Discovery of a Radio Supernova Remnant and Non-thermal X-rays Coincident with the TeV Sourc.pdf

a r X i v : a s t r o - p h / 0 5 0 5 1 4 5 v 2 1 3 J u l 2 0 0 5 DRAFT VERSION FEBRUARY 2, 2008 Preprint typeset using LATEX style emulateapj v. 11/26/04 DISCOVERY OF A RADIO SUPERNOVA REMNANT AND NON-THERMAL X-RAYS COINCIDENT WITH THE TEV SOURCE HESS J1813–178 C. L. BROGAN 1 , B. M. GAENSLER 2 , J. D. GELFAND 2 , J. S. LAZENDIC 3 , T. J. LAZIO 4 , N. E. KASSIM 4 , N. M. MCCLURE-GRIFFITHS 5 Draft version February 2, 2008 ABSTRACT We present the discovery of non-thermal radio and X-ray emission positionally coincident with the TeV γ- ray source HESS J1813–178. We demonstrate that the non-thermal radio emission is due to a young shell-type supernova remnant (SNR) G12.8–0.0, and constrain its distance to be greater than 4 kpc. The X-ray emission is primarily non-thermal and is consistent with either an SNR shell or unidentified pulsar/pulsar wind nebula origin; pulsed emission is not detected in archival ASCA data. A simple synchrotron+inverse Compton model for the broadband emission assuming that all of the emission arises from the SNR shell implies maximum en- ergies of (30 ? 450)(B/10μG)?0.5 TeV. Further observations are needed to confirm that the broadband emission has a common origin and better constrain the X-ray spectrum. Subject headings: acceleration of particles – supernova remnants – radio:ISM – Xrays:ISM – ISM: individual (G12.8-0.0, HESS J1813-178) 1. INTRODUCTION Based on theoretical arguments, it has become widely ac- cepted that a significant fraction of Galactic cosmic rays with energies up to the “knee” in the cosmic ray spectrum at ～ 10 15 eV are generated in shell type supernova remnants (SNRs) (e.g. Blandford Eichler 1987). While the detec- tion of non-thermal X-rays from the shells of several SNRs provides evidence that SNR shocks are efficient accelerators of . 1013 eV electrons (see e.g. Reynolds 1996), direct evi- dence is still lacking that (1) SNRs can accelerate particles all the way to 10 15 eV, and (2) SNRs efficiently accelerate pr