NuSTAR Detection of Nonthermal Bremsstrahlung from the Supernova Remnant W49B

Abstract

We report on NuSTAR observations of the mixed morphology supernova remnant (SNR) W49B, focusing on its nonthermal emission. Whereas radio observations as well as recent gamma-ray observations evidenced particle acceleration in this SNR, nonthermal X-ray emission has not been reported so far. With the unprecedented sensitivity of NuSTAR in the hard X-ray band, we detect a significant power-law-like component extending up to $\sim 20\mathrm{keV}$, most probably of nonthermal origin. The newly discovered component has a photon index of $\Gamma =1.4_{-1.1}^{+1.0}$ with an energy flux between 10 and 20 keV of $(3.3\pm 0.7)\times 10^{-13}\mathrm{erg}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$. The emission mechanism is discussed based on the NuSTAR data combined with those in other wavelengths in the literature. The NuSTAR data, in terms both of the spectral slope and of the flux, are best interpreted as nonthermal electron bremsstrahlung. If this scenario is the case, then the NuSTAR emission provides a new probe to sub-relativistic particles accelerated in the SNR.

arXiv comment7 pages, 3 figures, 2 tables, accepted for publication in ApJ Letters

References in corpus (24)

• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Detection of the Characteristic Pion-Decay Signature in Supernova Remnants
• Parameterization of Gamma, e^+/- and Neutrino Spectra Produced by p-p Interaction in Astronomical Environment
• A Spitzer Space Telescope Infrared Survey of Supernova Remnants in the Inner Galaxy
• Analytical solutions for energy spectra of electrons accelerated by nonrelativistic shock-waves in shell type supernova remnants
• Simultaneous Acceleration of Protons and Electrons at Nonrelativistic Quasiparallel Collisionless Shocks
• Neutral pion emission from accelerated protons in the supernova remnant W44
• Inverse Compton Emission from Galactic Supernova Remnants: Effect of the Interstellar Radiation Field
• New Catalogs of Compact Radio Sources in the Galactic Plane
• Suzaku Discovery of the Strong Radiative Recombination Continuum of Iron from the Supernova Remnant W49B
• Fermi-LAT Study of Gamma-ray Emission in the Direction of Supernova Remnant W49B
• The X-ray Line Emission from the Supernova Remnant W49B
• The Galactic Supernova Remnant W49B Likely Originates from a Jet-Driven, Core-Collapse Explosion
• A Near-Infrared and X-ray Study of W49B: A Wind Cavity Explosion
• ASCA View of the Supernova Remnant Gamma Cygni (G78.2+2.1): Bremsstrahlung X-ray Spectrum from Loss-flattened Electron Distribution
• The X-ray emission of the supernova remnant W49B observed with XMM-Newton
• Spatially Resolving a Starburst Galaxy at Hard X-ray Energies: NuSTAR, Chandra, AND VLBA Observations of NGC 253
• The supernova remnant W49B as seen with H.E.S.S. and Fermi-LAT
• Supernova remnant W49B and its environment
• Evidence for a neutral iron line generated by MeV protons from supernova remnants interacting with molecular clouds
• K-shell Emission of Neutral Iron Line from Sgr B2 Excited by Subrelativistic Protons
• The Origin of Recombining Plasma and the Detection of the Fe-K Line in the Supernova Remnant W28
• Flat Spectrum X-ray Emission from the Direction of a Molecular Cloud Associated with SNR RX J1713.7-3946
• Discovery of 6.4 keV line and soft X-ray emissions from G323.7$-$1.0 with Suzaku

Cited by in corpus (11)

• Evidence for Rapid Adiabatic Cooling as an Origin of the Recombining Plasma in the Supernova Remnant W49B Revealed by NuSTAR Observations
• ALMA CO Observations of the Mixed-Morphology Supernova Remnant W49B: Efficient Production of Recombining Plasma and Hadronic Gamma-rays via Shock-Cloud Interactions
• Theory of Electron Injection at Oblique Shock of Finite Thickness
• Shock-Cloud Interaction in the Southwestern Rim of RX J1713.7$-$3946 Evidenced by Chandra X-ray Observations
• Long-term evolution of non-thermal emission from Type Ia and core-collapse supernova remnants in a diversified circumstellar medium
• A broadband X-ray imaging spectroscopy in the 2030s: the FORCE mission
• Detection of the hard X-ray non-thermal emission from Kepler's supernova remnant
• X-ray and radio studies of SNR CTB 37B hosting the magnetar CXOU J171405.7-381031
• Probing Cosmic Rays with Fe K$\alpha$ Line Structures Generated by Multiple Ionization Process
• Suzaku and Fermi view of the supernova remnant 3C 396
• Nonthermal processes and particle acceleration in supernova remnants