* Astronomy

Title: PSR J1856+0245: Arecibo Discovery of a Young, Energetic Pulsar Coincident with the TeV Gamma-ray Source HESS J1857+026
Authors: J.W.T. Hessels, D.J. Nice, B.M. Gaensler, V.M. Kaspi, D.R. Lorimer, D.J. Champion, A.G. Lyne, M. Kramer, J.M. Cordes, P.C.C. Freire, F. Camilo, S.M. Ransom, J.S. Deneva, N.D.R. Bhat, I. Cognard, F. Crawford, F.A. Jenet, L. Kasian, P. Lazarus, J. van Leeuwen, M.A. McLaughlin, I.H. Stairs, B.W. Stappers, A. Venkataraman

We present the discovery of the Vela-like radio pulsar J1856+0245 in the Arecibo PALFA survey. PSR J1856+0245 has a spin period of 81ms, a characteristic age of 21kyr, and a spin-down luminosity Edot = 4.6 x 10^36 ergs/s. It is positionally coincident with the TeV gamma-ray source HESS J1857+026, which has no other known counterparts. Young, energetic pulsars create wind nebulae, and more than a dozen pulsar wind nebulae have been associated with very-high-energy (100GeV-100TeV) gamma-ray sources discovered with the HESS telescope. The gamma-ray emission seen from HESS J1857+026 is potentially produced by a pulsar wind nebula powered by PSR J1856+0245; faint X-ray emission detected by ASCA at the pulsar's position supports this hypothesis. The inferred gamma-ray efficiency is epsilon_gamma = L_gamma/Edot = 3.1% (1-10TeV, for a distance of 9kpc), comparable to that observed in similar associations.
    
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