[SN, SNR, and Isolated NS -- Oral ]

## New Deep X-ray and Radio Observations of G1.9+0.3

Kazimierz Borkowski, North Carolina State University
S.P.Reynolds (NCSU), D.A.Green (University of Cambridge), U.Hwang, I.Harrus, R.Petre (NASA/GSFC)

{\it Chandra} X-ray observations revealed G1.9+0.3 to be the youngest known Galactic supernova remnant (SNR), only $\sim 100$ yr old. Subsequent observations with the Very Large Array (VLA) confirmed this discovery. Both X-ray and radio emission are produced by relativistic electrons, accelerated in shocks with extreme (up to 14,000 km s$\^{-1}$) velocities, but their morphologies are strikingly different. A pronounced NE--SW radio asymmetry contrasts with a bipolar NW--SE X-ray emission that arises in shocks capable of accelerating electrons to $\sim 10-100$ TeV energies. Harder X-rays correlate with systematically varying X-ray brightness along the remnant's periphery. This may be interpreted in terms of the magnetic field obliquity dependence of the cosmic-ray acceleration efficiency, but observations available until now have not allowed for distinguishing between models with radically different field geometries. These models also fail to explain the strong NE--SW radio asymmetry. We present new deep {\it Chandra} and VLA observations that allow us to examine spatial morphologies and spectra of G1.9+0.3 in much greater detail than previously possible. We discuss how these observations advance our knowledge of particle acceleration in very fast SNR shocks.