Abstract
We present the discovery of two very-high-energy gamma-ray sources in an ongoing systematic search for emission above 100 GeV from pulsar wind nebulae in survey data from the H.E.S.S. telescope array. Imaging Atmospheric Cherenkov Telescopes are ideal tools for searching for extended emission from pulsar wind nebulae in the very-high-energy regime. H.E.S.S., with its large field of view of 5 degrees and high sensitivity, gives new prospects for the search for these objects. An ongoing systematic search for very-high-energy emission from energetic pulsars over the region of the Galactic plane between -60 degrees < l < 30 degrees, -2 degrees < b < 2 degrees is performed. For the resulting candidates, the standard H.E.S.S. analysis was applied and a search for multi-wavelength counterparts was performed. We present the discovery of two new candidate gamma-ray pulsar wind nebulae, HESS J1718-385 and HESS J1809-193. H.E.S.S. has proven to be a suitable instrument for pulsar wind nebula searches.
Highlights
It has long been known that pulsars can drive powerful winds of highly relativistic particles
The ratio of X-ray to γ-ray emission is related to the magnetic field in the nebula
Measurements of high-energy γ-ray radiation resulting from inverse Compton scattering have a considerable advantage in that they provide
Summary
It has long been known that pulsars can drive powerful winds of highly relativistic particles (see e.g. Gaensler & Slane 2006, for a review). In contrast to the Crab pulsar, the Vela pulsar is an order of magnitude older (∼11 kyr) and its nebula is significantly offset from the pulsar position, both in X-rays and VHE γ-rays, possibly due to the expansion of the supernova blast wave into an inhomogeneous interstellar medium (Blondin et al 2001) Offset nebulae in both X-rays and VHE γ-rays have been observed in the Kookaburra Complex (Aharonian et al 2006e) and for the PWN associated with the γ-ray source HESS J1825−137 (Aharonian et al 2005c, 2006f). The statistical significance of the resulting associations of the VHE γ-ray source with the pulsar is evaluated by repeating the procedure for randomly generated pulsar samples, modelled after the above-mentioned parent population In this search, it is found that pulsars with high spin-down energy loss rates are on a statistical basis accompanied by VHE emission. In the data set used for this search, other new VHE sources have been detected that are not associated with pulsars, and will be reported elsewhere
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