered pulsars, but also exhibits typical magnetar behavior like emission of X-rays powered by magnetic field decay.

The paper does not only deliver a comprehensive snapshot of the current understanding but also lays the groundwork for future research. The presence of faint emission structures and the high-resolution data from Chandra highlight the need for continued observation, which could provide further clarity on the magnetar's environment and evolution.

In conclusion, the findings of Blumer and Safi-Harb represent a significant contribution to the understanding of magnetar properties and their broader implications for neutron star physics. This paper emphasizes the complex nature of these objects, exploring the boundary where different types of neutron stars may overlap, and providing a basis for future research that could reshape how scientists interpret the life cycles and energy mechanisms of high-magnetic-field neutron stars.