Demystifying an unidentified EGRET source by VHE gamma-ray observations

In a novel approach in observational highenergy gamma-ray astronomy, observations carried out by imaging atmospheric Cherenkov telescopes provide necessary templates to pinpoint the nature of intriguing, yet unidentified EGRET gamma-ray sources. Using GeV-photons detected by CGRO EGRET and taking advantage of high spatial resolution images from H.E.S.S. observations, we were able to shed new light on the EGRET observed gamma-ray emission in the Kookaburra complex, whose previous coverage in the literature is somewhat contradictory. 3EGJ1420–6038 very likely accounts for two GeV gamma-ray sources (E> 1 GeV), both in positional coincidence with the recently reported pulsar wind nebulae (PWN) by HESS in the Kookaburra/Rabbit complex. PWN associations at VHE energies, supported by accumulating evidence from observations in the radio and X-ray band, are indicative for the PSR/plerionic origin of spatially coincident, but still unidentified Galactic gamma-ray sources from EGRET. This not only supports the already suggested connection between variable, but unidentified low-latitude gamma-ray sources with pulsar wind nebulae (3EGJ1420–6038 has been suggested as PWN candidate previoulsy), it also documents the ability of resolving apparently confused EGRET sources by connecting the GeV emission as measured from a large-aperture space-based gamma-ray instrument with narrow field-of-view but superior spatial resolution observations by ground-based atmospheric Cherenkov teleOlaf Reimer W.W. Hansen Experimental Physics Laboratory & Kavli Institute for Particle Astrophysics and Cosmology Stanford University Stanford, CA 94305-4085, USA Tel.: +1-650-724-6819, Fax: +1-650-725-2463 E-mail: [email protected] Stefan Funk Kavli Institute for Particle Astrophysics and Cosmology, SLAC Menlo Park, CA 94025, USA Tel.: +1-650-926-8979, Fax: +1-650-926-5566 E-mail: [email protected] scopes, a very promising identification technique for achieving convincing individual source identifications in the era of GLAST-LAT.