Learning About the Magnetar Swift J1834.9-0846 from its Wind Nebula

Abstract

The first wind nebula around a magnetar was recently discovered in X-rays around Swift~J1834.9$-$0846. We study this magnetar's global energetics and the properties of its particle wind or outflows. At a distance of $\sim 4$kpc, Swift~J1834.9$-$0846 is located at the center of the supernova remnant (SNR) W41 whose radius is $\sim 19$pc, an order of magnitude larger than that of the X-ray nebula ($\sim 2$pc). The association with SNR W41 suggests a common age of $\sim 5-100$kyr, while its spin-down age is $4.9$~kyr. A small natal kick velocity may partly explain why a wind nebula was detected around this magnetar but not around other magnetars, most of which appear to have larger kick velocities and may have exited their birth SNR. We find that the GeV and TeV source detected by Fermi/LAT and H.E.S.S., respectively, of radius $\sim 11$pc is most likely of hadronic origin. The dynamics and internal structure of the nebula are examined analytically to explain the nebula's current properties. Its size may naturally correspond to the diffusion-dominated cooling length of the X-ray emitting $e^{+}{e}^{-}$ pairs. This may also account for the spectral softening of the X-ray emission from the nebula's inner to outer parts. Analysis of the X-ray synchrotron nebula implies that (i) the nebular magnetic field is $\gtrsim 11\mu$G (and likely $\lesssim 30\mu$G), and (ii) the nebula is not powered predominantly by the magnetar's quiescent spin-down-powered MHD wind, but by other outflows that contribute most of its energy. The latter are most likely associated with the magnetar's bursting activity, and possibly dominated by outflows associated with its past giant flares. The energy source for the required outflows cannot be the decay of the magnetar's dipole field alone, and is most likely the decay of its much stronger internal magnetic field.

33 pages, 15 figures. Accepted for publication in MNRAS

References in corpus (11)

• 1E 1547.0-5408: a radio-emitting magnetar with a rotation period of 2 seconds
• Evolution of a buried magnetic field in the central compact object neutron stars
• The Prelude to and Aftermath of the Giant Flare of 2004 December 27: Persistent and Pulsed X-ray Properties of SGR 1806-20 from 1993 to 2005
• The Distance of the SNR Kes 75 and PWN PSR J1846-0258 System
• The Distances of SNR W41 and overlapping HII regions
• The Distances of SNRs Kes 69 and G21.5-0.9 from HI and 13CO Spectra
• VLA and XMM-Newton observations of the SNR W41/TeV Gamma-ray source HESS J1834-087
• Radio Spectrum and Distance of the SNR HB9
• A New, Low Braking Index For the LMC Pulsar B0540-69
• X-ray and radio observations of the magnetar Swift J1834.9-0846 and its dust-scattering halo
• Probing the gamma-ray emission from HESS J1834-087 using H.E.S.S. and Fermi LAT observations

Cited by in corpus (11)

• Implications of a "Fast Radio Burst" from a Galactic Magnetar
• Pulsar-wind nebulae and magnetar outflows: observations at radio, X-ray, and gamma-ray wavelengths
• The Sleeping Monster: NuSTAR observations of SGR 1806-20, 11 years after the Giant Flare
• On the Diversity of Compact Objects within Supernova Remnants II: Energy Loss Mechanisms
• Does the gamma-ray binary LS I +61°303 harbor a magnetar?
• Constraining Models of the Pulsar Wind Nebula in SNR G0.9+0.1 via Simulation of its Detection Properties using the Cherenkov Telescope Array
• Pulsar Wind Nebulae
• Natal kicks of compact objects
• Gamma-ray Emission of the Kes 73/1E 1841-045 Region Observed with the Fermi Large Area Telescope
• Prospects for gamma-ray emission from magnetar regions in CTAO observations
• Multiwavelength study of non-thermal emission in the Swift J1834.9-0846/W41 region