- A possible association of the new VHE gamma-ray source HESS J1825--137 with the pulsar wind nebula G18.0--0.7 doi link

Author(s): Aharonian F.A., Akhperjanian A.G., Chounet L.-M., Degrange B., Djannati-Ataï A., Dubus G., Espigat P., Feinstein F., Fontaine G., Gallant Y., Giebels B., Jacholkowska Agnieszka, Lemiere A., Lemoine-Goumard M., Leroy N., Martineau-Huynh O., Marcowith A., De Naurois M., Ouchrif M., Pita S., Punch M., Raux J., Rob L., Rolland L., Tavernet J.-P., Terrier R., Theoret C.G., Tluczykont M., Vasileiadis G., Vincent P.

(Article) Published: Astronomy & Astrophysics, vol. 442 p.L25-L29 (2005)
Links openAccess full text : arxiv

Ref HAL: in2p3-00025035_v1
Ref Arxiv: astro-ph/0510394
DOI: 10.1051/0004-6361:200500180
Ref. & Cit.: NASA ADS
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We report on a possible association of the recently discovered very high-energy $\gamma$-ray source HESS J1825--137 with the pulsar wind nebula (commonly referred to as G 18.0--0.7) of the $2.1\times 10^{4}$ year old Vela-like pulsar PSR B1823--13. HESS J1825--137 was detected with a significance of 8.1 $\sigma$ in the Galactic Plane survey conducted with the H.E.S.S. instrument in 2004. The centroid position of HESS J1825--137 is offset by 11\arcmin south of the pulsar position. \emph{XMM-Newton} observations have revealed X-ray synchrotron emission of an asymmetric pulsar wind nebula extending to the south of the pulsar. We argue that the observed morphology and TeV spectral index suggest that HESS J1825--137 and G 18.0--0.7 may be associated: the lifetime of TeV emitting electrons is expected to be longer compared to the {\it XMM-Newton} X-ray emitting electrons, resulting in electrons from earlier epochs (when the spin-down power was larger) contributing to the present TeV flux. These electrons are expected to be synchrotron cooled, which explains the observed photon index of $\sim 2.4$, and the longer lifetime of TeV emitting electrons naturally explains why the TeV nebula is larger than the X-ray size. Finally, supernova remnant expansion into an inhomogeneous medium is expected to create reverse shocks interacting at different times with the pulsar wind nebula, resulting in the offset X-ray and TeV $\gamma$-ray morphology.

Comments: 5 pages, 3 figures, to appear in Astronomy and Astrophysics Letters