Submitted to The Astrophysical Journal Preprint typeset using L ATEX style emulateapj v. 6/22/04 DISCOVERY OF A YOUNG, ENERGETIC 70.5 MS PULSAR ASSOCIATED WITH THE TEV GAMMA-RAY SOURCE HESS J1837−069

We report the discovery of 70.5 ms pulsations from the X-ray source AX J1838.0–0655 using the Rossi X-Ray Timing Explorer ( RXTE). PSR J1838–0655 is a rotation-powered pulsar with spin-down luminosity Ė = 5.5 × 1036 ergs s−1, characteristic age τc ≡ P/2Ṗ = 23 kyr, and surface dipole magnetic field strength Bs = 1.9 × 1012 G. It coincides with an unresolved INTEGRAL source and the extended TeV source HESS J1837–069. At an assumed distance of 6.6 kpc by association with an adjacent massive star cluster, the efficiency of PSR J1838–0655 converting spin-down luminosity to radiation is 0.8% for the 2–10 keV ASCA flux, 9% for the 20–300 keV INTEGRAL flux and ~3% for the >200 GeV emission of HESS J1837–069, making it a plausible power source for the latter. A Chandra X-ray observation resolves AX J1838.0–0655 into a bright point source surrounded by a 2′ diameter, centrally peaked nebula. The spectra of the pulsar and nebula are each well fitted by power laws, with photon indices Γ = 0.5(0.3–0.7) and Γ = 1.6(1.1–2.0) , respectively. The 2–10 keV X-ray luminosities of the pulsar and nebula are LPSR = 4.6 × 1034 d26.6 ergs s−1 and LPWN = 5.2 × 1033 d26.6 ergs s−1. A second X-ray source adjacent to the TeV emission, AX J1837.3–0652, is resolved into an apparent pulsar/PWN; it may also contribute to HESS J1837–069. The star cluster RSGC 1 may have given birth to one or both pulsars, while fueling TeV emission from the extended PWN with target photons for inverse Compton scattering.