Discovery of a Radio Supernova Remnant and Non-thermal X-ray(3)

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We present the discovery of non-thermal radio and X-ray emission positionally coincident with the TeV $\gamma$-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, a

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FIG.1.—(a)VLA90cmimageofG12.82–0.02with32′′×19′′resolution.ThecrossindicatesthepositionofHESSJ1813–178whichhasapositionaluncertaintyof1′ 2′(Aharonianetal.2005b).(b)Threecolorimageofthesameregionas(a),withred=Spitzer8µm,green=VLA20cm,andblue=VLA90cm.Thermalemissioniswhitetocyanorredincolor,whilenon-thermalemissionisdarkerblue.(c)RadiospectrumforSNRG12.8–0.0.Solidhexagonsymbolsarefromthecurrentworkat20and90cm.Theopenhexagonsymbolindicatesthe5σ4mupperlimit.The symbolsindicate uxdensitiesfromthe11cmBonn,6cmParkes,and3cmNobeyamasingledishsurveys(Reichetal.1990;Haynesetal.1978;Handaetal.1987).Theline(solidanddashed)showsapower-lawweightedleastsquares ttotheradiodataforν≥330MHz(90cm).

FIG.2.—ASCASISgreyscaleimageofAXJ1813–178intheenergyrange0.5–10keVsmoothedto30′′with90cmcontoursfromFig.1aat28,33,38,43,and48mJybeam 1overlaid(contourintervalsare2σ).Theblackcircleindicatesthepositionandangularextent(3′)ofHESSJ1813–178.InsetASCASISspectrumofAXJ1813–178extractedfrom3′regionencompassingtheradioshell.Thecrosssymbolsshowthedatawhilethesolidlineshowsthebest tpower-law(dottedline)plusRS(dashed)model.Theresidualsintheformoftheuncertaintyσareshowninthebottompanel.

We present the discovery of non-thermal radio and X-ray emission positionally coincident with the TeV $\gamma$-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, a

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FIG.3.—Fitstothebroadbandemissionassumingthatallthe uxoriginatesfromtheshellofSNRG12.8–0.0.BPNstandsforBonn,Parkes,andNobeyama.ThediagonalblacklinesindicateboththeuncertaintyintheHESS uxmeasurements,andthefactthatnospectralinformationhasyetbeenpublishedfortheTeVemission.Thetwomodelsindicatedbytheredandbluelinesshowtherangeofparameterspacethatbest tthedata:theredmodelusesthespectralindexfromthebest ttotheASCAdataNHof10.8×1022cm 2(blackX-rayspectrum),whilethebluemodelusesthespectralindeximpliedbythe1σlowerlimittoNHof8.9×1022cm 2(greenX-rayspectrum).Bothmodelsincludecontributionsfromsynchrotron(solidlines)andIC(dashedlines)mechanisms;wehaveassumedthatthe llingfactorofthemagnetic eldintheICemittingregionis15%.