* Astronomy

Title: Discovery of an Energetic 38.5 ms Pulsar Powering the Gamma-ray Source IGR J18490-0000/HESS J1849-000
Authors: E. V. Gotthelf (1), J. P. Halpern (1), R. Terrier (2), F. Mattana (2), ((1) Columbia University, (2) APC/CNRS University Paris 7)

We report the discovery of a 38.5 ms X-ray pulsar in observations of the soft gamma-ray source IGR J18490-0000 with the Rossi X-ray Timing Explorer (RXTE). PSR J1849-0001 is spinning down rapidly with period derivative 1.467(41)E-14 s/s, yielding a spin-down luminosity 1.0E37 erg/s, characteristic age 41.6 kyr, and surface dipole magnetic field strength 7.6E11 G. Within the INTEGRAL/IBIS error circle lies a point-like XMM-Newton and Chandra X-ray source that shows evidence of faint extended emission consistent with a pulsar wind nebula (PWN). The XMM-Newton spectrum of the point source is well fitted by an absorbed power-law model with photon index Gamma(PSR) = 1.12 ±0.14, N_H = 4.31(+0.58,-0.55)E22 cm^-2, and F(PSR;2-10keV) = 3.8E-12 erg/s/cm², while the spectral parameters of the extended emission are Gamma(PWN) = 2.1 and F(PWN;2-10 keV) = 8.7E-13 erg/s/cm². IGR J18490-0000 is also coincident with the compact TeV source HESS J1849-000. For an assumed distance of 7 kpc in the Scutum arm tangent region, the 0.35-10 TeV luminosity of HESS J1849-000 is 0.13% of the pulsar's spin down energy, while the ratio F(0.35-10 TeV)/F(PWN; 2-10 keV) of approx. 2. These properties are consistent with leptonic models of TeV emission from PWNe, with PSR J1849-0001 in a stage of transition from a synchrotron X-ray source to an inverse Compton gamma-ray source.

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